HomeMy WebLinkAboutBLD2007-01975 Proposed Rockery Design and Construction Recommendations - BLD Engineering / Geo-tech Reports - 10/9/2007 PROPOSED ROCKERY DESIGN AND
CONSTRUCTION RECOMMENDATIONS
BENNETT ROCK WALL
NEAR 11301 NORTH SHORE ROAD
BELFAIR, WA
CLIENT:
Mr. Phillip Bennett
Near 11301 North Shore Road
Belfair, Wa
BY:
N.L. OLSON AND ASSOCIATES, INC.
2453 BETHEL AVE. SE
PORT ORCHARD, WA 98366
(360) 876-2284
Project Number: 6800-07
R R
� — s
OCTOBER 9, 2007
N.L. OLSON & ASSOCIATES, INC.
Engineering, Planning and Surveying
October 9, 2007 Project Number: 6800-07
Attn: Mr. Phillip Bennett
Near 11301 North Shore Road
Belfair, Wa
Phone: (360) 277-3840
SUBJECT: Proposed Rockery Design and Construction Recommendations
Near 11301 North Shore Road
Belfair, WA o0(�
Tax Parcel Number: 322245000M2
Dear Mr. Bennett
We are pleased to submit our construction recommendations and design for the proposed rock
wall alignment.
We appreciate the opportunity to be of service to you on this project. If we can be of further
assistance or if you have any questions regarding this project, please contact our office.
Sincerely,
Wesley R. Johnson, P.E.
Project Engineer
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
F\6800 Bennett Rock Wall\Bennett Rockwall doc
Geotech Report Format (Mason County)
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TABLE OF CONTENTS
INTRODUCTION ......................................................................................................................1
SITELOCATION........................................................................................................................ 1
SITECONDITIONS .................................................................................................................... 1
PROPOSEDROCK WALL ALIGNMENT.......................................................................................... 1
SITE SOIL CONDITIONS AND GROUNDWATER............................................................................. 1
ROCK WALL RECOMMENDATIONS AND DESIGN CRITERIA..............................................1
TEMPORARY SLOPE AND PERMANENT SLOPE.............................................................................2
ROCK WALL DESIGN CONSIDERATIONS AND FOUNDATION CONSIDERATIONS ................................2
SUBSURFACEDRAINAGE.......................................................................................................... 3
SURFACERUNOFF...................................................................................................................3
CONSTRUCTIONMONITORING...................................................................................................3
ROCKWALL DESIGN AND DETAIL .............................................................................................3
SEISMIC..................................................................................................................................3
Probabilistic Peak Ground Motion Values (PGA) - (Slope Stability).................................... 4
Recommended Seismic Design Ground Shaking Parameters IBC - 2006.......................... 4
REPORTLIMITATIONS ...........................................................................................................4
STRUCTURAL NOTES AND DETAILS FOR ROCK WALL CONSTRUCTION
APPENDIX A: ROCK WALL STRUCTURAL CALCULATIONS
APPENDIX B: ARC GUIDELINES
PROPOSED ROCKERY DESIGN AND
CONSTRUCTION RECOMMENDATIONS
BENNETT ROCK WALL
NEAR 11301 NORTH SHORE ROAD
BELFAIR, WA
PARCEL NUMBER 32224500032
INTRODUCTION
The purpose of this report is to provide construction recommendations and a design for the
proposed rock wall alignment. The rock wall construction recommendations are presented in
the following and the structural calculations for the rock wall have been included in Appendix A
of this report.
SITE LOCATION
The property is located at the address of Near 11301 North Shore Road, Belfair WA, and
Mason County's Parcel Number: 322245000032.
SITE CONDITIONS
The northwest side of the property has been benched along the newly created access road
alignment exposing a temporary slope roughly 2 to 10 feet in height. The gradient of the
temporary slope has been cut to a roughly 1H:1V (Horizontal:Vertical) to near vertical
configuration. NLO has illustrated the site location and proposed rock wall alignment on the
structural drawings page 2 of 5 attached to this letter.
PROPOSED ROCK WALL ALIGNMENT
We understand the rock wall will have a maximum exposed wall height of roughly 2 to 10 feet,
face a linear distance of about 95 feet, and daylight towards the northeast and southeast ends
of the proposed wall's alignment. The area above the rock wall will slope up at a gradient of
less than 12 degrees for a distance of roughly 10 to 15 feet and flatten out along the access
road alignment to the northwest.
SITE SOIL CONDITIONS AND GROUNDWATER
During our Aug 14, 2007 site visit, we observed the exposed soil conditions along a temporary
slope graded along the proposed rock wall alignment. The exposed soil consisted of dense to
very dense poorly graded gravel and silty sand with gravel (glacial till).
ROCK WALL RECOMMENDATIONS AND DESIGN CRITERIA
We recommend that the rock wall's facing elements consist of large rock stacked with the large
rock along the base and decrease in size towards the top portion of the wall. The long
dimension of the rock along the facing shall be placed to avoid continuous joint planes in the
vertical direction. Each rock shall bear on a minimum of two rocks with good contact. The area
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
F\6800 Bennett Rock Wall\Bennett Rockwall doc
Geotech Report.Format (Mason County)
J
Project No. 6800-07
October 9, 2007
Page No. 2
between the facing rock and temporary slope will be backfilled with quarry spalls washed of
fines and wrapped with a filter cloth. A longitudinal subdrain with a minimum diameter of 4
inches with drainage rock placed at the base of the large rock. The drain rock enveloping the
perforated drainpipe should be wrapped with a filter cloth. The rock wall's construction
procedures are presented in more detail in the following.
TEMPORARY SLOPE AND PERMANENT SLOPE
As a preliminary guideline for temporary cuts, we recommend temporary slopes be made no
steeper than 1 H:1 V for the encountered soils. Temporary slopes or excavations should be
benched as required by safety regulations in effect at the time of construction. These temporary
slope recommendations are for native soils; flatter slopes may be required in wet weather or if
soil conditions other than those previously described are encountered. It is recommended that
a qualified representative of NLO make periodic inspections of temporary slopes and
excavations to provide early recognition of potential slope instability and erosion concerns. At
this time, we recommend a temporary slope of 1H:1V. The temporary slope base can be cut
near vertical for a height of 2 to 3 feet above the bottom portion of the keyway in very dense
glacial till soil conditions.
The contractor should be aware that the slope height, slope inclination, and excavation depths
(including utility trench excavations) should in no case exceed those specified in local, state, or
federal safety regulations; e.g., OSHA Health and Safety Standards for Excavations, 29 CFR
Part 1926, or successor regulations. Such regulations are strictly enforced and, if not followed,
the owner, the contractor, or the earthwork or utility subcontractors could be liable for
substantial penalties. The contractor should be made responsible for the stability of all
excavations and slopes during construction because they are continually on site and can
observe the stability of the exposed soils. In addition, the contractor should be prepared to
shore any unstable slope area and provide shoring as required by local, state, or federal laws or
codes. The provision of shoring design recommendations is beyond the authorized scope of
this report.
Temporary slopes recommendations are provided solely as a service to our client. NLO, under
no circumstances, assumes liability for the site with regard to safety or other construction
activities directed by the contractor.
ROCK WALL DESIGN CONSIDERATIONS AND FOUNDATION CONSIDERATIONS
Based on the encountered soil conditions and wall heights, we anticipate a wall footing
embedment depth of about 1 to 2 feet depending on rock wall height. For the rock wall's
design, an allowable soil bearing pressure of 2,500 pounds per square foot (psf) was utilized.
Based on the encountered soil conditions, we anticipate adequate bearing soils along the
proposed rock wall alignment. Prior to rock wall construction, we recommend inspection of the
rock wall keyway and footing subgrade by a N.L. Olson and Associate, Inc. (NLO)
representative. The rock wall's footing subgrade must consist of undisturbed dense native soil
or properly compacted structural fill. If structural fill is utilized along the rock wall alignment
foundation subgrade area, the structural fill must be compacted to relative density of 95 percent
of the modified proctor.
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 9 Fax: (360) 876-1487
r
Project No. 6800-07
October 9, 2007
Page No. 3
SUBSURFACE DRAINAGE
As a minimum, the subsurface drain should consist of a 4-inch diameter, SDR 35 (ASTM 3034)
perforated pipe laid perforations down, bedded in an envelope of free-draining sand and gravel.
Clean-outs should be provided at bends at convenient intervals, so that the drainage system
can be maintained in a well-functioning condition. The Intercepted groundwater from the rock
wall's subsurface drainage system should be tightlined away from the rock wall to a discharge
point that will not effect down slope structures, or properties.
Note: Flexible plastic piping (such as corrugated ADS-type piping) should not be used behind
the wall.
SURFACE RUNOFF
In a disturbed condition the soils located above and below the rock wall may be eroded by
channelized water or sheet flow from storm runoff. Therefore, it is recommended that all site
preparation and excavation work be completed during the normally drier portion of the year.
During periods of heavy rainfall, ditching should be used to divert water away from stripped
areas and visqueen should be used to cover the slopes and soil stockpiles to prevent erosion.
This covering also aids in preventing infiltration of water into the unprotected soils. All disturbed
soil areas and slopes should be replanted with fast-growing, deep-rooted grass, shrubs and
other ground cover as soon after final grading as possible. If the vegetation is not fully
established prior to the on set of wet weather, the slopes should be covered with visqueen to
aid in preventing excessive erosion and water infiltration.
CONSTRUCTION MONITORING
NLO should be retained to provide geotechnical services during construction. This is to
observe compliance with the design concepts, specifications or recommendations and to allow
design changes in the event subsurface conditions differ from those anticipated prior to the
start of construction. We do not accept responsibility for the performance of the rock wall or
provide final letters certifying successful completion of the rock wall unless we are retained to
review the construction drawings and specifications, and provide construction monitoring
services.
In the event that change in the nature, design, or location of the proposed construction is made,
or any physical changes to the site occur, recommendations are not be considered valid unless
the changes are reviewed by NLO and conclusions of this report are modified or verified in
writing.
ROCK WALL DESIGN AND DETAIL
Please see the rock structural notes for additional information concerning rock wall construction
calculations for the rock wall design included in Appendix A.
SEISMIC
NLO has reviewed the IBC for seismic design criteria for the proposed construction. The site's
ground acceleration was determined from the 2002 USGS Earthquake Hazard Program for the
Conterminous 48 States. The PGA was based on the following location 47.38006 Latitude and
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
Y
Project No. 6800-07
October 9, 2007
- Page No.4
—123.01457 Longitude. The interpolated probabilistic ground motion values (PGA) for
Horizontal peak acceleration and spectral acceleration are as provided in the following table.
Seismic Ground Shaking Summary
Probability Of Approximate Probabilistic Peak Spectral Acceleration(g)
ground motion (Site Class D)
exceedence Return Period
values PGA Period sec)
., (years) 9 0.2 sec 1.0 sec
i
10%in 50 years 475 .3222 1.243 .484
Probabilistic Peak Ground Motion Values (PGA) - (Slope Stability)
The site's ground acceleration was determined from the 2002 USGS Earthquake Hazard
Program. The interpolated probabilistic ground motion values (PGA), in %g, for the 10
robability of exceedance in 50 years was PGA=33.22%. The maximum horizontal ground
acceleration (Kh= 0.1661) was determined by dividing the PGA by 2.
Recommended Seismic Desiqn Ground Shaking Parameters IBC - 2006
NLO has reviewed the 2006 International Building Code (IBC) for seismic design criteria for the
proposed construction in regards to soil only. The IBC seismic design parameters for this site
include a seismic zone soil profile type D. The recommended seismic design ground shaking
parameters are the values in Seismic Parameter (2006 IBC) Table presented below for Site
Class D soils.
Seismic Parameters (2006 IBC) Values
Mapped Spectral Acceleration Short Period (Ss) 1.243
Mapped Spectral Acceleration For One Second (Si) 0.484
Site Class D
Short period Site Coefficient (Fa) 1.006
1-second Site Coefficient (FJ 1.516
MCE Spectral Response Acceleration for short period (SMs=SsxFa) 1.243
MCE Spectral Response Acceleration for one second (SM,=S,xFv) 0.734
Design Spectral Response Acceleration for Short Period (SDs=2/3xSMs) 0.829
Design Spectral Response Acceleration for one second (SD1=2/3xSM,) 0. 9
Design Peak Ground Acceleration (PGA=SDS x 0.4) Q�o
REPORT LIMITATIONS
This report has been prepared for the client regarding the design and construction of the rock
wall. Information presented in this report has been collected and interpreted in a manner
consistent with the level of care and skill ordinarily exercised by members of the profession
currently practicing under similar conditions, and in accordance with sound and generally
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
• Project No. 6800-07
October 9. 2007
--- -- —-- — - --- - -- - - - Page No. 5
accepted principles consistent with normal consulting practice. No other warranty, expressed or
implied, including (but not limited to) any warranty or merchantability or fitness for a particular
use has been made.
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
PROPOSED ROCK WALL DESIGN
NEAR 113 01 NORTH SHORE ROAD
ROCK WALL DESIGN
SHEET INDEX NEAR NORTH SHORE ROAD AND KAREN ROAD NE
1 TITLE SHEET BELFAIR WA
2 ROCK WALL OVERVIEW AND VICINITY MAP
3 ROCK WALL PROFILE STATIONS (0+00 TO 0+93)
4 ROCK WALL CROSS SECTIONS CONSTRUCTION DRAWINGS PREPARED FOR:
5 CONSTRUCTION NOTES
MR PHILLIP BENNETT
P.O. BOX 1863
BELFAIR, WA 98528-1863
xl:vlslorvs BY DATE J TITLE SHEE'T' rur.: SCALE: A6 SHOWN
LNO. DATE BY DESCRIP110N DESIGNED L DATE OCTOBER 8,2007
L-, N.L.Olson&Associates,Inc. NEAR 11301 NORTH SHORE ROAD MR. PHILLIP BENNETT �yGN�
pie ED Engineering, Planning and Surveying � OMAL BELFAIR, WASHINGTON P.O. BOX 1863 076800—
APPROVED (360) 876-2284 MASON COUNTY PARCEL #322245000032 BELFAIR, WA 98528-1863 XXXXXX
ACCEPTED 2453 Bethel Aranw,P.O.Box 637.Pal orchard.WA 9M are N� SHEET 1 OF 5
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VERIFIED BY NLO'S /Ft
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NOTE:CLIENT OR CONTRACTOR MUST
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VERIFY SETBACK DISTANCES FROM
ROADS AND PROPERTY LINES.
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REVISIONS BY DATE A3� ROCK WALL OVERVIEW AND VICINITY MAY IOIz: SCArE AS SHOW
NO. DATE BY DESCW7ION DEEMED m�J N.L.Olson&Associates,Inc. NEAR 11301 NORTH SHORE ROAD MR. PHILLIP BENNETT DATE: ocTCeEn 4 2om
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DRAWN Engineering, Planning and Surveying yb� 3"m BELFAIR, WASHINGTON P.O. BOX 1863 0_
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APPROVED (360) 876-2284 — XXXXXX
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NLO'S GEOTECHNICAL ENGINEER.
*NOTE: Rocks shown for illustration purposes only.
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REVISIONS BY DATE ROCK WALL PROFILE FOR SCALE: AS SHOW
NO. DATE BY DESCRIPTION --ED ��� MR. PHILLIP BENNETT DATE` OCTOBER a,2007
L_J N.L.Olson&Associates,Inc. ,�s NEAR 11301 NORTH SHORE ROAD
DRAWN Engineering, Planning and Surveying �.y� 313M BELFAIR, WASHINGTON P.O. BOX 1863 076800_
CHECKED �+PUL MASON COUNTY PARCEL #322245000032 BELFAIR, WA 98528-1863 XXXXXX
APPROVED (360) 876-2284
ACCEPTED 2453 BetAel!Meow,P.O.Bm�637,Port OreMrd,'IA 98M "�� SHEET 3 OF 5
CROSS SECTION D-D
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TEMPORARY BACK SLOPE
IMPERMEABLE SQL
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WALL HEIGHT / x Rorx �%i,-� ;� r9+
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CROSS SECTION B-B
Not To Scale
IMPERMEABLE SOIL
(Aft minimum thickness) MAX. — CROSS SECTION A-A
RISE Ito>: - _
BASAL OR GRANITE ROCK Not To Scale
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EXPBATTER
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5 tt _ TEMPORARY BACK SLOPE /I ., �.,,� TOTAL WA 25 HGHT r QUARRY SPALLS 4-6'WASHED OF FINES
WALL HEIGHT WALL HFlGHf 3.25 H6.5 ft6 —II /1.. � ] M'r+HKKxt _ PERFORATED PIPE SDR 3034 (b'DIAMETER)
4 rwH RDa( III=11 'Z NATIVE SQLS�L:c '^ `.',.a� 1' MIN. EMBEDMENT _III- 2
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_ PERFORATED PIPE SDR 3034 (4- DIAMETER) - �� -^ STRUCTURAL FILL '2NATIVE SOILS�L,i DRNN ROCK, NO FINES,WRAPED IN FlLnR CLOTH
1 5'MIN. EM E ENT 4 — �( ,
STRUCTURAL FILL r2NA SQLS�.,c .I I II IIII=1 I I, IIII DRAIN ROCK, NO FINES, WRAPED IN FILTER CLOTH
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3A`�3•a � ,
RLVISIONS BY DATE A ` ROCK WALL CROSS SECTIONS FOR, SCALE- AS SHOYN
AL-J N.L.Olson&Associates,Inc. DATE G NUMBETOBERR
4 2007
NO. DATE BY DESCRIPTION DESIGNED
NEAR 11301 NORTH SHORE ROAD MR. PHILLIP BENNETT DRAIMNC 11YI1ER:
DRAYM Engineering, Planning and Surveying .+dsle"'e BELFAIR, WASHINGTON P.O. BOX 1863 076800—
CHECKED APPROVED (360) 876-2284AL MASON COUNTY PARCEL #322245000032 BELFAIR, WA 98528-1863 XXXXXX
ACCEPTED 2453 Be"MenA P.O.Box 637.Port Orchwd,WA 96M6 °�N'� SHEET 4 OF 5
THE FOLLOWING RECOMMENDATIONS SHALL BE IMPLEMENTED INTO ROCK FOUNDATION PREPARATION: FOR THE ROCK WALL DESIGN CONSIDERATIONS, WE ANTICIPATE A
WALL CONSTRUCTION; WALL FOOTING EMBEDMENT DEPTH (D)WILL BE ABOUT D=1.5 FT FOR AN EXPOSED WALL HEIGHT
OF 8 FEET OR LESS AND D=2 FT FOR AN EXPOSED WALL HEIGHT GREATER THAN 8 FEET. FOR THE
*THE FACING ELEMENT WILL CONSIST OF LARGE BASAL ROCK THAT WILL ROCK WALL'S DESIGN, AN ALLOWABLE SOIL BEARING PRESSURE OF 2,500 POUNDS PER SQUARE
BE STACKED WITH THE LARGER ROCK ALONG THE BASE AND DECREASING FOOT(PSF)WAS UTILIZED. THE ROCK WALL'S FOOTING SUBGRADE MUST BE PROPERLY
IN SIZE TOWARD THE TOP PORTION OF THE ROCK WALL. COMPACTED TO RELATIVE DENSITY OF 95 PERCENT OF THE MODIFIED PROCTOR OR ON DENSE
NATIVE SOIL. THE SUBGW0E MUST BE INSPECTED BY NLO PRIOR TO PLACEMENT OF THE ROCK
*THE MINIMUM KEYWAY WIDTH SHALL BE EQUAL TO THE BASAL ROCK,AND WALL FACING, DRAIN ROCK AND SUBSURFACE DRAINAGE.
DRAIN ROCK.
SUBSURFACE DRAINAGE: A LONGITUDINAL SUBDRAIN WITH A MINIMUM DIAMETER OF 4 INCHES
*THE LONG DIMENSION OF THE ROCK ALONG THE FACING SHALL EXTEND SHOULD BE CONSTRUCTED AT THE BASE OF THE ROCK WALL FACING. THIS DRAIN SHOULD BE
PERPENDICULAR TO THE ROCK FACE. ROCK SHALL BE PLACED TO AVOID 4-INCH DIAMETER AND CONSIST OF SDR 35 (ASTM 3034) PERFORATED PIPE LAID PERFORATIONS
CONTINUOUS JOINT PLANES IN THE VERTICAL DIRECTION. EACH ROCK DOWN, BEDDED IN AN ENVELOPE OF FREE-DRAINING SAND AND GRAVEL MATERIAL. CLEAN-OUTS
SHALL BEAR ON A MINIMUM OF TWO ROCKS WITH GOOD CONTACT. SHOULD BE PROVIDED AT BENDS AND CONVENIENT INTERVALS, SO THAT THE DRAINAGE SYSTEM
CAN BE MAINTAINED IN A WELL-FUNCTIONING CONDITION.
*ONLY HAND OPERATED COMPACTION EQUIPMENT SUCH AS JUMPING NOTE: FLEXIBLE PLASTIC PIPING (SUCH AS CORRUGATED ADS-TYPE PIPING)SHOULD NOT BE USED
JACKS SHOULD BE OPERATED WITHIN THREE FEET OF THE WALL FACING IF BEHIND THE WALL.
NEEDED.
IMPERMEABLE SOIL STRUCTURAL FILL : IF STRUCTURAL FILL SHOULD BE UTILIZED ALONG THE PROPOSED ROCK WALL
(1ft minimum thickness) 3' RISE IN 8' MAX. ALIGNMENT THE MATERIAL MUST BE PLACED ON A FIRM, PROPERLY PREPARED SUBGRADE. FILL
FINISH GRADE MATERIALS SHOULD BE PLACED IN LOOSE LAYERS APPROXIMATELY 8 TO 12 INCHES THICK,
BASAL OR GRANITE ROCK MOISTURE CONDITIONED, AND COMPACTED TO 95% OF THE MAXIMUM DRY DENSITY AS
DETERMINED BY ASTM D-1557. STRUCTURAL FILL IS NOT TO BE PLACED WHEN OVER OPTIMUM,
2 MAN ROCK FILTER FABRIC N140 OR EQUIVALENT
WET, OR IF FREEZING WEATHER PREVENTS ACHIEVEMENT OF SPECIFIED COMPACTION
�
REQUIREMENTS. PRIOR TO ROCK WALL CONSTRUCTION, THE FILL MATERIAL INTENDED FOR
STRUCTURAL FILL NEEDS TO BE APPROVED BY A REPRESENTATIVE OF OUR FIRM.
BATTER 2 MAN ROCK o 0 o TEMPORARY BACK SLOPE
EXPOSED 1 NOTE:A GEOTECHNICAL ENGINEER MUST VERIFY
WALL HEIGHT TEMPORARY SLOPES AT THE TIME OF
WALL HEIGHT NATIVE SOILS�z
TOTAL 8 ft (MIN.) 4 MAN ROCK CONSTRUCTION. THE ENCOUNTERED SOIL AND
o t
9.5 ft (NO FILL) WEATHER CONDITIONS MAY REQUIRE
_ MODIFICATIONS TO THE TEMPORARY SLOPE
6 I I QUARRY SPALLS 4-6" WASHED OF FINES RECOMMENDATIONS MENTIONED IN THIS REPORT.
4 ROCK =I
ISTING
ADE �/ 4 MAN ROCK
PERFORATED PIPE SDR 3034 (4" DIAMETER)
j EMBEDMENT ZONE
I .t
STRUCTURAL FILL OR DRAIN ROCK, NO FINES, WRAPED IN FILTER CLOTH
UNDISTURBED DENSE NATIVE SOILS-' — — I —I
UNDISTURBED
SOILS — -- ---—
_-
NATIV
cv��a J�ti J
REVISIONS BY DATE 3 C 2
w %c-0ROCK WALL CONSTRUCTION NOTES FOR SCALE. AS sRowN
NO. DATE 0Y DESCRIPTION DESGNED IA\
-J N.L.Olson&Associates,Inc. NEAR t1301 NORTH ROAD MR. PHILLIP BENNETT DATE OCTOBER e,2007
L NUM
DRANK Engineering, Planning and Surveying ��e 710P �� BELFAIR, WASHINGTON P.O. BOX 1863 �_
CHECKED MASON COUNTY PARCEL 322245000032 BELFAIR, WA 98528-1863
APPROVED (360) 876-2284
XXXXXX
ACCEPTED 2463 B"h—m P.O.0°.637.P°rt Dished WA 9&W
SHEET 5 OF 5
Appendix A
APPENDIX A
STRUCTURAL CALCULATIONS
FOR ROCK WALLS
The single rock wall configuration will have a maximum exposed wall height 10 feet. The
proposed rock wall layout is shown the structural notes and details attached to the letter. For
our design assumptions, we have assumed the following;
• The exposed rock walls will have a maximum height of 10 feet, with 5, 8 and 10 exposed
wall heights utilized for our analyses to determine slide out and over turning.
• All the rock walls will be battered to a minimum of 6V:1 H.
• Dense soil was encountered along the proposed rockery alignment. The subgrade and
temporary back slope soils will need verification prior to rock wall placement.
• We recommend construction of the rock walls per the Associated Rock Wall Guidelines
(ARC), which has been included in this report with design calculations.
• If soil conditions vary from our design assumptions, we recommend modifications to our
rockery design assumption and design. Unless otherwise noted, we anticipate that the
rock walls will provide an erosion protection facing for the slope.
• Infinite slopes utilized to model light vehicle traffic surcharge loading about 50 psf.
• Traffic surcharge loading form North Shore Drive should not impose loads on wall.
• Slope placed above wall to prevent parking along top portion of rock wall alignment
The rock wall was designed as a gravity structure utilizing varying size rock to achieve the
adequate factors of the safety for sliding and overturning. The calculations for the rock wall are
presented in this appendix. The following soil information presented in the table below was
utilized for the rock wall design.
SOIL PARAMETERS _
Density' Cohesion Friction
Soil Type (pcf) (psf) (degrees)
1 Drainage Fill or Drain Rock 135 0 35
2 Retained Soil Ranges from 35 to 40 degrees 135 0 35
wlcohesion
3 Quarry S alls (4 to 6 inch) 135 0 35
4 Foundation Soil (Structural fill) 1 125 _0 35
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
WADE
M / �°�
e�sK OR QU)M FM
MTM Z A —I
tuu nmrr Z
WALLLHEW to n
6 -
14 11
2 �•r'�•7 Z s-y !V
zq
Z 3 -7 q
STRLXTUPA su
/ems x Y Ceh�i-ci� S
CROSS SECTION "
drat T?ScaleEE�t�g�
oft Pmi..tlickns) Y wf """
MTn z z -7 3 Z-
M K W�Hl IEJdff � r
en r
os n I
_.1 t3 MIN.DAWDMEWT �..
CO SEAS
Net To Smic.
E � Y
Bk%k OR DRAWTE ROCK 4,Z S
DPOSM
WALL HDGHT
TCYTAL
S n Ir
WALL HEIGHT
6.5 N
Im
1
U J
K
tBEDUENT
PA su '20,TNE SDaS/1—
Rock Wall October 9, 2007
Bennett
1. Determination of Structural Dimensions
Bb:= 3.3 Bb=Bottom width of wall in feet
Bt:= 1.72 Bt =Top width of wall in feet
0 a=Wall Batter measured clockwise in degrees
assumed zero more conservative
H,:= 6.5 Hw=Inclined height of wall in feet
Hemb 1.5 Hemb =Embedment depth in feet
He = Exposed wall height H =Wall Design height
He:= Hwy cos(a•deg) - Hemb He= 5 feet
�H:= He+ Hemb+ Bb•sin(a•deg) H=6.5 feet
O=Inclination of back wall measured clockwise from horizontal plane
Bb -Bt 180
0 := 90+ a - atan(( )) —
H, n
0 = 76.338 degrees
Note: A 9 degree backslope was utilzed. infinite slope accounts for traffic surcharge behind
wall. Note: area behind wall is broken slope.
9 degrees R=Inclination of ground slope behind wall
"e46S o
2. Determination of Earth Pressures utilized the various soils encountered in the
excavation to arrive at a soil unit weight of 135
Ibs/ft2
y := 135 y=Soil unit weight
�=Friction angle of retained soil assumes silty sand, sand and gravel conditions
overall soil friction average
:= 35
8=Friction angle between two dissimilar material say 3/4 � based on
gravelly silt soils encountered in subsurface excavation.
�n'= (4)
xpose Wall Fleight 5 ft Page Number (1)
Total height 6.5 ft j
• Rock Wall October 9, 2007
Bennett
Coulomb Eq.
sin(A•deg+ •deg)
2
Ka' 2
2 sin deg+ 5-de
g sin deg— (3 deg1)
sin(0 deg sin(A deg— S deg 1 +
[ sin(6•deg—5•deg)•sin(8•deg+ (3•deg)
K,= 0.41
P = Resultant of active pressure
Ka•W•y
P._
2
P= 1169.69
PH:= P•co490•deg—0•deg+ S•deg)
PH= 897.183
PV := P•sin(90•deg —0•deg+ 8-deg)
PV = 750.489
Expose Wall Height 5 ft Page Number (2)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
3. Evaluation of External Stability
Wall's Center of Gravity
The center of gravity (CG) of wall is estimated by taking moments of all unit masses
about the toe of the wall and then dividing the sum of the resisting moments by the weight of the
wall in X'Y' planes. The CG arms in X'Y' planes is then converted to CG in XY Planes.
The weight of the wall consist of all resisting masses including soil masses situated immediatey
behind the wall below the assumed failure plane. For simplifying calculations, all resisting soil
masses can be considered to be triangular in shape.
rock 140
....._...... t ...... ....... ...... y. f ....
E Mass Moment
Area I kl i Y I Weight x Y' I {
Mass Unit ft 2ft ft 1
^ � Ibs
Block 1 2.6 ! 1.86 6.25 364 677.04 2275
Block 2 3.7 1.81 4.74 s 518 937.58 2455.32 i
Block 3 5 1.8 I 3 700 1260 2100
Block 4 6 1.7 1 840 I 1428 I 840^ ^
Block 5 0 0 ! 0 1
Block 6 0 0 1
i. ..... . .. .. .. .........
Soil Unit 1 0 0 00 0_ _ 0
Soil Unit 2 0 0 0 0 0 0
:Soil Unit 3 0 0
Soil Unit 4 0 0 0 00 0 _ mm
E 4302.62 7670 32
.__ ...... ... .... __. _ . ._
Total 14.99
Weight 2422 Ibs
!Xeff 1.776474 feet
Yeff 3.166936 feet !
Pull these values from table
x.1.1•:= 1.78
yeff 3.17
weight of wall and soil resisting overturning
Weight:= 2422 Ibs
Expose Wall Height 5 ft Page Number(3)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
a =Horizontal arm of of W measured from toe XY plane
a:= cos(a•deg)•(xff+ yeff-tan(a•deg))
a = 1.78 feet
b =Verticle arm of PH measured from toe XY plane
b := H — Bb•sin(a•deg)
3
b =2.167 feet
e= Horizontal arm of Pv measured from toe in XY plane
N:= Bb•sin(90•deg —cc-deg) - 3•tan(90•deg—0•deg)
e = 2.773 feet
Evaluation of Overturning Stability
MR = Resisting Moment = Wa+Pve
MR:= Weight•a + (PV)•e
MR= 6392.517
Mp Driving Moment=PH B
MD := (P1l.b)
MID = 1943.897
FOSe := MR FOSo = 3.289
MD
Expose Wall Height 5 ft Page Number (4)
Total height 6.5 ft
Rock Wall
October 9, 2007
Bennett
Evaluation Of Sliding
F = Coefficant of friction between units
F tan( -deg)
AM
F = 0.7
N = Reaction at the base of the wall
:= Weight.cos(a•deg) + PV•cos(a•deg) + PH•sin(a•deg)
N=3172.489
Fr=sum of forces providing resistance to sliding
Fr:= N•F+ Weight.sin(a•deg) + PV•sin(a•deg)
N•F=2.221 x 103
Fr=2221.401
Weight.sin(a•deg) =0
Fd = Sum of forces driving the wall in sliding
Fd:= PH•cos(a•deg)
Fd= 897.183
F
FOSs:= r FOSS=2.48
Fd
Eccentricity 1 := Weight-cos(a•deg) + Pv•cos(a•deg) + PH•sin(a•deg)
N,:= N-cos(a•deg) Nh:= N•sin(a•deg)
Nv=3.172x 103 Nh=0
X = horizontal distance of normal force from toe
Weight•a+ PV•e - P1.1•b
X:_
Nv +Nh•tan(a•deg)
X= 1.402 feet
Expose Wall Height 5 ft Page Number(5)
Total height 6.5 ft
Rock Wall
October 9, 2007
Bennett
ex= eccentricty of the base reaction in feet from the center of the base of the wall
along the plane parrallel to the base of wall.
Bb X
ex:_ — —
2 cos(a•deg)
ex= 0.248
Bb— X Bb
Bb X <_ 2•
— cos(a•deg) 3
3 cos(a•deg)
Bb X Bb— X
= 1.1 = 1.402 — 1.898 2.Bb =2.2
3 cos(a•deg) cos(a•deg) 3
Seismic Analysis
Determine the tolerable wall displacement.
Ao:_ .332
d := 10•A0
d = 3.32 inches
Obtain a design value Kh Used method shown in Allan block engineering manual
page 54 to determine Kh.
.2�
Kh:=- .67-Ao•(A0)
d
Assume Kv=O
Kh=0.125 K 0
Use the value Kae to determine to obtain the wall weight and apply a factor of safety to this value.
Seismic Section
2
Ka•II`•y
p P = 1169.689 0 = 76.338
Expose Wall Height 5 ft Page Number (6)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
= 9-deg
Active Case for local ground acceleration for fill soils
From AASHTO Manual and Monobe-Okabe Method for Kae
0s:= (90 —0)•deg X,,:= 0
�s:= 0-deg Kh 180
yr := tan(( —
1 —Kv n
W =7.205
ss = 4'0s
c040 s —Os— W'deg)2
Kae 1 :— 2
2 in os — p —yr•deg
cos(yr•deg)•cos(9s) •cos(Ss+ As + y�•deg) 1 + sinSs+ �s •s
cos(6s+ As+ yr•deg)•cos(p —0s)
Kael =0.545
Ka=0.41
Dynamic Earth Force
K -2
PAF:= I.Kae I'Y+? (1 + Kv) :— a' 'Y
2
PAE = 1554.038 P= 1169.69
APAE:= PAE —P
PAE =384.349
Expose Wall Height 5 ft Page Number(7)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
Resolve the active earth force and the dynamic earth force into horizontal and vertical
components.
DFdyn:= OPT Ss=26.25 deg DFdyn =384.349
DFdynh:= DFdyn•cos(Ss) cos(Q =0.897 DFdynv:= DFdyn•sin(Ss)
DFdynh=344.712 DFdynv = 169.993
Fah:= (P)•co#s) Fav:= P•sin(Ss)
Fah = 1049.062 Fav= 517.34
cos(90•deg—0-deg+ S•deg) = 0.767
P.00490•deg—0•deg + 8-deg = P-sin(90•deg — 0•deg + 8-deg)
PH = 897.183 Pv = 750.489
Determine Resisting Forces Used Method described in Allen Block Manual
For determination of sliding and overturning
Weight of Wall Facing
Determine resisting forces
Os =35 deg
Weight of wall facing per linear foot
Weight=2.422 x 103 lbs
Maximum frictional resistance against sliding -(does not include passive resistance)
Frl :_ Weight+ Fav+ DFdynv)-tan(or) Weight= 2.422 x 103
DFdynv= 169.993 Fav= 517.34
Fr 1 = 2.177 x 103
Safety factor against sliding
F
FSsliding r DFdynh= 344.712
Fd+ DFdynh
FSsliding = 1.789 requires "FS.sliding" greater than or equal to 1.1
Expose Wall Height 5 ft Page Number(8)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
P. 3 + APAE'(.6H)
hl :_
Mos:_ (Fah)•h I-cos(Ss) PAE
Mos = 2441.909
MR NIR = 6.393 x 103
FSoLseismic
Nfos
FSot.seismic = 2.618
Weight•a + (Fav)•h
FSot.seismicl :_
(Fah)'h cos(Ss)
Summary of Calculations
Results for Rockery Static Evaluation
Evaluation of Overturning Stability, Static FOSci,=3.289, 0I(�1 t
Evaluantion Of Sliding , Static
FOSS 1}76 k 2 ; ell 11 1
Results for Rockery Seismic Evaluation
Evaluation Of Sliding , Seismic
requires "FSslidin." greater than or equal to 1.1
Evaluation Of Overturning , Seismic F"�ot,seismic
requires "FSot.seismic" greater than or equal to 1.1
Expose Wall Height 5 ft Page Number(9)
Total height 6.5 ft
Rock Wall October 9, 2007
Bennett
1. Determination of Structural Dimensions
Bb:= 3.9 Bb=Bottom width of wall in feet
Bt:= 1.72 Bt =Top width of wall in feet
a := 0 a = Wall Batter measured clockwise in degrees
assumed zero more conservative
H,:= 9.5 HW=Inclined height of wall in feet
Hemb 1.5 Hemb =Embedment depth in feet
He = Exposed wall height H = Wall Design height
He:= H�v-cos(a•deg) — Hemb He= 8 feet
AH:= He+ Hemb+ Bb•sin(a•deg) H=9.5 feet
O=Inclination of back wall measured clockwise from horizontal plane
Bb—Bt 180
0 := 90 + a —atan(( )) —
Hkv rt
0 = 77.076 degrees
Note: A 9 degree backslope was utilzed. infinite slope accounts for traffic surcharge behind
wall. Note: area behind wall is broken slope.
R := 7 degrees R=Inclination of ground slope behind wall
`Z4'.s c 0
2. Determination of Earth Pressures utilized the various soils encountered in thus
exca to arrive at a soil unit weight of 135
Ibs/ft2
y := 135 y=Soil unit weight
�=Friction angle of retained soil assumes silty sand, sand and gravel conditions
� := 35 overall soil friction average
6=Friction angle between two dissimilar material say 3/4 � based on
gravelly silt soils encountered in subsurface excavation.
IV = (4)'�
Expose Wall Height 8 ft Page Number(1)
6to8ft j
Total height 9.5 ft/-
Rock Wall October 9, 2007
Bennett
Coulomb Eq.
sin(0•deg + �•deg)2
Ka' 2
rr g — (3•deg 11
sin(0•deg)2•sin(0•deg—S•deg) sin •deg + S•deg •sin •de
L1 + � JJ
sin(0•deg —5•deg)•sin(0•deg + (3•deg)
Ka= 0.389
P = Resultant of active pressure
Ka H2•y
P:_
2
P=2371.79
PH:= P•cos(90•deg — 0•deg + 5-deg)
PH = 1838.684
PV := P•sin(90•deg — 0•deg+ 8-deg)
Pv = 1498.212
Expose Wall Height 8 ft Page Number(2)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
3. Evaluation of External Stability
Wall's Center of Gravity
The center of gravity (CG) of wall is estimated by taking moments of all unit masses
about the toe of the wall and then dividing the sum of the resisting moments by the weight of the
wall in X'Y' planes. The CG arms in X'Y' planes is then converted to CG in XY Planes.
The weight of the wall consist of all resisting masses including soil masses situated immediatey
behind the wall below the assumed failure plane. For simplifying calculations, all resisting soil
masses can be considered to be triangular in shape.
frock 140
l i Spalls _..... 135
..._....__...._._... l ._....._ ... .. . ........_.... _ L ......Mass Moment i
Area XI Y'I Weight X i Y'
Mass Unit ftA2 ft ; ft a Ibs
Block 1 ry 2.6 2.2 1 8.8 364 800.8 3203.2
Block 2 3.7 F--2.14 7.3 518 1108.52 3781.4
Block 3 4.93 — 2.1 56 690.2 1449.42 3865.12
Block 4 j 6.24 2.04 3 6 873.E ; 1782.144 3144.96
Block 5 9 1 98 1 36 1260 2494.8 1713.6 i
Block 6 _. 0 0 .. 0.... .. _, 0 1 0 0 I s
k € _.. ....... -
!._-_ ___. _ _...
Soil Unit 1 0 0 0 Omm _.� 0 0
Soil Unit 2 0 0 1 0 0 1 0 0 !
Soil Unit 3 0 0 0 0 1 0 0
,S
oil Unit 4, 00 ; 0 0 _ _0 i 0
7635.684 15708 28
.. _........... ..._.... ._... .... ...._........... i........... ... .................
Total 26.66 I
Weight 3705.8 Ibs } I
xef f 2.060468 feet
Yeff 4.238836 feet
Pull these values from table
xeff:= 2.06
Yeff 4.23
weight of wall and soil resisting overturning
Weight:= 3705 Ibs
Expose Wall Height 8 ft Page Number(3)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
a =Horizontal arm of of W measured from toe XY plane
a:= cos(cAeg)•(xeff+ yeff•tan(a•deg))
a = 2.06 feet
b =Verticle arm of PH measured from toe XY plane
H
b :_ — - Bb•sin(a•deg�
3
b = 3.167 feet
e= Horizontal arm of Pv measured from toe in XY plane
e= Bb•sin(90•deg - cc-deg) - H
3•tan(90•deg-0-deg)
e = 3.173 feet
Evaluation of Overturning Stability
MR = Resisting Moment= Wa+Pve
MR:= Weight•a+ (PV)•e
MR= 12386.625
Mp Driving Moment=PH B
MD :_ (PI I.b)
MD = 5822.499
FOSO:_ MR— FOS0 = 2.127
MD
Expose Wall Height 8 ft Page Number(4)
6to8ft
Total height 9.5 ft
Rock Wall October 9,2007
Bennett
Evaluation Of Sliding
F = Coefficant of friction between units
F tan(�.deg)
AM
F = 0.7
N = Reaction at the base of the wall
N:= Weight.cos(a•deg) + PV•cos(a•deg) + PH•sin(a•deg)
N= 5203.212
Fr= sum of forces providing resistance to sliding
Fr:= N•F + Weight•sin(a•deg) + PV•sin(a deg)
Fr= 3643.328 N•F= 3.643 x 103
Weight.sin(a•deg) = 0
Fd = Sum of forces driving the wall in sliding
Fd:= P11•c0s6deg)
Fd= 1838.684
F
FOS,:= r FOSs = 1.98
Fd
Eccentricity N:= Weight.cos(a•deg) + Pv•cos(a•deg) + PH•sin(a•deg)
N,:= N•cos(a•deg) Nh:= N•sin(a•deg)
N,= 5.203 x 103 Nh = 0
X = horizontal distance of normal force from toe
Weight•a + PV•e — P1I-b
X:=
Nv + Nl,•tan(a•deg)
X = 1.262 feet
Expose Wall Height 8 ft Page Number(5)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
ex= eccentricty of the base reaction in feet from the center of the base of the wall
along the plane parrallel to the base of wall.
Bb X
ex
2 cos((x deg)
ex= 0.688
Bb X Bb—X Bb
< 2.
— cos(a•deg) 3
3 cos(a•deg)
Bb X
Bb = 1.3 X = 1.262 — 2.638 2•Bb = 2.6
3 cos(a•deg) cos(a•deg) 3
Seismic Analysis
Determine the tolerable wall displacement.
Ao:= .332
d := 10•Ac
d = 3.32 inches
Obtain a design value Kh Used method shown in Allan block engineering manual
page 54 to determine Kh-
Kh
AO).2�
Kh:= .67•Ao•(
d
Assume Kv=O
Kh = 0.125
Kv := 0
Use the value Kae to determine to obtain the wall weight and apply a factor of safety to this value.
Seismic Section
2
P:= P = 2371.792 0 = 77.076
nn 2
Expose Wall Height 8 ft Page Number (6)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
7•deg
Active Case for local ground acceleration for fill soils
From AASHTO Manual and Monobe-Okabe Method for Kae
Os:_ (90—0)•deg K,:= 0
�s'_ �-deg Kh 180
:= tan(( —
1 —K, n
yr = 7.205
8s = 4'�s
c040s —Os — W'de8)2
kae 1
2
—
2 Ss + Os •sin os — Pyr•deg
cos(yr•deg�•cos(Os� •cos(8s + Os + yi•deg� 1 + sin
cos(Ss+ 0s + y•deg)•COO —0s)
Kael =0.513
Ka=0.389
Dynamic Earth Force
1 Ka'w'Y
PAE:= _.1{ael'Y'H •�1 + K��
2 2
PAE=3125.051 P=2371.79
APAE:= PAE—P
APAE=753,259
Expose Wall Height 8 ft Page Number (7)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett _- __ - ---
Resolve the active earth force and the dynamic earth force into horizontal and vertical
components.
DFdvn := APAE Ss = 26.25 deg DFdvn = 753.259
DFdynh:= DFdyn•cos(Ss) cos(6s) = 0.897 DFdynv := DFdyn•sin(5s)
DFdynh = 675.577 DFdynv = 333.158
Fah:= (P)•cosOs) Fav:= P•sin(6")
Fah= 2127.196 Fav= 1049.017
cos(90•deg -0•deg + 6-deg) = 0.775
P P•cos(90•deg-0•deg + 6-deg) ,= P•sin(90•deg - 0•deg+ 8-deg)
P
PH = 1838.684 V = 1498.212
Determine Resisting Forces Used Method described in Allen Block Manual
For determination of sliding and overturning
Weight of Wall Facing
Determine resisting forces
�s= 35 deg
Weight of wall facing per linear foot
Weight=3.705 x 103 Ibs
Maximum frictional resistance against sliding - (does not include passive resistance)
Frl :_ Weight+ Fav + DFdynv)•tan(0 Weight= 3.705 x 103
DFdynv = 333.158 Fav= 1.049 x 103
Frl =3.562 x 103
Safety factor against sliding
Fi.
1'Ssliding Fd + DI=dYnh DFdynh = 675.577
requires "FS.sliding" greater than or equal to 1.1
Fssliding= 1.449
Expose Wall Height 8 ft Page Number(8)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
--
P.(H) + APAE•(.6H)
3
hl :_
Mos:= (Fah)-h I cos(ds) PAE
Mos = 7206.42
MR MR= 1.239 x 104
FSot.seismic'_ —
MOS
FSot.seismic= 1.719
Weight•a + (Fav)'li
FSot.seismic l
(Fah)'h
coskos)
Summary of Calculations
Results for Rockery Static Evaluation
Evaluation of Overturning Stability, Static FOSS=2.1271
1,C71
Evaluation Of Sliding , Static 9$1.•; " Ic '\�1
c
Q C.i �' )
Results for Rockery Seismic Evaluation
Evaluation Of Sliding , Seismicsltdir�g ``f`
requires "FSsliding" greater than or equal to 1.1
Evaluation Of Overturning , Seismic F§pt seismie= 1,719 u k -1`A
requires "FSot.seismic" greater than or equal to 1.1
Expose Wall Height 8 ft Page Number(9)
6to8ft
Total height 9.5 ft
Rock Wall October 9, 2007
Bennett
1. Determination of Structural Dimensions
Bb 4.5 Bb=Bottom width of wall in feet
Bt:= 1.78 Bt =Top width of wall in feet
a := 0 a = Wall Batter measured clockwise in degrees
assumed zero more conservative
H,:= 12 HW =Inclined height of wall in feet
Hemb:= 2 Hemb =Embedment depth in feet
He = Exposed wall height H =Wall Design height
He:= H,.cos(a•deg) - Hemb He= 10 feet
H:= He+ Hemb+ Bb•sin(a•deg) H= 12 feet
NW
O=Inclination of back wall measured clockwise from horizontal plane
Bb - Bt 180
0 := 90 + a - atan(( )) —
H, n
0 = 77.229 degrees
Note: A 9 degree backslope was utilzed. infinite slope accounts for traffic surcharge behind
wall. Note: area behind wall is broken slope.
R := 9 degrees p=Inclination of ground slope behind wall {�
40
2. Determination of Earth Pressures utilized the various soils encountered in the b gs
excavation to arrive at a soil unit weight of 135
Ibs/ft2
y := 135 y=Soil unit weight
�=Friction angle of retained soil assumes silty sand, sand and gravel conditions
overall soil friction average
:= 35
S=Friction angle between two dissimilar material say 3/4 �based on
gravelly silt soils encountered in subsurface excavation.
31
6:= 4 J Q�
6 = 26.25
/ Expose Wall Height 1(J ft Page Number (1)
C to 10 ft
otal height 12 ft,"/
Rock Wall October 9, 2007
Bennett
Coulomb Eq.
sin(A•deg + �•deg)2
Ka:= 2
�_ rr (fsinO
in •deg + S•deg •sin •deg— p•deg �
sin(6•deg sin(A•deg—S•deg)L1 + JI( •deg—8-deg)•sin(0•deg+ p•deg)
Ka= 0.399
P = Resultant of active pressure
Ka H2•y
P:_
2
P=3881.35
PH := P•cos(90•deg— 0•deg+ S•deg)
PH = 3015.467
PV := P•sin(90•deg — 0•deg+ 8-deg)
PV = 2443.729
Expose Wall Height 10 ft Page Number(2)
8to10ft
Total height 12 ft
Rock Wall October 9, 2007
Bennett
3. Evaluation of External Stability
Wall's Center of Gravity
The center of gravity(CG) of wall is estimated by taking moments of all unit masses
about the toe of the wall and then dividing the sum of the resisting moments by the weight of the
wall in X'Y' planes. The CG arms in X'Y' planes is then converted to CG in XY Planes.
The weight of the wall consist of all resisting masses including soil masses situated immediatey
behind the wall below the assumed failure plane. For simplifying calculations, all resisting soil
masses can be considered to be triangular in shape.
rocky 140
Spalls 135
_... ._.
. .. _....... 1 _Mass Moment
Area Weight x Y I
_ ..... ... ..._.............
. .........
Mass Unit fft12 I ft ft Ibs I
I Block 1 2.6 2.59 1162 364 942.76 4229.68 ��
_ _ _ _.. p_ _
Block 2 3.67 2,54 10.1 513.8 1305.052 5189.38
I Block 3 4.93 i 2.5 8.35 690.2 1725.5 5763.17
Block 4 6.24 1 2.97 7 , 873.6 2594,592 6.115.2
Block 5 9 I 2.37 1 4 1260 2986.2 5040
Block 6 11 2.31 1 5 1540 3557.4 # 2310 1
.. - ...._ ... ...... ._.
k
Soil Unit 1 0 00 0 0 0
Soil Unit 2 0 00 0 ; 0 0
Soil Unit 3 . 0.� ..0 � _�. 0 O______tM._ 0 0 .___
.Soil Unit 4.......
13111.5....._28647.43
Total 42.57
m
( Weight 5241.E Ibs
Xeff, 2.501432 feet
IYerr 5.465398 feet
Pull these values from table
xefi-:= 2.5
yeff:= 5.5
weight of wall and soil resisting overturning
Weight:= 5241 Ibs
Expose Wall Height 10 ft Page Number(3)
8 to 10 ft
Total height 12 ft
Rock Wall October 9, 2007
Bennett
a =Horizontal arm of of W measured from toe XY plane
a:= cos(a•del-)•(xeff+ yeff-tan(a•deg))
a = 2.5 feet
b =Verticle arm of PH measured from toe XY plane
b := H - Bb•sin(a•deg)
3
b =4 feet
e = Horizontal arm of Pv measured from toe in XY plane
H
�= Bb•sin(90-deg -a•deg) - 3•tan(90•deg -0-deg)
e = 3.593 feet
Evaluation of Overturning Stability
MR = Resisting Moment= Wa+Pve
MR:= Weight•a + (PV)•e
MR = 21883.633
Mp Driving Moment=PH B
MD := (PH•b)
MI) = 12061.869
FOSe := MR FOS, = 1.814
My
Expose Wall Height 10 ft Page Number(4)
8 to 10 ft
Total height 12 ft
Rock Wall October 9,2007
Bennett
Evaluation Of Sliding
F = Coefficant of friction between units
F:= tan(�.deg)
F = 0.7
N = Reaction at the base of the wall
N:= Weight.cos(a•deg) + PV•cos(a•deg) + PH•sin(a•deg)
N= 7684.729
Fr= sum of forces providing resistance to sliding
Fr:= N•F + Weight•sin(a•deg) + PV•sin(a•deg)
N•F= 5.381 x 103
Fr= 5380.905
Weight.sin(a•deg) = 0
Fd = Sum of forces driving the wall in sliding
Fd:= PII•cos(o•deg)
Fd =3015.467
Fr
FOSS:= — FOSS = 1.78
Fd
Eccentricity /N:= Weight.cos(a•deg) + PV•cos(a•deg) + PH•sin(a•deg)
VW
N, := N•cos(a•deg) Nh:= N•sin(a•deg)
N, = 7.685x 103 Nh = 0
X = horizontal distance of normal force from toe
Weight•a + PV•e - PH•b
X:_
N, + Nh•tan(a•deg)
X= 1.278 feet
Expose Wall Height 10 ft Page Number(5)
8to10ft
Total height 12 ft
Rock Wall October 9, 2007
Bennett
ex = eccentricty of the base reaction in feet from the center of the base of the wall
along the plane parrallel to the base of wall.
Bb X
ex 2 cos(a•deg)
ex= 0.972
Bb < X Bb- X 2 Bb
3 cos(a•deg)
cos((x•deg) 3
Bb = 1.5 X - 1.278 Bb- X - 3.222 Bb
3 cos(a•deg) cos(a deg) 2- 3 = 3
3
Seismic Analysis
Determine the tolerable wall displacement.
Ao:_ .332
d := MAo
d = 3.32 inches
Obtain a design value Kh Used method shown in Allan block engineering manual
page 54 to determine Kh.
A .25
Kh:_ .67•A0•( o
d
Assume Kv=O
Kh = 0.125 K,:= 0
Use the value Kae to determine to obtain the wall weight and apply a factor of safety to this value.
Seismic Section
2
Ka.}1`•Y
P:= P = 3881.347 0 = 77.229
1M
Expose Wall Height 10 ft Page Number (6)
8to10ft
Total height 12 ft
Rock Wall October 9, 2007
Bennett
'= 9-deg-
Active Case for local ground acceleration for fill soils
From AASHTO Manual and Monobe-Okabe Method for Kae
0s:_ (90 — 0)•deg Kam:= 0
�s := 0-deg Kh 180
W := tan((1 — K,
TI
W = 7.205
3
Ss 4'�s
cos(�s —0s — W•deg)
Kae l 2
2 sin Ss+ �s sin �s — R — y� deg
cosy .deg)•cos(0s� cos�Ss + 0s + y� deg 1 +
(3
cos(Ss+ Os + kV•deg)•cos( —Os)
Kael = 0.531
Ka=0.399
Dynamic Earth Force
p 1 K H2 1 + K K H2 y
AE 2' ae l Y' v) a
�p._
2
PAE = 5165.909 P = 3881.35
OPAE PAE — P
OPAE= 1284.562
Expose Wall Height 10 ft Page Number(7)
8to10ft
Total height 12 ft
Rock Wall October 9, 2007
Bennett
Resolve the active earth force and the dynamic earth force into horizontal and vertical
components.
DFdyn := APAE DFdyn = 1284.562
Ss =26.25 deg
DFdynh:= DFdyn•cos(Ss) cos(S,) = 0.897 DFdyn, := DFdyn•sin(Ss)
DFdynh = 1152.089 DFdynv = 568,147
Fah:_ (P)•cos(Ss) Fav:= P•sin(Ss)
Fah= 3481.074 Fav = 1716.676
cos(90•deg — 0-deg + 8-deg) = 0.777
Pam:=P•cos(90•deg — 0•deg + S•deg) P•sin(90•deg — 0-deg + 8-deg)
Pam:=
P
PH =3015.467 V =2443.729
Determine Resisting Forces Used Method described in Allen Block Manual
For determination of sliding and overturning
Weight of Wall Facing
Determine resisting forces �s =35 deg
Weight of wall facing per linear foot
Weight= 5.241 x 103 Ibs
Maximum frictional resistance against sliding - (does not include passive resistance)
Frl :_ (Weight+ Fa, + DFdynv)•tan(0 Weight= 5.241 x 103
DFdynv = 568.147 Fav = 1.717 x 103
Fr1 = 5.27 x 103
Safety factor against sliding
Fl DFd n 1152.089
Fssliding�= Y h=
Fd + DFdynh
FS,liding— 1.291 1 requires "FS.sliding' greater than or equal to 1.1
Expose Wall Height 1Oft Page Number(8)
8to loft
Total height 12 ft
Rock Wall October 9,2007
Bennett
P.`H) + OPAE•(.61H)
hl ;_ 3
Mos:= (Fah)•hl•cos(6s) PAE
Mos = 14972.614
MR MR=2.188x 104
FSot.seismic
Mos
FSot.seismic = 1.462
Weight•a + (Fa,)']'
FSot.seismicl �_
(Fah)'h
cos(6s)
Summary of Calculations
Results for Rockery Static Evaluation
Evaluation of Overturning Stability, Static FOSo w 1.814 C.(Cki
Evaluation Of Sliding , Static t(A`1
Results for Rockery Seismic Evaluation
Evaluation Of Sliding , Seismic �Ssfitifng . '1'z e �t `aLI
requires "FSsliding" greater than or equal to 1.1
Evaluation Of Overturning , Seismic ot.seismic=,1 462 c"Ic 1`,L7
requires "FSot.seismic" greater than or equal to 1.1
Expose Wall Height 1Oft Page Number(9)
8to10ft
Total height 12 ft
Appendix A
June 19, 2006
APPENDIX 8: ARC GUIDELINES
P.O. Box 637. 2453 Bethel Avenue • Port Orchard, Washington 98366
Phone: 1(800) 755-1282 • Fax: (360) 876-1487
AO '
toAssociated Rockery Contractors
Rock Wall construction
Guidelines
P.O. Box 1794 • Woodinville, Washington 98072
Association Representative
(425) 481-3456 or
(253) 838-4836
ARC ROCKERY CONSTRUCTION GUIDELINES
Contents
Section 1
Introduction: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.01.1 Historical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.01.2 Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Section 2
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.01.1 Rock Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.01.2 Frequency of Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.01.3 Rock Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.01.4 Submittals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Section 3
Rock Wall Construction
3.01.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.01.2 Geotechnical Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.01.3 Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.01.4 Workmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.01.5 Changes to Finished Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.01.6 Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.01.7 Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.01.8 Fill Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.01.9 Fill Construction Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.01.10 Rock Wall Keyway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.01.11 Keyway Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.01.12 Rock Wall Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.01.13 Rock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.01.14 Rock Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.01.15 Face Inclination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.01.16 Voids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.01.17 Drain Rock Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.01.18 Surface Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figures
Plate A - Typical Rockery Detail Native Cut, Any Height Over 4 Feet
Plate B - Typical Rockery Detail Overbuilt Fill Construction, Rockery 8 Feet or less in
Height
Plate C - Typical Rockery Detail Geogrid Reinforced Fill Construction, Rock Wall 8 feet
or More in Height
Plate D - Post Construction Guideline
Plate E - Typical Bulkhead Wall Section
Rockery Examination Record
ARC ROCKERY CONSTRUCTION GUIDELINES
Section 1
Introduction
1.01.1 Historical Background
These rock wall construction guidelines have been developed in an effort to provide a
more stringent degree of control on materials and construction methodology in the
Pacific Northwest, and elsewhere. They have been assembledfrom numerous other
data presently in use in the area, from expertise provided by local geotechnical
engineers, and from the wide experience of the members of the Associated Rockery
Contractors (ARC).
1.101.2 Goal
The primarygoals of this document are to develop appropriate methods of construction
for rock walls, including those of less than over four feet in height, and to provide a
means of verifying the quality of materials used in construction and the workmanship
employed in construction. These guidelines have also been developed in a manner that
makes them, to the best of ARC's knowledge, more stringent than the others
construction methods or requirements presently in use by local municipalities.
Section 2
Materials
2.01.1 Rock Quality
All rock shall be sound, angular ledge rock that is resistant to weathering. The longest
dimension of any individual rock should not exceed three times its shortest dimension.
Acceptability of rock will be determined by laboratory tests as hereinafter specified,
geologic examination and historical usage records.
All rock delivered to and incorporated in the project shall meet the following Minimum
specifications:
a. Absorption Not more than 2.0%for igneous
ASTM C-127 and metamorphic rock types and
AASHTO T-85 3.0% for sedimentary rock types.
b. Accelerated Expansion Not more than 15% breakdown.
(15 days) CRD-C-148 *1, *2
C. Soundness(MsSO4 at 5 cycles) Not greater than 5%loss.
ASTM C-88 or CRD-C-137
ARC ROCKERY CONSTRUCTION GUIDELINES
d. Unconfined Compressive Strength Intact strength of 6,000 psi,
ASTM D-2938 or greater
e. Bulk Specific Gravity (155pcf) Greater than 2.48
ASTM C-127
AASHTO T-85
*1. The test sample will be prepared and tested in accordance with Corps of
Engineers Testing procedure CRD-C-148, "Method of Testing Stone for
Expansive Breakdown on Soaking in Ethylene Glycol."
*2. Accelerated expansion tests should also include analysis of the fractures and
veins found in the rock.
2.01.2 Frequency of Testing
Quarry sources shall begin testing program when either becominga supplier or when
a new area of the source pit is opened. The tests described in Section 2.01.1 shall be
performed for every four thousand (4000) tons, for the first twelve thousand (12,000)
tons of wall rock supplied to establish that specific rock source. The tests shall then be
performed once a year, every forty thousand (40,000)tons(whichever occurs first), or
at an apparent change in material. If problems with a specific area in a pit, or with a
particular material, are encountered the initial testing cycle shall be restarted.
2.01.3 Rock Density
Recognizing that numerous sources of rock exist, and that the nature of rock will vary
not only between sources but also within each source, the density ofthe rock shall be
equal to,or greater than, one hundred fifty-five(155)pcf. Typically,rocks used for rock
wall construction shall be sized approximately as follows:
�iock'S,ze >. Rock Weight Average Nmi nsion,
One Man 50-200 pounds 12 to 18 inches
Two Man 200-700 pounds 18 to 28 inches
Three Man 700-2000 pounds 28 to 36 inches
Four Man 2000-4000 pounds 36 to 48 inches
Five Man 4000-6000 pounds 48 to 54 inches
Six Man 6000-8000 pounds 54 to 60 inches
ARC ROCKERY CONSTRUCTION GUIDELINES
In rock walls of greater than eight feet in free-standing height it should not be possible
to move the large sized rocks (four to six-man size)with a pry bar. If these rocks can
be moved,the rock wall should not be considered capable of restraining any significant
lateral load. However, it is both practical and even desirable that smaller rocks,
particularly those used for"chinking"purposes, can be moved with a pry bar to achieve
the "best fit".
2.01.4 Submittals
The rock source shall present current geologic and test data for the minimum guidelines
described in Section 2.01.1 on request by either the rock wall contractor, the owner,or
the applicable public agency.
Section 3
Rock Wall Construction
3.01.1 General
Rock wall construction is a craft and depends largely on the skill and experience of the
builder. A rock wall is a protective system which helps to retard the weathering and
erosion process acting on an exposed cut or fill soil face.While by its nature(the mass,
size and shape of the rocks) it will provide some undetermined degree of "mass" or
"gravity' retention, it is not typically a designed or engineered system in the sense a
reinforced concrete retaining wall would beconsidered designed or engineered. The
degree of retention achieved is dependent on the size of rock used; that is,the"mass"
or weight,and the height of the rock wall being constructed. The larger the rock, the
more competent the rock wall. To develop an appropriate degree of competency, all
rock walls in excess of four feet in height should be built on a "mass" basis, i.e. by the
ton, NOT on a square foot of exposed face basis.
To provide a competent and adequate rock wall structure, all rock walls constructed in
front of either cuts or fills eight feet and over in height should be bid and constructed in
accordance with these guidelines and the geotechnical engineer's supplemental
geotechnical recommendations. Both the ARC guidelines and the supplemental
geotechnical recommendations should be provided to prospective bidders before
bidding and the start of construction.
3.01.2 Geotechnical Engineer
The geotechnical engineer retained to provide necessary supplemental rock wall
construction guidelines shall be a practicing geotechnical/civil engineer licensed as a
professional civil engineer in the State of Washington. He or she should have at least
ARC ROCKERY CONSTRUCTION GUIDELINES
four years of professional employment as a geotechnical engineer in responsible
charge, including experience with fill construction and stability and rock wall
construction. The geotechnical engineer should be hired either by the rock wall
contractor or the owner.
It is CRITICAL that the geotechnical engineer visit the site of a proposed rockery before
providing any geotechnical recommendations whatsoever. This visit provides the
opportunity for the geotechnical engineer to evaluate the proposed wall location and
alignment, and to determine if there are any potential site related concerns that might
detrimentally impact the rockery's "design"or construction. Failure to conduct this site
visit could result in damage to the constructed wall or even to a wall failure.
3.01.3 Responsibility
The ultimate responsibility for rock wall construction should remain with the rock wall
builder. However, rock walls protecting moderate to thick fills, with steep sloping
surfaces above or below them, with multiple steps or stages, with foundation or other
surcharge loads affecting them, protecting sandy or gravelly soils subject to raveling,
with seepage or wet conditions, or that are greater than eight feet in free-standing
height, all represent special"design"conditions and require consultation and/or advice
from a suitably qualified geotechnical engineer.
3.01.4 Workmanship
All workmanship is guaranteed by the rock wall contractor and all materials are
guaranteed by the supplying quarry for a period of six years from the date of completion
of erection, providing no modification orchanges to the conditions existing at the time
of completion are made.
3.01.5 Changes to Finished Product
Such changes include, but are not necessarily limited to, temporary excavation of
ditches or trenches for any utility within a distance of less than five feet from the back
of the top of the rock wall;excavation made eitherwithin a distance equal to at least two
thirds of the free-standing wall height in front of the toe of a rock wall, or that will
penetrate an imaginary line extended at a 1 H:1 V (Horizontal:Vertical)slope from the
front edge of the rock wall toe(see figure D);removal of any material from the subgrade
in front of the wall,excavation of material from any location behind the rock wall within
a distance at least equal to the rock wall's height, the addition of any surcharge or other
loads within a similar distance of the top of the wall, or surface or subsurface water
forced, directed, or otherwise caused to flow behind the rock wall in any quantity.
ARC ROCKERY CONSTRUCTION GUIDELINES
3.01.6 Slopes
Slopes above rock walls should be kept as flat as possible, but should not exceed
2H:1 V unless the rock wall is "engineered" specifically to provide some restraint to the
surcharge load imposed by the slope. Any slope existing above a completed rock wall
should be immediatelycovered with vegetation bythe ownerto help reduce the potential
for surface water flow induced erosion. It should consist of a deep rooted, rapid growth
vegetative mat, and will typically be placed by hydroseeding and covered with a mulch.
It is often useful to overlay the seed and mulch with either pegged in-place jute matting,
or some other form of approved geotextile or erosion control blanket, to help maintain
the seed in-place until the root mat has an opportunity to germinate and take hold,
3.01.7 Monitoring
All rock walls constructed against cuts or fills of greater than four feet in height shall be
period icallymonitored during construction bythe geotechnical engineerto verifythatthe
nature and quality of the materials being used are appropriate, that the construction
procedures are appropriate, and that the rock wall is being constructed in a generally
professional manner and in accordance with this ARC guideline and any supplemental
geotechnical recommendations. Past experience indicates that a minimum of two visits
of limited duration is typically acceptable for monitoring purposes of single-stage walls
of less than fifty(50)feet in length. For walls of greater than fifty(50)feet but less than
one hundred (100)feet in length three monitoring visits are considered the minimum
acceptable. For walls of greater than one hundred (100)feet in length an appropriate
monitoring program shall be developed bythe geotechnical engineer. Fora multi-stage
rock wall the minimum acceptable numberof monitoring visits shall be considered at
two visits for each stage of the wall.
The monitoring agent, typically the geotechnical engineer of record, shall maintain a
written record of the nature and condition of the segment of the rock wall being
monitored during that visit. An example of a Rockery Examination Record suitable for
this form of documentation is attached to this ARC Guideline for informational purposes.
Where there is a slope above or below the rockery wall it is important that the
monitoring agent make a visual assessment of the slopes' stability, and record the
results. Additionally,the inclination of the slope either-in degrees or as a H:V slope,
shall be approximately determined and recorded.
When the monitoring agent is checking a rocks soundness as it is struck with a
hammer (see attached Rockery Examination Record) one of several "sounds" will be
generated. A"clink"or"ringing ping"typically results from afresh and competent rock
with little or no defects. A duller "thud" or "clonk" sound is more indicative of a poor
quality rock, often with many seams or defects. The duller"thudding" sound is often
exhibited by a rock that has a high tendency to rapidly deteriorate back into a highly
ARC ROCKERY CONSTRUCTION GUIDELINES
weathered and "soft" rock or even to a "soil." Where such rocks are encountered the
contractor should be requested to move the rock to the upper row or to a lowersegment
of the wall where it can more easily be reached and removed when it degrades without
causing any significant disruption to the completed wall.
On completion of the rock wall,the geotechnical engineer should submit to the client,
the rock wall contractor, and to the appropriate municipality, copies of his rock wall
examination reports along with a final report summarizing rock wall construction.
3.01.8 Fill Compaction
Where rock walls are constructed in front of a fill,it is imperative that the owner ensure
the fill be placed and compacted in a manner that will provide a competent fill mass.
To achieve this goal, all fills should consist of relatively clean, organic and debris free,
granular material with a maximum size of four inches. Ideally, but particularly if
placement and compaction is to take place during the wet season, they should contain
no more than five percent fines (silt and clay sized particles) passing the number 200
mesh sieve).
All fills should be placed in thin lifts not exceeding ten (10) inches in loose thickness.
Each lift should be compacted to at least 95 percent of the maximum dry density, as
determined by Modified Proctor, before any additional fill is placed and compacted. In-
place density tests should be performed by an independent testing agency at random
locations within each lift of the fill using either a nuclear density testing gauge or a more
traditional sand cone device to verify that this degree of compaction is being achieved.
Failure to achieve this degree of compaction could result in the imposition of a greater
lateral load on the rock wall that could, over time, cause lateral movement or even
"failure" of the rock wall. This situation is to be avoided!
3.01.9 Fill Construction Reinforcement
There are two methods of constructing a fill. The first, which typically applies to rock
wallsof lessthan eightfeet in free-standing height, is to overbuild and then cut back the
fill. The second,which applies to all rock walls of greater than eight feet in height, is to
construct the fill using a geogrid or geotextile reinforcement.
Overbuilding the fill allows for satisfactory compaction of the fill mass out beyond the
location of the fill face to be protected. Overbuilding also allows the earthwork
contractor to use larger and more effective compaction equipment in his compactive
efforts, thereby typically achieving a more competent fill mass. Cutting back into the
well compacted fill also typically results in construction ofa competent near vertical fill
face against which to build the rock wall. This option is pictorially depicted on Plate B,
attached.
ARC ROCKERY CONSTRUCTION GUIDELINES
For higher rock walls the use of a geogrid or geotextile fabric to help reinforce the fill
results in construction of a more stable fill face against which to construct the rock wall.
This form of construction leads to a longer lasting more stable rock wall and helps
reduce the risk of significant long term maintenance.
This latter form of construction requires a design by the geotechnical engineerfor each
specific case. The vertical spacing of the reinforcement, the specific type of
reinforcement, the distance it must extend back into the fill,the amount of lapping and
the construction sequence must be determined on a case by case basis. This option
is pictorially depicted on Plate C, attached.
3.01.10 Rock Wall Keyway
The first step in rock wall construction,after general excavation,is to construct a keyway
in which to install or"set"the basal row of rock forming the rock wall. The keywayshall
comprise a shallow trench of not less than twelve (12) inches in depth, extending for
the full length of the rock wall.If the rock wall is a waterfront bulkhead wall the Minimum
keyway depth shall be two feet, measured from the natural beach elevation in front of
the wall that existed before wall construction began. The keyway subgradeshould be
slightly inclined back towards the face being protected. It is typicallydug as wide as the
rock wall (including the width of the drain rock layer). If thecondition of the cut face is
of concern, the keyway should be constructed in sections of manageable length, that
is, of a length that can be constructed in one shift or one day's work,or if a waterfront
wall between high tides.
The competency of the keywaysubgrade to support the rock wall shall be verified by the
geotechnical engineers' probing with a small diametersteel rod. The rod shall have a
diameter of between three-eighths and one-half inch, and shall be pushed into the
subgrade in a smooth unaided manner under the body weight of the prober only.
Penetration of up to six inches,with some difficulty,shall indicate a "competent" keyway
subgrade unless other factors in the geotechnical engineer's opinion shall be considered
to indicate otherwise.
Penetration in excess of six inches,with ease, shall indicate a "soft"subgrade and one
that could require treatment. Shallowsoft areas of the subgrade can be "firmed up" by
tamping a layer of coarse quarry spalls into the subgrade.
Where a rock wall is being "analyzed" or "engineered" as a wall capable of at least
partially restraining a lateral load it is often appropriate to install a layer of coarse,
angular crushed rock over the prepared keyway subgrade to enhance the frictional
resistance between the subgrade and basal rock and, thus, the walls ability to resist
sliding. This crushed rock layer should be not less than six inches in thickness,after
being firmlytamped into the subgrade, and should typically comprise "fines free"two to
four inch sized crushed rock "quarry spalls" or crushed recycled concrete.
1
ARC ROCKERY CONSTRUCTION GUIDELINES
3.01.11 Keyway Drainage
Upon completion of keyway excavation, a four-inch minimum diameter perforated or
slotted, smooth-walled rigid plastic drain pipe, or equivalent approved in writing by a
geotechnical engineer,should be installed at the rear of the keyway, behind the basal
rock. It should be bedded on and surrounded by a free-draining crushed rock. It is
critical to exercise due care when setting rocks to prevent the pipe from being
inadvertently crushed by pieces of the rock wall rock. This drain pipe should be installed
with sufficient gradient to initiate flow either to one end or the other, or to a low point,
and the outfall should be connected by unperforated tightline to a positive and
permanent discharge.
Positive and permanent drainage should be considered to mean an existing, or to be
installed,storm drain system,a detention or retention pond,drain swale,or other stable
native site feature or previously installed collection system.
Where a rock wall is being installed as a waterfront bulkhead wall subject to tidal and
current activitythe above-described drain pipe becomes redundant and may be omitted.
With hydraulic/tidal fluctuations the water penetrating through the rock wall will drain
back out through the void spaces far more rapidly than can be achieved by the basal
drain.
In arid regions, such as Eastern Washington and Nevada, where there is little risk of
seepage occurring the basal drain pipe may be omitted. However, the minimum
thickness of drain rock should be installed to help protect the soil face behind the
constructed wall, and to assist in "blocking" or "chinking" the voids between the
individual rockery rocks.
3.01.12 Rock Wall Thickness
The individual rock wall thickness should be equal to the thickness of the recommended
size of rock plus the thickness of the drain rock layer. This thickness, which will be
determined on a case by case basis, will be dependant on the specific rock sizes
recommended for each individual rock wall. For example, if four-man rock is used the
rock wall thickness will be approximately five feet(rock width plus twelve [12] inches of
drain rock).
If the rock wall is to act, even in part, as a "retaining"structure it is critical that the size
and mass of the in-place rock is adequate to resist the applied load. In some instances
it maybe necessary to install more than one row of rock. In this case it is imperative
that the owner and rock wall contractor seek the advice of a professional geotechnical
engineer before proceeding with construction.
ARC ROCKERY CONSTRUCTION GUIDELINES
3.01.13 Rock Selection
The contractor should have sufficient space available so that he can select from among
a number of stockpiled rocks for each space in the rock wall to be filled. Rockswhich
have shapes which do not match the spaces offered by the previous course of rock
should be placed elsewhereto obtain a betterfit. Rock should be of a generally cubical,
tabular or rectangular shape and selected in accordance with Section 2.01.3 of this
Guideline. Any rocks of basically rounded or tetrahedral form should be rejected or
used for filling large void spaces.
It is also important to select rocks that do not exhibit any significant cracks, seams or
foliation joints so that, once in-place,the individual rocks do not break, split or crumble
and thereby create a weak zone within the constructed wall. It is acceptable to install
individual rocks with cracks, seams, or foliation joints in a wall providing that theycan
be firmly and adequately confined by the surrounding rocks. It is critical that the cracks,
seams or foliation joints do NOT allow for portions of the rock to spall off and fallout of
the wall. Similarly,considerable care should be exercised by the rock wall contractor
to avoid installing any rock with a weakened or"scabbing"face that might spall off and
fall out of the wall, or off the wall face.
3.01.14 Rock Placement
The first course of rock should be placed on firm unyielding soil,or onto the previously
installed layer of crushed rock. There should be full contact between the rock and soil
or crushed rock surface,which may require shaping of the ground surface or slamming
or dropping the rocks into place so that the soil or angular crushed rock covered
subgrade better conforms to the rock face bearing on it. The bottom of the first course
of rock should be a minimum of twelve (12) inches below the lowest adjacent site
grade,or not less than two feet for a waterfront bulkhead wall per Section 3.01.10 of this
Guideline.
As the rock wall is constructed, the rocks should be placed so that there are no
continuous joint planes in either the vertical or lateral direction. Wherever possible,
each rock should bear on a least two rocks below it. Rocks should be placed so that
there is some bearing between flat rock faces rather than in or on spaces between the
underlying rocks. The upper plane of each rock between courses (the top surface of
rock), should slope back towards the protected soil face and away from the face of the
rock wall.
Because stacked rocks exhibit a tendency to "topple" outwards it is crucial that
individual rocks NOT be stacked like shoe boxes in any wall regardless of the total
height. Whilst an occasional rock will,simply because of its shape or size, be stacked
atop another, stacking must not become a practice. If rocks are stacked like shoe
ARC ROCKERY CONSTRUCTION GUIDELINES
boxes the rock wall contractor shall be instructed to "deconstruct" the affected portion
of the wall and to rebuild it in strict accordance with these ARC Guidelines.
It is also critical that no rock be set into any wall with a top surface sloping downwards
out of the wall face. This will create a potential plane of weakness, if not of failure,
within the wall and should be avoided at all costs. If any rock is seen to be placed within
a wall with this outwards sloping surface the rock wall contractor must be directed to
remove it and replace it before proceeding with wall construction. No completed rock
wall shall be accepted by the geotechnical engineer if any rock within the structure
exhibits this outwards sloping geometry.
It is also important to place as much mass of rock in-place as possible to create a stable
rock wall. In addition to the selection of appropriately sized rocks,it is also important,
wherever possible,to install the rocks with the longest dimension set back towards the
soil face being protected. This is of particular importance when construction a rock
bulkhead wall that is likely to be subject to tidal and/or hydraulic action.
Smaller rocks (one or two-man size)are often used to create an aesthetically pleasing
"top edge" to a rock wall. This is an acceptable practice provided none of the events
described in Section 3.01.5 of this Guideline occur, and that people are prevented form
climbing or walking on the finished wall. This is the owner's responsibility.
Where a rock wall is constructed as a waterfront bulkhead it is critical that the ends of
the wall either abut a neighboring bulkhead wall, or that a "return" back into the
protected site be constructed. Where the wall abuts its neighbor the placement of the
end rocks becomes a critical element of the walls construction since these end walls
must make as close contact with the neighboring wall as is possible to avoid developing
any significant void spaces. The wall contractor must make every reasonable effort to
install rocks that can be set essentially "flush" against the neighboring wall.
Where a "return" is constructed the contractor must excavate an extension of the
keyway approximately at a right angle (90 degrees)to the wall alignment back into the
site. Where there is the potential for tidal activity above the toe of the wall it is
important that this return extend for a distance sufficient to install a minimum of three
rocks of equal size to those used in the construction of the wall face. For example, if
five-man size rocks (average dimension of about fifty[50] inches)are used in the wall
the return should be approximately thirteen (13)to fourteen (14)feet long. Wherever
possible, any space between the return rocks and the excavated soil face should be
carefully and thoroughly backfilled with two to four inch sized coarse, angular, crushed
rock "quarry spalls" or recycled concrete.
I
ARC ROCKERY CONSTRUCTION GUIDELINES
3.01.15 Face Inclination
The face of the rock wall should be inclined at gradient of about 1 H:6V back towards the
face being protected. The inclination of the wall face shouldnot be constructed flatter
than 1 H:4V.
3.01.16 Voids
Because of the nature of the product used to construct a rock wall, it is virtually
impossible to avoid creating void spaces between individual rocks. However, it should
be recognized that voids do not necessarily constitute a problem in rock wall
construction. As the size of rock used to build a rock wall increases,i.e.to six-man size,
the void spaces between individual rocks should be expected to be larger due simply
to the rock dimensions and shape.
Where voids of greater than six inches in dimension exist in the face of a rock wall they
should be visually examined to determine if contact between the rocks exists within the
thickness of the rock wall. If contact does exist, no further action is required. However,
if there is no rock contact within the rock wall thickness the void should be"chinked"with
a smaller piece of rock.
Because the loss of drain rock or of the soil being protected by the rock wall must be
avoided, "chinking" of these larger void spaces is a critical element in rock wall
construction. To create a stable wall,and particularly if the wall is to be a waterfront
bulkhead wall subject to tidal and hydraulic impacts, all chinking shall be carried out
from the rear face of the wall. In this manner the chinking rocks can be firmly set into
the voids and braced againstthe inboard sides of the wall rocks thereby enhancingtheir
ability to resist being "flushed" or "picked" out of the wall. Whilst recognizing this form
of chinking can slow down the speed with which a contractor can erect a rock wall,this
methodology is considered to be of critical importance to the long term stability and
structural integrity of a constructed rock wall and its attendant drainage system.
3.01.17 Drain Rock Layer
In order to provide some degree of drainage control behind the rock wall, and as a
means of helping to prevent the potential loss of soil through the face of the rock wall,
a rock drainage"filter"layer shall be installed between the rear face of the rock wall and
the soil face being protected. This drain rock layer should be a minimum of twelve(12)
inches in thickness. For rock walls of greater than eight feet in free-standing height
should be at least eighteen (18)inches thick. It should be composed of two to four inch
sized crushed rock quarry spalls,crushed recycled concrete,or other material approved
in writing by the geotechnical engineer.
3.01.18 Surface Drainage
It is the owner's responsibilityto intercept surface drainagefrom above the rock wall and
direct it awayfrom the rock wall to a positive and permanent discharge well below and
beyond the top or toe of the rock wall. Use of other drainage control measures should
be determined on a case-by-case basis by the geotechnical engineer prior to the
contractor bidding on the project.
ARC ROCKERY CONSTRUCTION GUIDELINES
If a random wall rock extends back to the exposed soil face, it is not necessary that the
filter rock layer extend between it and the soil face providing it does extend around the
rock and behind those in contact with it.
Depending on soil type and the potential for water seepage, a geotextile fabric may or
may not be required. This can be determined on a case-by-case basis by the
geotechnical engineer during design and prior to bidding.
Where a wall is to act as a waterfront bulkhead wall it is of greater importance to reduce
the risk of hydraulic activity degrading the protected soil face and removing soil from
behind the wall and thereby potentially creating void spaces. In all bulkhead wall
locations,with the possible exception of an exposed cemented glacial till soil,a layer of
protective geotextile shall be installed against the exposed soil face. The geotextile
should be anchored along the top of the excavation and draped down over the exposed
soil face and then across the keyway subgrade. The toe edge of the geotextile shall
be anchored-in-place by the basal row of wall rock. Itis critical the any geotextile be
installed in strict accordance with the manufacturers specifications since failure to do
so can void any warranty or guarantee.
It is also important that the geotextile be installed in very close contact with the soil face
or subgrade surface to avoid the risk of developing pockets' of loose fabric in which soil
fines can collect and "block" the geotextile, a situation that can lead to failure of the
geotextile and developmentand imposition of large unforeseen lateral loads on thewali.
Close contact between the geotextile and the soil can be achieved with the assistance
of numerous hand installed steel pins or wooden stakes.
The following tabulation, though not all inclusive, provides the names of several
geotextiles that are suitable for this purpose:
► AMOCO 4504 or AMOCO 4546
► Carthage Mills FX-60HS
► Mirafi 180N
► Synthetic Industries Geotex 311
• Webtec TerraTex N04 or TerraTex SD
In arid regions the geotextile layer may be omitted unless that area where the wall is
built is subject to periodic "flash" flooding. Where "flash" flooding may be a riak the
geotextile should be included as a precautionary measure.
1
Schematic Only-Not to Scale
2
1(�
H
r - o 'IIrr� D
/ D
I '�Q
b
Fig_ A. Rockery Section Fig.B_ Rockery Elevation
NOTES
• Rockery construction is a craft and depends largely on the - The long dimension of the rocks should extend back towards
skill and experience of the builder. the cut or fill face to provide maximum stability.
• A rockery is a protective system which helps retard the Rocks should not be stacked like shoe boxes.They should
weathering and erosion process on an exposed soil face. be placed to avoid continuous joint planes in vertical or
• While by its nature(mass,size and shape of the rocks)it lateral directions wherever possible.Whenever possible
will provide some degree of retention,it is not a designed each rock should bear on two or more rocks below it,with
or engineered system in the sense a reinforced concrete good flat-to-flat contact.
retaining wall would be considered designed or • All rockeries over 4 feet in height should be constructed
engineered. on basis of wall mass,not square footage of face,and
• The degree of retention achieved is dependent on the size should be subject to e0gineering"design"by geotechnical
of the rock used;that is,the mass or weight,and the engineer.
height of the wall being constructed.The larger the rock, Approximate Approximate
the more competent the rockery should be. Size Weight-lbs. Diameter
- Rockeries should be considered maintenance items that
will require inspection and repair.They should be 1 Man 50-200 12-18"
located so that hey can be reached by a contractor if 2 Man 200-700 18-28'
repairs become necessary. 3 Man 700-2000 28-36"
• Maximum inclination of the slopes above and behind 4 Man 2000-4000 36-48"
rockeries should be 2:1 (Horizontal:Vertical). 5 Man 4000-6000 48-54"
- Minimum thickness of rock filter layer b=12 inches. 6 Man 6000-8000 54-60"
• Minimum embedment D=12 inches undisturbed native
soil or compacted till placed in accordance with report Reference:Local quarry weight study using average weights
recommendations. of no less than six rocks of each man size conducted in
• Maximum rockery height H= feet. January,1988.
• Rockeries greater than 8 feet in height to be installed LEGEND
under periodic or full time observation of the geotechnical
engineer. o
-Rocks should be placed to gradually decrease in size with t3 Op.4 Drainage materials to consist of clean angular 4 to
increasing wall height in accordance with geotechnical 2 inch spalis,or other material approved by the
Q
engineers recommendations. geotechnical engineer.
- Minimum width of keyway excavation,b,should be equal
to the thickness of the basal rock(as determined by the Surface seal;may consist of impervious soil or a fine
geotechincal engineer)plus bd. free-draining granular material.
Undisturbed firm Native soil.
Drain pipe:4-inch minium diameter,perforated or
slotted,rigid,smooth-walled,plastic ADS pipe laid
with a positive gradient to discharge under control
well away from the wall.
a
_ Plate
TYPICAL ROCKERY DETAIL
NATIVE CUT,ANY HEIGHT OVER 4 FEET
J
Schematic Only-Not to Scale-
0 W'
4
t bd
6 II_
• ��.0 VCR\� /t' � i .O ,.�
p
b
-- Lo
LEGEND
�II QQ�Q Crushed rock or crushed concrete drain rock material ranging between 4 and 2 inches in size and free of
a::o ra organics,with less than 5 percent fines(silt and clay size particles passing the No-200 mesh sieve).
Structural fill overbuild,compacted to at least 95%of maximum dry density as determined by Modified
Proctor.
Compacted structural fill consisting of free-draining organic-free material with a maximum size of 4 inches.
to at least 95 percent f
Should contain no more than 7 percent fines(described above),compacted p o
Modified Proctor maximum dry density.
Perforated or slotted,smooth-walled,plastic drain pipe with 4 inch minimum diameter bedded on and
surrounded by crushed rock filter material,described above.
DDesignates size or rock required, i.e. 5-man.
NOTES
- All fill should be placed in thin lifts not exceeding 10 inches in loose thickness_Each layer should be compacted to
no less than 95 percent of maximum dry density,as determined by Modified Proctor.
- Thickness of crushed filter rock layer,bd, should be no less than 12 inches-
- Depth of burial of basal layer of rock, D,should be no less than 12 inches.
- Free-standing height of rockery, H,should not exceed feet.
- Lateral extent of fill overbuild, Lo,should be no less than H feet.
Estimated width of keyway excavation, b, should be equal to the thickness of the basal rock (as determined
by the geotechnical engineer) plus bd.
TYPICAL ROCKERY DETAIL Plate
'o OVERBUILT FILL CONSTRUCTION ROCKERY
8 FEET OR LESS IN HEIGHT B
Schematic Only- Not to Scale
` 7 � 4Q O'c�:•
_ _ t
Z
g
r a 1
H b� Z
oQa� t
Z
d o
,�[5 , - -- ' tiD z
� oob'D'o t
- ` :'¢:�,
D �'.Do:4 Zb=0.6 ft.
1
•---- b � - LR -
LEGEND
'QQj�Q Crushed rock or crushed concrete drain rock material ranging between 4 and 2 inches in size and free of
organics,with less than 5 percent fines(silt and clay size particles passing the No.200 msh sieve):
f— Compacted structural fill consisting of free-draining material with a maximum size of 4 inches.Should
tt contain no more than 7 percent fines(described above),compacted to at least 95 percent of Modified
Proctor maximum dry density.
Undisturbed firm Native soil
Geogrid reinforcement approved by geotechnical engineer.
0 Perforated or slotted,smooth-walled, plastic drain pipe with 4 inches minimum diameter bedded on and
surrounded by crushed rock filter material,described above.
❑5 Designates size or rock required,i.e.5-man.
NOTES
- All fill should be placed in thin lifts not exceeding 10 inches in loose thickness.Each layer should be compacted to
no less than 95 percent of maximum dry density,as determined by Modified Proctor_
• Length of reinforcing geogrid, LR shall be feet.
- Geogrid reinforcement layer spacing,Z,shall be____feet as determined by the geotechnical engineer.
- Height of rock wall, H, should not exceed feet.
- Thickness of crushed drain rock layer, bd,should be no less than 12 inches.
- Depth of burial of basal layer of rock, D,should be no less than 12 inches.
• Minimum width of keyway excavation,b,should be equal to the thickness of the basal rock(as determined by
geotechnical engineer)plus bd-
TYPICAL ROCKERY DETAIL Plate
GEOGRID REINFORCED FILL CONSTRUCTION
AR ROCK WALL 8 FEET OR MORE IN HEIGHT
a.. C