Report • RECEIVED
AUG 182015
CITY OF TIGARD `1r.
BUILDING DIVISION GeoPacific
IegIneerin4.Nec.
Real-World Geotechnical Solutions
Investigation • Design •Construction Support
August 18, 2015
Project No. 14-3260
JT Roth Construction
12600 SW 72"d Avenue
Portland, Oregon 97223
Email: AustinIR JTRothinc.com
SUBJECT: GEOTECHNICAL ENGINEERS' ROCK WALL DESIGN
MEDALLION MEADOWS LOT 18
TIGARD, OREGON
Enclosed are our calculations and recommendations for design of the rockery walls to be
constructed on Lot 18. Based on our site observations, the rock wall will be up to 8 feet in
exposed height. We recommend that the walls be constructed to our requirements by a qualified
rock wall builder. Based on our observations of the site conditions and existing grading. soil
parameters were assumed as follows:
Active earth pressure for fill wall up 5 feet exposed vertical and level backfill— 41 pcf
Coefficient of friction —0.54
Unit weight of rock— 139 pcf
Unit weight of retained soil — 125 pcf
Allowable bearing pressure—4000 psf
Finished backslope —up to 7 foot tall, 2H:1V slope above
Based on our calculations, the proposed wall have adequate factors of safety against sliding and
overturning. The boulder backfilling, sizing, batter and placement is in accordance with the
attached detail, Figure 1. Minimum boulder(s) width for the base course of boulders is 5.33 feet
for a wall up to 8 feet in retained height. The long axis of the boulders was oriented perpendicular
to the wall face. The attached Rockery Wail Detail shows generally how the walls are to be
constructed.
We have prepared this report for the owner and their consultants for use in design of this project
only. This report should be provided in its entirety to prospective contractors for bidding and
estimating purposes; however, the conclusions and interpretations presented in this report should
not be construed as a warranty of the subsurface conditions. Experience has shown that soil and
groundwater conditions can vary significantly over small distances. Inconsistent conditions can
occur between explorations that may not be detected by a geotechnical study. If, during future
site operations, subsurface conditions are encountered which vary appreciably from those
described herein, GeoPacific should be notified for review of the recommendations of this report.
and revision of such if necessary.
Sufficient geotechnical monitoring, testing and consultation should be provided during
construction to confirm that the conditions encountered are consistent with those indicated by
14835 SW 72nd Avenue Tel (503) 598-8445
Portland, Oregon 97224 Fax (503) 941-9281
• Lot 18 Medallion Meadows
GeoPacific Project No. 14-3260
explorations. Recommendations for design changes will be provided should conditions revealed
during construction differ from those anticipated, and to verify that the geotechnical aspects of
construction comply with the contract plans and specifications.
Within the limitations of scope, schedule and budget, GeoPacific attempted to execute these
services in accordance with generally accepted professional principles and practices in the fields
of geotechnical engineering and engineering geology at the time the report was prepared. No
warranty, expressed or implied, is made. The scope of our work did not include environmental
assessments or evaluations regarding the presence or absence of wetlands or hazardous or toxic
substances in the soil, surface water, or groundwater at this site. We appreciate this opportunity
to be of service.
Sincerely,
GEOPACIFIC ENGINEERING, INC.
PRp Ope
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EXPIRES:06130/20/7
James D. Imbrie, G.E., C.E.G
Principal Geotechnical Engineer
Attachments: Rockery Wall Detail Figure 1
Design Calculations
2 GEOPACIFIC ENGINEERING, INC.
/Y\r` 14835 SW 72nd Avenue
GeoPacific Portland, Oregon 97224 Lot 18 Medallion Meadows FIGURE 1
GeoPacific
1111 Tel: (503)598-8445 Fax: (503)841-9281 Project No 14-3260
,,-1
ROCK SIZE SCHEDULE(See note 3 below) ROCKERY WALL DESIGN
D(FT) MIN WT. (LBS.) TYPICAL SIZE(IN ) MAXIMUM WALL HEIGHT(H)=8 FEET
-2H:1V slope above
2 1,500 36 X24 X18
DRAWING NOT TO SCALE
5 4,000 42 X 36 X 30
48X30X30
8 8,000 64 X 48 X 36
60X54X42
• 1
•
D is distance from base
of boulder to top of wall t -
4±1
(D= H for toe boulder)
D (vanes)
•
•
H
V
Toe Boulder(s)
12 IN MIN 5 3-ft min length 4"-0 CRUSHED AGGREGATE WITH
for 8-foot wall NO MORE THAN 7%FINES PASSING
•
6 IN THE NO 200 SIEVE,LIGHTLY TAMPED
4 3 INCH MIN.DIAM.PERFORATED
MIN KEYWAY PLASTIC PIPE ADS HIGHWAY GRADE
CONSTRUCTION NOTES: WIDTH= 0 75H OR EQUIVALENT
1. Keyway subgrade and embedment should be verified by GeoPacific Engineering, Inc. For walls supporting fill,an engineered fill
should be overbuilt and then trimmed back so that the wall is constructed against a stable excavated face of compacted engineered fill
2.Rocks should have a cubical,tabular,or semi-rectangular shape that roughly matches the space created by the previous rock
course Rocks should be laid flat with the long dimension oriented perpendicular to the wall and extending towards the excavation
face Rocks should be staggered such that each rock bears on at least two rocks below and vertical joints are discontinuous Rock
placement and wall integrity should be checked(by builder)by lightly hammering on the top of each rock with excavator bucket
3. Minimum rock sizes for a level backfill condition should be determined using the ROCK SIZE SCHEDULE above,where D is the distance
from the base of the rock to the top of the wall Rocks should be no smaller than 1,500 lbs. For sloping backfill,rocks should be 50%
• larger than the smallest size
4 Voids greater than 6 inches wide where there is no contact between adjacent rocks should be chinked with a small rock.
5. Backfill behind the rocks should consist of a minimum 12-inch-wide sheet of 4--0 crushed aggregate with no more than 7%fines
passing the U S Standard No 200 sieve. Backfill should be placed in 12 inch lifts and lightly compacted to an unyielding state as
each course of rocks is placed
6 Structures supported above the wall should either be at least 1 6H horizontal from the front base of the wall or footings deepened as
determined by a geotechnical engineer. This detail is applicable to the subject project only and should not be used for other projects
7. Cap boulder should be a minimum of 36 inches wide to minimize potential dislodging of boulders during a seismic event.
`Y•. Rockery Wall Design Calculations
GeoPacific 9
Job Name: Lot 18 Medallion Meadows
Project No.: 14-3260
Wall Configuration: 8' max exposed height rockery-
2:1 slope above
Wall Diagram and Geometric Definitions Assumptions
Wall Materials
►, Specific Gravity of Rock 2 68
Porosity Assumption of wail 20 percent
•
—.1 Elf Unit Weight of Rock Wall 139 pcf
` •-t••• Coeffc ent of friction 0.54
:x
,.;�r: Soil and Surcharge Loading
-.',`:?:L"--
Phi(Retained Soil) 34 degrees
Ht ?, Unit Weight(Retained Soil) 125 pcf
+T'��s+ Phi(Foundation Soil) 34 degrees
-�f - =7,1 ,, Unit Weight(Foundation Soil) 125 pcf
,r,-= Cohesion(Foundation Soil) 0 psf
• C'+ Live Load Surcharge 0 psf
.▪, Dead Load Surcharge 0 psf
• r'!6 ,p Depth to groundwater 10 ft
ez4 - •'t d„+ ; All Bearing Cap •Sett.Landed 4000 psi
a,1 k K, 0.33
Kv
354
14 .I Passive Pressure 442 pcf
I LI EFP 410ccf
Required Static Factor of Safety
Overturning 1 5
Sliding I 15
Static Results Bearing Caeacily i 3
Overturning Moment I 6833 lb-ft Walt Geometry
Sliding Force I 2050 lbs Batter 4 :1
H1 9 ft
Vertical Weight 5686 ibs H2 1 ft
Resisting Mcrnenl 18202 lb-ft L1 5.33 ft
dl 0.5 ft
Resisting Passive 221 lbs Backsiope 28 degrees
Base Friction 3068 lbs _ Gstance to Sion=Break .: 7 ft
Tur;al ShOrng Resistance' 3068 lbs
Y 449 ft
drm 3 20 ft
Average Bearing Pressure 1422 psf d2 2 50 ft
Maximum Bearing Pressure 2841 psf Wall Taper Angle for Vert Wt 7 degrees
Bearing Pressure Area 4 5 ft
Ultimate Bearing Capacity(Terzaghil 14459 psf e(vertical weight) 0 52 ft
'Conservatively neglects passive resistance e(resultant vertical force) 0 67 ft
Equivalent facing width 4 0 ft
Static Supporting Calculations
Coefficient of Friction=C 8•tan(34 degrees)=0 54
Overturning Moment=(41.0 pcf•(9 ft+1 ft)"2/2•(9 ft+1 ft)/3) =6833 lb-ft
Sliding Force=(41 0 pcf•(9ft+If t)"2/2)lbs=2050 lbs
Vertical Weight=(((9 ft+1 ft)•5 33 ft)-((9 ft+1 ft)^2'tan 7 13))•139 36 pcf =5686 lbs
Resisting Moment =5686 lbs•3 20 ft=18202 lb-ft Terzhaghi's Bearing Capacity Factors
Resisting Sliding=0 54•5686 lb=3068 lbs Na 36 50
Passive Resistance=442 pcf•0 5(1 ft+0 5 ft)^2=221 lbs N, 52.64
Total Sliding Resistance=3068 lbs(not including passive resistance) N, 39 59
Area=5.33ft+(2.O.5 ft)=45ft"2
Eccentricity of Vertical Weight=sin7 13•(4 49 ft-(tan7 13•5.3 ft/2))=0.516 ft
Eccentricity of Resultant Vertical Force=(6833 lb-ft-(5686 lbs•0 52 ft))/5686 lbs=0.665 ft
Equivalent Footing Width=5 33 ft-(2•0 67 ft)=4 0 ft
Maximum Bearing Pressure(Toe)=5686 lb/4 0 ft'(1+(6•0 665 ft 14 5 ft))=2841 psf
Average Bearing Pressure=5686 lb/4 0 ft+(130 psf•0 5 ft)=1422 psf
Ultimate Bearing Capacity=(Opsf•52 84)+(0.5•130 pcf•4 0 ft•39 59)+(130•1 00 ft•36 50)=14459 psf
F S Overturning=18202 lb-ft/6833 lb-ft=2 66
F S Sliding=3068 lb/2050 lb=1 50
. F S Beanng Capacity(Settlement Limited)=4000 psf/2841 psf=1 41
F S Bearing Capacity(Terzaghl)=14459 psf/2841 psi=10 2
Stabilty Results -Static Condition
F.S.Overturning= 2.66 > 1.5 OK
F.S.Sliding= 1.50 < 1.5 A$s (' 1 _ 454
F.S.Bearing Cap.(Sett.Limited)= 1.41 > 1 OK
F.S.Bearing Cap.(Terzagle)= 10.2 > 3 OK
ioP Rocker Wall Seismic Design Calculations
GeoPacitic Y 9
Job Name: Lot 18 Medallion Meadows
Project No.: 14-3260
Wall Configuration: 8'max exposed height rockery-
Seismic Assumptions
Honzcntai AcceleraLOr(.l 0 09 %g
Ka, 0 43
Km 3 36
Passive Pressure 420 pcf
EFP 536 pcf
e(resultant vertical force) 1 03 ft
Equivalent fooling width 4 0 ft
Required Seismic Factor of Safety
Overturning 1 1
Sliding 1 1
Bearing Capacity 15
Seismic Results
Overturning Moment 8925 lb-ft
Sliding Force 2678 lbs
Vertical Weight 5686 lbs
Resisting Moment 18202 lb-ft
Resisting Passive 473 lbs
Base Friction 3068 lbs
Total Sliding Resistance 3068 lbs
Average Bearing Pressure 1487 psf
Maximum Bearing Pressure 3924 psi
Ultimate Bearing Capacity(Terzagh i 14459 psf
Seismic Supporting Calculations
Overturning Mcment=(53 6 pcf•(9 ft+1 ft)^2/2"(9 ft+1 ft)/3)=8925 lb-ft
Sliding Force=(53 6 pcf•(9 ft+1 ft)^2/2)=2678 lbs
Resisting Moment =5686 Ibs'3 20 ft=18202 lb-ft
Resisting Sliding=0 54•5686 lb=3068 lbs
Passive Resistance=420 pcf•0 5(1 ft+0 5 ft)^2=473 lbs
Total Sliding Resistance=3068 lbs(not including passive resistance)
Eccentricity of Vertical Weight=sin7 13'(4 49 ft-(tan7 13•5 3 ft/2))=0 516 ft
Eccentricity of Resultant Vertical Force=(6833 lb-ft-(5686 lbs 0 52 ft))/5686 lbs=0 665 ft
Maximum Bearing Pressure(Toe)=5686 lb/4 0 ft•(1+(6•1 033 ft/ 4 0 ft))=3924 psf
Average Bearing Pressure=5686 lb/4 0 ft+(130 psf"0 5 ft)=1486 8 psf
Ultimate Bearing Capacity=(0 psf`52.64)+(0 5.130 pcf•4 0 ft"39 59)+(130•1 00 11•36 50)=14459 psf
F S Overturning=18202 lb-ft/8925 lb-ft=2 04
F S Sliding=3C68 lb/2678 lb=1 15
F S Bearing Capacity(Settlement Limited) =4000 psf/3924 psf=1 02
F S Beanng Capacity(Terzaghi) =14459 psf/3924 psf=3 7
Final Summary-Seismic Condition
F.S.Overturning= 2.04 > 1.1 OK
F.S.Sliding= 1.15 > 1.1 OK
F.S.Bearing Cap.(Sett.Limited)= 1.02 > 1 OK
F.S.Bearing Cap.(Terzaghi)= 3.7 > 1.5 OK
Notes:
Beanng Capacity is based on Terzhagi s method of analysis and/or settlement-limited searing capacity input by the design engineer
All calculations are per foot of wall
Assume kv=0
Passive resistance in front of wall is not included in sliding resisting forces.
Live surcharges are not included in seismic calculations
Dead load surcharges are included in seismic calculations
Assume backcut(wall to soil batter angle)is vertical