HomeMy WebLinkAbout30578 (46)TRIAD FOUNDATION ENGINEERING INC
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IMI EAST RAILROAD STREET, SUITE 100, CITY OF INDUSTRY, CA 91748
TELEPHONE (816) W2313
FAX (818) $10401115
Job # 88-494
Sun -Ray
1724 Leaning Pine
Diamond Bar, Ca. 91765
Subject: Supplemental Geotechnical Data
and Review of Revised Grading Plan
22105 Rim Fire Lane
Diamond Bar, Ca.
References:
Gentlemen:
7')
AAR 2 1 ( J,
1) Preliminary Soils & Geologic Investigation
by Triad Foundation Engineering, Inc.
dated 9-8-88
2) County Geologic Review Sheet dated 11-21-88
Additional geologic data down slope shows a slight steepening of
the apparent dip shown on the attached Cross Sections A -A' and
B -B'. Stability calculations contained in our Preliminary Report
on the natural slope indicate it to have an acceptable factor 6f
safety of 1.5.
The present grading concept is to place a fill to support the
house. As drawn on the plan it appears this fill will slope at an
average angle of will be supported by a high
cribwall at the property line. It appears this wall will be as
high A_p Jp 'ill encroach onto theportionofw
restricted, _,VPo area", Th / is area has been designated as an area of
shallow slumping and sliding. Access to the house will be by a
long driveway from Rim Fire and will also be on fill.
The Tract is sewered and the house will be connected to this
system. It is expected that no effluent will be introduced into
the subsurface.
ConclMsions and Recommend4tions
1. The natural slope has an adequate factor of safety.
2. The placement of the proposed fill should.,,,,act as a "buttress"
axe--improvethe site stability.
3.A11 fill will, In f In thebeo,roc ' k.
r*as .of the ,shallow slumping -a'na, alko-i d# , _,,k vs and benchshallow
ir, M101- 1- 1 " 4 .
qpp -.P-y benching
will be required to'rdkove all disturbed bedrock.
4. The placement of all fill is subject to geologic inspection to
insure proper keying and benching are being maintained.
5. The ll, as =alit« has no dr4i,pgp benchs. a e From the top ofI
the proposed cribwall to pad grade is estimated to be as high as*
75fi6tIf-appears that,,_thrpe,, J,ght-f pot wide benches mai '-
he side of 'tlip p
y'. be in
oder. TheJ t, Ju c p, , t s e Inror rease
the,,,,ile,,i4
6. Proposed fill slopes will be constructed from imported soils
whose source is not known at this timef,, Calculations enclosed
indicate that a proposedV171"' Tbolt-J,rIgh fill slope can be safely
3-5' , and Cconstructedwithsoilshavift//' strengths ofv, i".1111
3,0,0,/ p/s//,. Any imported soils must be tested and approved by the
Soils Engineer prior to importing to insure these minimum shear
strengths(' Revised calculations could also be required when better
grading plans are available.
Fill slopes constructed at 1 1/2:1 gradients must be over filled
a minimum three feet and trimmed back to the compacted, inner core.
This will be difficult and costly with a large retaining wall at
the toe of slope.
The opportunity to be of service to you has been appreciated. If
you have any questions, please do not hesitate to call.
Respectfully submitted,
0 0 K
TRIAD FOUNDATION ENGINEERING, INC.
f
William G. Uhl Frank C. S illman
gT,
0
C.E.G. 502 G.E. 805
WGU;FCS/lms
Enclosures:
c
P, m 0
CE RT1F i ED
ENG NEER NG
GEOLOGIST
Geologic Map
Cross Sections A & B
Slope Stability Calculations
Addressee (4)
0
f ESS/
C S
C'7
Z5
L -J Exi),
07 --
Ci
I.
ry ff J I
SIVRFICIAL SLOPE STABILITY
FLOW LINES
SLOPE SURFACE
PATH
ASSUME: 2) SATURATION TO FAILURE PATH
2) PERMEABILITY SUFFICIENT To PERMIT FLOW
Pw - WATER PRESSURE HEAD
Ws = SATURATED SOIL UNIT WEIGHT
Ww - UNIT WEIGHT OF SOIL WATER
U - SOIL PORE WATER PRESSURE
Pw - 9 COS2 a
U - ww COS2 OL
FD - iF VS sin 2 OC
pR - Z (WS-Ww) COS2 OC tan 0 + C
F.S. 2 M (ws-ffy) cos 2 4 tan 0 + 2a
Ws (2) sin 2
F2 (300)
120 (4) sin 68
1.8
PARAMETERS
TRIAD FOUNDATION ENGINEERING, Inc.
88-494" 7 0- 3t2l/89 FS PLATEJ06no*. By:
ROTATIONAL ANALYSIS USING JANBU'S DIMENSIONLESS PARAMETERS
Harvard Soil Mechanics Series No, 46)
SECTION
Fill Slope
SHEAR STRESS PARAMETERS
Unit Weight, 'y 120 lbs,./cu.'.ft.
Cohesion, C lbs . /sq-. ft- ,..
Angle of Internal Friction, + degrees
Tangent .4
CALCULATIONS
Height of Section 70 feet
Slope of Section 1}.1
YH
C
0 2 8
xc YCH
Tan + - 19.6
Ncf (from Janbu's curves) 44
FACTOR OF SAFETY
F. S. - Ncf YH 1.57
TRIAD FOUNDATION ENGINEERING, Inc.
Consulting Geologists - Soils Engineering
Jab no: 88-494°,; Date: _ 3121/89 Scale: By; Fs