HomeMy WebLinkAboutXWF~00013. Conclusion and Recommendation Updates
C/TY OF DIAMOND BAR
GRAD/NG AND DRA/NAGS PLAN
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Based on MTC's three verification test pits/borings, research of available data and
reference reports, and years of experience observing similar properties in similar
settings and review of the development plans, it is the finding of MTC Engineering
that repairing the residence, stabilizing the pad and appurtenances are feasible from a
geologic and soils engineering standpoint provided the recommendations of this
report are properly incorporated into design and are implemented during construction.
3.1. GeotechnicalIssues
The building pad and residence have experienced lateral and vertical
displacement consistent with a developing landslide. The base of the failure
consists of weathered bedrock and possibly ancient slide debris, which are
present beneath the keyway, slope and house. This weathered bedrock
including possibly ancient slide debris is weak in the southerly and
southwesterly directions due to the orientation of bedding and the southwest
plunging fold axis. Based upon the previous -manometer survey contours and
distress patterns by IG and SMC, a landslide graben is developing beneath the
southwestem portion of the residence. The house will fail catastrophically if
no remedial method is to stop the landslide creeping.
Due to a landslide creeping beneath the southwestern portion of residence, a
structural engineer should evaluate the structural integrity of the dwelling,
including the retaining walls and framing. Relatively low density of the fill,
moderate potentials for hydro -collapse and consolidation of the fill and open
fractures in the bedrock all indicate there is a potential for additional
settlement to the pad, house and concrete flatwork, regardless if the pad is
stabilized laterally. The house should be underpinned to bedrock to eliminate
the potential for additional settlement and stabilize underneath potential
landslide. Deepened foundations consisting of friction piles tied with grade
beams are recommended. The jet grouting is recommended to densify
underlying fill and bring slabs back to level. The structural engineer should
provide recommendations for bringing the framing back to level. A
replacement swimming pool should also derive support in the bedrock.
Soldier piles should be installed to provide lateral support to the building pad.
The piles should be spaced a maximum of 10 feet on center and be designed
to retain the earth between the ground surface and the bedrock (about 36 feet).
The soldier piles should be downhole-logged to verify the depth to competent
bedrock. Due to the thickness of the retained earth, tie -back anchors may be
required to assist the piles. The recommended bearing material for soldier
piles and the earth anchors is the bedrock. The recommended soldier piles are
shown on Figure 1.
Since original keyways appear to be not deep enough to stabilize the fill
slopes, keyways may need to be modified for stabilizing the fill slopes.
3.2. Foundation Design
3.2.1. Deepened Foundations
Drilled, cast -in -place concrete friction caissons are recommended to
support replacement structures and/or to underpin the existing -
structures. Caissons should be a minimum of 24 inches in diameter and
a minimum of 10 feet into bedrock. Piles may be assumed fixed at 3
feet into bedrock. The piles may be designed for a skin friction of 600
pounds per square foot for the portion of pile in contact with the
bedrock. Caissons should be spaced a maximum of 8 feet on center
along the perimeter of the house which is shown on Figure 1. The
caissons may be designed to an equivalent fluid pressure of 45 pcf.
The earth pressure is to be applied from existing grade to the top of the
bedrock. Friction caissons used to support structures stabilized mass
should be designed for an arbitrary creep force of 5 kips, distributed
evenly over the upper 5 feet of caisson shah. Passive earth pressure
may be computed as an equivalent fluid having a density of 500
pounds per cubic foot. The maximum allowable earth pressure is 6,000
pounds per square foot. All caissons should be tied in two horizontal
directions with grade beams if applicable. Grade beam should have a
minimum of 2 feet wide and 2 feet deep.
3.2.2. Grouting
3.2.2.1. Compaction Grouting
Compaction grouting is recommended to enhance the performance
of fill soils underlying portions of the existing building. This method
is commonly known to provide a practical, and generally cost-
effective means for improving the strength and compressibility
properties of fill soil.
Grouting should be performed from the bottom -up. Grouting should
extend to a depth of 5 feet into the underlying bedrock materials; and
continue through the underlying fill soil material up to within 5 feet
below ground surface. Grout points should be adjusted to avoid
conflicts with existing improvements.
Approximate volume of treated is estimated to be 50,000 cubic feet.
We estimate that an injected grout volume of about 5 percent of the
total soil volume will be necessary to achieve the desired
improvement. Thus, for a 5 percent volumetric displacement of the
soil, this mitigation will require the injection of approximately 2,500
cubic feet of grout. Drill quantities are estimated at 1,000 lineal feet
based an 8-foot grid spacing of grout points. The grouting contractor
should independently verify these volumes prior to submitting a
construction bid.
Grouting Criteria
The following recommendations should be implemented in the construction
protocol for the compaction grouting specialty- contractor _ _
1. Grout injection points placed on a rectangular grid pattern with maximum
spacing of eight (8) feet throughout the area to be grouted. Grouthole
locations are shown on Figure 1.
2. The anticipated treatment interval for the injection points should start from
5 feet into bedrock materials; approximately 10 to 35 feet below ground
surface and continue in maximum three foot vertical stages upward to 5
feet below ground surface.
3. According to industrial standard, any settlement greater than '/+ inches
within building area has to be remediated. Based on this rule, for a spacing
of eight (8) feet on a rectangular grid pattern, we estimate a total of 46
injection points will be needed shown on Figure 1. However, the actual
number of injection points will depend on their field layout, which will be
influenced by the actual site conditions encountered. The specialty
grouting contractor should independently verify the number of points prior
to submitting a construction bid.
4. The contractor should employ the services of a utility location specialist to
provide the precise location of buried utility lines prior to grouting, in
order to avoid damage to any utility lines.
5. All grouting equipment should have accurate, working and certified
gauges for monitoring pumping pressures. Grout pumps shall be capable
of pumping at pressure of up to 600 psi as measured at the point of
injection.
6. A means of determining the quantity of grout within one cubic foot per
stage shall be established. The project geotechnical engineer shall review
and approve the method of determining the quantity of grout placed.
7. Injection quantities based on pump piston strokes shall be verified using a
known volume container, and by reconciling, with delivery records, all
delivered grout constituents. Reported grout quantities shall be based on
an average yield of 22.5 cubic feet of grout per ton of moist -delivered
sand.
8. The grout shall consist of a mixture of sand, silt and a minimum of 10
percent Portland cement by weight, mixed with sufficient water to attain a
thick, mortar -like consistency having a slump no greater than 2-inches per
ASTN Test Method C-143. Type II cement may be used in the grout mix
design.
9. Grouting shall be done at alternate injection points in a
_ _---.. __. _"primary/secondary~' _sequence, _such . that_ _no..._ two ._adjacent_ locations- . are.-_. _ ... _-
grouted consecutively.
10.Injwdon points shall be cased in order to allow efficient tramfer of
hydraulic energy to the soil at each injection stage and minimize the flow
of grout up to the ground surface.
11. Grouting shall be performed from the bottom up in maximum 3-foot
vertical stages. At no time shall the injection rate exceed 2.0 cubic feet per
minute.
12. Grout shall be continuously injected at each stage - until one of -- the
following stopping criteria: (a) the maximum recommended grout take is
achieved, (b) a sustained injection pressure greater than 150 psi (near
surface) and 300 psi (at depth) or (c) monitoring indicates a heave of the
ground surface of 0.005-foot (about 1/16-inch) whichever occurs first.
Verification of the compaction grouting operations should be based on a
thorough review and evaluation of the grouting records, including grout
pressures and volumes. The verification process should include the
placement of at least 3 verification grout holes (see Lamb and Hourihan,
1995) placed at the center of four planned grout holes as selected by the
Geotechnical Consultant. The verification holes should show both
consistent sustained grout pressures and lower grout volumes than
adjacent planned grout holes.
3.2.2.2. Contact Grouting -
This method considered to be most feasible for restoring subgrade contact
with the floor slab where there is a void space beneath, is by means of a
process called "Mud jacking" or, as it is now referred to, contact grouting.
This process involves injecting a fluid, cement/fly ash material through holes
drilled in the slab concrete. The grout is injected at low pressure and relatively
close spacing, to fill the void spaces between the underside of the floor slab
and the subgrade soil materials. Contact grouting criteria are provided in more
specific detailed below.
Grouting Criteria
The following criteria are presented with the intention of filling voids that
may have developed between the bottom of the slab on grade and the
subgrade soil materials. These recommendations are not intended to densify or
stabilize the subgrade soil materials beneath the slab on grade, but rather,
merely to restore subgrade support for the floor slab. The contractor should
employ sufficient injection points to assure that the contact grouting will
achieve a uniform contact between the floor slabs on grade and the subgrade.
The contractor must (a) have all underground utility lines accurately located
_ and (b) lay out and adjust the injection points so that no utility lines are
damaged or plugged by the contact grouting operation.
The following items should be incorporated into the contact grouting
specifications:
1. Grout pumps should be capable of pumping a fluid grout at constant low
pressures (50 psi or less) and the point of injection.
2. It is important that injection pressures are kept low enough to prevent
excessive lifting of the floor slab beyond the minimum needed for re-
leve g.
3. All contact grouting equipment should have accurate, working and
certified gauges for monitoring pumping pressures and grout quantities.
Injection quantities based on pump piston strokes should be verified using
a known volume container.
4. A grout mix acceptable for this application is based on Caltrans criteria,
and consists of cement and fly ash. The proportions range from 1:2.2 to
1:2.6 (ratio of cement to fly ash): The cement may be Type II, and the fly
ash may be Class F for this project. To achieve a relatively low
permeability grout, the water to cementitious material ratio should not
exceed 0.50.
5. The contractor should exercise care in grouting such that buried utility
lines are properly located prior to contact grouting, and are not damaged,
broken or filled with grout during the contact grouting operation.
6. Grout should be continuously pumped at each injection point until it
begins appearing at adjacent coreholes. The adjacent holes should be
plugged, and the process repeated from succeeding injection points until
there are no visible voids in any coreholes.
7. Finally, the holes cored through the floor slab concrete should be filled
with a non -shrink cementitious material.
The capacities of the anchors and the assumed design values should be
determined by testing of the initial anchors as determined by the
structural engineer. For preliminary design purposes, it is estimated
that cast -in place friction anchors will develop an average value of 900
pounds per square foot. Post or pressure grouted anchors will develop
much higher bond stresses and capacities. Only the frictional
resistance developed in the bonded zone of the bedrock will be
effective in resisting lateral loads. If the anchors are spaced at least six
feet on center, no reduction -in the capacity of anchors need be -
considered due to group action.
The anchors may be installed at angles of 20 to 40 degrees below the
horizontal. Caving and slouging of the anchor hole should be
anticipated and provisions made to minimize such caving and
sloughing. To minimize chances of caving and sloughing, that portion
of the anchor shaft with the active wedge should be backfilled with
sand before testing the anchor. This portion of the shaft should be
filled tightly and flush with the face of the excavation. The sand
backfill should be placed by pumping, the sand may contain a small
amount of cement to facilitate pumping. The installation, testing and
performance criteria for anchors should be developed by the structural
engineer.
All of the anchors should be pretested to at least 150 percent of the
design load. The structural engineer should specify the allowable
elongation and creep for 200 percent and 150 percent tests. After a
satisfactory test, each anchor should be locked -off at the design load.
The locked -off load should be verified by rechecking the load in the
anchor. If the locked -off load varies by more than 10 percent from the
design load, the load should be reset until the anchor is locked -off
within 10 percent of the design load.
The structural engineer should provide appropriate recommendations
for centralizers and corrosion protection. The installation of the
anchors and the testing of the completed anchors should be observed
by a representative of the geotechnical engineer.
3.2.6. Structural Slab and Concrete Decking
Floor slab and concrete decking should be structurally designed to
derive support in the bedrock via deepened foundations.
Decking that caps a retaining wall should be provided with a flexible
joint to allow for the normal one to two percent deflection of the
retaining wall._Decking that does not cap_ a_retaining_ wall should not
be tied to the wall. The space between the wall and the deck will
require periodic caulking to prevent moisture intrusion into the
retaining wall backfill.
3.2.7. Swimming Pool
A replacement swimming pool should be structurally designed to
derive support in the bedrock via deepened foundations. All pool walls
should be designed as free-standing. If the spa is to be attached to the
pool, the spa should be founded at the same -depth as the portion of the
pool it adjoins.
3.2.8. Fill Slopes
Based upon IG's field measurements and documents review, the fill
slopes were in fact manufactured at gradients of 2:1 to 1.5:1. Any
sloping is steeper than a 2:1 gradient It should be trimmed to a 2:1
slope. Based on the grading plan designed by HP Engineering, original
keyways may be only 15 feet wide and 2 feet deep. Repair keyways at
the toe of fill slope are recommended as shown on Figure I in red.
Keyways should be a minimum of 20 feet wide and 4 feet deep into
existing fill or bedrock.
3.2.9. Corrosivity Test
Chemical laboratory tests were conducted to evaluate the soil
corrosion potential and the attack on concrete by sulfate soils. Based
on the test results, sulfate test result is 39 parts per million (ppm),
Type I or II cement is recommended for use. pH value is 6.9. Chloride
value is I I I ppm, and the resistivity value is 620 cm -ohm (saturated
condition). It is our opinion that a potential corrosion problem from
on -site soil is severe; all underground piping should consider corrosion
protection measures.
3.2.10. Drainage
Final grading should provide a positive drainage to divert surface
water away from the foundation areas in compliance with the local
jurisdiction's grading requirements. All pad drainage should be
collected and diverted away from the proposed structures in non -
erosive devices. Roof gutter should be provided to collect runoff water
and divert to down spouts leading down to the ground surface and
discharge off -site. Planters adjacent to deck or slope should be
designed with concrete bottom and subdrains leading away from the
deck or slope area. Proper surface and subsurface drainages should be
_ _ _ _ provided_ _to - _divert runoff water away from the deck area.! AlI
underground plumbing fixtures should be leaked free. Proper drainage
should also be provided to divert surface water away from the deck
MTC Engineering, Inc.
5924 Temple City Blvd., Temple City, CA 917801 Toll Free 1-888-MTC-ENGR
CITY OF DIAMOND BAR
GEOTECHNICAL ENGINEER'S STATEMENT OF COMPLIANCE APPROVED BY: LEGAL DESCRIPTION
THIS PLAN HAS BEEN REVIEW BY MTC ENGINEERING, INC. CITY OF D ND TRACT NO. 30091 LOT 99
AND DEEMED TO BE IN CONFORMANCE WITH TH
RECOMMENDATIONS IN OUR REPORTS) DATED 0/13/16 �` �• ��
PROJECT NO. 1420-1-1 SGA4 DAVID L CITY ENGINE R RCE 44053 DATE
REVIEW WAS LIMITED TO THE GEOTECHINICAL ASPECTS OF THE
�, PLAN ONLY. WE MAKE NO REPRESENTATION AS TO THE PLAN REVIEWED FOR THE CITY OF DIAMOND BAR BY:
R T � ACCURACY OF DIMENSIONS, MEASUREMENTS, CALCULATIONS,
OR ANY PORTION OF THE DESIGN. PENCO ENGINEERING
; �. t1��.} 16842 VON KARMAN AVENUE, SUITE 150
_ REVIEWED BY: ��e p�� IRVI E, CA 92 6 L IA
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SOILS ENGINEER: ��Eas'o^'gt ENGINEERING GEOLOGIST �� x+°� ii � wa d� BRENT CHAMBERLAIN RCE 41889 DATE
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�`g� Z �'�`.v �'�` * :� ` PLAN PREPARED BY:
CALL TOLL FREE
1-800-227-2600
2 Working Days Bef ore You Dig
Grout Monitoring
This monitoring is intended to verify that no untended lifting of the slab
occurs during the compaction grouting. Some lifting of the floor slabs on
grade is desirable to re -level the building and slab surfaces to within
construction tolerance. Monitoring devices, such as manometers, stadia levels,
dial indicators, etc. should be of sufficient precision to record surface
movement of 0.005-foot (about 1/16-inch), with the bench mark location
located beyond the grouting zone of influence. Both compaction grouting and
contact grouting operations should be observed by a representative of our
Slab on Grade
Cracking and separations in the existing slabs on grade should be repaired as
determined by the Project Geotechnical or Structural Engineer. The subgrade
for any damaged and removed portions of the floor slabs should be prepared
as recommended by the Project Geotechnical or Structural Engineer.
3.2.3. Foundation Settlement
Foundations designed -and installed in accordance with - the
recommendations outlined in this report are anticipated to undergo a
total settlement of less than one inch and differential settlement
between adjacent columns will be less than 1/2 inch, under static
loading condition.
3.2.4. Soldier Piles
Cast -in -place concrete soldier piles are recommended to support the
downhill perimeter of the pad. Soldier piles should be a minimum -of
24 inches in diameter and a minimum of 15 feet into bedrock. Piles
may be assumed fixed at 4 feet into bedrock. The piles may be
designed for a skin friction of 600 pounds per square foot for that
portion of pile in contact with the bedrock. Soldier piles should be
spaced a maximum of 10 feet on center. The soldier piles may be
designed to an equivalent fluid pressure of 45 pcf. The earth pressure
is to be applied from existing grade to the top of the bedrock. Due to
arching between the piles, the design equivalent fluid pressure should
be multiplied by the pile spacing.
The friction value may be increased by one third for short duration
wind or seismic loading. Resistance to lateral loading may be provided
by passive earth pressure within the bedrock.
Passive earth pressure may be computed as an equivalent fluid having
a density of 500 pounds per cubic foot. The maximum allowable earth
pressure is 6,000 pounds per square foot. For design of isolated piles,
the allowable passive and maximum earth pressures maybe increased
by 100 percent. Piles spaced more than 2.5 times pile diameters on
center may be considered isolated.
3.2.5. Tie -Back Earth Anchors
Tie -back earth anchors may be employed to assist the soldier piles in
resisting lateral forces. Pressure grouted anchors are recommended.
Anchors should derive support (bonded length) in the bedrock. The
bonded length of anchors should extend at least 20 feet into bedrock or
greater length if necessary to develop the desired capacities.
C 76834
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NAME DA E NAME c. - (J f q DATE
`y,. ,��' APPLE ENGINEERING GROUP
F+. 9080 TELSTAR AVENUE, SUITE 309
ELM NTE, CA 91731
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ENGINEER GEOLOGIST CEG DA 1 1 /06/2017
GUOXIN MIAO RCE 73059 DATE
QRpFESSION
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OWNER: BO DU & FENG YONG D
P.O. BOX 4521' IRVINE, CA 92612
714-686-9297
SITE ADDRESS: 1941 FLINT ROCK RD. DIAMOND BAR, CA 91765
TYPE OF PLAN
SOIL ENGINEER'S
RECOMMENDATIONS
IN THE CITY OF DIAMOND BAR
DRAWN BY: Mike CHECK BY: SCALE: DRAWING NUMBER
DATE: 11 06 2017REVISED: JOB NO: 17098 2 OF 6
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