HomeMy WebLinkAboutCT 16-03; Beach Village Life 1 Mixed Use; SUPPLEMENTAL GEOTECHNICAL RECOMMENDATIONS; 2017-10-23Geotechnical • Geologic • Coastal • Environmental
5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosollsinc.com
Beach Village Life 1, LLC
c/o Karnak Planning and Design
614 Calle Vicente
San Clemente, California 92009
October 23, 2017
Attention: Mr. Robert Richardson
W.O. 6942-A1-SC
Subject: Supplemental Geotechnical Recommendations, Proposed Mixed-Use Hotel,
Spa, and Condominiums, Christiansen Way, Carlsbad, San Diego County,
California, Assessor's Parcel Number (APN) 203-173-02-00
Dear Mr. Richardson:
In accordance with your request and authorization, GeoSoils, Inc. (GSI) is providing this
summary of our supplemental geotechnical recommendations for the preliminary design
of building foundations of the proposed six-story mixed-use structure at the subject site.
The purpose of our work was to assist the project structural engineer with the design of the
proposed structure, following our discussions during a September 20, 2017 design team
meeting. The scope of work GSI performed for this study included a review of existing
subsurface and laboratory test data (GSI, 2015), geotechnical engineering analyses, and
the preparation of this summary report. Unless specifically superseded herein, the
conclusions and recommendations contained in GSI (2015) are still considered valid and
applicable, and should be appropriately implemented during the balance of project design
and construction.
CAST-IN-DRILLED HOLE (CIDH) PILE FOUNDATION RECOMMENDATIONS
During the aforementioned design team meeting, there was collective agreement that
supporting the proposed structure on CIDH pile foundations is necessary to accommodate
the anticipated vertical and lateral building loads; to mitigate building surcharges on
proposed water wells and underground water storage tanks; and to provide temporary
support of the building in the event that proposed water wells and underground water
storage tanks require repairs and/or maintenance over the life of the project. The use of
a hybrid foundation system, whereby portions of the proposed building are supported
CIDH piles and other building areas are supported by shallow foundations. However, due
to seismic performance requirements for the building superstructure, it was decided that
a hybrid foundation system would not be the most advantageous nor cost-effective
solution.
From a geotechnical viewpoint, CIDH piles with minimum 12-inch diameters should be
used to support building walls and columns. The piles should be interconnected with
minimum 12-inch square reinforced grade beams. The structural engineer may
superceded the aforementioned minimum geotechnical recommendations based on the
actual structural engineering requirements for th e project. On a preliminary basis, CIDH
piles should encounter and be minimally embedded 3 feet into suitable, unweathered
Santiago Formation. Based on the available subsurface data and our understanding of the
proposed development, the CIDH piles will gain axial support primarily from old paralic
deposits and the underlying Santiago Formation. Unweathered Santiago Formation is
anticipated to occur at approximate elevations 14 feet, 17 feet, and 17½ feet National
Geodetic Vertical Datum of 1929 (NGVD29) near the easterly end, center, and westerly end
of the proposed building, respectively. This corresponds to depths of approximately 30
to 34 feet below the existing grades, with the greatest depths to unweathered
Santiago Formation likely occurring near the westerly margin of the site. Actual pile
embedment and lengths will be based on the axial and lateral capacities required by the
project structural engineer. CIDH piles should be spaced at a maximum of 8 feet on center
unless the structural designer's calculations can support greater pile spacings. CIDH piles
should also support all building columns. Pile spacing should not be less 1.5 times the
pile diameter. The piles should be designed by the structural engineer based on the
applicable structural axial and lateral loads and the following geotechnical design
parameters:
Lateral Passive Resistance For the portion of the pile located in engineered fill, observed and tested by the
(applicable below the point of geotechnical consultant, the passive pressure may be taken as 250 psf per foot of
fixity only) pile depth to a maximum value of 2,500 psf. For the portion of the pile located with
the old paralic deposits, the passive pressure may be taken as 350 psf per foot of
pile depth to a maximum value of 3,000 psf. For the portion of the pile located in
suitable unweathered Santiago Formation, the passive pressure may be taken as
500 psf per foot of pile depth, to a maximum value of 5,000 psf -increase by one-
third for short duration wind and seismic loading
Allowable Axial Capacity Tip Capacity: 3,500 lb/ff for a pile extending at least 5 feet into suitable,
unweathered Santiago Formation -increase by one-third for short duration wind
or seismic loading. This assumes a drilled excavation this is generally free of
standing water with a clean bottom.
Point of Fixity At least 2.0 times the pile diameter below the bottom of the grade beam. This
should be reevaluated once the vertical and lateral pile loads have been provided
to GSI.
CIDH Pile Construction
1. The excavation and installation of th e drilled piles should be observed and
documented by the project geotechnical consultant to evaluate the recommended
depth.
Beach Life VIiiage 1, LLC
APN 203-173-02-00, Carlsbad
File: e\wp12\6900\6942a1 .sgr GeoSolls, Inc.
W.O. 6942-A1-SC
October 23, 2017
Page 2
2. Based on the available subsurface data, the drilled excavations for CIDH pile
installation will encounter perched water between approximate elevations 20½ to
22½ feet NGVD29. The regional groundwater table would be encountered if drilled
excavations extend near O feet NGVD29. Drilled excavations that encounter
perched water should be cased. The bottom of the casing should be at least 4 feet
below the top of the concrete as the concrete is poured and the casing is
withdrawn. Prior to concrete placement, water should be pumped from the drilled
excavations and a bottom clean-out tool should be used to collect any loose
material or mud from the bottom of the drilled excavation. The bottom of the
concrete pump hose should consist of a steel pipe at least 15 feet in length
(i.e., tremie). To begin concrete placement, this pipe should be placed at the
bottom of the cleaned pile excavation. During concrete placement, concrete should
not be allowed to free fall more than 5 feet in order to reduce the potential for
concrete segregation.
3. The exact depths of piles should be determined during the final precise grading
plan review.
4. Owing to the potential for piles to come into contact with soils with high soluble
chlorides or brackish groundwater, given the site's proximity to the Pacific Ocean·,
proper low slump concrete, with a maximum water/cement ratio of 0.40 and a
minimum compressive strength of 5,000 pounds per square inch (see Exposure
Class C2 in Table 4.3.1 of American Concrete Institute [ACI 318-11 ]), should be
used and should be delivered through tremie pipe. We recommend that concrete
be placed through the tremie pipe immediately subsequent to the approval of the
drilled excavation and steel cage placement. Care should be taken to prevent
striking the walls of the excavations with the tremie pipe during concrete placement.
Vibration of concrete to reduce the potential for segregation should be performed.
5. Consideration should be given to the use of reinforcing steel that is corrosion
protected. This may include the use of epoxy coating or "double corrosion
protection," which has been local practice.
6. All pile and grade beam excavations should be observed and approved by the
geotechnical consultant prior to placement of concrete forms and reinforcement.
The exact planned pile lengths should be reviewed and approved during the plan
review stage of development, prior to construction.
7. CIDH pile steel reinforcement cages should have spacers to allow for a minimum
spacing of steel from the side of the pile excavation, per code.
8. Concrete and steel used in the foundation should be tested by a qualified materials
testing consultant for strength, bar arrangement, and mix design and reviewed by
the project structural consultant.
Beach Life Village 1, LLC
APN 203-173-02-00, Carlsbad
File: e\wp1 2\6900\6942a1 .sgr GeoSolls, Inc.
W.O. 6942-A1 -SC
October 23, 2017
Page 3
CAST-IN-DRILLED-HOLE (CIDH) PILE AXIAL CAPACITY
Axial capacity for the proposed CIDH piles was analyzed using the computer program
SHAFTv6.0 (Ensoft, Inc., 2007). The analysis incorporated the subsurface and laboratory
data collected in preparation ofGSI (2015), and an assumed maximum column load of200
kips (100 tons), as communicated by a SUN Structural Engineering, Inc. representative
during the September 20, 2017 design team meeting. Axial capacities were analyzed for
12-, 18-, 24-, 30-, and 36-inch diameter CIDH piles. Pile capacity charts, presenting results
of the analyses, are provided as Figures 1 and 2. Figure 1 is applicable to CIDH piles
within the easterly portion of the building. Figure 2 is applicable to CIDH pile within the
westerly portion of the building.
The pile lengths required to support a 200-kip (100-ton) load with the aforementioned pile
diameters within the easterly portion of the proposed building are presented in the
following table:
AXIAL CAPACITY VERSUS DEPTH -EASTERLY PORTION OF PROPOSED BUILDING
I PILE DIAMETER (INCHES} I PILE LENGTH {FEET} I
12 ±47
18 ±39
24 ±35
30 ±32
36 ±31
The pile lengths required to support a 200-kip (100-ton) load with the aforementioned pile
diameters within the westerly portion of the proposed building are presented in the
following table:
AXIAL CAPACITY VERSUS DEPTH -WESTERLY PORTION OF PROPOSED BUILDING
I PILE DIAMETER {INCHES}
12
18
24
30
36
Beach Life Village 1, LLC
APN 203-173-02-00, Carlsbad
File: e\wp12\6900\6942a1 .sgr
I
GeoSolls, Inc.
PILE LENGTH {FEET) I
±41
±33
±29
±26
+25
W.O. 6942-A1-SC
October 23, 201 7
Page 4
0
0 ....
0 100 200
T -T
Beath VUlage Life CIOH Easterly Portion or Building
Total Capacity w/F.S. (tons)
300 400 500 600 r
700
TT '
800
t ' '
g l ___________ : -----' _ --1 _______ 1 -----·---------------
900 1000
-1
--.J_
ft
o Dia=l.5 ft
11 Dia-2 ft.
o Dia~2.s n
o Dia•3 ft
' .
' .
'
'
'
'
' .
.
.
' .
'
'
.
.
.
1
SAND
SAND
SAND
SAND
. ' ' .
. . ' .
,GW '
' ' ' '
. ' . '
' ' . ' . ' . ' . ' ' .
. ' . '
' . . .
' ' . .
' ' ' '
GW . ' . ' . . . .
' ' ' .
. ' ' ' . . . ' . . 1 ' . . . .
' ' • •
. . . 1
W.O. 6942-A1-SC
FIGURE 1
g ... C. c!
C
C
C N
0
~r
~
C ....
C
V) r
~
r
~
100 200
Beach Village Life CIDH Wulerly Portion of Building
Tolal Capacily w/F.S. (tons)
300 400 500
l ~ 1 T '
I
-i -I
r -
I
600
1 I
~ -
700 • r 800 900
l
1000 1100
' -I
I
v Dia-I ft
o Dia=l.5 ft
A Dia-2 ft
o Dia=2.5 ft
SAND
SAND
SAND
,GW ,
GW
---------~----'----o Dia-3 ft -----· ----·-----· ----' _______ ..L ____ _,
W.O. 6942-A1-SC
FIGURE 2
Axial pile capacities of each individual pile within a pile group should be reduced by the
factors provided in the following table to account for group actions.
CENTER-TO-CENTER PILE SPACING AXIAL CAPACITY REDUCTION FACTOR (PILE DIAMETERS)
.2'._3 No Reduction
1.5 50 Percent
Between 1.5 and 3 Use Straight-Line Interpolation
Total lateral foundation capacity can be evaluated based on soil to concrete passive
resistance on grade beams above the piles, assuming grade beam embedment into
recompacted fill soils. For preliminary purposes, lateral pile capacity may be taken as 1 O
percent of the axial pile capacity. Additional lateral pile analyses can be performed once
estimated column, wall, and pile head reactions are provided.
Since some or all of the piles will extend below the water table, GSI does not recommend
"belling" the pile tip below the water table/perched water. In addition, we do not
recommend pile diameters less than 12 inches. GSI should review the foundation plans
and corresponding structural calculations prior to construction.
LIMITATIONS
The conclusions and recommendations presented herein, are professional opinions.
These opinions have been derived in accordance with current standards of practice, and
no warranty, either express or implied, is given. Standards of practice are subject to
change with time. GSI assumes no responsibility or liability for work or testing performed
by others, or their inaction; or work performed when GSI is not requested to be onsite, to
evaluate if our recommendations have been properly implemented. Use of this report
constitutes an agreement and consent by the user to all the limitations outlined above,
notwithstanding any other agreements that may be in place. In addition, this report may
be subject to review by the controlling authorities. Thus, this report brings to completion
our scope of services for this portion of the project.
Beach Life Village 1, LLC
APN 203-173-02-00, Carlsbad
File: e\wp12\6900\6942a1 .sgr GeoSolls, Inc.
W.O. 6942-A1-SC
October 23, 201 7
Page 7
If you have any questions or comments regarding this letter, please do not hesitate to
contact the undersigned.
GeoSoils, Inc.
~tl~ Mel-k!:.11,
Engineering Geologist, CEG 1340 Geotechnical Engineer, GE 2320
4~ Ryan B. Boehmer
Project Geologist
RBB/JPF/DWS/jh
Attachment: Appendix -References
Distribution: (3) Addressee (via US Mail and email)
(1) SUN Structural Engineering, Inc., Attention: Mr. Changhua Sun
(via US Mail and email)
Beach Life Village 1, LLC
APN 203-173-02-00, Carlsbad
File: e\wp12\6900\6942a1 .sgr GeoSoils, Inc.
W.0 . 6942-A1-SC
October 23, 2017
Page 8
APPENDIX
REFERENCES
Ensoft, Inc., 2007, SHAFT v6.0 for Windows; computer program for the study of drilled
shafts under axial loads.
__ , 2007, LPILE Plus V5 .0 for Windows; a computer program for the analysis of piles
and drilled shafts under lateral loads.
GeoSoils, Inc., 2016, Geotechnical response to City of Carlsbad Engineering Department
plan check comments, Beach Village Life 1 Mixed Use, APN 203-173-02-00,
Carlsbad, San Diego County, California, CT 16-03/RP 16-09/CDP16-16, W.O. 6942-
A 1-SC, dated June 20.
__ , 2015, Preliminary geotechnical evaluation, APN 203-173-02-00, Carlsbad,
San Diego County, California, W.O. 6942-A-SC, dated September 11.
Karnak Planning and Design, 2017, Architectural plans for: Mixed use hotel, spa, and
condominiums, 300 Christiansen Way, Carlsbad, CA 92008, Sheets A-101 , A-102,
A-103, A-201 , A-202, A-301 , and A-302, Scale: 1/a-inch = 1 foot, Project No.:
20150806 _ a, dated September 18.
Naval Facilities Engineering Command, 1986, Soil mechanics design manual 7.01 ,
Change 1 September: U.S. Navy.
__ , 1986, Foundations and earth structures, design manual 7.02, Change 1
September: U.S. Navy.
Spear and Associates, Inc., 2017, Preliminary grading plan for: Beach Village Life,
Christiansen Way, Sheet 2 of 2, 10-scale, Drawing No. C-2, dated April 21.
State of California Department of Transportation, 2008, Foundation manual, dated
November.
GeoSoils, Inc.