HomeMy WebLinkAboutSubsoil Study for Foundation Design 12.14.16H-P~l<UMAR
Geotechnical Engineering I Engineering Geology
Materials Testing I Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED SHOP BUILDING
566 LATHAM RANCH ROAD
GARFIELD COUNTY, COLORADO
PROJECT NO. 16-7-628
DECEMBER 14, 2016
PREPARED FOR:
JEFF BAILEY
P.O. BOX 211
NEW CASTLE, CO 81647
(bgdandmore@comcast.net)
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY ....................................................................................... -I -
PROPOSED CONSTRUCTION ................................................................................................ -I -
SITE CONDITIONS ................................................................................................................... - 1 -
FIELD EXPLORATION ............................................................................................................ - 2 -
. SUBSURFACE CONDITIONS ................................................................................................. -2 -
FOUNDATION BEARING CONDITIONS .............................................................................. -3 :.
DESIGN RECOMMENDATIONS ............................................................................................ - 3 -
FOUNDATIONS .................................................................................................................... -3 -
FLOOR SLABS ...................................................................................................................... -4 -
SURFACE DRAINAGE ......................................................................................................... - 5 -
LIMITATIONS ........................................................................................................................... -5 -
FIGURE I -LOCATION OF EXPLORATORY BORING
FIGURE 2 -LOG OF EXPLORATORY BORING
FIGURE 3 -SWELL-CONSOLlDA TION TEST RESULTS
TABLE 1-SUMMARY OF LABORATORY TEST RES UL TS
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H-P~ KUMAR Project No. 16-7-628
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed shop building to be located at
566 Latham Ranch Road, Garfield County, Colorado. The project site is shown on Figure I.
The purpose of the study was to develop recommendations for the foundation design. The study
was conducted in accordance with our agreement for geotechnical engineering services to Jeff
Bailey dated December 5, 2016.
A field exploration program consisting of an exploratory boring was conducted to obtain
infonnation on the subsurface conditions. Samples of the subsoils and bedrock obtained during
the field exploration were tested in the laboratory to determine their classification,
compressibility or swell and other engineering characteristics. The results of the field
exploration and laboratory testing were analyzed to develop recommendations for foundation
types, depths and allowable pressures for the proposed building foundation. This report
summarizes the data obtained during this study and presents our conclusions, design
recommendations and other geotechnical engineering considerations based on the proposed
construction and the subsurface conditions encountered.
PROPOSED CONSTRUCTION
The proposed shop building will be a one story 40 feet by 40 feet structure. Ground floor will be
slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths
between about 3 to 4 feet. We assume relatively light foundation loadings, typical of the
proposed type of construction.
If building loadings, location or grading plans change significantly from those described above,
we should be notified to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The building area had a gravel drive running through it with a fence across the southern portion
at the time of field exploration. There was a one story residence over a walkout basement to the
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east of the build area. The terrain was nearly flat sloping down to the south at about 2% grade.
Vegetation consisted of weeds and partially stripped of vegetation and topsoil with a pile of
weeds in the middle of the build area.
FIELD EXPLORATION
The field exploration for the project was conducted on December 8, 2016. One exploratory
boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The
boring was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted
CME-45B drill rig. The boring was logged by a representative of H-P/Kumar.
Samples of the subsurface materials were taken with a 2 inch 1.0. spoon sampler. The sampler
was driven into the subsoils and bedrock at various depths with blows from a 140 pound hammer
falling 30 inches . This test is similar to the standard penetration test described by ASTM
Method D-1586. The penetration resistance values are an indication of the relative density or
consistency of the subsoils and hardness of the bedrock. Depths at which the samples were taken
and the penetration resistance values are shown on the Log of Exploratory Boring, Figure 2. The
samples were returned to our laboratory for review by the project engineer and testing.
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils consist of about 8 feet of stiff to medium stiff with depth, slightly sandy to sandy, silty
clay overlying about 3 1/i feet of highly weathered sandy claystone bedrock underlain by very
hard sandstone/siltstone bedrock. The bedrock is the Wasatch Formation. Drilling in the very
hard bedrock with auger equipment was difficult.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and density, and unconfined compressive strength analyses. Results of swell-
consolidation testing performed on a relatively undisturbed drive sample of the upper clay soil,
H-P ~KUMAR Project No. 16-7-628
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presented on Figure 4, indicate low to moderate compressibility under conditions of loading and
wetting. The laboratory testing is summarized in Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were moist to
very moist with depth. The very hard bedrock was slightly moist.
FOUNDATION BEARING CONDITIONS
The natural clay soils have low bearing capacity and low to moderate compressibility mainly
under loading. Lightly loaded spread footings placed on the upper natural clay soils can be used
with a risk of settlement. The subsoils are moist and become highly moist with depth. Footings
should be placed on the upper, lower moisture content stiff soils.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, we recommend the building be founded with spread footings bearing
on the natural soils at a maximum depth of about 3 feet below existing ground surface.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
l) Footings placed on the undisturbed natural, stiff clay soils should be designed for
an allowable bearing pressure of 1,500 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about 1 inch to 1 1i~ inches.
2) The footings should have a minimum width of 18 inches for continuous walls and
2 feet for isolated pads.
3) Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement
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of foundations at least 36 inches below exterior grade is typically used in this
area.
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 12 feet.
Foundation walls acting as retaining structures (if any) should also be designed to
resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at
least 55 pcf.
5) All existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the stiff natural soils. The exposed
soils in footing area should then be moisture adjusted to near optimum and
compacted. The bearing soils should be protected against frost and concrete
should not be placed on frozen soils.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade
construction. To reduce the effects of some differential movement, floor slabs should be
separated from all bearing walls and columns with expansion joints which allow unrestrained
vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. The requirements for joint spacing and slab reinforcement should be established by the
designer based on experience and the intended slab use. A minimum 4 inch layer of relatively
well graded sand and gravel such as ~·4-inch road base should be placed beneath slabs for support.
This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4
sieve and less than 12~-'0 passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site soils devoid of vegetation and topsoil or imported granular soil such as road base.
H-P ~--KUMAR Project No 16-7-628
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SURF ACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the building has been completed:
I) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 3
inches in the first I 0 feet in paved areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least 5
feet from foundation walls.
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area at this time. We make no warranty either express or implied.
The conclusions and recommendations submitted in this report are based upon the data obtained
from the exploratory boring drilled at the location indicated on Figure I, the proposed type of
construction and our experience in the area. Our services do not include detennining the
presence, prevention or possibility of mold or other biological contaminants (MOBC) developing
in the future. If the client is concerned about MOBC, then a professional in this special field of
practice should be consulted. Our findings include interpolation and extrapolation of the
subsurface conditions identified at the exploratory boring and variations in the subsurface
conditions may not become evident until excavation is performed. If conditions encountered
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during construction appear different from those described in this report, we should be notified so
that re-evaluation of the recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
Respectfully Submitted,
H-P~KUMAR
~~
Shane M. Mello, Staff Engineer
Reviewed by:
SMM/ksw
cc:
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H-P%-KUMAR Project No . 16-7-628
-------60 0 60 120
APPROXIMATE SCALE-FEET
H-P~KUMAR LOCATION OF EXPLORATORY BORING Fig. 1
BORING 1
0
8/12
WC=18.2
DD=IOB
5 6/12
WC=22.3
00=117
-200=93
UC=9SO
10
12/12 w w
"'-I
:i: .... Q..
w
0
15 50/1
.:·· , . . . ,.,
\ :--;
20 .. 50/0 . .
25
H-P~KUMAR
LEGEND
1/1 CLAY (CL); SILTY, SLIGHTLY SANDY TO SANDY, MEDIUM STIFF Lj TO STIFF, MOIST TO VERY MOIST, BROWN.
[71 HIGHLY WEATHERED CLAVSTONE BEDROCK; SANDY, SILTY, STIFF, k_j MOIST, PURPLISH BROWN. WASATCH FORMATION.
[J SANDSTONE/SILTSTONE BEDROCK; VERY HARD, SLIGHTLY MOIST, '
DARK RED, WASATCH FORMATION.
' p DRIVE SAl.IPLE, 2-INCH t.D. CALIFORNIA UHER SAMPLE.
8/12 DRl1VEO SPAOMUPLED BHLOMWMECROUrHTAw' NINDl3CATIENS TEHSATW8 BLORWEOSUloRrED A 4 - N A G 0 CH ERE
TO DRIVE THE SAMPLER 12 INCHES.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON DECEMBER 8, 2016
WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
2. THE LOCATION or THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE
SITE PLAN PROVIDED.
3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT
MEASURED AND THE LOG OF THE EXPLORATORY BORING IS
PLOTIED TO DEPTH •
4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED
ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN
MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT
THE TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (X) (ASTM 0 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
-200 == PrRCENTAGE PASSING NO. 200 SIEVE (ASH.I D 11-40).
UC = UNCONFINED COMPRESSIVE STRENGTH (psi) (ASTM D 2166).
LOG OF EXPLORATORY BORING Fig. 2
0 r-----
z
0
~
-2
§! -3
0
Ill z
0
u -4
,I J.0
H-P~KUMAR
SAMPLE OF: Sandy Clay
FROM: Boring 1 0 2.5'
WC=18.2",DD=108 pcf
APPU£0 PRESSURE -KSF 10
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
SWELL-CONSOLIDATION TEST RESULT
100
Fig. 3
H -P ~KUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 16-7-628
SAMPLE LOCATION NATURAL NATURAL GRADATION A TTERBERG LIMITS UNCONFINED PERCENT
MOISTURE DRY GRAVEL SAND PASSING LIQUID PLASTIC COMPRESSIVE
BORING DEPTH CONTENT DENSITY N0.200 LIMIT INDEX STRENGTH SOIL TYPE
(%) ("la)
SIEVE
(ft) (%) (ocf\ ("/•) (%) fPSF}
1 2Y2 18.2 108 Sandy Clay
5 22.3 117 93 950 Silty Clay