HomeMy WebLinkAboutSUN DISK VILLAGE FINAL SUBDIVISION - 15 91A - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTi Iv
SUBSURFACE -;SOILS INVESTIGATION
-,1-FOR---
SUNDISK SUBDIVISION FIRST FILING
FORT COLLINSj,COLORADO
5.
FOUNDATION & SOILS ENGINEERING, INC.
320 N. Cleveland
Loveland, Colorado 80537
F O U N D A T I O N R E C O M M E N D A T I O N S
The selection of the foundation type for a given situation and
structure is governed by two basic considerations. First, the
foundation must be designed so as to be safe against shear failure
in the underlying soils; and second, differential settlement or
other vertical movement of the foundation must be controlled at a
reasonable level.
Two basic controls are available to us in selecting the foundation
type and allowable loads. These are the standard penetration test
and consolidation swell testing. The ultimate bearing capacity of
the foundation soil or rock depends upon the size and shape of the
foundation element, the depth below the surface, and the physical
characteristics of the supporting soil.
_n o n s we l.l.i.n g—sands-and--c-l-a ys—a-r-e=encountered—a-t—f o ot-kng
elevations, we recommend the use of continuous balanced spread
footings and/or grade beams proportioned using an allowable bearing
value of 1,500 PSF (1/2 live load + dead load). To counteract
swelling pressures in the upper clays, we recommend a minimum of
500 PSF be maintained on all footings.
The foundation walls and other structural elements should be
designed by a qualified structural engineer for the appropriate
loading conditions. All footings should be placed below any topsoil
L
or fill unless the fill has specifically been placed and compacted
-- for support of footings. All exterior footings should be placed
' below frost depth to provide adequate cover for frost protection,
L�
thirty inches in this area.
If isolated areas of loose or soft soil are exposed during final
I.:.; footing excavation, these soil areas should be removed down to
undisturbed, acceptable soils prior to placement of the footings.
Footings can then be placed directly upon the acceptable soil, or
the excavation can be backfilled up to the desired footing bearing
L_.
elevation. All fill should be placed and compacted in accordance
i
_ with the recommendations contained in the Section "Site Grading and
Utilities", and Appendix A of this report.
Basement construction is feasible at this site. However, due to the
depth of groundwater, where basement or other habitable lower
levels are to be located within three (3) feet of the existing
groundwater_e.levat.ion.,__we._recommend—that—such --lower—levels—be
provided with a perimeter drainage system. The drainage system
should contain a four (4) inch diameter perforated drain pipe
encased in a minimum of twelve (12) inches of clean, 3/4 inch
gravel graded in accordance with ASTM C 33-78. The drain pipe
should extend around the entire inside perimeter of all lower
levels. The invert shall be placed a minimum of four (4) inches
below the bottom of the footing and/or grade beam to facilitate
moisture transfer to the system. The gravel should be placed a
minimum of eight (8) inches over the pipe the full width of the
N
e
trench.
The above drain system should be run at 1/8 inches per foot minimum
i
to either a sump constructed in the basement or "daylighted" well
beyond the foundation system. The sump should be a minimum of
eighteen (18) inches diameter by three (3) feet deep and surrounded
by at least six (6) inches of clean gravel similar to that provided
around the drain. The sump should'be provided with a pump designed
L
to discharge all flow to the sump a minimum of five (5) feet beyond
the backfill zone.
The following recommendations should be followed in the design of
the foundation system:
1. All footings and<or grade beams should be below frost depth
(30") .
2..—Foundation—wa-lls--should--be---rein-forced- wi-th—rebar—to—span—an
- unsupported length of ten (10), feet. Rebar should be run
continuously around corners and be properly spliced.
3. Bearing walls should be omitted in the basement. Partitions
should be hung from the floor joists and beams supported by
adjustable steel columns.
4. It is our opinion that a basement is feasible for this site,
however, all footings placed within three (3) feet of the
a
e
existing groundwater elevations should be protected by a
perimeter drain as detailed above.
5. All footings and/or grade beams should bear on the same type
of soil.
6. We recommend the performance of an excavation inspection for
each lot to make a final determination on foundation types.
F L 0 0 R S L A B S
Soils at proposed foundation elevations are stable at their natural
moist condition, however, should their moisture content increase,
heaving will result, particularly in the upper clays. This phenom-
enon can result in cracking of the garage slabs or other shallow
slabs -on -grade. In our opinion, the only positive solution is to
use a structural floor _sy_stem_which_allo.ws_the_f-loor—to-be i-sola-ted
from the underlying soils. This is suite exoPnsivP AnA in
opinion, is not warranted provided the owner is willing to accept
'the risk of damage. With the above in mind, construction of the
structure, as much as possible, should be done to accommodate
movement of the slabs without damage. We recommend the following:
1. Slabs should be constructed "free floating", isolated from all
bearing members by use of 1/2 inch isolation material.
10
2. Provide a two (2) inch minimum void space above or below
Linterior nonload bearing partitions where floors consist of
slabs -on -grade.
L
L3. Eliminate underslab plumbing where feasible. Where such
plumbing is unavoidable, it should be pressure tested during
construction to minimize leaks which would result in wetting
(, of the subsoils.
4. Separate slabs -on -grade into panels by use of control joints.
We recommend joints be placed no more than fifteen feet on
center.
5. Garage slabs should be underlain with a four inch layer of
clean, crushed rock or gravel to help distribute floor loads.
Deeper slabs placed within three (3) feet of the groundwater
table should be underlain by a minimum of eight (8) inches of
-,—cr.ushed—rock_-or -gravel-,--to provide --a --cap-il-la-ry—brea-k
should moisture penetrate under the slab.
6. Due to the proximity of the -groundwater levels, any lower
levels (i.e. basements) located within three (3) feet of the
groundwater levels, should be provided with a perimeter drain
as described above.
11
7. All exterior slabs should be constructed using a more durable
concrete containing Type II cement with higher air contents
and lower water cement ratios.
S I T E G R A D I N G A N D U T I L I T I E S
Specifications pertaining to site grading are included below and
in Appendix A of this report. It is recommended .that the upper
twelve (12) inches of topsoil below building, filled and paved
areas be stripped and stockpiled for reuse in planted areas. The
upper six (6) inches of the subgrade below building, paved and
filled areas should be scarified and recompacted two percent (2%)
wet of optimum moisture to at least ninety-five percent (95%) of
Standard Proctor Density ASTM D-698-78 (See Appendix A of this
report).
Id -consist _of_the_onsi.te-sandy so-il—o.r—i-mpo-r-ted
' materials approved by the geotechnical engineer. Fill should be
placed in uniform six to eight (6-8) inch lifts and mechanically
compacted two percent (2%) wet of optimum moisture to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D-698-
78.
At this time, the extent of.the existing underground utilities is
not known. Groundwater levels are at such depths that it may
interfere with installation of additional underground utilities.
12
Dewatering of trenches should be anticipated in deeper excavations.
P A V E M E N T R E C O M M E N D A T I O N
Flexible Pavements
It is our opinion that flexible pavements are suitable for the
proposed roadways at the site. The flexible pavement should consist
of asphaltic concrete underlain by crushed aggregate base course
or asphaltic concrete underlain by plant mix bituminous base
course. Using the City of Fort Collins "Design Criteria and
Standards For Streets", a serviceability index of 2.0, a regional
factor of 0.5, an "R"-Value of 13, a twenty (20) year design life,
an 18k ESAL of 36,500, we recommend the following pavement
thicknesses:
Asphaltic Concrete
311
Class__5-Aggrega.te-Base--Cour--se ---6"
Total 911
Asphaltic Concrete
Plant Mix Bituminous Base
Total
2"
2"
411
The subgrade below the proposed asphalt pavement should be prepared
in accordance with the recommendations discussed in Appendix A of
. this report. Finished subgrade below all roadways shall be placed
at least three (3) feet above the existing groundwater table.
Roadway subgrade should not be founded upon fill unless placed and
compacted in accordance with our recommendations. Upon proper
preparation of the subgrade, base course shall be placed and
compacted near optimum moisture to at least ninety-five (95)
percent of Standard Proctor density as determined according to ASTM
D698-78.
It is recommended that the asphaltic concrete be placed in maximum
of two to three (2-3) inch lifts at the proper temperature and
compaction for the type of asphalt used.
All asphalt shall meet City of Fort Collins standards and specific-
ations and shall be placed in accordance with these requirements.
The crushed aggregate shall meet CDOH specifications and have a
minimum "R"-Value of 78. Plant mix bituminous base shall have a
minimum "Rt"_Value of 90, _while the_asphaltic_concre-te—sha-l-l—ha-ve
a minimum "Rt"-Value of 95. These values should be verified by
laboratory tests. Field density tests should be taken in both the
base course and asphalt under the. direction of the geotechnical
engineer.
Rigid Pavements
As an alternate, five (5) inch unreinforced concrete pavement may
be used for all onsite roadways. This section is based upon the
above design criteria, a modulus of subgrade reaction of 10o psi,
14
an "R"-Value of 13, a 20 yea.r design life, and a concrete with a
modulus of rupture of 550 psi.
Concrete pavement should be placed directly on the subgrade that
has been uniformly and properly prepared in accordance with the
above recommendations. All concrete used in the paving shall met
ASTM specifications, with all aggregate conforming to ASTM C-33
specifications. The concrete should be designed with a minimum
modulus of rupture of 550 pounds per square inch in twenty-eight
(28) days. It is recommended that laboratory mix designs be done
to determine the proper proportions of aggregates, cement, and
water necessary to meet these requirements. It is essential that
the concrete have a low water -cement ratio, an adequate cement
factor, and sufficient quantities of entrained air. Joints should
be carefully designed and constructed in accordance with the City
of Fort Collins "Design Criteria and Standards for Streets" to
ensure good performance of the pavement. It is recommended that all
concrete pavement be .placed. i.n_acco.rdance_w.i-th-Ci-ty-o-f—For-t C-oll--i-ns
specifications. Should paving be done during cold weather,
acceptable cold weather procedures as outlined in the City
specifications should be utilized. The concrete pavement should be
properly cured and protected in accordance with the above specific-
ations. Concrete injured by frost should be removed and replaced.
It is recommended that the pavement not be opened to traffic until
a flexural strength of 'four hundred (400) pounds per square inch
is obtained or a minimum of fourteen (14) days after the concrete
has been placed.
15
L A N D S C A P I N G A N D D R A I N A G E
Every precaution should be taken to prevent wetting of the subsoils
and percolation of water down along the foundation elements.
Finished grade should be sloped away from the structure on all
sides to give positive drainage. A minimum of twelve (12) inches
L fall in the first ten (10) feet is recommended. Sprink-ling systems
should not be installed within 'ten (10) feet of the structure.
Downspouts are recommended and should be arranged to carry drainage
L..
from the roof at least five (5) feet beyond the foundation walls.
Backfill around the outside perimeter of the structure, except as
noted above, should be compacted at optimum moisture, or above, to
at least ninety percent (90%) of Standard Proctor Density as
determined by ASTM Standard Test D-698. A suggested specification
for placement of backfills is included as Appendix A.
The_backfill placed immediately adjacent--to-the - founder-ti-on-wa-l-l-s, if not properly compacted, can be expected to settle with resulting
damage to sidewalks, driveway aprons, and other exterior slabs -on -
grade. To avoid settlement and disfigurement of the slabs in the
event that the backfill is not properly compacted, we recommend
that concrete slabs which must span the backfill be supported by
the foundation walls. This is conventionally done by use of a brick
ledge or haunch. The slab should be reinforced as necessary for the
span involved.
16
FOUNDATION I
ENGINEERING
Consulting
Engineers, Ltd
M1r4 n it Y i
4 Y
May 13, 1991
Commission No. 1119-08-01-01
Giuliano & Father
1708 E. Lincoln
Fort Collins, CO 80524
Dear Mr. Giuliano,
The enclosed report presents the results of a subsurface soils
investigation for Sundisk Subdivision. First Filing, a proposed
subdivision of Fort Collins, Colorado:``'
In summary, low to nonswelling' soils were encountered in the
borings. Care should be taken during and after construction to
minimize the potential for foundat.ion..and floor movement.
The attached geotechnical report`> presents the results of our
investigation and recommendations--',concerning..design and construc-
tion of the foundation system and support of floor slabs.
We appreciate the opportunity, to,'be -of service to you on this
project. If you have any questions, please call.
R e s p f u �� OF Coto
a
rn :.KEYIN WHtff PATIERSON' w
Ke in Patterson, P.E. ' = nuMeER `L =
FOUNDA ON & SOILS ENGINEEg ,IN001 ;`�
KWP/kmp `�,�FOpo.,,,,.,•,,.;.•OP ``;
rr,urnnn�„ r�
320 North Cleveland Avenue 0 Loveland, Colorado 80537 0 (303) 663-0138
G E N E R A L I N F O R M A T I O N
The data presented herein were collected to help develop designs
and cost estimates for this project. Professional judgments on
design alternatives and criteria are presented in this report.
These are based on evaluation of technical information gathered,
Lpartly o❑ our understanding of the characteristics of the structure
proposed, and partly on our experience with subsurface conditions
in the area. We do not guarantee the performance of the project in
any respect, only that our engineering work and judgments rendered
meet the standard of care of our profession.
The test holes drilled were spaced to obtain a reasonably accurate
picture of subsurface conditions for design purposes. These
variations are sometimes sufficient to necessitate modifications
in design.
_W e—recommend __that—c o ns t r uc-t i o n—be—con-t i-nu o us l y—ob P e r-v ed—by—a
qualified soils technician trained and experienced in the field to
take advantage of all opportunities to recognize some undetected
condition which might affect the performance of the foundation
systems.
17
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Date May 12, 1991
Commission No. 1119-08-01-01
[�ITGFi—
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BORING. LOCATION MAP
FIG. 5
Date May 12, 1991
Commission No. 1119-08-01-01
LEGEND
OF SOILS SYMBOLS
FILL
°00o0
)o
c4
�QO
GRAVELS
SANDS
SILTS
\ON
o o\
GRAVELS, SAND &
�. cNR
SILT COMBINATIONS
SANDY GRAVELS,
0j
.o•
GRAVELLY SANDS
SILTY SANDS,
'\
SANDY SILTS
N,
SANDY CLAYS,
CLAYEY SANDS
SAND, SILT & CLAY
COMBINATIONS
CLAYS
WEATHERED BEDROCK
SILTSTONE
CLAYSTONE
r--
SANDSTONE
LIMESTONE
GRANITE
SHELBY TUBE SAMPLE
STANDARD PENETRATION
TEST SAMPLER*
„WATER TABLE AT
TIME OF DRILLING
HOLE CAVED
* 20/12 indicates that 20 blows
of a 140 lb. hammer falling
30" was required to penetrate
12"
FOUNDATION ENGINEERING
FIG. 6
c�
Date May .12, 1991
Commission No.1119-08--01,01
BORING. LOGS
ME
W
�1f
..
1.
.
+ u I
FOUNDATION ENGINEERING
FIG. 7
Date May 12, 1991
Commission No. 1119-08-01-01
BORING. LOGS
9'-Omil11
I �.►
_
�.
�ILI
M
- -
--
I
/10
it
;_ I FOUNDATION ENGINEERING FIG. 8
1
FOUNDATION ENGINEERING
SUMMARY OF LABORATORY TEST RESULTS
Sample Location
Natural
Moisture
Dry Deaeit
DryNatDen
Gradation
Percent
Passing
Atterberg Limits
Unconfined
Compressive
Standard
Penetration
Soil or
,
;
Role
Depth
Content (Z)
CPCP1
Gravel
Sand
No. 200
Liquid
Plasticity
Strength
Blovs/Ft.
Bedrock Type
(Feet)
(;) I
(x)
Sieve
Limit
Inaex
(PSF)
1
3-4
20.7
104.6
9,000+
Sandy clay
1
4-5
7.2
i
28/12
Clayey sand
1
8-9
26.0
i
4/12
Sandy silt
1
15-16
17.5
5/12
Silty clay
2
3-4
10.0
14/12
Sandy clay
2
7-8
14.4
117.0
Sandy clay
2
8-9
23.0
7/12
Silty sand
3
3-4
10.7
108.4
Clayey sand
3
4-5
6.8
16/12
Sandy clay
3
7-8
14.3
7/12
Silty sand
4
2-3
15.8
105.3
Sandy clay
4
3-4
12.5
12/12
Sandy clay
0
TABLE OF CONTENTS
Letter of Transmittal
Scope
Site Description
Field Investigation
Laboratory Testing Procedures
Subsurface Conditions
Foundation Recommendations
Floor Slabs
Site Grading and Utilities
Pavement Recommendation
Landscaping and Drainage
General Information
Consolidation Swell Tests
Test Boring Location Map
Legend of Soil Symbols
Boring Logs
Summary of Test Results
"R"-Value
Suggested Specifications for Placement
of Compacted Earth Fills and/or Backfills
i
1
2
2
4
5
7
10
12
13
16
17
Figures 1 - 4
Figure 5
Figure 6
Figures 7 & 8
Figures 9 & 10
Figure 11
Appendix A
ii
FOUNDATION ENGINEERING
i
l SUMMARY OF LABORATORY TEST RESULTS
Sample Locstion
Nacaral
1lois[ure
Content (Z)
Natu;al
Orp IleaslC
CPCF1
Gradation
Percent
No. 200
Sieve
Atterberg LimitsOnconfined
Compress mpressive
Strength
(PSF)
Standard
Peaetration
Blows/Ft.
soil or
Bedrock type
Hole
Depth
(Feet)
Gravel
(Z).
I
Sand
(Z)
Liquid
t.imit
Plasticity
Inge:
4
5
8-9
4-5'
17.0
12.2
i
5/12
11/12
Silty sand
Sandy clay
5
5
7-8
8-9
13.7
13.8
103.0
23 j
I
42
8/12
Clayey sand
Sandy clay
I
I
o w
In
m
N
fA
O `C
r
z N
O.
O
r
O
r
No Text
L�
APPENDIX A
Suggested Specifications for Placement of Compacted Earth Fills
and/or Backfills.
G E N E R A L
iA soils engineer shall be the owner's representative to supervise
and control all compacted fill and/or compacted backfill on the
project. The soils engineer shall approve all earth materials prior
to their use, the methods of placing, and the degree of compaction
obtained. A certificate of approval fromthe soils engineer will
be required prior to the owner's final acceptance of the filling
operations.
M A T E R I A L S
The soils used for compacted fill beneath interior floor slabs and
backfill around foundation walls shall be impervious and non -
swelling for the depth shown on the drawings. No material shall be
placed in the fill having a maximum dimension of six (6) inches or
greater. All materials used in either compacted fill or compacted
backfill shall be subject to the approval of the soils engineer.
P R
E P A R
A T
I O N O
F S
U B G R A
D E
All
topsoil
and
vegetation
shall
be removed
to a depth satisfactory
to the soils engineer before beginning preparation of the subgrade.
The subgrade surface of the area to be filled shall be scarified
to a minimum depth of six (6) inches, moistened as necessary, and
compacted in a manner specified below for the subsequent layers of
fill. Fill shall not be placed on frozen or muddy ground.
1
P L A C I N G F I L L
No sod, brush, frozen material or other deleterious or unsuitable
material shall be placed in the fill. Distribution of material in
the fill shall be such as to preclude the formation of lenses of
material differing from the surrounding material. The materials
shall be delivered to and spread on the fill surface in such a
IL' .
manner as will result in a uniformly compacted fill. Prior to
L compacting, each layer shall have a maximum thickness of eight (8)
inches; and its upper surface shall be approximately horizontal.
M O I S T U R E C 0 N T R 0 L
The fill material in each layer, while being compacted, shall as
nearly as practical contain the amount of moisture required for
optimum compaction; and the moisture shall be uniform throughout
the fill. The contractor may be required to add necessary moisture
to the backfill material in the excavation if, in the opinion of
the soils engineer, it is not possible to obtain uniform moisture
contact by adding water on the fill surface. If, in the opinion of
the soils engineer, the material proposed for use in the compacted
is too wet to permit adequate compaction, it shall be dried in an
acceptable manner prior to placement and compaction.
C O M P A C T I O N
When an acceptable, uniform moisture content is obtained, each
layer shall be compacted by a method acceptable to the soils
engineer and as specified in the.for.egoing report as determined by
I
the Standard Proctor Test (ASTM D698). Compaction shall be
performed by rolling with approved tamping rollers, pneumatic -tired
rollers, three -wheel power rollers, or other approved equipment
`a
well suited to the soil being compacted. If a sheepsfoot roller is
used, it shall be provided with cleaner bars so attached as to
Lprevent the accumulation of material between the tamper feet. The
roller should be so designed that the effective weight can be
increased.
M O I S T U R E- D E N S I T Y D E T E R M I N A I 0 N
I� Samples of representative fill materials to be placed shall be
furnished by they contractor to the soils engineer for determination
of maximum density and optimum moisture for these materials. Tests
for this determination will be made using methods conforming to
requirements of ASTM D698. Copies of the results of these tests
will be furnished to the contractor. These test results shall be
the basis of control for compaction effort.
D E
N S I T
Y
T E S T S
The
density
and
moisture content of each layer of compacted fill
I_ will be determined by the soils engineer in accordance with ASTM
D1556 or D2167. Any material found to not comply with the_m.in.imum
specified density shall be recompacted until the required density
is obtained. The results of all density tests will befurnishedto
both the owner and the contractor,by the soils engineer.
M
S C 0 P E
The following report presents the results of our subsurface soils
investigation on the proposed Sundisk Subdivision First Filing,
situate in the Southwest Half of Section 26, Township 7 North,
Range 69 West, of the 6th Prime Meridian, Larimer County, Colorado.
This investigation was performed for Giuliano & Father at the
request of Mr. John Giuliano.
We understand the site is to be developed into single family resi-
dences. Construction is to be typical wood frame type and brick
veneer and as such, should generate only light loading, on the
order of 1,000 to 2,000 PLF. Concentrated loads, if any, should not
eed 15-to 20-K-IPS- -
The purpose of this investigation is to identify subsurface condi-
tions and to obtain test data to properly design and construct the
foundation system, floor slabs, and roadway pavements. The
conclusions and recommendations presented in this report are based
upon the aquired field and laboratory data and previous experience
with similar soils in the area.
I7i
S I T E D E S C R I P T I O N
The site is located north of Horsetooth Road on the east side of
Windmill Drive in Fort collins, Colorado. The proposed 25 lot
W subdivision is bounded on the north, east and south by developed
properties. Some development of the property has taken place at the
site as noted by the presence of manholes and a detention pond to
the northwest. An irrigation 'or drainage ditch is located along the
north boundary. The parcel slopes gently towards the north and
northeast and appears to have had some degree of overlot grading
done in the past. Vegetation consists of grasses and weeds.
F I E L D I N V E S T I G A T I O N
The field investigation consisted of five (5) borings at selected
locations on,the site. Distances between borings are as indicated
he—a.t.tached—test—bo.r-ing—l-oca-ti-on--map-,---F-i-gu-r-e--5. The—bo-r-i-ngs
were advanced using a four (4) inch diameter continuous flight
power auger. All borings were continued to depths considered
sufficient for the purposes of this -report as set forth in the
scope.
Complete logs of the boring operation are shown on the attached
figures and include visual classifications of each soil, location
of soil changes, standard penetration test results, and water table
measurement at the time of this investigation.
01
I
iThe borings were located out by Foundation & Soils Engineering Inc.
Distances from the referenced features to the boring locations as
indicated on the attached diagram are approximate and were made by
pacing. Angles for locating the borings were estimated. Elevations
I� of the borings, are approximate and were obtained by the drill
crew, using a hand level and rod. The elevations were referenced
to an assumed elevation of one hundred (100) feet using the north
j bonnet bolt at the fire hydrant located at the south-central end
of the project. The approximate location of the benchmark is. shown
on the attached boring location map, Figure 5. The locations and
elevations of the borings should be considered only to the degree
- implied by the methods used to make those measurements.
As the boring operation advanced, an index of soils relative
density and consistency was obtained by use of the standard
penetration test, ASTM Standard Test D-1586. The penetration test
result listed on the log is the number of blows required to drive
inch-sp-l--i-t-spoon-sampler-one-(-1)—foot--i-nto-und-i s-to-r-bed
soil by a one hundred and forty (140) pound hammer dropped thirty
(30) inches.
Specific conditions at each boring location are indicated on each
individual boring log. The stratification boundaries shown on the
boring logs represent the approximate location of changes in soil
and rock types. In situ, the transition between the different
strata can and often is gradual.
I
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Undisturbed samples for use in the laboratory were taken in three
(3) inch O.D. thin wall samplers (Shelby), pushed hydraulically
into the soil in accordance with ASTM D-1587. In this sampling
procedure, a seamless steel tube with a beveled cutting edge is
pushed hydraulically into the ground to obtain a relatively
undisturbed sample of cohesive or moderately cohesive soil. All
samples were sealed in the field and preserved at natural moisture
content until time.of test.
L
L A B O R A T O R Y T E S T I N G P R O C E D U R E S
The recovered samples were tested in the laboratory to measure
their dry unit weights and natural water contents. A calibrated
hand penetrometer was used to estimate the approximate unconfined
strength of the samples. The calibrated hand penetrometer has been
correlated with unconfined compression tests and provides a better
estimate_o_f_so_i.l_cons.i.s.tency_-than vi.sual_exami.na_tion_alo.ne_.
Atterberg limits tests and one-dimensional swell tests were
performed on selected samples to evaluate the plasticity and
expansive nature of the naturalcohesive soils or rock. In the
swell test, a trimmed specimen is placed in a one-dimensional
confinement ring and a vertical load is applied. After seating, the
sample is inundated with water and the height change of the
specimen is recorded. The confining load is then incrementally
increased until the specimen is compressed to its original volume.
Results of those tests are presented in the end of this report.
The laboratory testing program was undertaken to measure critical
shear and consolidation -swelling characteristics of the soil.
Additional testing included tests necessary to verify visual
classification and moisture content of soils from borings and "R"-
Value tests to determine the soils support characteristics under
roadways.
S U B S U R F A C E C O N D I T I O N S
The subsurface conditions appear to be relatively consistent
throughout the site. Minor amounts of clayey fills were found to
overlie a sandy clay which overlies sand with stratified clays and
silts to the depths explored.
Fill materials were found_i.n__the_upper—one__(_1.)—foot--of Pest —Holes
1, 3 and 4. The fills consist of primarily sandy clays. The extent
of the fills appears to be scattered. Isolated areas could contain
amounts of questionable fill that could effect the performance of
structures at the site. Therefore, we recommend that no foundations
be placed on the existing fills at the site.
Clays containing moderate to high percentages of sand underlie the
fills where encountered and the surface elsewhere. Laboratory and
field tests indicate that these deposits exhibit moderate bearing
5
capacities with potentials for low to moderate swelling when
Lwetted. These deposits were encountered to depths ranging from two
to four (2-4) feet at the site with no distinct contact observed
L�
with the underlying sands.
Primarily sands are found to underlie the clay. The upper reaches
Lappear to contain a higher percentage of clay, however, grade to
a course sand with depth. Lenses of clay and silt were found
L.�
interbeded in the sands to the depths explored. Thin gravel layers
�. were occasionally encountered in the borings. Laboratory and field
tests indicate that these deposits exhibit moderate bearing
capacities, however, shear strengths decrease at or above the
groundwater table.
Ground water observations were made as the borings were being
advanced and immediately after completion of the drilling opera-
tion. At the time of our field investigation, ground water was
it
encountered_at_appr_ox.imate 1y 7=8__fee.t_a.t—Test_Ho.1e 4_,_to—ten—(_1.0.)
feet in Test Hole 1. Due to the high groundwater encountered at
this site, it is our opinion that the proposed residences, if
constructed over a basement, will require perimeter drainage
systems.
2