HomeMy WebLinkAboutReports - Soils - 04/11/1972 TF.BLE OF CONTENTS
Table of Contents i
Letter of Transmittal . . . . . . . . . . . . . . . .. . . . . . . . . . . ii
Report . . . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. 1--7
Test Boring Location Plan 8
Key to Borings . . . . . . . . • . . . . . . . . . . . . . . . . . • . . . . . . . 9
Log of Borings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10--13
Consolidation-Swell Test Data 14-17
Summary of Test Results 18--22
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-24
_i_
Empire Laboratories, Inc.
Materials and Foundation Engineers
April l Z, 1972
Mr. Orm Sherwood
Rhoades Inc.
Savings Building
Fort ColZino, Colorado 80524
Dear Ur. Sherwood:
We are pleased to submit our .deport of a SoiZe and Foundation
Investigation prepared for the proposed development located
southeast of Fort Collins, Colorado, as requested.
Baeod upon our findings in the subsurface, we feel that the
site is suitable for the proposed construction, providing the
design criteria and recommendations as set forth in this report
are met. The accompanying report presents our findings in the
subsurface and our reoommendations based upon these findings.
Very truly yours,
EMPIRE LABORATORIES, I17C.00�&/je gt44oe
Reil R. Sherrod
Engineering Geologist
rro
Reviewed b y: E ski
9EgISTER000
F�
Chestar C. Smith, P.E. o 4808 ti 1
Vice President \CP�9�F,
T �GIkEfR� Q
�TF OF CTO
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OFFICE AND LABORATORY-214 NORTH HOWES + P.O.BOX 149 • FORT COLLINS,COLORADO 80521 • TELEPHONE AREA 303/484-M9
REPORT
OF A
SOILS AND rouNDP-Tio 3
INVESTIGATION
FOR
SIR. ORYa SHERWOOD
i ORT COLLius, COLOr-J.DO
PROJECT ANO. 1123-72
BY
LABOR))= ;IES , INC.
214 MORTH HOWE'S S.'i.ELT
FORT COLLINS , COLORLDO
50)521
REPORT
OF A.
SOILS AND FOUNDATION 111VESTIGATIUN
SCOPE
This report presents the results of a Soils and Foundation
Investigation prepared for the proposed development located at
the northwest corner of Warren Lake, southeast of Fort Collins,
Colorado: The investigation was carried out by means of test
borings and laboratory testing of samples obtained from these
borings.
The objectives of this investigation were to (1) determine
the suitability of the site for construction purposes, (2) make
recommendations regarding the design of the substructures, and
(3) recommend certain precautions -v :hich should be taken because
of adverse soil and/or groundwater conditions.
SITE I3r" T-STIGATION
The field investigations, carried out on 1-larch 22 and 24,
1972, consisted of drilling, logging , and sampling fifteen test
borings. The locations of t-he test borings are shown on the
Test Boring Location Plan included on page of this report.
Borings logs prepared from: the field logs aA shown on pages
thru 13 . These logs shrn soils encountered, location of same
pling, and groundwater at the time of the investigation.
r
All borings were advanced with a four-inch diameter,
continuous-type, power-flight auger drill. During the drilling.
operations, an engineering geologist from Empire Laboratories,
Inc. , was present and made a continuous visual inspection of
the soils encountered.
SITE LOCATION .4 D 1-)£SCRIPTICN
The proposed site is located south of Horsetooth Road along
the northwest edge of Warren lake, southeast of Fort Collins,
Colorado. more particularly,, the site is described as a tract
of land situate in the North 1/2 of Section 3S, Township 7 North
Range 69 West of the 5th P.M. , Lorimer County, Colorado.
The site, currently under vegetation, consists of well ir-
ri.gated-:farm land. The site is relatively flat to gently
sloping and has good positive drainage from both the east and
south to Warren Lake. The Larimer County No. 2 Canal forms the
southwest border of the site.
LABORATORY TESTS ARID EXAMINATION
Samples obtained from the test borings were subjected to
testing and inspection in the laboratory to provide a sound
basis for determining the physical properties of the soils en-
countered. Moisture contents, dry unit weights, unconfined
compressive strengths, water soluble sulfates, swelling poten-
tials and the Atterberg Limits were determined. A summary of
the test data is included on pages thru 22_� Consolidation
characteristics and/or shelling potleltials were also determined,
and curves showing this data are included on pages 24 thru 17.
SOIL AND GT?C}blffWATER CONDITIONS
:`he soil profile at the site consists of strata of materi-
als arranged in different combinations. In order of increasing
depths, they are as follows:
(1) Silty T_o 1 : The entire site is overlain by
a one-foot lager of silty topsoil. The upper
six inches of the topsoil have been penetrated
by plant roots and organic matter and should
not be used as a bearing soil or as backfill
material.
(2) Silty Clair: The silty clay stratum underlies
the topsoil over the majority of the site and
extends Co depths of two to eleven and one-
half feet below the surface. The clays are
plastic and exhibit moderate bearing charac-
teristics. The natural moisture contents of
the silty clays vary from dry to moist. When
Fretted, the dry to damp silty clays exhibit
slight swelling potentials and precautions
should be taken to prevent wetting of the
silty clay stratum.
(3) Eandy Silt)_ Clay; This layer underlies the
upper clays in the area of Borings No. 1
thru 8 north of Warren Lake. the sandy silty
clay stratum extends to depths of six and one--
half to greater than fifteen and ore-half
feet below* the surface. The silty clays con-
tain varvin_cl amounts of sand, are plastic and
exhibit low to moderate tearing capacities
in their camp to moist natural state. when
wetted, the shearing strengths of the lower
clay stratum are reduced and consolidation
occurs.
(4) Cla.ystone (Redreck) : T.he bedrock underlies
the upper clays an6 topsoil along the north-
west and t3esterh portion of the site in tie
-2-
area of Borings No. 8 thru 15. The claystone
has encountered at a depth of one to eight
feet below the surface and extends to greater
depths. she upper one and one-half to three
and one-half feet of the bedrock is highly
weathered, however, the underlying bedrock is
firm and exhibits high bearing characteristics.
Mien wetted, the clafstone exhibits high swell-
ing potentials and every precaution should be
ta:�en to prevent wetting of the bedrock stratum.
(5) Croundwater: Lt the time of the investigation,
free groundv-ater was encountered at depths of
three and one-half to twelve feet helot:° the
surface in the area of Borings No. 1, 2 , 3 and
S. No free grcundwater was encountered to
depths of f iftc;on feet 'Oelow the surface in
ti:e remainder of t'.c site. It should be notes'
that these water levels are subject to chancre
due to seasonal variations, irrigation flows
on or adjacent to the ;property and changes in
the level of Warren Lake.. Borings i.o. 1, 4 ,
S . 11 and 14 t.cre cased for the purpose of
monitoring groundwater during the irrigation
season.
RECOMMENIDT.'_MIS AND DISCT�SSTCN
Pounelation
Due to differences in the physical properties of the soils
encountered at the site , the area will be divided into t4To parts
in this report for the purpose of determining foundation types
and bearing values of the soils encountereC. Area I shall con-
sist of the northeastern portion of the site in the area of
Borings No. •1 thru ;. Ixea II will consist of the remainder of
the site.
Area I
In view of the type of structures proposed and the soils
encountered in this area, it is recor-a-nended that the substruc-
tures be supported by conventional-type , continuous spread
footings. All footings should be founded on the original undis-
turbed soil a ninimum of thirty inches below finished grade for
frost protection. The undisturbed nature of the soil should be
verified 'by a soils engineer prior to placement of any founda-
tion concrete.- Footings at the above level should be designed
for a raxi*rum allowable bearing capacity of two thousand pounds
(2 , 0001) per square foot (dead load plus maximum live load) .
To counteract swelling pressures, which will develop if the dry
clay soils become wetted, all footings should be designee: for
-3-
a minimum dead load of five hundred pounds (500#) per square
foot.
The predicted settlement under the above maximum loading
should be less than 0.50 inch, generally considered to be
within acceptable tolerances.
Area II
Due to the soil conditions encountered in the remainder of
the site, it is recommended that th6 substructures in this area
be supported by a pier and grace beaus type of foundation.
Using this type of foundation system, the structure is supported
by piers drilled into the bedrock stratum and structurallarade
beams spanning the piers. The pier is supported partially
through end bearing and partially through skin friction. it is
recommended that the piers be straight shaft and that they be
drilled a minimum of two feet into the firm bedrock stratum.
Piers at this level may be designed for a maximum end-bearing
pressure of fifteen thousand pounds (15,000#) per square foot
(dead load plus maximum live load) . It is estimated that a
skin friction of fifteen hundred pounds (1,5000 per square foot
will be developed for that portion of the pier embedded in the
sound bedrock stratum. To counteract swelling pressures, which
will develop if the subsoils become wetted, all piers should be
designed for a minimum dead load of seventy five hundred pounds
(7,5009) per square foot. It is essential that all grade beans
spanning piers have a four inch minimum void between the bottom
of the beau and the soil below.
It is strongly recommended that a soils engineer be present
during the drilling operations to (1) identify the sound bed-
rock stratus, (2) make certain that proper penetration into the
bedrock is obtained, and (3) make sure that all drill holes are
dewatered and thoroughly cleaned prior to placing any concrete. -
R feasible foundation alternate in this area, where foot-
ings are at least three feet above the bedrock stratum, would
be conventional-type, continuous spread footings and/or grade
beams. All footings and/or grade beams should be placed on the
original undisturbed soil at a minirmum.depth of thirty inches
below finished grade for frost protection. The three foot
minimum requirement between the bedrock stratum and the bottom
of the footing should be verified tby a noils engineer prior to
design and excavation. Footings at the above level placed in
the original undisturbed soil may be designed for a maximum
allowable bearing capacity of three thousand pounds (3,0000) per
square foot (dead load plus maximum live load) . To counteract
swelling pressures, which will develop if the subsoils become
wetted, all footings and/or grade beams should be designed for
a minimum dead load of one thousand pounds (1,000) per square
foot. The predicted settlement under the above maximum loading
should be less than 0.50 inch, generally considered to be within
an acceptable tolerance.
-4-
Basements
Basement construction is feasible within both areas of the
site providing the finished basement slabs are placed a minimum
of two feet above the maximum seasonal groundwater elevation.
In view of the high groundwater levels encountered in the area
of Borings No*. 2 and 3, it is recommended that garden level or
conventional crawl space construction be considered in this area
in lieu of basement construction.
If for some reason the finished floor slabs are placed
within two feet of the maximum seasonal groundwater levels, the
foundation walls should be designed both structurally and hy-
draulically to counteract groundwater pressures. Also in this
case, a sump pump should be provided in the basement area,.
Slabs on Grade
It is felt because of swelling pressures exerted by the
soil encountered over the entire site, that the only positive
solution for a slab is a structural floor system with a void
beneath it. However, the cost of this type of system would be
prohibitive. with certain precautions and knowing some risk is
involved, it is felt that a floating floor slab is feasible. It
is recommended that all slabs on grade be placed directly on
the undisturbed soil which has been slightly wetted doyen prior
to placement of any concrete. All slabs on grade should be
structurally independent oE. bearing eiembers -and should be rein-
forced with reinforcing sunning through the construction joints.
Fill material supporting slabs on grade at the upper level
should be a non--expansive, granular material compacted slightly
wet of Optimum moisture to at lea#t ninety percent (90%) of
Standard Proctor Density (See Appendix A) . To minimize and con-
trol shrinkage cracks, which will develop in slabs on grade, it
is suggested that control joints be placed every fifteen to
twenty feet and that the total area between these joints be not
greater than four hundred (400) square feet.
It is further recommended that all non-bearing partitions
placed on floor slabs be provided with a slip joint (either top
or bottom) such that the pressure applied by heaving floor slabs
will not damage the floor above. It is emphasized that if the
subsoils are kept dry, movement under slabs on grade will not
occur, however, if moisture is permitted to reach the subsoils,
below the slabs heaving will occur.
GENERAL RPCOK4ENDATIONS
{1) Laboratory test results indicate that water
soluble sulfates in the soil are positive, and
a Type II cement should be used in all con-
crete exposed to the soil.
-5-
(2) Finished grade should be sloped away from the
structures on all sides to give positive drain-
age. It is suggested that ten percent (10%)
for the first ten feet away from the structures
be provided.
(3) Backfill around the outside perimeter of the
structures should be mechanically compacted
at optimum moisture to at least eighty-eight
percent (88%) of Standard Proctor Density.
Puddling should not be permitted as a method
of compaction. (See Appendix A) .
44) All pluatbing and utility trenches underlying
slabs and paved areas should be backfilled
with an approved material compacted to at
least ninety percent (90%) of Standard Proctor
Density. Puddling should not be permitted as
a method of compaction. (See Appendix A) .
(5) Cutters and downspouts should be provided on
the structures in such a manner that water from
the roof area is discharged well ibey nd the
backfill area.
(6) underground sprinkling systems should not be
installed within ten feet of the structures,
and this recommendation should be taken into
account in the landscape planning.
(7) Plumbing under blabs should be eliminated
wherever possible since pluabing failures are
quite frequently the source of free water which
causes slab heave.
(8) An attempt should be made to proportion footing
and/or pier sizes in such a manner that the
unit loads applied to the soil are nearly equal
in order that differential settlements will be
minimized.
(9) It is recommended that all compaction require-
ments specified herein be verified in the field
with density tests performed under the super-
vision of an experienced soils engineer.
(10) It is recommended that a registered profes-
sional engineer design the substructures and
that he take into account the findings and
recommendations of this report.
GVIE RAL COMMENTS
The analysis -and recommendations submitted in this report
are based upon the data obtained fron the soil borings performed
-6-
at the locations indicated on the Location Site Flan. This re-
port does not reflect any variations which may occur between
these borings. The nature and extent of variations between the
borings may not become evident until course of construction. If
variations then appear evident, it will be necessary for a re-
evaluation of .the recommendations of this report to be* made
after performing on-site observations during the construction
period and noting the characteristics of any variations.
y
-7-
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KEY TO BORING LOGS
Oda
FILL e e b GRAVEL
♦ SILT A` -SAND & GRAVEL
® �'►
CLAYEY SILT p
,►� SILTY SAND & GRAVEL
SANDY SILT o COBBLES
o•
CLAY e o SAND, GRAVEL & COBBLES
zSILTY CLAY ® WEATHERED BEDROCK
SANDY CLAY SILTSTONE BEDROCK
SAND CLAYSTONE BEDROCK
SILTY SAND SANDSTONE BEDROCK
CLAYEY SAND ® LIMESTONE
a a
SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 24 HOURS AFTER DRILLING
5/12 Indicates that 5 blows of a 140 pound hammer falling 30 Inches was required to penetrate 12 inches.
EMPIRE LA80R II's_ Iltr_ - -- ---- -
LOG OF BORINGS
EC E VATIOIV vo.I NO.2 NO-,Jo.
4995 — -—
4990 — — —
10
4985
3112_ . 2 12 —
5/12
4980 — — — oz
o
/ - -
4975 �_• _
5/12 8 12 •�.lo
2 2 :•
4970 — —
-Al
7/12
4965
-10-
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
LEVATION o,545 No.fo.
5005
5000 - -
9 12
4995 8 12
i •�
� 7 2
•�' 12 12 - -
4990
V1112 •,.
4 -
4985 -
4/12 ;•
•i - - 24 6 -
7/12
4980
-11-
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
ELE VAT/O N. NO. O.10 No. N5.12
5010 -
5005 - -
1
5000 22 6
21/12 33/12 -
4995 18/6 23 6
11/12 -
4990
- i 30/6
2 - 19 12 -
985,',
20/6 -
4980
-12-
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
1EVAraN o.73 o. o
5020
5015 - -
28/12
5010 24 6
- 24 6
5005 - -
5d 12
5000
35 1
4995
34 6
4990
46/12
-13-
EMPIRE LABORATORIES, INC.
CONSOLIDATION TEST
Note: Sample taken from boring No. 1 @ 3. 0
. 55 '
. 54
0
a
0
0
. 53
. 51
0.1 0.5 1 5 10 50 100
APPLIED PRESSURE - KIPS/SQ. FT.
-14-
EMPIRE LABORATORIES, INC.
CONSOLIDATION TEST
Note: Sample taken from boring No. 8 @ 3.0
.47
.46
O
a
a
0
0
> A
ro .45
.44
0.1 0.5 1 5 10 50 100
APPLIED PRESSURE — KIPS/SQ. FT.
-15-
EMPIRE LABORATORIES, INC.
f
CONSOLIDATION--SWELL TEST
BORING NO. 4 DEPTH 3. 0
.4700 DRY DENSITY 1194
% MOISTURE 19 . 1.
. 4600 - -
0
a
_o
.9500
.4400 - -
.4300 0 0.5 1.0 5 10
APPLIED PRESSURE-TONS/SQ. FT.
0
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0
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0
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2 - - -
0 0.5 1.0 5 10
APPLIED PRESSURE-TONS/SQ. FT.
-16-
EMPIRE LABORATORIES, INC.
CONSOLIDATION--SWELL TEST
BORING NO 12 DEPTH 3.0
- DRY DENSITY 115, 0
% MOISTURE 19.8
.4318 -
.4315 -
4�32 -
ex
0
.4509
.4306 -
0 0.5 1.0 5 10
APPLIED PRESSURE-TONS/SQ. FT.
1•. 0
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-17-
EMPIRE LABORATORIES, INC.
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SUMMARY OF TEST RESULTS
SWELLING PRESSURES
Boring % Moisture Dry Density Swelling
No. Depth Before Test P. C. F.. Pressure PSF
7 3. 0 11. 5 113. 3 410
10 3. 0 22. 7 100. 9 755
13 3. 0 14 . 3 108 . 1 17.25
13 7. 0 15. 4 113.5 2400
14 7. 0 10.3 109. 6 1600
15 3. 0 13.1 110.7 1140
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ATTERBERG SUMARY
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Boring Number
& Depth 2 @ 3. 0 5 @ 3. 0 8 @ 3. 0 15 @ 3. 0
Liquid Limit 32 .6 30. 7 23.4 46 . 3
Plastic Limit 18.1 17.5 14 . 3 23.0
Plasticity Index 14. 5 13. 2 9 .9 23. 3
Passing 200 71.3 63.5 49 .7 62 . 8
Group Index 9.4 7. 1 3.4 11. 8
Classification
Unified CL CL SC-SM CL
A.A.S.H.O. A-6 (9) A-6 (7) A-4 (3) A-7-6 (12)
APPENDIX A
Suggested Specifications for Placement of Compacted Earth Fills and/or
Backfills
GENERAL
A soils engineer shall be the owner's representative to inspect and
control all compacted fill and/or compacted backfill placed 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 from the soils engineer will be
required prior to the owner's final acceptance of the filling operations.
MATERIALS
Soils used for all compacted fill beneath interior floor slabs shall be a
granular, non-expansive type. Compacted earth backfill placed adja-
cent to foundation walls shall be an impervious, non-expansive material.
No material having a maximum dimension of greater than six inches
shall be placed in any fill. All materials proposed for use in com-_
paeted fill and/or compacted backfill shall be approved prior to their
use by the soils engineer.
PREPARATION OF SUBGRADE
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 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.
PLACING FILL
No sod, brush, frozen material or other deletrious 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 manner as will
result in a uniformly compacted fill. Prior to compacting, each layer
shall have a maximum thickness of eight inches; and its upper surface
shall be approximately horizontal.
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MOISTURE CONTROL
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 content
by adding water on the fill surface. If, in the opinion of the soils
engineer, the material proposed for use in the compacted fill is too
wet to permit adequate compaction, it shall be dried in an acceptable
manner prior to placement and compaction.
COMPACTION
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 foregoing report as determined by the standard
Proctor test (ASTM D698-70). Compaction shall be performed by
rolling with approved tamping rollers, pneumatic-tired rollers, three-
wheel power rollers, or other approved equipment well-suited to the
soil being compacted. If a sheepfoot roller is used, it shall be pro-
vided with cleaner bars so attached as to prevent the accumulation
of material between the tamper feet. The rollers should be so designed
that the effective weight can be increased.
MOISTURE - DENSITY DETERMINATION
Samples of representative fill materials to be placed shall be furnished
by the 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 D698-70. 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.
DENSITY TESTS
The density and moisture content of each layer of compacted fill
will be determined by the soils engineer in accordance with ASTM
D1556-68, D2167-66, or D2922-71. Any material found to not comply
with the minimum specified density shall be recompacted until the
required density is obtained. The results of all density tests will be
furnished to both the owner and the contractor by the soils engineer.
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