Creekview Add PD-LR 87121716:14 ~-~IATH~,I MA[ER CHSLTNG ENGINEERS P. 30
"3
Subsurface Investigation
MR. BILL THOMPSON, TRUSTEE
Creek View Addition
Utility Trenching Design
Bethel Road, Coppall, Texas
Repo=t to
MR. BILL THOMPSON, TRUSTEE
Dallas, Texas
By
Hooper Engineering Laboratories, Inc.
28?0 Walnut Hill Lane
Dallas, Texas 7~229
Tel 21~/351-6~19
HEL Job No. 87.229
Oeoember 17, 1~87
16:15 -~NAT~ MAIER CNSLTNG ENSINEERS P. 19
TABLE OF CONTENTS
INTROOUCTION ..........
FIELD EXPLORATION . ·
LABORATORY TESTING
GENERAL CONDITIONS
Topography · ·
Geology of th~ Site ·
Soil/Rock Profile . . ,
Ground Water . .., .
RECOMMENDATIONS
Cut Slopes for Open Utility Trenches .
Spaced Sheeting. . - ....
Foundations fo~ Aerial'Sewer'Line ....
LIMITATIONS . ·
SUMMARY OF LABORATORY TEST RESULTS o -.
BORING LOCATIONS
LOG OF BORINGS
?
8
9
10
12
17
18
07,,27,.'90 16:1~ -.'-'IATHAN MAIER CNSLTNG Et, EiINEE~ P. 18
INTRODUCTION
This investigation wes conducted to determine the
technical engineering characteristics of the subsurface soil/
rock profile at the proposed location fo~ the Creek View
Addition, a residential development on Bethel Road in Coppell,
Texas. The SUOSUrfaoe conditions were evaluateO in oroer to
formulate recommendations for the type of open utility t~ench-
lng system that is best suited to this particular site. Soil
parameters are also provided for trench shoring design.
Thirteen test borings were drilled at specific loca-
tions that were selected by the geotechnical engineer to repre-
sent the areas to be covered Dy water lines, storm sewer lines
and sanitary sewer lines that are shown on preliminary d~awings
furnished to the geotecnnical engineer by the civil ensinee~.
Each of the test borings was drilled to a depth greater than
the depth of the inOicated utility trenches.
A drawing is included in this report that notes the
boring locations referenced to the property lines and streets
shown on thm site plan furnished to the geotechnical engineer
by the civil engineer.
FIELD EXPLORATION
Test borings were advanced with a truck mounted rotary
drill u~tng a continuous flight, hollow stem auger, and since
this method of drillin9 does not require the use of water,
there was no moisture contamination of the subsurface soils
that were sampled.
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~?/27-90 16:12 ~*~ IATHAH MA!ER CNSLTNG ENGIHEERS P. 17
UndisturOed samples of the subsurface cohesive soils
and rock were obtained through the hollow stem auger using a
thin wall Shelby tube sampler, and the samples were ejected Sn
the field to examine for sample quality and testaOility.
The low cohesion soils found in the subsurface pro?ile
cannot Oe sampled in a condition that would allow for effective
strength testing in the laboratory, and were evaluated in-place
using the Standard Penetration Test apparatus. This test con-
slats Of driving a two inch diameter, split-spoon sampler into
the soil layer with blows ?rom a 140 pound weight dropped with
a 30 inch free ?all. The number of blows required to drive the
allowable Oearing capacity for the coarse graiA soil, anG the
Dlow count is shown on the boring logs at the test depth.
The hard sandy clay and firm grey shale found in the
subsurface profile at this site were tested in-place using the
Texas Cone Penetrometer. This test consists of driving a three
inch diameter cone iDto the soil o~ rock stratum with blows
from a 170 pound weight dropped with a 2~ inch f~ee fall. The
number of blows required to drive the cone 12 inches or the
distance penetrated with 100 blows is a value that can be
corre!atad to allowaOle bearing capacity for the soil or rock
stratum. The blow count penetration is recorded on the boring
icg at the test depth.
Each soil and rock sample was sealed in a polyethylene
bag to maintain the in-place moisture content, and packed in a
protective wooden box for transporting to the laboratory.
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07/~7/90 16:12 ,--~NATHAH MAIER CHSLTHG ENGINEERS P. 16
LABORATORY TESTING
Each soil sample was v£sualiy examineQ by an expe:i-
enced soils technician, and classified acco:ding to the Unified
Soil Classification System.
Undisturbed soil samples we:e trimmed to required
testing dimensions, and we:e tested fo: unconfined comp:essive
strength. The :esults of this test gives the cohesion or sheet
st:ength of the soil sample, which is useful in indicating-the
~llowa~le side slope fo: open excavations.
Representative samples of each fine grain soil type
found in the subsurface soil profile were tested for Attache=9
Limit values. These index values give sn indication of the
clay content and cohesion that can be expected in the soil.
Cea:se grain sells weze tested for the quantity of
particle sizes fine: than the 200 mesh sieve to assist in the
classification of the soil type~ and to evaluate the in-place
penetration test results.
GENERAI. CONDITIONS - Topography
The g:ound surface at this ~esidentlal development
site on Bethel Road has level to gently sloping to steeply
sloping re:cain. There is an almost solid cover of small to
medium to very large trees growing on the site.
Geology of Ina ~ite - Tat:ace Deposit/Eagle Ford Shale
This site is located in an a:ea of Dallas County where
the p:ima:y geological formation, the Eagle Fo:d Shale, is
eve=lain by a thick deposit of alluvial terrace materials. The
87.229
16:11 ~"~tATHAH MAIER CNSLTNG ENGINEERS P. 15
alluvial soils a=e thoroughly mixed during the t=anspo=ting o?
the materials, and the te~ace deposit normally consists of
soil sizes, including clay, silt, sand and gravel. The terrace
deposit varies laterally, changing from fine g=ain soil to
coarse grain soil in very short distances. Hormally, the
face soil is a high plasticity clay or silt that may Be subject
to significant sh~ink/sweil volume changes with seasonal chan-
9es in soil moisture content.
The Eagle Fozd Shale formation is of Cretaceous Age
and was formed by the buildup of clay at the bottom of a shal-
low inland sea approximately ninety million years ago. The
formation is predominantly shale, normally varying in consis-
tency f~om ~ So~t to medium ha~d zock, and there are t~in len-
ses of limestone found at various depths in the formation. An
occasional thin layer of bentonitie clay is another variable
featur~ of the Eagle Fo~d Shale ~o~mation.
Long ~erm weathering of the £agle Fo~d Shale results
in a residual soil that is notorious for the amount of sh~in~/
~ell volume changes that oocur with changes in soil moisture
content. Clay mine=als in the ~esidual soil a=e highly expa~-
sive, and gzound au=face movements on the orde~ of two to six
inches are not unusual fo~ these =esidual clay soils as the
soil moistu=e content changes with the seasons. Changes in
soil moistu=e content extend to a depth of ten to twelve feet
below the ground surface in this area, and below this depth,
the soil moisture content is considered to be ~sl~tively stable
from yea= to yea=.
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16:11 '~ATHAN MAIER CHSLTNG ENGI,~EERS P. 14
The unweathered shale is usually found below depths of
fifteen feet, and there is some variability in the hardness of
successive layers in the shale. For this reason, straight
shaft drilled piers are normally used for foundations that a=e
based in the shale. Allowable bearin9 capacities are moderate
to low for the base of the piers in the unweathered shale, but
side ~esistance capacities add additional support ?or piers
that penetrate into the shale, and the formation is used for
the support o? single sto~y to high rise structures.
Soil/ROCk Profile
The subsurface soil/rock p~ofiles are quite variable
over :he fifty acre site. Generally, the surface soil is a low
plasticity clayey sand~ then a thick laye= of sandy clay
clay~ and then a firm sandy shale is found to extend to the
termination depth of the test borings. Some layers of sand and
clayey sand are found in the soil/rock profiles.
There are four 9eneral soil cz rock types found in the
subsurface profiles; shale, sandy clay or clay, clayey sand,
and sa~d. Each of the soil or ~ock types will allow a differ-
ant cut slope in utility t=ench excavation, and each soil
rock type should be identifiable by the utility cont=actor.
The boring logs show each soil type at the test bo~ing
tions, but in areas between the test borings, the soil layers
will vary in thickness and order of occurance. A sample of
each soil type is available fo~ inspection at Hooper Engineer-
ing Laboratories, Inc.
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16:10 ~-~IATHAN MAIER CHSLTNG E~EiINEERS P. 15
SHALE is ~ firm rock at this site. In-place
penetration test results show the rock has good cohesion, and
is classified as an unfractured rock. The unf~actured rock is
stable in a vertical cut slope for trenches twenty feet or less
in height.
SANOY CLAY OR CLAY is a soil that has predominantly
clay size particle~. The sandy clay and clay at this ~it~ has
good cohesion, and is classified as a Type A soil. A Type A
soil is stable on a out slope of three fourths ~orizontal to
one vertical for trenches twelve feet or less in height, open
for less than twenty four hours. For trenches deeper t~an
twelve feet and less than twenty feet, out slopes shoulO be cut
at one horizontal to one vertical.
CLAYEY SAND is soil that has predominantly sand size
particles, but has sufficient clay particles present to give
the ~oil some cohesion. Clayey sand, as it ~as found at this
site, has good cohesion, an~ is classified as a Type 8 soil. A
~ soil is stable on a cut slope of one ~orizontal to one
vertical for trenches twelve feet or less in ~eight, open for
less than twenty four hours.~ For trenches deeper than twelve
fee~ ~nd less than twenty feet, out slopes should be cut at one
and one half horizontal to one vertical.
SAND is a soil that has very few clay or silt size
particles. Sand has no cohesion, and will flow to a stable
slope, and is classified as a Type C. soil. A TyDe
stable on ~ cut slope of two horizontal to one vertical
t~enches t~ent¥ feet o~ less in height.
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16:10 -*NATHAN MAIER CNSLTNG ENGINEERS P. 12
groun~ Water
Ground water was found in one of the twelve test bOr-
ings drilled for the utility trench investigation, at a depth
of eleven feet below the existing ground surface. Test boring
nine was Orilled in the area where the sanitary sewer is aOove
ground, and the water table was found at a depth of sixteen
feet at that time.
RECOMMENDATIONS - Cut Slopes for Open Utility Trenches
There are four soil or rock types found in the subsur-
fact soil/rock profile at this site, and each type of mater~al
will allow for a different cut slops in utility trench excava-
tions. The four soil and rock iypes were described and classi-
fied in the Soil/Rock Profile section of this report, page 5.
The following table shows the different soil and rock types
with the ~llowable cut slopes foz open u:ility trenches.
Type Description w~ Unit Steepest Allowable Slope
Weight Horizontal : Vertical
pcf pc~ Depth 0-12 ft Depth 12-20 ft
Rock Fi~m shale 20 1~0 vertical vertical
A Firm ~lay 20 125 ]/A : I 1 : 1
B Clayey sand ~0 12'~ I : 1 1 1/2 : l
B Sand ~P = ~0 80 12~ 2 : 1 2 : i
C Submerged soil 80 1~0 2 : 1 2 : I
Notes:
1. If there is any indication of general or local instability,
slopes should be cut back at least 1/4 hot : 1 vert flatter
than a stable slope.
2. Trenches 0-12 ft will be open less than 24 hours. If open
longe~ ~han 2A hours, uss 12-20 ~eet values fo~ cut slope.
' 87. 229 ?
16:09 NATHAH MAIER CNSLTHG EN~IHEERS P. 11
~. Soil Oeneath the ware= table is classed as Type C soil.
4. Profiles with two or more soil types should be classified
in accordance with the weakest layer.
~. Spaced shoring systems are permitted in Type A and Type B
cohesive soils with maximum center to center spacing in
accordance with the table in Spaced Sheetin9 section, page 8.
The plans show the allowable conf[gu=ations for sloped
excavations, and the maximum height of vertical cuts in soil.
The utility con~acto~ can use any of the configurations that
£s desirable fo= his operations, but the slope of the cut will
be in accordance ~ith the above table of values.
A brief daily inspection is required by a rep=esenta-
[iv~ of the geotechnical engineer. Slopes of open trenches,
shoring members and spacin9 will be measured and reported to
the utility contractor at the site. A written repo=t will be
suOmitted daily to the owne=.
Spaced Sheet~pg
Spaced sheeting is permitted in Type A and Type B
cohesive soils. The ?ollowing table outlines maximum fente~ to
center spacing ~o~ spaced sheeting for long term exoavations.
Trench Depth, in feet
Type Description ~ tO 10 10 to 15
A ~irm olay ~ feet 4 feet
B Clayey sand ~ feet 2 feet
87.22~ 8
07×27.t~0 16:0~ ~"~NATHRN MAIER CI~SLTNG ENGINEERS P. 10
foundations for Aerial Sewer Line
The aerial sewer line that crosses Grapevine Creek at
the east end of the site will require stable foundations to
maintain the g=ades in the pipeline. Test boring nine drilled
tn th£s a=ea shows a dark g=ey to g~ey and orange c~ay to a
depth of ten feet, a stiff sandy clay to a depth of f~f[een
f~et~ w£th the wate~ table indicated at sixteen feet. The near
su=face clay has high plast~city cha=acter£stics (Pi =
£nd£cating the clay is an active so£[ thai wi[~ have some
shrink/swell mevement w[~h changes in soil moistu=e content.
Foundations should be based tn the rel~tlvely stable moisture
content soil belo~ a depth of ten feet. Drilled and belled
pie= foundations should be used to support the pipeline and the
base of the pie~s should be based at a depth o? tan ?eat below
the existin9 g~ound surface. An allowable bearing capacity of
~000 p~?. should be used in the design of the foundations.
Belled pie~s should have a minimum bell to shaft ratio
of t~o to one to resist the uplift forces caused by seellin9
~oil movement. Swelling soil movement ~ill =esult in an uplift
skin f~ic[ion applied to the top ?ire feet o? pie=, and the
amount of fo=ce should be computed using a skin friction value
o? 1~00 ps? applied for the full ?ire ?eat- The tensile
stress =esulting from the uplift force will ~equire that rein-
forcing steel is used in the pier shaft, and the quantity
s~eel should be sufficient to ~esist the full uplift force that
could occur p=ior to the time that dead load is applied to the
top or the pier. Reinforcin9 steel should extend fo= the full
87 o 22~ ~
~?/27/~0 16:1~I~ '~ N~THt~N MFt[ER CNSITNG ENGINEERS P. 09
length of the shaft.
Water may be encountered during the ~rillin9 of some
plats, and may require the use of temporary casing to prevent
the intrusion of water into the pier hole. Temporary casing
will not be required if the drilling operations can be handled
in such a way that no more than one inch of water is in the
hole st the time of concreting.
The clay deteriorates with exposure to drying air, and
concrete shoulO bs placed in the pier hole within eight hours
of completing the drilling. Pier Doles le~t open longer than
eight hours should be re=penetrated prior to fill~n9 with con-
crete.
Concrete for the pie:s should be ~esigned for a slump
of six inches, end a collection hopper should be specified to
assure that the cc~crets drops vertically into the pier hole
without segregating.
Continuous inspection of the pier drilling operations
b~ a representative of the geotechnical engineer is ~equire~.
The inspector can assu~e that the p~oper bearing stratum ~s
penetrated, that the bells ere full size, clean and dry at the
time of concrete placement, and that proper procedures are used
in constructing the piers.
LIMITATIONS
~very effort h~s been made to properly evaluate the sub-
su~f~¢e conditions at this site based on the samples recov-
ered '?rom the test bo:ings and the results of la~oratory tests
87.229
TO
0'?."2'?,-'91D 16:08 "~NATHAN MAIER CNSLTNG EHGI~EERS ~-~ P. 08
on these samples. Howeve:, it must be recognize~ that the con-
ciustons :eached in this report we:e based on the conditions at
the thirteen test boring locations. Out p:ofesstonal serv£ces
we:e performed, our findings were obtaine~ and out :ecommenda-
tions prepared in accozdance with gene:ally accepted engineer-
tng p:inc£pies and practices.
Should any unusual conditions be encountered during
construction o? this p=oject, this o??ioe should be noti?ieO
immediately so that ?u=ther investigation and supplemental
~ecommendattons can be made.
Respect?ully submitted,
C. Day,ow Hoope~, M. Eng=., P.E.
Consulting Geote~hnical Enginee=
Texas 181D7
87.22g 11
16:O8 ~NRTHAN MRIER CNSLTNG 5{q~li-{EHRS _..~ P.O?
6URR~RY OF LABOR~TORY TE~T RESULT6
Depth Soil 9eKrlptiD.
Feet
Class
0 CLAYEY 9~D, dark bromn,
SC
2 9ANDY CLAY~ da~k brotm,
CL
4 SANDY CLAY, bra#ns
9 SANDY CLAY~ light grey k orange,
CL
14 9ANDY CLAY~ tan t btam,
SANDY SI~E, grey,
0 CLAYEY 9AND, braun,
2 flll#JY CLAY, braunt
¢ S~NDY C~AY, tan b braes,
CL
CL
0 CLAYEY SNIO, dark brolm,
SC*
2 CLAYEY sireD, brown,
4 8]IND, btam,
9 SHALEY CLAY, grly~
0 ~llOt bt'om1t
dOB NO, 67.229
dater Dry Liquid Plasticity UncoefleBd Unit
Content Unit Lisit Index Cotpreeetve Strain
del~ht Strength
~ poi Z ~ ksf ~
11.2 0.9
33 19 I1.$ 1.0
ll.O 1,9
11.4 9.7
22 6 11.0 1.~
30.82 Hinua 200 Mb 5.9
229 12
07/~x90 16:~7 '~NATHAN MA!ER CNSLTNG EIGINEERS ~ P. 06
SUHH~R¥ OF L~BOR~TOR¥ TEST REgULTS
~orln~ hpth ~ot! ~escriptio~
4 2
4 14
~ 2
5 14
& 2
& 9
7 2
CLAYEY 8~4~ tint
OdkYEY gA#l), tie,
CLIWEY BAND, taa~
~DY ~, ~lYt
9ANDY gHeE, grey~
~Y ~Ye tan & grmye
S~Y ~Y~ t~n k groy~
~Y ~E~ grey,
~Y ~E, grey,
9H~ ~Y, tan ~ gray,
~Y ~Yt dark br~t
CL
87.229
l:! l)lclablr 1987
Yat~ Dry Liquid Plasticity Uncoaftntd Unit
Content Unit Linit Index Co#resalv. Strain
Ibtght 9tr~gth
7,8 2.3
6~ $& 11,1 1.7
11,7 4.9
30 l& I1,1 1.1
10.7 2.0
87. 229 13
0?/2?/90 16:0'7 ~' I'IATHAN MAIER CNSLTNG ENGINEERS ~ P. 05
5UHHARY OF L~BORATORY TEBT RESULT9
CL
S/kNI)Y SH~Es greys
9h
6P
9~#9Y CLAY, oruges
~DY ~AY,
~Y~ light br~
SILTY ~Y, ltghk br~n,
9~DY ~ br~ t
~Y, dirk br~
~AY~ dark br~t
~Y~ light grey & or~ge~
9 14 6NIDY CLAY, light grey
9 19 CLAYEY SM O, light broNfl,
I0 2 CI.AY~Y gANg, bro~,
BC
JOB )iD. 87.229
December ~997
Mater ~c Liquid Plasticity Unce~fLfled Unit
StreflqLh
~ pc? ~ ~ KS? A
4.4
4.0 7.2
11.1 l,I
28 13 11o2 1.3
76 45 4.5 3.3
7,6 3,3
10.7
lt.o 1,6
IO, g 1.8
3~ iS 3,0
87.229
14
0?..'2?,'90 16: 06 ~NATHAN MA I ER CNSLTNG ENG ! NEERS ~-~ P. 04
6UHH~RY OF L~6OR~TOR¥ TE6T RESULT6 ~0~
Feet
tO 4
!0 i4
lO
11 0
II 2
ti 4
11 9
12 o
12 I
t2 9
13 2
1] 4
9AND,
i{ANO¥ CLAY, tan t orange,
SA#DY 9~M.E~ grey,
~Y ~ND~ d~k
~DY ~AY light bray
9~Y ~Y, light br~t
~y~ }~ (lark ~r~
~DY CLAY, bruin,
9~Y ~Y, bruin,
~Y ~Y, rHdtah br~n,
~Oj taI
BP
9P
K
CL
CL
NO, 87.229 1~ Dlce~lblr 1967
h'y Liquid Plasticity Unconfined that
Unit Liilt Indn Coepressive Btrain
lilight 9trnflgLh
Kf X T ksf {
tl,O
5.9 2.9
30 16 7.9 2.3
10.7
28.01 Niflus 200 Mb
87. 229 15
16:06 ~'~NATHAN MAIER CNSLTNG ENGINEERS P. 03
6UHHBRY OF LABORATORY TEST RE6DLT9
Depth Boil Description
Feet
Chss
SANDY ~iiAL. E, ~rey,
~108 NO. 87.229
1~ Decmmber 1987
Hater DPy Liquid Plasticity Unconfined Unit
Content Unit Liiit Inden Coeprflstvm Strain
Height Strength
67. 229 16
2?/90 16:~ ~ NATHAN MAIER CNSLTNG ENGII'EERS P. 0~
/
I
! \
// ',,2 \
,
0
~7.22~ 17