HomeMy WebLinkAboutADDENDUM 3 - CSP 8790 Geotechnical Report
Addendum No. 3 CSP 8790
McKinney Sidewalk Audra to Loop 288 Page 1 of 1 220015-1
McKinney Sidewalk Audra to Loop 288
CSP 8790
ADDENDUM NO. 3
The Plans, Specifications and Contract Documents for the above-referenced project are hereby
revised and amended as follows:
PROJECT MANUAL & SPEC BOOK
1. The McKinney Street Pedestrian Bridge Geotechnical Engineering Report referenced in
SC-5.03A of Section 00 73 01 Supplementary Conditions in the Project Spec Manual is
attached to this Addendum.
END OF ADDENDUM No. 3 CHANGES
MCKINNEY STREET PEDESTRIAN BRIDGE
DENTON, TEXAS
JULY 17, 2024
TABLE OF CONTENTS
1.0 PROJECT DESCRIPTION ...................................................................................................... 1
2.0 PURPOSE AND SCOPE ......................................................................................................... 1
3.0 FIELD AND LABORATORY INVESTIGATION ........................................................................ 2
3.1 General .............................................................................................................................. 2
3.2 Laboratory Testing .............................................................................................................. 2
3.2.1 Unconfined Compression Tests ........................................................................................ 3
4.0 SITE CONDITIONS ................................................................................................................. 3
4.1 Stratigraphy ........................................................................................................................ 3
4.2 Groundwater ....................................................................................................................... 4
5.0 FOUNDATION RECOMMENDATIONS ................................................................................... 5
5.1 Straight-sided Drilled Shafts ............................................................................................... 5
5.1.1 Drilled Shaft Construction Considerations ......................................................................... 6
5.2 Lateral Load Parameters .................................................................................................... 7
6.0 OTHER CONSTRUCTION ...................................................................................................... 8
6.1 Utility and Service Lines ..................................................................................................... 8
6.2 Exterior Flatwork................................................................................................................. 8
6.3 Surface Drainage ................................................................................................................ 9
6.4 Landscaping ....................................................................................................................... 9
6.5 Site Grading ..................................................................................................................... 10
6.6 Excavations ...................................................................................................................... 10
7.0 SEISMIC CONSIDERATIONS ............................................................................................... 11
8.0 LIMITATIONS ........................................................................................................................ 11
APPENDIX A – BORING LOGS AND SUPPORTING DATA APPENDIX B – GENERAL DESCRIPTION OF PROCEDURES
GEOTECHNICAL INVESTIGATION MCKINNEY STREET AND PEDESTRIAN BRIDGE DENTON, TEXAS
1.0 PROJECT DESCRIPTION
This report presents the results of the geotechnical investigation conducted for the new
pedestrian bridge, to be located approximately 900 feet east of the intersection of East
McKinney Street and North Woodrow Lane in Denton, Texas.
At the time of the field investigation, the proposed site was covered with short height grass
with the existing pavement road between the two borings. Based upon visual site observation
and available maps from the USGS topographic view maps (www.ngmdb.usgs.gov), the
proposed site area of the pedestrian bridge slopes down from the northwest towards the
southeast with an overall topographic relief of about 7 feet.
Final grading plans were not available during the time of this report preparation.
Recommended design parameters provided herein should be expected to change should
there be significant quantities of cut or fill; therefore, we recommend that this office be
permitted to review final grading and design plans prior to construction to confirm and/or
revise the conclusions and recommendations provided herein.
2.0 PURPOSE AND SCOPE
The purpose of this investigation was to:
•Identify the subsurface stratigraphy and groundwater conditions present at the
site.
•Evaluate the physical and engineering properties of the subsurface soil and
bedrock strata for use in geotechnical analyses.
•Provide geotechnical recommendations for use in the design and construction
of the proposed structure and related site work.
The scope of this investigation consisted of:
•Drilling and sampling two (2) borings:
o Borings B1 and B2 were drilled at the south and north side of McKinney
Street, respectively within the footprint of the pedestrian bridge to
depths of about 40 feet below existing grade.
•Laboratory testing of selected soil and bedrock samples obtained during field
investigation.
•Preparation of a Geotechnical Report that includes:
o Recommendations for the design and construction of the bridge
foundation.
o Recommendations for earthwork.
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DENTON, TEXAS
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3.0 FIELD AND LABORATORY INVESTIGATION
3.1 General
The borings were advanced utilizing truck-mounted drilling equipment outfitted with
continuous flight augers. Undisturbed samples of cohesive soils and bedrock were
obtained using 3-inch diameter tube samplers, which were advanced into the soils in
1-to 2-foot increments by the continuous thrust of a hydraulic ram located on the drilling
equipment. After sample extrusion, a hand penetrometer measurement was performed
on each cohesive soil to provide an estimate of soil stiffness.
Some subsurface materials were tested and sampled in general accordance with the
Standard Penetration Test (ASTM D1586). During this test, disturbed samples of
subsurface material are recovered using a nominal 2-inch O.D. split-barrel sampler.
The sampler is driven into the soil strata with an automatic hammer utilizing the energy
equivalent of a 140-pound hammer falling freely from a height of 30 inches and striking
an anvil located at the top of the drill string. The number of blows required to advance
the sampler in three consecutive 6-inch increments is recorded, and the number of
blows required for the final 12 inches is noted as the “N”-value. The test is terminated
at the first occurrence of either of the following: 1) when the sampler has advanced a
total of 18 inches; 2) When the sampler has advanced less than one complete 6-inch
increment after 50 blows of the hammer; 3) when the total number of blows reaches
100; or 4) if there is no advancement of the sampler in any 10-blow interval.
Bedrock materials were intermittently tested in-situ using cone penetration tests in order
to determine their resistance to penetration. For this test, a 3-inch diameter steel cone
is driven by the energy of a 170-pound hammer falling freely from a height of 24 inches
and striking an anvil located at the top of the drill string. Depending on the resistance
of the soil and bedrock materials, either the number of blows of the hammer required
to provide 12 inches of penetration is recorded (as two increments of 6 inches each),
or the inches of penetration of the cone resulting from 100 blows of the hammer are
recorded (as two increments of 50 blows each).
All samples obtained were extruded in the field, placed in plastic bags to minimize
changes in the natural moisture condition, labeled according to the appropriate boring
number and depth, and placed in protective cardboard boxes for transportation to the
laboratory. The approximate locations of the borings performed at the site are shown
on the boring location map included in Appendix A. The specific depths, thicknesses,
and descriptions of the strata encountered are presented on the individual Boring Log
illustrations, which are also included in Appendix A. Strata boundaries shown on the
boring logs are approximate.
3.2 Laboratory Testing
Laboratory tests were performed to identify the relevant engineering characteristics of
the subsurface materials encountered and to provide data for developing engineering
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design parameters. The subsurface materials recovered during the field exploration
were initially logged in the field by the drill crew and were later described by a Staff
Engineer after the samples arrived in the laboratory. These descriptions were later
refined by a Geotechnical Engineer based on results of the laboratory tests performed.
All recovered soil samples were classified and described in part using the Unified Soil
Classification System (USCS) and other accepted procedures.
In order to determine soil characteristics and to aid in classifying the soils, classification
testing was performed on selected samples as requested by the Geotechnical
Engineer. Classification testing was performed in general accordance with the following
ASTM testing standards:
• Moisture Content ASTM D2216
• Atterberg Limits ASTM D4318
• Percent of Particles Finer than No. 200 Sieve ASTM D1140
Additional tests were performed to aid in evaluating strength and chemical
characteristics, which consisted of the following:
• Unconfined Compressive Strength of Soil Samples ASTM D2166
The results of these tests are presented at the corresponding sample depths on the
appropriate Boring Log illustrations. The classification tests are described in more detail
in Appendix B (General Description of Procedures).
3.2.1 Unconfined Compression Tests
Unconfined compressive strength testing was performed on selected cohesive
soils. These tests were performed in general accordance with ASTM D2166.
During each test, a cylindrical specimen is subjected to an axial load that is
applied at a constant rate of strain until either failure or a large strain (i.e.,
greater than 15 percent) occurs. Once the test is completed, the unit weight of
the sample is determined based on the moisture content.
4.0 SITE CONDITIONS
4.1 Stratigraphy
Based upon a review of the recovered samples, as well as the Geologic Atlas of Texas,
Sherman Sheet, this site is characterized by soil and bedrock strata associated with the
Woodbine Formation. The Woodbine formation consists of sand, sandy clay, and clay
soils underlain by shale and sandstone. The subsurface materials of the Woodbine
geological formation often have little consistency and uniformity in deposition. The
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deposition of the sand, sandy clay, clay, sandstone, and shale layers can be very erratic
and highly variable.
Dense and irregular shaped masses of very hard well cemented sandstone and
concretions are known to occur randomly within the formation. If encountered,
specialized excavation equipment may be needed to penetrate these materials.
Boring B1 - Southside of East McKinney Street
At the surface of the boring, sandy lean clay soils were encountered. The clay soils
encountered are stiff to very stiff in soil consistency, various shades of brown and gray
in color, and contained varying amounts of calcareous nodules. The clay soils extended
to a depth of about 14 feet below existing grade.
Beneath the clay soils, clayey sand soils were encountered, which were loose to
medium dense in soil condition, brown and gray in color, and extended to a depth of
about 24 feet below existing grade.
Underlying the overburden soils, weathered shale of varying degrees were
encountered. The weathered shale strata were soft in rock hardness, brown and gray
in color, and extended to a depth of about 31 feet below existing grade.
Directly underlying the weathered shale, fresh shale bedrock was encountered. The
fresh shale was hard to very hard in rock hardness, dark gray in color, and extended to
maximum explored depth.
Boring B2 - Northside of East McKinney Street
At the surface of the boring, clayey sand soils were encountered to a depth of 2 feet
below existing grade. The clayey sand was dense in soil condition, dark brown in color
and contained varying amounts of calcareous nodules and gravel.
Beneath the sandy soils, sandy lean clay soils were encountered to a depth of 14 feet
below existing grade. The clay soils encountered were very stiff in soil consistency and
contained various shades of brown and gray in color and contained varying amounts of
calcareous nodules.
Underlying the overburden soils, weathered shale of varying degrees were
encountered to a depth of 34 feet. The weathered shale strata were very soft to medium
hard in rock hardness, brown and gray in color.
Directly underlying the weathered shale, fresh shale bedrock was encountered and
extended to the maximum explored depth. The shale was soft to very hard in rock
hardness, dark gray in color.
4.2 Groundwater
Groundwater seepage was encountered in Boring B1 at a depth of about 15 feet during
drilling and at a depth of about 8 feet upon completion of drilling activities. Groundwater
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seepage was not encountered in Boring B-2. Groundwater is often contained within the
joints, fractures and other rock mass defects present in bedrock strata. When
intercepted, these defects can produce appreciable amounts of water for a period of
time, especially if those defects are extensive and well inter-connected. Groundwater
levels should be anticipated to fluctuate with seasonal and annual variations in rainfall
and may vary as a result of development and landscape irrigation.
5.0 FOUNDATION RECOMMENDATIONS
The proposed new bridge can be supported on straight sided drilled shaft foundation. Design
parameters for these reinforced concrete shafts are presented below.
5.1 Straight-sided Drilled Shafts
The auger-excavated, straight-sided, reinforced concrete drilled shafts can be founded
in the weathered or fresh shale bedrock. The weathered shale was countered at a depth
of 24 feet below existing grade in boring B-1 and at a depth of 14 feet below existing
grade in boring B-2. The fresh shale was encountered at a depth of 31 feet below
existing grade in boring B-1 and at a depth of 29 feet in boring B-2 . We recommend
that straight-sided drilled piers for structural loads be a minimum of 18 inches in
diameter and penetrate a minimum of 3 feet into the shale bedrock bearing stratum to
utilize the full amount of end bearing.
Straight-sided drilled shafts may be designed to transfer imposed loads into the bearing
stratum using a combination of end-bearing and skin friction as outlined in Table 1
below. As there is appreciable strain-compatibility between the weathered shale and
fresh shale strata, the side friction capacities of both may be utilized in the shaft design.
The allowable side friction to resist the axial loads can be taken from 10 feet below the
top of final grade or below any temporary casing.
Table 1. Recommended Drilled Shaft Design Parameters
Material Approximate Depth Below Existing Grades (ft)
Allowable Skin Friction (psf)
Allowable End Bearing (psf)
Overburden soils 0-24 800 --
Weathered Shale 14-31 1,500 7,500
Fresh Shale >31 5,000 25,000
The shafts should be provided with sufficient steel reinforcement throughout their length
to resist potential uplift pressures that will be exerted by overburden soils. Uplift forces
acting on individual shafts will be resisted by the dead weight of the structure, plus the
stratum-to-concrete adhesion acting on that portion of the shaft that is in contact with
the strata from the top of shale bedrock strata or below the bottom of any casing used
whichever is greater. For the near surface soils, we recommend using an uplift pressure
of 500 psf over an average depth of 10 feet. Typically, one-half (½) of a percent of steel
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by cross-sectional area is sufficient for this purpose (ACI 318). However, the final
amount of reinforcement required should be determined based on the information
provided herein, and should be the greater of that determination, or ACI 318.
There is no reduction in allowable capacities for shafts in proximity to each other.
However, for a two-shaft system, there is an 18 percent reduction in the available
perimeter area for side friction capacity for shafts in contact (tangent). The area
reduction can be extrapolated linearly to zero at one shaft diameter clear spacing.
Please contact this office if other close proximity geometries need to be considered.
We anticipate that a straight-sided drilled pier foundation system designed and
constructed in accordance with the information provided in this report will have a factor
of safety in excess of 2.5 against shear failure and may experience settlements of small
fractions of an inch.
5.1.1 Drilled Shaft Construction Considerations
Groundwater seepage was encountered in Boring B1 at a depth of about 15
feet during drilling and at a depth of about 8 feet upon completion of drilling
activities. Groundwater seepage was not encountered within Boring B-2.
Groundwater is often contained within the joints, fractures and other rock mass
defects present in bedrock strata.
Temporary casing may be required and should be available on site in the event
that excessive groundwater seepage is encountered that cannot be controlled
with conventional pumps, sumps, or other means, or in the event that excessive
sidewall sloughing occurs. Ideally, concrete should be onsite during drilling
operations, so it can be placed immediately after drilling of each shaft is
complete.
The installation of all drilled piers should be observed by experienced
geotechnical personnel during construction to verify compliance with design
assumptions including: 1) verticality of the shaft excavation, 2) identification of
the bearing stratum, 3) minimum pier diameter and depth, 4) correct amount of
reinforcement, 5) proper removal of loose material, and 6) that groundwater
seepage, if present, is properly controlled. Geotex would be pleased to provide
these services in support of this project.
During construction of the drilled shafts, care should be taken to avoid creating
an oversized cap ("mushroom") near the ground surface that is larger than the
shaft diameter. These “mushrooms” provide a resistance surface that near-
surface soils can heave against. If near-surface soils are prone to sloughing, a
condition which can result in “mushrooming”, the tops of the shafts should be
formed in the sloughing soils using cardboard or other circular forms equal to
the diameter of the shaft.
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Concrete used for the shafts should have a slump of 8 inches ± 1 inch. Individual
shafts should be excavated in continuous operation and concrete should be
placed as soon as after completion of the drilling as is practical. All pier holes
should be filled with concrete within 8 hours after completion of drilling. In the
event of equipment breakdown, any uncompleted open shaft should be
backfilled with soil to be redrilled at a later date. This office should be contacted
when shafts have reached the target depth but cannot be completed.
5.2 Lateral Load Parameters
The following soils and rock geo-parameters for lateral analysis of drilled shafts for use
in LPILE® or other lateral load software. These values are based on stratigraphy,
laboratory data and experience. The recommended model layer is “Stiff Clay w/o Free
Water”, and “Weak Rock”. The depth ranges are based on the borings drilled. We
recommend that the lateral resistance parameters be neglected for the uppermost 3
feet of soil materials to account for seasonal and annual cyclic variations in soil
desiccation and contraction and a lack of confining pressure. These parameters were
selected to conservatively approximate the subsurface conditions across the site.
Table 2. Subsurface Soil and Bedrock Materials
Stratum
Depth Encountered
Below Existing Grades
(ft)
Software Material
Designation
Unit Weight
(pcf)
Native Soils 14-24 Stiff Clay w/o Free Water 100
Clayey Sand (B1) 14-24 Submerged Sand 60
Weathered Shale 14-31 Weak Rock 120
Fresh Shale >31 Weak Rock 120
Table 3. Recommended Geotechnical Parameters for Soil and Bedrock Strata
Stratum Depth
(feet)
Friction
Angle
(degrees)
Undrained
Cohesion
(psf)
Unconfined
Compressive
Strength - Rock
(psi)
Modulus
(psi) RQD
Strain
Factor
ε50
Native Clays 0-15 NA 1500 NA 500 NA 0.01
Clayey Sand (B1) 15 - 24 26° NA NA NA NA NA
Weathered Shale 25 – 30 NA NA 75 4,000 NA 0.0007
Fresh Shale >31 NA NA 100 10,000 85 0.0005
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6.0 OTHER CONSTRUCTION
6.1 Utility and Service Lines
To reduce the potential for post-construction vertical movement due to soil moisture
changes, we recommend capping existing soil moistures beneath wet utility flowlines
by placing a minimum 30-mil vapor barrier across the bottoms of utility trench
excavations, followed by placement of a minimum 8-inch-thick layer of flowable fill or
lean concrete (e.g., 1 to 2 sack mix) over the barrier, followed by placement of a
maximum of 2 inches of sand passing the #8 sieve for leveling purposes, to form the
cap at the bottom of the trench. Standard trench widths should be adequate with this
procedure. The edges of the vapor barrier should extend up sufficiently to allow
wrapping of the bedding material and the pipe after installation and prior to backfilling
the trench with compacted soil. We anticipate that dry to average soils will be present
along the trench bottoms. These materials should be undercut 12-inches and reworked
and recompacted to between 92% and 96% of ASTM D698 (Standard Proctor) and to
a moisture content that is at least three percentage points above the optimum (≥+3%).
Backfill for utility lines should consist of on-site material and should be placed in
accordance with the following recommendations. The on-site fill soil should be placed
in maximum 6-inch compacted lifts, compacted to a minimum of 95 percent of the
maximum dry density, as determined by ASTM D698 (Standard Proctor), and be placed
at a moisture content that is within two (2) percentage points (± 2%) of optimum
moisture content, as determined by that same test. It is not uncommon to realize some
settlement along the trench backfill. We also recommend that the utility trenches be
visually inspected during the excavation process to ensure that undesirable fill that was
not detected by the test borings does not exist at the site. This office should be notified
immediately if any such fill is detected.
Utility lines connected to the structure may experience differential movement in
response to changing moisture conditions in expansive soil. These movements may
result in damage to the lines, especially at connections. Flexible connections or
oversized penetration sleeves are recommended to account for potential differential
movement between the building and utilities.
Utility excavations should be sloped so that water within excavations will flow to a low
point away from the active construction where it can be removed before backfilling.
Compaction of bedding material should not be water jetted. Compacted backfill above
the utilities should be on-site clays to limit the percolation of surface water. Utility
trenches extending under structures should include fat clay or concrete cut-off collars
at the perimeter/edge to prevent the transmission of water along trench lines.
6.2 Exterior Flatwork
Concrete flatwork should include high tensile steel reinforcement to reduce the
formation and size of cracks. Flatwork should also include frequent and regularly
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spaced expansion/control joints and dowels to limit vertical offsets between neighboring
flatwork slabs. Structure entrances should either be part of the structure or designed to
tolerate vertical movement without inhibiting access. The moisture content of the
subgrade should be maintained up to the time of concrete placement. If subgrade soils
are allowed to dry below the levels recommended herein, additional moisture
conditioning of the soils may be required. These recommendations are intended to
reduce possible distress to exterior flatwork but will not prevent movement and/or
vertical offsets between slabs.
6.3 Surface Drainage
Proper drainage is critical to the performance and condition of proposed structure’s
foundations and flatwork. Positive surface drainage should be provided that directs
surface water away from these elements. Where possible, we recommend that exterior
grades slope away from foundations at the rate of five (5) percent in the first five (5)
feet, and preferably ten (10) feet away. The slopes should direct water away from the
structure and these grades should be maintained throughout construction and the life
of the structure.
The location of gutter downspouts should be designed such that these items will not
create moisture concentrations at or beneath the structure or flatwork. Downspouts
should discharge well away from the structure and should not be allowed to erode
surface soil.
Moisture related issues can be positively addressed by constructing continuous exterior
flatwork that extends to the proposed structure line. Where this occurs, the joints
created at the interface of the flatwork and proposed structure line should be sealed
with a flexible joint sealer to prevent the infiltration of water. Open cracks that may
develop in the flatwork should also be sealed. The joint and any cracks that develop
should be resealed as they become apparent and should be part of a periodic
inspection and maintenance program.
6.4 Landscaping
Landscaping against and around the exterior of the structure can adversely affect
subgrade moisture resulting in localized differential movements if not properly
maintained. If used, landscaping should be kept as far away from the foundation as
possible, and positive drainage away from the structure should be designed,
constructed, and maintained. Landscaping elements (such as edging) should not
prohibit or slow the drainage of water that could result in water ponding next to
foundations or edges of flatwork. When feasible, irrigation lines and heads should not
be placed in close proximity to the foundation to prevent the collection of water near
the foundation or flatwork, particularly in the event of leaking lines or sprinkler heads.
Trees (if planned) should not be placed in proximity to the structure or movement
sensitive flatwork, as trees are known to cause in localized soil shrinkage due to
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desiccation of the soil by the root system, possibly leading to differential movements of
the structure. The desiccation zone varies by a tree, but trees should not be planted
closer to structures than the mature tree height, and in no case, should the dripline of
the mature tree extend closer than 10-feet of rooflines structure. To the extent practical,
it is recommended that trees scheduled for removal (where required) in the vicinity of
the proposed structure and pavements be removed as far in advance of slab
construction as possible, ideally by several months or longer. This will tend to restore
a more favorable soil moisture equilibrium which will, in turn, tend to minimize the
potential for greater than anticipated post-construction ground movements. A moist but
not overly wet soil condition should be maintained at all times in all landscaped areas
near the structure after construction to minimize soil volume changes caused by
changing soil moisture conditions.
6.5 Site Grading
Expansive clay cut and fill slopes should be gentle and preferably should not exceed 4
horizontals to 1 vertical (4H: 1V).
Excess water ponding on and beside roadways, sidewalks, and ground-supported
slabs can cause unacceptable heave of these structures. To reduce this potential
heave, good surface drainage should be established. In addition, final grades in the
vicinity of structures, pavements, and flatwork should provide for positive drainage
away from these elements.
6.6 Excavations
Excavations greater than 5 feet in height/depth should be in accordance with OSHA
29CFR 1926, Subpart P. Temporary construction slopes should incorporate excavation
protection systems or should be sloped back. Where the excavation does not extend
close to building lines, these areas may be laid back. Where space allows, temporary
slopes should be sloped at 1.5 horizontal to 1 vertical (1.5H: 1V) or flatter.
Where excavation slopes greater than five (5) feet in height cannot be laid back, these
areas will require the installation of a temporary retention system or shoring to protect
the existing construction, restrain the subsurface soils and maintain the integrity of the
excavation. We recommend that monitoring points be established around the retention
system and that these locations be monitored during and after the excavation activities
to confirm the integrity of the retention system.
The slopes and temporary retention system should be designed and verified by the
contractor's engineer and should not be surcharged by traffic, construction equipment,
or permanent structures. The slopes and temporary retention system should be
adequately maintained and periodically inspected to ensure the safety of the excavation
and surrounding property.
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7.0 SEISMIC CONSIDERATIONS
The seismic site classification is based on the 2018 International Building Code (IBC) and
is a classification of the site based on the type of soils encountered at the site and their
engineering properties. Based on the general geologic information gathered in accordance
with Table 20.3-1 of ASCE 7-10, we recommend that Soil Site Class “C” be used at this site.
8.0 LIMITATIONS
The professional geotechnical engineering services performed for this project, the findings
obtained, and the recommendations prepared were accomplished in accordance with
currently accepted geotechnical engineering principles and practices.
Variations in the subsurface conditions are noted at the specific boring locations for this
study. As such, all users of this report should be aware that differences in depths and
thicknesses of strata encountered can vary between the boring locations. Statements in the
report as to subsurface conditions across the site are extrapolated from the data obtained at
the specific boring locations. The number and spacing of the exploration borings were
chosen to obtain geotechnical information for the design and construction of a bridge
structure. If there are any conditions differing significantly from those described herein,
Geotex should be notified to re-evaluate the recommendations contained in this report.
Recommendations contained herein are not considered applicable for an indefinite period of
time. Our office must be contacted to re-evaluate the contents of this report if construction
does not begin within a one-year period after completion of this report.
The scope of services provided herein does not include an environmental assessment of the
site or investigation for the presence or absence of hazardous materials in the soil, surface
water, or groundwater.
All contractors referring to this geotechnical report should draw their own conclusions
regarding excavations, construction, etc. for bidding purposes. Geotex is not responsible for
conclusions, opinions or recommendations made by others based on these data. The report
is intended to guide preparation of project specifications and should not be used as a
substitute for the project specifications.
Recommendations provided in this report are based on our understanding of information
provided by the Client to us regarding the scope of work for this project. If the Client notes
any differences, our office should be contacted immediately since this may materially alter
the recommendations.
This report has been prepared for the exclusive use of our client for specific applications to
the project discussed and has been prepared in accordance with generally accepted
geotechnical engineering practices. No warranties, express or implied, are intended or
made. Site safety, excavation support, and dewatering requirements are the responsibility
of others. In the event that changes in the nature, design, or location of the project as outlined
in this report are planned, the conclusions and recommendations contained in this report
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shall not be considered valid unless Geotex reviews the changes and either verifies or
modifies the conclusions of this report in writing.
APPENDIX A - BORING LOGS AND SUPPORTING DATA
**BORING LOCATIONS ARE INTENDED FOR GRAPHICAL REFERENCE ONLY**
N.T.S.
DENTON TEXAS
SHEET NO.
DATE DRILLED
June 26, 2024
PLAN OF BORINGS
MCKINNEY STREET PEDESTRIAN BRIDGE G1
KEY TO SYMBOLS AND TERMS
CONSISTENCY: FINE GRAINED SOILS
CONDITION OF SOILS
SECONDARY COMPONENTS
WEATHERING OF ROCK MASS
TCP (values)
< 8
8 - 20
20 - 80
80 - 5 in./100
0 in. - 5 in./100
Relative Density (%)
0 - 15
15 - 35
35 - 65
65 - 85
85 - 100
SPT (blowcounts)
0 - 2
3 - 4
5 - 8
9 - 15
16 - 30
> 30
PP (tsf)
< 0.25
0.25 - 0.5
0.5 - 1.0
1.0 - 2.0
2.0 - 4.0
> 4.0
CONSISTENCY OF SOILSLITHOLOGIC SYMBOLS
CONDITION: COARSE GRAINED SOILS
QUANTITY DESCRIPTORS
RELATIVE HARDNESS OF ROCK MASS
SPT (blowcounts)
0 - 4
5 - 10
11 - 30
31 - 50
> 50
Description
No visible sign of weathering
Penetrative weathering on open discontinuity surfaces,
but only slight weathering of rock material
Weathering extends throughout rock mass, but the rock
material is not friable
Weathering extends throughout rock mass, and the rock
material is partly friable
Rock is wholly decomposed and in a friable condition but
the rock texture and structure are preserved
A soil material with the original texture, structure, and
mineralogy of the rock completely destroyed
Designation
Fresh
Slightly weathered
Moderately weathered
Highly weathered
Completely weathered
Residual Soil
Description
Can be carved with a knife. Can be excavated readily with
point of pick. Pieces 1" or more in thickness can be broken
by finger pressure. Readily scratched with fingernail.
Can be gouged or grooved readily with knife or pick point.
Can be excavated in chips to pieces several inches in size
by moderate blows with the pick point. Small, thin pieces
can be broken by finger pressure.
Can be grooved or gouged 1/4" deep by firm pressure on
knife or pick point. Can be excavated in small chips to
pieces about 1" maximum size by hard blows with the point
of a pick.
Can be scratched with knife or pick. Gouges or grooves 1/4"
deep can be excavated by hard blow of the point of a pick.
Hand specimens can be detached by a moderate blow.
Can be scratched with knife or pick only with difficulty.
Hard blow of hammer required to detach a hand specimen.
Cannot be scratched with knife or sharp pick. Breaking of hand
specimens requires several hard blows from a hammer or pick.
Trace
Few
Little
Some
With
Designation
Very Soft
Soft
Medium Hard
Moderately Hard
Hard
Very Hard
< 5% of sample
5% to 10%
10% to 25%
25% to 35%
> 35%
Condition
Very Loose
Loose
Medium Dense
Dense
Very Dense
Consistency
Very Soft
Soft
Medium Stiff
Stiff
Very Stiff
HardARTIFICIALAsphalt
Aggregate Base
Concrete
Fill
SOILROCKLimestone
Mudstone
Shale
Sandstone
Weathered Limestone
Weathered Shale
Weathered Sandstone
CH: High Plasticity Clay
CL: Low Plasticity Clay
GP: Poorly-graded Gravel
GW: Well-graded Gravel
SC: Clayey Sand
SP: Poorly-graded Sand
SW: Well-graded Sand
!
"
!
#$%&'()$%*++$,-)
,-)'.$/'',01/' %2
,-)'.$/'',01/' %2
3
"
!
#$%&'%-%2/(%4)++$,-)
56/-7#$%&'%-%2/(%4)++$,-)
8%2#$%&'()$%*++$,-)
,-)'.$/'',01/' %2
,-)'.$/'',01/' %2
!
" 9
9
" 9
9
18
22
10
11
8
11
4.5+
3.5
3.0
2.5
2.5
1.75
1.75
596.0 ft
586.0 ft
579.0 ft
114.5
16.3
15.1
16.5
14.9
14.0 ft
24.0 ft
31.0 ft
SANDY LEAN CLAY (CL); very stiff to hard; brown, dark brown,
gray, dark gray; trace calcareous nodules
CLAYEY SAND (SC); loose to
medium dense; brown, gray
SHALE; slightly to moderatelyweathered; soft; brown, gray
SHALE; fresh; hard to very hard; dark
gray
S
S
S
S
S
S
S
B
T
N
B
32, 50=4.5"
13, 50=1.0"
57
48
4.3
Swell(%)LL(%)PL(%)PI
TotalSuction(pF)
Hand
Pen. (tsf)orSPT
orTCP
BORING LOG
GraphicLog DUW(pcf)Depth(ft)
0
5
10
15
20
25
30
35
Atterberg Limits
Clay(%)
PAGE 1 OF 2
MC(%)
Legend: S-Shelby Tube N-Standard Penetration T-Texas Cone Penetration C-Core B-Bag Sample - Water Encountered
REC
(%)RQD
(%)
SampleType
Hand
Pen. (tsf)orSPT
orTCP
B1
Passing
#200Sieve
(%)
Unconf.Compr.Str (ksf)
CLIENT: Westwood Professional Services
LOCATION: Denton, TexasPROJECT: McKinney Street Pedestrian Bridge
DRILLED BY: Octavio Herrera (Geotex)
START DATE: 6/26/2024 DRILL METHOD: Cont. Flight Auger/Cont. Push
LOGGED BY: Mohamed Ali (Geotex)
FINISH DATE: 6/26/2024
GROUND ELEVATION: Approx. 610 feet
GPS COORDINATES: N33.215494, W97.108884
PROJECT NUMBER: G24-2002
569.9 ft
40.1 ft
SHALE; fresh; hard to very hard; darkgray
End of boring at 40.1'
Notes:-seepage at 15 feet during drilling-water at 8 feet at completion
T
B
T
50=1.0".50=1.0"
50=0.75",50=0.5"
Swell(%)LL(%)PL(%)PI
TotalSuction(pF)
Hand
Pen. (tsf)orSPT
orTCP
BORING LOG
GraphicLog DUW(pcf)Depth(ft)
35
40
45
50
55
60
65
70
Atterberg Limits
Clay(%)
PAGE 2 OF 2
MC(%)
Legend: S-Shelby Tube N-Standard Penetration T-Texas Cone Penetration C-Core B-Bag Sample - Water Encountered
REC
(%)RQD
(%)
SampleType
Hand
Pen. (tsf)orSPT
orTCP
B1
Passing
#200Sieve
(%)
Unconf.Compr.Str (ksf)
CLIENT: Westwood Professional Services
LOCATION: Denton, TexasPROJECT: McKinney Street Pedestrian Bridge
DRILLED BY: Octavio Herrera (Geotex)
START DATE: 6/26/2024 DRILL METHOD: Cont. Flight Auger/Cont. Push
LOGGED BY: Mohamed Ali (Geotex)
FINISH DATE: 6/26/2024
GROUND ELEVATION: Approx. 610 feet
GPS COORDINATES: N33.215494, W97.108884
PROJECT NUMBER: G24-2002
30
33
11
11
19
22
4.5+
2.75
2.75
3.5
3.0
4.5+
4.5+
4.5+
610.0 ft
598.0 ft
593.0 ft
583.0 ft
109.2
9.9
18.1
15.6
18.3
20.9
15.7
17.2
2.0 ft
14.0 ft
19.0 ft
29.0 ft
CLAYEY SAND (SC); dense; darkbrown; trace to few calcareous
nodules and gravel
SANDY LEAN CLAY (CL); very stiff;dark brown, brown, dark gray; trace to
few calcareous nodules
SHALE; moderately to highly
weathered; very soft; brown
SHALE; slightly to moderatelyweathered; very soft to medium hard;
brown, gray
SHALE; fresh; soft to very hard; darkgray
S
S
S
S
S
S
S
S
B
T
B
50=3.5",
50=2.0"
46
52
11.2
Swell(%)LL(%)PL(%)PI
TotalSuction(pF)
Hand
Pen. (tsf)orSPT
orTCP
BORING LOG
GraphicLog DUW(pcf)Depth(ft)
0
5
10
15
20
25
30
35
Atterberg Limits
Clay(%)
PAGE 1 OF 2
MC(%)
Legend: S-Shelby Tube N-Standard Penetration T-Texas Cone Penetration C-Core B-Bag Sample - Water Encountered
REC
(%)RQD
(%)
SampleType
Hand
Pen. (tsf)orSPT
orTCP
B2
Passing
#200Sieve
(%)
Unconf.Compr.Str (ksf)
CLIENT: Westwood Professional Services
LOCATION: Denton, TexasPROJECT: McKinney Street Pedestrian Bridge
DRILLED BY: Octavio Herrera (Geotex)
START DATE: 6/26/2024 DRILL METHOD: Cont. Flight Auger/Cont. Push
LOGGED BY: Mohamed Ali (Geotex)
FINISH DATE: 6/26/2024
GROUND ELEVATION: Approx. 612 feet
GPS COORDINATES: N33.215831, W97.109125
PROJECT NUMBER: G24-2002
571.9 ft
40.1 ft
SHALE; fresh; soft to very hard; darkgray
End of boring at 40.1'
Notes:-dry during drilling-dry at completion
T
B
T
50=0.75",50=0.5"
50=0.5",50=0.25"
Swell(%)LL(%)PL(%)PI
TotalSuction(pF)
Hand
Pen. (tsf)orSPT
orTCP
BORING LOG
GraphicLog DUW(pcf)Depth(ft)
35
40
45
50
55
60
65
70
Atterberg Limits
Clay(%)
PAGE 2 OF 2
MC(%)
Legend: S-Shelby Tube N-Standard Penetration T-Texas Cone Penetration C-Core B-Bag Sample - Water Encountered
REC
(%)RQD
(%)
SampleType
Hand
Pen. (tsf)orSPT
orTCP
B2
Passing
#200Sieve
(%)
Unconf.Compr.Str (ksf)
CLIENT: Westwood Professional Services
LOCATION: Denton, TexasPROJECT: McKinney Street Pedestrian Bridge
DRILLED BY: Octavio Herrera (Geotex)
START DATE: 6/26/2024 DRILL METHOD: Cont. Flight Auger/Cont. Push
LOGGED BY: Mohamed Ali (Geotex)
FINISH DATE: 6/26/2024
GROUND ELEVATION: Approx. 612 feet
GPS COORDINATES: N33.215831, W97.109125
PROJECT NUMBER: G24-2002
0
5
10
15
20
25
30
0 2 4 6 8 10 12 14STRESS (psi)STRAIN, %
16.5 114.5
(pcf)CompressiveStrength (psi)
29.7
UNCONFINED COMPRESSION TEST
CLIENT: Westwood Professional ServicesPROJECT: McKinney Street Pedestrian Bridge
PROJECT NUMBER: G24-2002 LOCATION: Denton, Texas
Borehole Depth
6.0
Description MC%
SANDY LEAN CLAY (CL); brown, dark brown, gray, dark grayB1
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5 6 7 8STRESS (psi)STRAIN, %
17.2 109.2
(pcf)CompressiveStrength (psi)
77.8
UNCONFINED COMPRESSION TEST
CLIENT: Westwood Professional ServicesPROJECT: McKinney Street Pedestrian Bridge
PROJECT NUMBER: G24-2002 LOCATION: Denton, Texas
Borehole Depth
24.0
Description MC%
SHALE; slightly to moderately weathered; brown, grayB2
APPENDIX B - GENERAL DESCRIPTION OF PROCEDURES
ANALYTICAL METHODS TO PREDICT MOVEMENT
INDEX PROPERTY AND CLASSIFICATION TESTS
Index property and classification testing is perhaps the most basic, yet fundamental tool available
for predicting potential movements of clay soils. Index property testing typically consists of
moisture content, Atterberg Limits, and Grain-size distribution determinations. From these results
a general assessment of a soil’s propensity for volume change with changes in soil moisture
content can be made.
Moisture Content
By studying the moisture content of the soils at varying depths and comparing them with the
results of Atterberg Limits, one can estimate a rough order of magnitude of potential soil
movement at various moisture contents, as well as movements with moisture changes. These
tests are typically performed in accordance with ASTM D2216.
Atterberg Limits
Atterberg limits determine the liquid limit (LL), plastic limit (PL), and plasticity index (PI) of a soil.
The liquid limit is the moisture content at which a soil begins to behave as a viscous fluid. The
plastic limit is the moisture content at which a soil becomes workable like putty, and at which a
clay soil begins to crumble when rolled into a thin thread (1/8” diameter). The PI is the numerical
difference between the moisture constants at the liquid limit and the plastic limit. This test is
typically performed in accordance with ASTM D4318.
Clay mineralogy and the particle size influence the Atterberg Limits values, with certain minerals
(e.g., montmorillonite) and smaller particle sizes having higher PI values, and therefore higher
movement potential.
A soil with a PI below about 15 to 18 is considered to be generally stable and should not
experience significant movement with changes in moisture content. Soils with a PI above about
30 to 35 are considered to be highly active and may exhibit considerable movement with changes
in moisture content.
Fat clays with very high liquid limits, weakly cemented sandy clays, or silty clays are examples of
soils in which it can be difficult to predict movement from index property testing alone.
Grain-size Distribution
The simplest grain-size distribution test involves washing a soil specimen over the No. 200 mesh
sieve with an opening size of 0.075 mm (ASTM D1140). This particle size has been defined by
the engineering community as the demarcation between coarse-grained and fine-grained soils.
Particles smaller than this size can be further distinguished between silt-size and clay-size
particles by use of a Hydrometer test (ASTM D422). A more complete grain-size distribution test
that uses sieves to relative amount of particles according is the Sieve Gradation Analysis of Soils
(ASTM D6913). Once the characteristics of the soil are determined through classification testing,
a number of movement prediction techniques are available to predict the potential movement of
the soils. Some of these are discussed in general below.
POTENTIAL VERTICAL MOVEMENT
A general index for movement is known as the Potential Vertical Rise (PVR). The actual term
PVR refers to the TxDOT Method 124-E mentioned above. For the purpose of this report the term
Potential Vertical Movement (PVM) will be used since PVM estimates are derived using multiple
analytical techniques, not just TxDOT methods.
It should be noted that all slabs and foundations constructed on clay or clayey soils have at least
some risk of potential vertical movement due to changes in soil moisture contents. To eliminate
that risk, slabs, and foundation elements (e.g., grade beams) should be designed as structural
elements physically separated by some distance from the subgrade soils (usually 6 to 12 inches).
In some cases, a floor slab with movements as little as 1/4 of an inch may result in damage to
interior walls, such as cracking in sheet rock or masonry walls, or separation of floor tiles.
However, these cracks are often minor, and most people consider them 'livable'. In other cases,
movement of one inch may cause significant damage, inconvenience, or even create a hazard
(trip hazard or others).
Vertical movement of clay soils under slab on grade foundations due to soil moisture changes
can result from a variety of causes, including poor site grading and drainage, improperly prepared
subgrade, trees and large shrubbery located too close to structures, utility leaks or breaks, poor
subgrade maintenance such as inadequate or excessive irrigation, or other causes.
PVM is generally considered to be a measurement of the change in height of a foundation from
the elevation it was originally placed. Experience and generally accepted practice suggest that if
the PVM of a site is less than one inch, the associated differential movement will be minor and
acceptable to most people.
SETTLEMENT
Settlement is a measure of a downward movement due to consolidation of soil. This can occur
from improperly placed fill (uncompacted or under-compacted), loose native soil, or from large
amounts of unconfined sandy material. Properly compacted fill may settle approximately one
percent of its depth, particularly when fill depths exceed 10 feet.
SPECIAL COMMENTARY ON CONCRETE AND EARTHWORK
RESTRAINT TO SHRINKAGE CRACKS
One of the characteristics of concrete is that during the curing process shrinkage occurs and if
there are any restraints to prevent the concrete from shrinking cracks can form. In a typical slab
on grade or structurally suspended foundation there will be cracks due to interior beams and piers
that restrict shrinkage. This restriction is called Restraint to Shrinkage (RTS). In post tensioned
slabs, the post tensioning strands are slack when installed and must be stressed at a later time.
The best procedure is to stress the cables approximately 30% within one to two days of placing
the concrete. Then the cables are stressed fully when the concrete reaches greater strength,
usually in 7 days. During this time before the cables are stressed fully, the concrete may crack
more than conventionally reinforced slabs. When the cables are stressed, some of the cracks will
pull together. These RTS cracks do not normally adversely affect the overall performance of the
foundation. It should be noted that for exposed floors, especially those that will be painted,
stained, or stamped, these cracks may be aesthetically unacceptable. Any tile which is applied
directly to concrete or over a mortar bed over concrete has a high probability of minor cracks
occurring in the tile due to RTS. It is recommended if tile is used to install expansion joints in
appropriate locations to minimize these cracks.
UTILITY TRENCH EXCAVATION
Trench excavation for utilities should be sloped or braced in the interest of safety. Attention is
drawn to OSHA Safety and Health Standards (29 CFR 1926/1910), Subpart P, regarding trench
excavations greater than 5 feet in depth.
FIELD SUPERVISION AND DENSITY TESTING
Field density and moisture content determinations should be made on each lift of fill at a rate of
one (1) test per lift per 3,000 square feet of fill area, with a minimum of two (2) tests performed
per lift within the building pad, one (1) test per lift per 100 linear feet of grade beam and/or footing
backfill, one (1) test per lift per 100 linear feet in flatwork areas, and one (1) test per lift per 100
linear feet of utility trench backfill. Supervision by the field technician and the project engineer is
required. Some adjustments in the test frequencies may be required based upon the general fill
types and soil conditions at the time of fill placement.
It is recommended that all site and subgrade preparation, proof rolling, and pavement construction
be monitored by a qualified engineering firm. Density tests should be performed to verify proper
compaction and moisture content of any earthwork. Inspection should be performed prior to and
during concrete placement operations. Geotex would be pleased to perform these services in
support of this project.
14805 Trinity Boulevard, Fort Worth, Texas 76155
Geotechnical 817.529.8464 Corporate 903.420.0014
www.geotex-engineering.com
Texas Engineering Firm Registration # F‐12796
Oklahoma Engineering Firm Certificate of Authorization CA 7181