Report of geotechnical investigation of the El Reno Residency salt shed, Yukon, Oklahoma

              REPORT OF GEOTECHNICAL INVESTIGATION
EL RENO RESIDENCY SALT SHED
YUKON, OKLAHOMA
PROJECT NO. 11029
INTRODUCTION .................................................................................................................. 1
GENERAL .......................................................................................................................................... 1
PROPOSED CONSTRUCTION................................................................................................................ 1
SCOPE OF WORK ............................................................................................................................... 1
FIELD AND LABORATORY INVESTIGATIONS .................................................................. 2
FIELD EXPLORATION ......................................................................................................................... 2
LABORATORY TESTING...................................................................................................................... 3
SITE DESCRIPTION............................................................................................................. 3
SURFACE CONDITIONS ....................................................................................................................... 3
SITE GEOLOGY .................................................................................................................................. 3
SUBSURFACE CONDITIONS ................................................................................................................ 4
GROUNDWATER CONDITIONS ............................................................................................................ 5
SOLUBLE SULFATES ........................................................................................................................... 5
CONCLUSIONS AND RECOMMENDATIONS ..................................................................... 6
FOUNDATION RECOMMENDATIONS ........................................................................................ 6
CONSTRUCTION CONSIDERATIONS ......................................................................................... 9
ENVIRONMENTAL CONSIDERATIONS ................................................................................... 11
CLOSURE .......................................................................................................................... 12
APPENDICES
APPENDIX A – Field Investigation
APPENDIX B – Laboratory Results
APPENDIX C – General Notes
REPORT OF GEOTECHNICAL INVESTIGATION
EL RENO RESIDENCY SALT SHED
YUKON, OKLAHOMA
PROJECT NO. 11029
INTRODUCTION
General
This report presents the results of the geotechnical investigation performed for the
proposed Super Salt Shed located at 15100 Northwest 36th Street in Yukon, Oklahoma.
The purpose of this investigation is to evaluate the subsurface conditions at the site and
to provide recommendations pertaining to the geotechnical aspects of the proposed
project.
Proposed Construction
The project will include the construction of a salt shed with a footprint of approximately
6,500 square feet. The walls will be 12 feet tall by one foot thick cast in place concrete,
and it will have a 10” thick concrete slab. It will have a fabric roof and an approximate
2,900 square foot canopy area. Spread footings are the desired foundations system.
No below grade construction is anticipated for this project. Floor slab loads are
approximated to be 1,500 psf. Exact grade changes for the site have not been provided
at this time, but are anticipated to be minimal (less than 5 feet).
Scope of Work
The scope of this investigation includes the following:
1. Review of previous geotechnical and geological information of this site and
sites near this site. This was augmented with data obtained during the field
investigation phase of the project.
2. Investigation of the foundation suitability of the subsurface soils by drilling
and sampling a total of 2 boreholes within the planned project area.
3. A laboratory testing program consisting of moisture content, Atterberg limits,
sieve, and soluble sulfate testing on the soils encountered.
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Project No. 11029
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4. Recommendations regarding foundation support of the proposed building.
The discussion includes a shallow footing foundation system.
5. General construction and earthwork recommendations.
6. Sustainability recommendations in regard to site construction and
construction materials.
FIELD AND LABORATORY INVESTIGATIONS
Field Exploration
Subsurface exploration was performed April 27, 2011. The boring locations were staked
in the field by a representative of Red Rock Consulting. This was done by pacing
distances with a measuring wheel and estimating angles from known site references as
depicted on an aerial map that was provided by Cobb Engineering. The locations of the
borings should be considered accurate only to the degree implied by the methods used
to define them.
The subsurface exploration program consisted of drilling 2 borings to depths of
approximately 21.5 feet under the full time supervision of an engineer. The approximate
boring locations can be found on the Boring Location Diagram in Appendix A.
The borings were advanced using a truck-mounted CME 55 drill rig. Draft boring logs of
the subsurface conditions encountered were developed in the field. Representative
samples were obtained using the split-barrel sampling procedures (Standard Penetration
Test, SPT) in general accordance with ASTM D-1586.
The SPT test uses a standard, 2-inch O.D., split-barrel sampling spoon that is driven
into the bottom of the boring with a 140 pound automatic drive hammer falling 30 inches.
The blows per foot, N, is the number of blows required to advance the sampling spoon
the last 12 inches, or less, of an 18-inch sampling interval. The N value is used to
estimate the in-situ relative density of granular soils, the consistency of cohesive soils,
and the hardness of weathered bedrock.
Samples were collected and transported back to the lab for further classification and
testing. The final boring logs were developed from the draft logs and observations and
test results of the samples returned to the laboratory. The stratigraphic contacts
indicated are only for the specific dates and locations reported and, therefore, are not
necessarily representative of other locations and times. The boring logs, presenting
conditions encountered at each location explored, are included in Appendix A.
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Laboratory Testing
Representative soil samples were tested to refine the field classifications and evaluate
physical properties of the soils which may affect the geotechnical aspects of project
design and construction.
The laboratory testing program included the following:
• Moisture content tests in general accordance with ASTM Method D2937
• Liquid and Plastic Limits of soils in general accordance with ASTM D4318
• Washed No. 200 US Standard Sieve test in general accordance with ASTM
Method D1140
• Soil Classification in general accordance with ASTM D2487
• Soluble Sulfate tests in general accordance with OHD L-49
The results of the physical laboratory tests conducted are shown on the boring logs in
Appendix A and laboratory results in Appendix B.
SITE DESCRIPTION
Surface Conditions
At the time of the field investigation the borings were located within a large empty gravel
lot, which is approximately 3 acres. The lot was covered with 2 to 4 inches of 1 to 2 inch
diameter aggregate base. The site was surrounded by a chain link fence and there were
existing buildings and vehicles in the northeast corner. The borings were located in the
southwest corner of the lot.
The site appeared to drain towards the southeast with no significant grade change. The
site was dry during the drilling activities and the drilling rig did not experience any
difficulty maneuvering around the site.
Site Geology
Division Four of the “Engineering Classification of Geological Materials”, published by
the Oklahoma Department of Transportation (ODOT) indicates the project site is
underlain by a subunit of the Flowerpot Unit (Pf) called the Chickasha Subunit (Pfc).
This Flowerpot unit consists dominantly of brick-red, blocky, regular-bedded, silty shale,
containing some thin interbedded soft red sandstones. The upper portion contains some
thin beds of gypsum.
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The total thickness of the unit varies from about 425 to 470 feet with a general thinning
to the northwest.
The Flowerpot unit outcrops in a broad 10 to 18 mile wide pattern across central
Canadian County and southwestern Kingfisher County in Division Four.
Topographically, the unit varies from nearly level topography to a “badlands topography
consisting of many deeply eroded gullies.
This Chickasha subunit is composed of a random mixture of shales, siltstones,
sandstones, clay, gall, and siltstone conglomerates. Rocks of identical rock character
are repeated at many different levels within the subunit. Cross-bedding is typical of the
subunit and generally differentiates it from the inter-fingering shales of the overlying
Flowerpot unit.
The subunit thins consistently northward from about 330 feet in southern Canadian
County, to 20 feet at Okarche, to 115 feet in western Kingfisher County, where it loses
its identity in Blaine County in Division Five.
The subunit outcrops in Canadian and Kingfisher Counties of Division Four. Detailed
geology of Kingfisher county is unavailable, and its approximate out-crop pattern is
estimated in the county by using topographic features.
The subunit generally forms rolling to gently rolling topography being either grass
covered or cultivated throughout its outcrop area.
Subsurface Conditions
Information collected during the investigation indicates that the overburden materials
were comprised of lean clay and lean clay with sand which extended from the surface to
the top of bedrock, which was encountered at approximately 20 feet in borings B-1 and
B-2. . Borings B-1 and B-2 were located beneath approximately 2 to 4 inches of
aggregate base.
The overburden was underlain by soft to moderately hard shale that extended to the
boring termination depths of 21.5 feet. For more a more detailed report of the soils
encountered in the borings please see the boring logs in Appendix A.
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Groundwater Conditions
Groundwater conditions were monitored during the advancement of the borings and
immediately after the completion of drilling. At these times, groundwater was not
encountered in either of the borings.
To obtain more accurate groundwater level information, long-term observations in a well
or piezometer that is sealed from the influence of surface water would be needed.
Fluctuations in groundwater levels can occur due to seasonal variations in the amount of
rainfall, runoff, altered drainage paths, and other factors not evident at the time borings
were advanced. Consequently, the contractor should be aware of this possibility while
constructing this project.
Soluble Sulfates
Sulfates are naturally occurring in some soils. If combined with calcium based materials,
such as cement, sulfate rich soils can expand up to 250 percent of the original size when
exposed to moisture.
Based on soluble sulfate test results, low levels of soluble sulfates were encountered
across the project site. Levels encountered on the project site were between 240 ppm
and less than 200 ppm. Soluble sulfate levels are included in the laboratory results in
Appendix B.
A level of 200 ppm is the lowest and “greater than 8,000 ppm” is the highest reportable
level when using the colorimeter method OHD L-49. Soluble sulfate levels less than
3,000 ppm are considered to be too low to be of concern when considering the soil for
lime stabilization. Soluble sulfates are not anticipated to be a problem at this project
site.
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CONCLUSIONS AND RECOMMENDATIONS
FOUNDATION RECOMMENDATIONS
Recommendations pertaining to the building pad, floor slab subgrade and foundation
system are discussed below.
Building Pad Preparation
Building pad preparation for the proposed structure should include removal of the
existing aggregate base, vegetation, topsoil and any other unsuitable materials which
may be encountered. Removal depths should be determined at the time of construction
by a representative of Red Rock Consulting.
Floor Slab Subgrade
Structures, such as the one proposed for this site, are generally designed for post-construction
vertical floor slab movements of less than 1 inch. Based on the Atterberg
limits test results of the on-site soils and assuming a minimum natural dry in-situ soil
condition and a zone of influence (average depth of relatively constant moisture) of 8 feet
below the existing ground surface, the evaluation indicates a PVR of less than 1 inch for the
ground level. The weight of the structure was not included in the potential vertical heave
estimation.
The in situ soils at the existing grade are adequate to provide direct support of the floor
slab. Procedures for developing a moisture conditioned and compacted soil zone
beneath the floor slab are included below.
• The floor slab area for the structure plus approximately 5 feet in each horizontal
direction must be stripped of all aggregate base, vegetation and topsoil.
• The work area should then be proofrolled with a loaded, tandem-axle dump truck
weighing at least 25 tons to locate any areas that are soft or unstable. The
proofrolling should involve overlapping passes in mutually perpendicular
directions. Where rutting or pumping is observed during proof rolling, the soft
and/or unstable soils should be excavated and replaced with a low volume
change soil as described below.
• After proofrolling and completing any corrective work, the work area should be
scarified to a depth of 8 inches, moisture conditioned and compacted. The
moisture content of the scarified soil should be adjusted to its optimum value or
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above, as determined by a standard Proctor test (ASTM D-698), prior to being
compacted to at least to 95 percent of its maximum dry density.
• After all of the above recommended steps have been successfully completed, fill
material can be placed, where needed. The fill should consist of an approved
low volume change soil that is free of organic matter and debris, placed in lifts
not exceeding 9 inches in loose thickness and compacted to at least 95 percent
of the maximum dry density and at least to its optimum moisture content or
above as determined by a standard Proctor test (ASTM D-698). Low volume
change soils are defined to be cohesive materials having a liquid limit less than
40 and a plasticity index between 5 and 15. The zone of compacted fill meeting
these criteria should extend beyond the building footprint as described above for
stripping.
• The minimum recommended moisture content must be maintained in the building
pad materials until the floor slab is constructed. Drainage must be developed
sloping away from the building to prevent water from ponding along the perimeter
and affecting future floor slab performance.
• The geotechnical engineer or a representative of the geotechnical engineer
should be present to verify the above recommendations are implemented
successfully.
The use of a vapor retarder is recommended beneath concrete slabs-on-grade that will
be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or
when the slab will support equipment sensitive to moisture. When using a vapor
retarder, the slab designer and slab contractor should refer to ACI 302 for procedures
and cautions regarding the use and placement of a vapor retarder.
Shallow Footing Foundation Systems
A shallow footing foundation system can be used to support the proposed building.
Spread footings for columns and continuous footings within the existing overburden
material at a depth of 2.5 feet can be designed for allowable unit bearing pressures of
1,800 psf and 1,500 psf, respectively. If the allowable pressures given are not adequate for
the loads anticipated for this project, please contact Red Rock Consulting for either drilled
pier or geogrid reinforcement recommendations.
The footings should all bear on similar material. In this case, the footings will bear within
the existing overburden material. In no event should footings bear on different material,
such as some footings on overburden soil and some footings on fill or bedrock material.
Footings bearing on different materials could result in differential settlement of the building.
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Continuous footings should have a minimum width of at least 16 inches and isolated
column footings should have a minimum width of at least 30 inches. To provide
protection from frost heave and to help maintain constant moisture content in the soils
below the footings and slabs, perimeter footings are recommended to bear at least 2.5
feet below final outside grade. Interior footings may be placed at a shallower depth.
The foundation excavations should be observed by a representative of Red Rock
Consulting prior to steel or concrete placement to document that the foundation materials
are consistent with the materials discussed in this report. The bottom of the footings should
be probed to identify and locate soft areas. Cavities formed as a result of excavation of soft
or loose soil zones should be backfilled with lean concrete or properly compacted low
volume change fill.
After opening, footing excavations should be observed and concrete placed as quickly as
possible to avoid exposure of the footing bearing surfaces to wetting and drying. Surface
run-off water should be drained away from the excavations and not be allowed to pond. If
possible, the foundation concrete should be placed during the same day the excavation is
made. If footing excavations are left open for more than one day, they should be protected
to reduce evaporation or entry of moisture.
If all site preparation procedures are conducted as outlined above, long-term movement
is expected to be less than 1 inch. Differential movement across the structure is not
expected to exceed approximately ½ inch.
IBC Building Code Site Coefficient
From the geotechnical investigation and subsequent laboratory tests, the on-site soils
yield a Site Coefficient “D.” This site coefficient is based on a maximum boring depth of
21.5 feet. To obtain a more accurate site coefficient, a deeper boring (100 feet, as per
the code), or more extensive testing must be used to evaluate the subsurface conditions.
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Project No. 11029
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CONSTRUCTION CONSIDERATIONS
Construction in Expansive Soils
Expansive soils were not encountered on this project site. The following information has
been assimilated after examination of numerous projects constructed in active soils.
These recommendations are presented here as a convenience to the designers and
contractors. If these features are incorporated into the overall design of the project, the
performance of the structure should be improved.
• Special considerations should be given to completion items outside the structure
area, such as stairs, sidewalks, etc. They should be designed to adequately
sustain the potential vertical movements mentioned in the report.
• The general ground surface should be sloped away from the structure on all
sides so that water will always drain away from the structure. Water should not
be allowed to pond near the structure after the slab and/or foundation has been
placed.
• Roof drainage should be collected by a system of gutters and downspouts and
transmitted by pipe to a storm drainage system where the water can drain away
without entering the building subgrade.
• Sidewalks should not be structurally connected to the structure. They should be
sloped away from the structure so that surface water will drain away.
• Sprinkler lines and sprinkler heads, if used, should not be placed alongside the
sidewalls of the structure, but should be placed away from the structure such that
the water will be sprayed towards the structure. The purpose of this
recommendation is to mitigate the ponding and subsequent percolation of water
into the soils beneath the structure causing detrimental vertical movements in the
event that a sprinkler line or sprinkler head ruptures.
• Utilities that project through the slabs on grade should be designed with either
some degree of flexibility or with sleeves. Such design features will help to
reduce the risk of damage to the utility lines as vertical movements occur.
• Backfill for utility lines or along grade beams should consist of onsite material. If
the backfill is too dense or dry, swelling may form a mound along the ditch line.
The soils should be processed through the previously discussed compaction
criteria. If non-plastic soil is used for bedding, a clay plug should be constructed
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at the slab on grade face to diminish access to the interior of the slab from
percolating water transmitted through the bedding material.
• During construction, every attempt should be made to limit the extreme wetting or
drying of the subsurface soils since swelling or shrinkage will result. Standard
construction practices of providing surface water drainage should be used. A
positive slope of the ground away from the foundations and select fill excavations
and ditches is recommended along with ditches or swales provided to carry off
the runoff water both during and after construction.
Wet Weather Earthwork
During or after wet weather, it may be necessary to import granular materials to protect
open subgrade soils. It may also be necessary to install a granular working pad to
support construction equipment. Delays in site earthwork activities should be anticipated
during periods of heavy rainfall. Additionally, site clearing and stripping activities may
expose subgrade material that may be damaged if subjected to disturbance from
construction traffic.
When a granular working base is used to protect open subgrade material and
construction equipment, the base should consist of a suitable thickness of crushed rock
or ballast placed by end-dumping off an advancing pad of rock fill. Because construction
practices can greatly affect the amount of rock required, we recommended that if
conditions require the installation of a granular working blanket, the design, installation
and maintenance be made the responsibility of the contractor. After installation, the
working blanket should be compacted with a minimum of four overlapping passes with a
smooth-faced steel drum or grid roller.
Construction Monitoring
Red Rock Consulting should be retained to provide construction monitoring services
during earthwork activities and foundation construction. The purpose of field monitoring
services is to confirm that site conditions are as anticipated, to provide field
recommendations as required based on conditions encountered and to document the
activities of the contractor to assess compliance with the project recommendations
provided by Red Rock Consulting.
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ENVIRONMENTAL CONSIDERATIONS
The environmental effect of construction projects is a growing concern in our industry.
Some points for consideration of the environment regarding site construction and
construction materials are summarized in the following paragraphs. These points should
be incorporated into the design and construction of this project for a more
environmentally friendly result. The following is only a summary. For a more in-depth
discussion on sustainable design and construction, please contact Red Rock Consulting.
SITE CONSTRUCTION
Sedimentation and Erosion Control
Reduce pollution from construction activities by controlling soil erosion, waterway
sedimentation and airborne dust generation. This can be accomplished most efficiently
by using seeding or mulching and silt fence.
• Seeding or Mulching – If, for some reason, the excavated site is left open for an
extended amount of time, soil erosion should be retarded by using seeding or
mulching to cover and hold the soils.
• Silt Fence – Prevent sedimentation of the storm sewer or receiving streams by
constructing silt fence (posts with a filter fabric media) around the project site.
The silt fence is used to remove sediment from stormwater that may runoff the
construction site.
CONSTRUCTION MATERIALS
Local Materials
Increase the demand for building materials and products that are extracted and
manufactured within the region, thereby supporting the use of indigenous resources and
reducing the environmental impacts resulting from transportation of materials. Examples
of local materials that could be considered in the construction of this project include
cement, fly ash, water, recycled concrete and/or aggregate and sand.
Recycled Materials
Reuse building materials and products in order to reduce demand for virgin materials
and to reduce waste, thereby reducing impacts associated with the extraction and
processing of virgin resources. Examples of recycled materials that could be considered
in the construction of this project include recycled concrete and aggregate.
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CLOSURE
The data presented in this report are based on site conditions as they existed at the time
of the field exploration. The conditions encountered in the exploratory borings are
representative subsurface conditions within the study area.
This report was prepared for the exclusive use of Cobb Engineering, ODOT and their
agents and consultants. It should be made available to prospective contractors for
information and factual data only and not as a warranty of subsurface conditions similar
to those interpreted from the boring logs or discussions presented herein.
APPENDIX A
32
33
15
16
17
17
SPT
SPT
SPT
SPT
SPT
SPT
83.5
82.3
2" AGGREGATE BASE
LEAN CLAY with SAND, red brown, medium stiff to stiff
LEAN CLAY, red, shaley, hard
SHALE, red, soft
Boring Completed and Backfilled, 4/27/11
10
7
5
11
32
22
50/5.5"
17
18
19
18
18
14
NOTES Southwest Corner of Shed
GROUND ELEVATION
LOGGED BY JTU
DRILLING METHOD 4" augers - CME 55
HOLE SIZE 6 in
DRILLING CONTRACTOR DSO - Drilling Services of Oklahoma GROUND WATER LEVELS:
CHECKED BY KKB
DATE STARTED 4/27/11 COMPLETED 4/27/11
DURING DRILLING none
0 hrs AFTER DRILLING none
Cave In Depth open
LIQUID
LIMIT
PLASTIC
LIMIT
PLASTICITY
INDEX
SAMPLE TYPE
ATTERBERG
LIMITS
GRAPHIC
LOG
FINES CONTENT
(%)
DEPTH
(ft)
0
5
10
15
20
MATERIAL DESCRIPTION
BLOW
COUNTS
MOISTURE
CONTENT (%)
PAGE 1 OF 1
BORING NUMBER B-1
PROJECT NAME El Reno Residency Salt Shed
PROJECT LOCATION El Reno, Oklahoma
CLIENT Cobb Engineering
PROJECT NUMBER 11029
P.O. Box 30591
Edmond, OK 73003
Telephone: 405-562-3328
GEOTECH BH COLUMNS 11029 LOGS.GPJ DATA TEMPLATE.GDT 5/3/11
33 16 17
SPT
SPT
SPT
SPT
SPT
SPT
85.5
3 1/2" AGGREGATE BASE
LEAN CLAY, red brown, medium stiff to hard
Iron stains from approximately 10 feet
SHALE, red brown with gray, moderately hard
Boring Completed and Backfilled, 4/27/11
6
6
6
9
30
13
35
50/3"
18
19
21
19
15
14
NOTES Northeast Corner of Shed
GROUND ELEVATION
LOGGED BY JTU
DRILLING METHOD 4" augers - CME 55
HOLE SIZE 6 in
DRILLING CONTRACTOR DSO - Drilling Services of Oklahoma GROUND WATER LEVELS:
CHECKED BY KKB
DATE STARTED 4/27/11 COMPLETED 4/27/11
DURING DRILLING none
0 hrs AFTER DRILLING none
Cave In Depth open
LIQUID
LIMIT
PLASTIC
LIMIT
PLASTICITY
INDEX
SAMPLE TYPE
ATTERBERG
LIMITS
GRAPHIC
LOG
FINES CONTENT
(%)
DEPTH
(ft)
0
5
10
15
20
MATERIAL DESCRIPTION
BLOW
COUNTS
MOISTURE
CONTENT (%)
PAGE 1 OF 1
BORING NUMBER B-2
PROJECT NAME El Reno Residency Salt Shed
PROJECT LOCATION El Reno, Oklahoma
CLIENT Cobb Engineering
PROJECT NUMBER 11029
P.O. Box 30591
Edmond, OK 73003
Telephone: 405-562-3328
GEOTECH BH COLUMNS 11029 LOGS.GPJ DATA TEMPLATE.GDT 5/3/11
APPENDIX B
Tested By:
Project #
Ordered By:
Lab#
Bore
Hole
Depth Liquid
Limit
Plastic
Index
%
Moist.
- 200
Sieve
-80
Sieve
- 40
Sieve
-10
Sieve
-4
Sieve
-3/8'
Sieve
-1/2"
Sieve
-3/4"
Sieve
-1"
Sieve
-1 1/2"
Sieve
Sulfate
B-1 2' 32 17 17.0 83.5 <200 ppm
B-1 4' 17.5 <200 ppm
B-1 7' 33 17 18.6 82.3 <200 ppm
B-1 10' 18.1 213 ppm
B-1 15' 18.3 240 ppm
B-1 20' 13.8 240 ppm
B-2 2' 18.1
B-2 4' 33 17 18.8 85.5
B-2 7' 20.7
B-2 10' 19.0
B-2 15' 14.9
B-2 20' 13.9
OKC # 64
J.Orth ODOT #3181
11029 Cobb # 09061.65
Project: El Reno Salt Shed
4/27/11
SUMMARY SHEET
K.Bumpas
Date Received:
Client: Red Rock Consulting, LLC
Report Date: 5/2/11
APPENDIX C
GENERAL NOTES
The Unified Soil Classification System is used to identify the soil unless
otherwise noted.
UNIFIED SOIL CLASSIFICATION SYSTEM ASTM D 2487
b Distinguishing between M and O classifications requires identifying organic components by
observation, odor, or other testing.
SOIL PROPERTY SYMBOLS
N Standard “N” penetration: Blows per foot
Qu Unconfined Compressive Strength, tsf
Qp Penetrometer value, tsf
Mc Water Content, %
LL Liquid Limit, %
PI Plasticity Index, %
DD Natural Dry density, pcf
Apparent groundwater levels
DRILLING AND SAMPLING SYMBOLS
BS Bag Sample
SPT Split Spoon – 1 3/8” I.D., 2” O.D., except where noted
ST Shelby Tube – 3” O.D., except where noted
AU Auger Sample
TC Texas Cone Penetrometer
DCP Dynamic Cone Penetrometer
RELATIVE DENSITY AND COSNISTENCY CLASSIFICATIONS
DEGREE OF PLASTICITY OF COHESIVE SOILS
Degree of
Plasticity
Plasticity
Index
Swell Potential
None 0 to 4 Very Low
Slight 5 to 9 Low
Medium 10 to 19 Low to Medium
High 20 to 39 Medium to High
Very High 40+ Very High
MOISTURE CONDITION OF COHESIVE SOILS
Description Condition
Moisture
Content
Absence of
moisture, dusty,
dry to touch
Dry 0 to 10%
Damp but no
visible water
Moist 10 to 30%
Visible free water Wet 30 to 70%
COHESIVE SOILS
CONSISTENCY SPT Qu – (tsf)
Very Soft <2 0.00 – 0.25
Soft 2 to 4 0.25 – 0.50
Medium Stiff 5 to 8 0.50 – 1.00
Stiff 9 to 14 1.00 – 2.00
Very Stiff 15 to 30 2.00 – 4.00
Hard 31+ 4.00+
COHESIONLESS SOILS
RELATIVE DENSITY SPT
Very Loose <4
Loose 4 to 10
Medium Dense 11 to 30
Dense 31 to 50
Very Dense 51+
QUALITY OF ROCK CORE
CORE
QUALITY
R.Q.D. CONDITIONS
Excellent
Quality
90 –
100%
Unweathered
Good Quality 75 – 90% Slightly Weathered
Fair Quality 50 – 75%
Moderately
Weathered
Poor Quality 25 – 50% Highly Weathered
Very Poor
Quality
<25%
Completely
Weathered
PARTICAL SIZE
DESCRIPTION SIZE
Boulders 11.81 in.
Cobbles 2.95 in.
Gravel 0.19 in.
Course Sand 0.08 in.
Medium Sand 0.02 in.
Fine Sand 0.003 in.
Silt 0.0002 in.
Major Divisions Group
Symbol Typical Names
Course-
Grained Soils
More than 50%
retained on the
No. 200 sieve
Gravels
50% or more of course fraction retained
on the No. 4 sieve
Clean
Gravels
GW Well-graded gravels and gravel-sand mixtures, little or no fines
GP Poorly graded gravels and gravel-sand mixtures, little or no fines
Gravels
with
Fines
GM Silty gravels, gravel-sand-silt mixtures
GC Clayey gravels, gravel-sand-clay mixtures
Sands
50% or more of course fraction passes
the No. 4 sieve
Clean
Sands
SW Well-graded sands and gravelly sands, little or no fines
SP Poorly graded sands and gravelly sands, little or no fines
Sands
with
Fines
SM Silty sands, sand-silt mixtures
SC Clayey sands, sand-clay mixtures
Fine-Grained
Soils
More than 50%
passes the
No. 200 sieve
Silts and Clays
Liquid Limit 50% or less
ML Inorganic silts, very fine sands, rock four, silty or clayey fine sands
CL Inorganic clays of low to medium plasticity, gravelly/sandy/silty/lean clays
OL Organic silts and organic silty clays of low plasticity
Silts and Clays
Liquid Limit greater than 50%
MH Inorganic silts, micaceous or diatomaceous fine sands or silts, elastic silts
CH Inorganic clays or high plasticity, fat clays
OH Organic clays of medium to high plasticity
Highly Organic Soils PT Peat, muck, and other highly organic soils
Prefix: G = Gravel, S = Sand, M = Silt, C = Clay, O = Organic Suffix: W = Well Graded, P = Poorly Graded, M = Silty, L = Clay, LL < 50%, H = Clay, LL > 50%