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The date and time that the borings are started, completed, and of water level measurements.
Closure of borings.
Boring logs provide the basic information for the selection of test specimens. They provide background data
on the natural condition of the formation, on the ground water elevation, appearance of the samples, and the
soil or rock stratigraphy at the boring location, as well as areal extent of various deposits or formations. Data
from the boring logs are combined with laboratory test results to identify subgrade profiles showing the extent
and depth of various materials at the subject site. Soil profiles showing the depth and the location of various
types of materials and ground water elevations are plotted for inclusion in the geotechnical engineer’s final
report and in the plans and specifications. Detailed boring logs including the results of laboratory tests are
included in the text of the report.
The top of each boring log provides a space for project specific information: name or number of the project,
location of the project, drilling contractor (if drilling is contracted out), type of drilling equipment, date and
time of work, drilling methods, hammer weight and fall, name of personnel logging the boring, and weather
information. All information should be provided on the first sheet of each boring log.
BORING LOCATIONS AND ELEVATIONS
The boring location (coordinates and/or station and offset) and ground surface elevation (with datum) must
be recorded on each boring log. Procedures discussed in Section 2.5.3 should be used for determining the
location and elevation for each boring site.
The subsurface conditions observed in the soil samples and drill cuttings or perceived through the
performance of the drill rig (for example, rig chatter in gravel, or sampler rebounding on a cobble during
driving) should be described in the wide central column on the log labeled “Material Description”, or in the
remarks column, if available. The driller's comments are valuable and should be considered as the boring
log is prepared. In addition to the description of individual samples, the boring log should also describe
various strata. The record should include a description of each soil layer, with solid horizontal lines drawn
to separate adjacent layers. It is important that a detailed description of subsurface conditions be provided
on the field logs at the time of drilling. Completing descriptions in the laboratory is not an acceptable
practice. Stratification lines should be drawn where two or more items in the description change, i.e., change
from firm to stiff and low to high plasticity. Minor variations can be described using the term 'becoming'.
A stratification line should be drawn where the geological origin of the material changes and the origin (if
determined) should be designated in the material description or remarks column of the log. Dashed lines
should be avoided.
The stratigraphy observations should include identification of existing fill, topsoil, and pavement sections.
Careful observation and special sampling intervals may be needed to identify the presence and thickness of
these strata. The presence of these materials can have a significant impact on the conclusions and
recommendations of the geotechnical studies.
Individual strata should be marked midway between samples unless the boundary is encountered in a sample
or special measurements are available to better define the position of the boundary.
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Information regarding the sampler types, date & time of sampling, sample type, sample depth, and recovery
should be shown on each log form using notations and a graphical system or an abbreviation system as
designated in Figures 4-4 and 4-5. Each sample attempt should be given a sequential number marked in the
sample number column. If the sampler is driven, the driving resistance should be recorded at the specified
intervals and marked in the sampling resistance column. The percent recovery should be designated as the
length of the recovered sample referenced to the length of the sample attempt (example 550/610 mm).
SOIL DESCRIPTION AND SOIL CLASSIFICATION
Soil description/identification is the systematic, precise, and complete naming of individual soils in both
written and spoken forms (ASTM D-2488, AASHTO M 145), while soil classification is the grouping of
the soil with similar engineering properties into a category based on index test results; e.g., group name and
symbol (ASTM D-2487, AASHTO M 145). It is important to distinguish between visual identification and
classification to minimize conflicts between general visual evaluation of soil samples in the field verses a more
precise laboratory evaluation supported by index tests. During progression of a boring, the field personnel
should only describe the soils encountered. Group symbols associated with classification should not be used
in the field. Visual descriptions in the field is often subjected to outdoor elements, which may influence
results. It is important to send the soil samples to a laboratory for accurate visual identification by a
technician experienced in soils work, as this single operation will provide the basis for later testing and soil
profile development. Classification tests can be performed by the laboratory on representative samples to
verify identification and assign appropriate group symbols. If possible, the moisture content of every sample
should be performed.
The soil's description should include as a minimum:
Apparent consistency (for fine-grained soils) or density adjective (for coarse-grained soils)
Water content condition adjective (e.g., dry, damp, moist, wet)
Minor soil type name with "y" added if fine-grained minor component is less than 30 percent but
greater than 12 percent or coarse-grained minor component is 30 percent or more.
Descriptive adjective for main soil type
Particle-size distribution adjective for gravel and sand
Plasticity adjective and soil texture (silty or clayey) for inorganic and organic silts or clays
Main soil type name (all capital letters)
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Descriptive adjective “with” for the fine-grained minor soil type if 5 to 12 percent or for the coarse-
grained minor soil type if less than 30 percent but 15 percent or more (note some practices use the
descriptive adjectives “some” and “trace” for minor components).
Descriptive term for minor type(s) of soil
Inclusions (e.g., concretions, cementation)
Geological name (e.g., Holocene, Eocene, Pleistocene, Cretaceous), if known, (in parenthesis or in
The various elements of the soil description should generally be stated in the order given above. For example:
Soft, wet, gray, high plasticity CLAY, with f. Sand; (Alluvium)
Coarse-grained soils: Dense, moist, brown, silty m-f SAND, with f. Gravel to c. Sand; (Alluvium)
When changes occur within the same soil layer, such as change in apparent density, the log should indicate
a description of the change, such as “same, except very dense”.
Consistency and Apparent Density
The consistency of fine-grained soils and apparent density of coarse-grained soils are estimated from the blow
count (N-value) obtained from Standard Penetration Tests (AASHTO T-206, ASTM D 1586). The
consistency of clays and silts varies from soft to firm to stiff to hard. The apparent density of coarse-grained
soil ranges from very loose to firm to dense and very dense Suggested guidelines in Tables 4-1 and 4-2 are
given for estimating the in-place consistency or apparent density of soils from N-values.
The apparent density or consistency of the soil formation can vary from these empirical correlations for a
variety of reasons. Judgment remains an important part of the visual identification process. Mechanical tools
such as the pocket (hand) penetrometer, and field index tests (smear test, dried strength test, thread test) are
suggested as aids in estimating the consistency of fine grained soils.
In some cases the sampler may pass from one layer into another of markedly different properties; for
example, from a dense sand into a soft clay. In attempting to identify apparent density, an assessment should
be made as to what part of the blow count corresponds to each layer; realizing that the sampler begins to
reflect the presence of the lower layer before it reaches it.
The N-values in all soil types should be corrected for energy efficiency, if possible (ASTM D 4633). An
energy efficiency of 60% is considered the reference in the U.S. In certain geotechnical evaluations of coarse-
grained soil behavior (relative density, friction angle, liquefaction potential), the blow count (N-value) should
be normalized to a reference stress of one atmosphere, as discussed in Chapters 5 and 9.
Note that N-values should not
be used to determine the design strength of fine grained soils.
Water Content (Moisture)
The amount of water present in the soil sample or its water content adjective should be described as dry,
moist, or wet as indicated in Table 4-3.
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The color should be described when the sample is first retrieved at the soil's as-sampled water content (the
color will change with water content). Primary colors should be used (brown, gray, black, green, white,
yellow, red). Soils with different shades or tints of basic colors are described by using two basic colors; e.g.,
gray-green. Note that some agencies may require Munsell color and carry no inferences of texture
designations. When the soil is marked with spots of color, the term “mottled” can be applied. Soils with a
homogeneous texture but having color patterns which change and are not considered mottled can be described
ON OF THE A
ITY OF COARSE-
4 - 13
VES TO DESCR
BE WATER CONTENT OF SO
No sign of water and soil dry to touch
Signs of water and soil is relatively dry to touch
Signs of water and soil wet to touch; granular soil exhibits some free water when densified
Type of Soil
The constituent parts of a given soil type are defined on the basis of texture in accordance with particle-size
designators separating the soil into coarse-grained, fine-grained, and highly organic designations. Soil with
more than 50 percent of the particles larger than the (U.S. Standard) No. 200 sieve (0.075 mm) is designated
coarse-grained. Soil (inorganic and organic) with 50 percent or more of the particles finer than the No. 200
sieve is designated fine-grained. Soil primarily consisting of less than 50 percent by volume of organic
matter, dark in color, and with an organic odor is designated as organic soil. Soil with organic content more
than 50 percent is designated as peat. The soil type designations follow ASTM D 2487; i.e., gravel, sand,
clay, silt, organic clay, organic silt, and peat.
Coarse-Grained Soils (Gravel and Sand)
Coarse-grained soils consist of gravel, sand, and fine-grained soil, whether separately or in combination, and
in which more than 50 percent of the soil is retained on the No. 200 sieve. The gravel and sand components
are defined on the basis of particle size as indicated in Table 4-4.
The particle-size distribution is identified as well graded or poorly graded. Well graded coarse-grained soil
contains a good representation of all particle sizes from largest to smallest. Poorly graded coarse-grained soil
is uniformly graded with most particles about the same size or lacking one or more intermediate sizes.
Gravels and sands may be described by adding particle-size distribution adjectives in front of the soil type
following the criteria given in Table 4-5. Based on correlation with laboratory tests, the following simple
field identification tests can be used as an aid in identifying granular soils.
Feel and Smear Tests
: A pinch of soil is handled lightly between the thumb and fingers to obtain an
impression of the grittiness or of the softness of the constituent particles. Thereafter, a pinch of soil is
smeared with considerable pressure between the thumb and forefinger to determine the degrees of roughness
and grittiness, or the softness and smoothness of the soil. Following guidelines may be used:
Coarse- to medium-grained sand typically exhibits a very harsh and gritty feel and smear.
Coarse- to fine-grained sand has a less harsh feel, but exhibits a very gritty smear.
Medium- to fine-grained sand exhibits a less gritty feel and smear which becomes softer and less
gritty with an increase in the fine sand fraction.
Fine-grained sand exhibits a relatively soft feel and a much less gritty smear than the coarser sand
Silt components less than about 10 percent of the total weight can be identified by a slight
discoloration of the fingers after smear of a moist sample. Increasing silt increases discoloration and
softens the smear.
4 - 14
: A small sample of the soil is shaken in a test tube filled with water and allowed to settle.
The time required for the particles to fall a distance of 100 mm is about 1/2 minute for particle sizes coarser
than silt. About 50 minutes would be required for particles of .005 mm or smaller (often defined as "clay
size") to settle out.
For sands and gravels containing more than 5 percent fines, the type of inorganic fines (silt or clay) can be
identified by performing a shaking/dilatancy test. See fine-grained soils section.
: Sand and gravel particles can be readily identified visually but silt particles are
generally indistinguishable to the eye. With an increasing silt component, individual sand grains become
obscured, and when silt exceeds about 12 percent, it masks almost entirely the sand component from visual
separation. Note that gray fine-grained sand visually appears siltier than the actual silt content.
ON FOR GRAVELS AND SANDS
300 mm +
300 mm to 75 mm
75 mm to 19 mm
19 mm to #4 sieve (4.75 mm)
#4 to #10 sieve
#10 to #40 sieve
#40 to #200 sieve
Measurable and visible to eye
Measurable and visible to eye
Measurable and barely discernible to the eye
Boulders and cobbles are not considered soil or part of the soil's classification or description, except under
miscellaneous description; i.e., with cobbles at about 5 percent (volume).
VES FOR DESCR
ON FOR SANDS AND GRAVELS
< 30% m-f sand or < 12% f. gravel
Coarse to medium
< 12% f. sand
Medium to fine
< 12% c. sand and > 30% m. sand
< 30% m. sand or < 12% c. gravel
Coarse to fine
> 12% of each size
12% and 30% criteria can be modified depending on fines content. The key is the shape of the particle-size
distribution curve. If the curve is relatively straight or dished down, and coarse sand is present, use c-f, also
use m-f sand if a moderate amount of m. sand is present. If one has any doubts, determine the above
percentages based on the amount of sand or gravel present.
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