CHAPTER 3.
LABORATORY TESTING
Section 1.
INTRODUCTION
1. SCOPE. This chapter covers laboratory test procedures, typical test
properties, and the application of test results to design and construction.
Symbols and terms relating to tests and soil properties conform, generally,
to definitions given in ASTM Standard D653, Standard Definitions of Terms
and Symbols Relating to Soil and Rock Mechanics found in Reference 1, Annual
Book of ASTM Standards, by the American Society for Testing and Materials.
2. RELATED CRITERIA. For additional requirements concerning laboratory
tests for highway and airfield design, see the following:
Subject
Source
Airfield Pavements......................................NAVFAC DM-21 Series
and
DM-21.03
Pavements, Soil Exploration, and Subgrade Testing.......NAVFAC DM-5.04
3. LABORATORY EQUIPMENT.
For lists of laboratory equipment for performance
of tests, see Reference 2,
Soil Testing for Engineers, by Lambe, Reference
3, The Measurement of Soil
Properties in the Triaxial Test, by Bishop and
Henkel, and other criteria
sources.
4. TEST SELECTION FOR DESIGN.
Standard (ASTM) or suggested test
procedures, variations that may
be appropriate, and type and size of sample
are included in Tables 1, 2, 3,
and 4. Table 5 lists soil properties
determined from such tests, and
outlines the application of such properties
to design. ASTM procedures are
found in Reference 1.
a. Sample Selection. Samples to be tested should be representative,
i.e. they should be similar in characteristics to most of the stratum from
which they come, or be an average of the range of materials present. If
this appears difficult because of variations in the stratum, it may be
necessary to consider subdivisions of the stratum for sampling, testing, and
design purposes. In general, tests on samples of mixed or stratified
material, such as varved clay, should be avoided; usually such results are
not indicative of material characteristics; and better data for analysis can
be obtained by testing the different materials separately. Undisturbed
samples for structural properties tests must be treated with care to avoid
disturbance; an "undisturbed" sample found to be disturbed before testing
normally should not be tested. Fine-grained cohesive samples naturally
moist in the ground should not be allowed to dry before testing, as
irreversible changes can occur; organic soils are particularly sensitive.
Soils with chemical salts in the pore water may change if water is added,
diluting the salt concentration, or if water is removed, concentrating or
precipitating the salt. Organic soils require long-term low temperature
(60deg.C) drying to avoid severe oxidation (burning) of the organic
material.
7.1-117
Change 1, September 1986
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