TABLE 1
Types of Bituminous Surfaces
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*
*
*
*
Suitable Surfaces
*
*
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*
*Parking*Primary*Secondary*Tertiary*
Description
*
* lots * roads * roads
* roads *
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*Hot-mix asphalt concretes ..........* Yes * Yes
* Yes
* Yes
*
* Cold-Mix bituminous mixes mixed in *
*
*
*
*
* place..............................* No
* No
* Yes
* Yes
*
*Sand asphalt........................* Yes * No
* Yes
* Yes
*
*Bituminous surface treatment........* Yes * No
* No
* Yes
*
*Penetration macadam.................* Yes * No
* Yes
* Yes
*
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Section 2. SOIL EXPLORATION AND SUBGRADE TESTING
1. PRELIMINARY INVESTIGATIONS. Preliminary site reconnaissance and soil
investigations include the use of soils and geologic maps, aerial photographs,
and geophysical exploration to ascertain the general soil conditions. See
NAVFAC DM-7 for a complete description of techniques and procedures for
preliminary surveys.
2. EXPLORATORY BORINGS. Use appropriate auger and split tube sampling to
determine subsurface soil types and to develop soil profiles.
a. Spacing of Borings. The maximum spacing of borings along the centerlines
of proposed roads should be 300 feet. In areas of widely varying soil types, a
spacing of 100 feet or less may be required. Locate additional borings in
areas where abrupt changes in profile occur.
b. Depth of Borings. Borings should be deep enough to develop soil profiles
which are representative of the local soil conditions. As a general guide, for
most sections of roadway, the following minimum depths should be used:
(1) Cut Sections. To 6 feet below finished grade.
(2) Shallow Fill Sections. In shallow fill sections where the weight of
the fill is small compared with traffic loads, conduct borings to a minimum
depth of 6 feet below existing grade.
(3) Other. Deeper borings are required wherever structures are located,
in high fill areas, and where soft compressible soils are encountered. For
guidance on proper boring depth, see NAVFAC DM-7.
3. SOIL CLASSIFICATION. Classify all soils using the Unified Soil
Classification System according to Military Standard (MIL-STD) 619. The
engineering characteristics of soils classified by the Unified Method are
given in Table 2.
3
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