b. Preliminary Exploration. This may include borings to recover
samples for identification tests only.
c. Detailed Exploration. This phase normally includes borings,
disturbed and undisturbed sampling for laboratory testing, standard
penetration resistances, and other in situ measurements. At critical sites
it may also include test pits, piezometer measurements, pumping tests, etc.
d. Construction/Post Construction Phases. Further evaluation of
foundation conditions may be required during the construction phase.
Monitoring of the site or structure may be necessary throughout the
construction and post construction phases.
Section 2.
PUBLISHED SOIL AND GEOLOGICAL MAPS
1. SOURCES. Data on the physical geology of the United States are
available in maps and reports by government agencies, universities, and
professional societies (see Table 1). These sources often contain
geological information on foreign countries.
2. PREVIOUS INVESTIGATIONS. For studies in developed areas, collect
information from previous work on foundations and subsurface conditions.
a. Shipyard or Waterfront Areas. These locations often have undergone
cycles of expansion and reconstruction with older foundations remaining
buried in place. Records of former construction may contain information on
borings, field tests, groundwater conditions, and potential or actual
sources of trouble.
b. Evaluation. Review of data from previous work should receive the
greatest attention of any phase in a reconnaissance investigation.
Section 3.
REMOTE SENSING DATA METHODS
1. SOURCES. Remote sensing data are acquired by imagery recovery
devices and their transporting media. Aerial photographs are the most
common type with coverage of almost the entire United States available at
scales from 1:12,000 to 1:80,000. With the advent of improving technology,
space programs and data gathering satellites, a wealth of other remote
sensed data are now available for use. Table 2 summarizes the types of data
most commonly used in engineering studies. Photos at larger scale up to
1:2000 are available for some locations from state agencies and commercial
aero-photogrammetric firms.
2. UTILIZATION. Use of photographs and mosaics is routine in most large
engineering studies such as highway and airfield work. Other forms of
remote sensing data are used on a more selective basis when required. For a
complete description on the use of imagery in earthquake analysis, see
Reference 2, Imagery in Earthquake Analysis, by Glass and Slemmons. For
unfamiliar sites, the air photographs aid in planning and layout of an
appropriate boring program.
7.1-51
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