Soil Exploration - Soil Properties: Testing, Measurement, and Evaluation - page 6

Aerial photographs can provide geologic information over large
areas. Proper interpretation of these photographs may reveal land pat-
terns, sinkhole cavities, landslides, surface drainage patterns, and the
like. Such information can usually be obtained on a more widespread
and thorough basis by aerial photography than by visiting the project
site. Specific details on this subject are, however, beyond the scope of
this topic. For more information, the reader is referred to the many
topics available on aerial photo interpretation.
After carefully collecting and studying available pertinent infor-
mation, the geotechnical engineer should visit the site in person,
observe thoroughly and carefully, and interpret what is seen. The abil-
ity to do this successfully requires considerable practice and experience;
however, a few generalizations are given next.
To begin with, significant details on surface conditions and general
information about subsurface conditions in an area may be obtained by
observing general topographical characteristics at the proposed job site
and at nearby locations where soil was cut or eroded (such as railroad
and highway cuts, ditch and stream erosion, and quarries), thereby
exposing subsurface soil strata.
The general topographical characteristics of an area can be of signif-
icance. Any unusual conditions (e.g., swampy areas or dump areas, such
as sanitary landfills) deserve particular attention in soil exploration.
Because the presence of water is often a major consideration in
working with soil and associated structures, several observations
regarding water may be made during reconnaissance. Groundwater
tables may be noted by observing existing wells. Historical high water-
marks may be recorded on buildings, trees, and so on.
Often, valuable information can be obtained by talking with local
inhabitants of an area. Such information could include the flooding his-
tory, erosion patterns, mud slides, soil conditions, depths of overburden,
groundwater levels, and the like.
One final consideration is that the reconnoiterer should take nu-
merous photographs of the proposed construction site, exposed subsur-
face strata, adjacent structures, and so on. These can be invaluable in
subsequent analysis and design processes and in later comparisons of
conditions before and after construction.
The authors hope the preceding discussion in this section has made
the reader aware of the importance of reconnaissance with regard to soil
exploration at a proposed construction site. In addition to providing im-
portant information, the results of reconnaissance help determine the
necessary scope of subsequent soil exploration.
At some point prior to beginning any subsurface exploration, it is
important that underground utilities (water mains, sewer lines, etc.) be
located to assist in planning and carrying out subsequent subsurface
exploration.

After all possible preliminary information is obtained as indicated in the
preceding section, the next step is the actual subsurface soil exploration.
It should be done by experienced personnel, using appropriate equipment.

STEPS OF SOIL
EXPLORATION