Engineering properties of soil at a site is
essential for proper design and construction of any structure. The field and
laboratory investigations are required. The objective is selection of
foundation and its depth, and to find the bearing capacity, settlement analysis
etc. are to be done.
Soil exploration may be needed for deciding
remedy of any foundation failure of a structure. The design and construction of
pavements of airport and high ways will also depend upon soil strata and
properties
Uses of Soil Exploration
- To determine nature of soil
- To know depth and thickness of
soil strata and its horizontal extent
- Location of GWT
- Obtain soil and rock samples
- To determine in-situ soil
properties
Site Investigation
To get information regarding surface conditions, which
is necessary for planning construction technique. Engineer have to know accessibility to site to men and
materials, Nature of site to find cost of site clearance, Availability of water
and electric supply. Information of subsurface conditions is also needed.
Site investigation may involve
reconnaissance, study of maps, aerial photography, earth cutting in the nearby
wells etc.
Reconnaissance
It involves an inspection of the site and
study topographical features. This will give useful information about the soil
and ground water conditions and help the engineer to plan program of
exploration. Ground water conditions are often reflected in the presence of
springs and type of vegetations. Valuable information about earth fills,
knowledge of any difficulty encountered during the construction of nearby
buildings may be obtained by enquiry.
Study of Maps
Information on surface and subsurface
conditions in the area are available with survey of India and Geological survey
of India from topo sheets .
A geological study must be done. The
purpose o f which is to establish, nature of underlying deposits. The type of
soil and rock and also want to study about any defects in soil that is cracks
or caves To evaluate the availability of natural resources such as oil ,gas and
minerals. Problems may arise out of
mining activity. Seismic potential activity is also studied. Maps are
available about Earth quakes and zones.
Aerial Photography
Its now well developed method by which site
investigation may be done. From air photo underground condition may be
estimated.
Land form represents the total effect of
environment and geological history on the underlying rock and soil foundations.
Soil Exploration
Generally , the methods available for soil
exploration may be classified as
- Direct methods- Test pits and
trenches
- Semi-direct methods- borings
- Indirect methods- soundings or penetration tests and geo physical methods
Test pits
Soils can be inspected in
their natural condition. The soil samples can be tested in the laboratory for
strength and other properties. This is done only for minor structures
Boring
Making bore holes in to the ground to obtain rock samples. Common methods are:
- Auger boring
- Auger and shell boring
- Wash boring
- Percussion drilling
- Rotary drilling
Drilling are done for rock strata.
Soil investigation for the construction of
a civil project is very important. At top a strata may be hard but under that
it may be organic matter.
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