Methods of exploration:
There are 4 methods of exploration
1. Open excavation
2. Borings
3. Geophysical method
4. soundings and penetration tests
1. Open excavation:
· This is suitable for shallow depth up to 3m
· For this, test pits, test trenches
and open borings are used
2. Borings:
· these are used for depths > 3m or
when difficult groundwater conditions are met.
1. Auger boring:
§ This method is suitable
identification of various types of soils and also for getting information about
the depth of the groundwater table.
§ Hand-operated augers are used upto
depth of 6m in soft soil whereas power-driven augers are used for greater depth
in harder strata
2. Wash boring:
§ This method is used below the water table
and is suitable for all types of soil except hard rock.
3. Percussion drilling:
§ It is used when the hole is to be
made is very hard or soft rock because in both cases, auger or wash borings can
not be used i.e. bouldery and gravelly strata
4. Rotary drilling:
§ This method is used for rocks, clays
and sands
3. Geophysical method:
· This method consists of identification
of underground material by measuring the change in the character of the surface
material due to the presence of different types of sub-surface materials.
· This method is very useful to explore
large areas much more rapidly and economically than borings methods
· The various geophysical methods of
subsurface exploration are:
§ Seismic refraction method
§ Electrical resistively method
4.Sounding and penetration tests:
· These methods are used to measurement
of the resistance to penetration of a driving rod, sampling spoon, a cone etc.
under dynamic or static loading
· The most commonly use soundings tests
are
o
Standard
penetration test
o
cone
penetration test
These methods of soil exploration are
useful for cohesionless soils.
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