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general characters and structures of rock formations such as their stratification, folding
and faulting and igneous intrusions, and
the trend and rate of weathering and erosion in the area.
Geology of the site
The single most important feature that must be known thoroughly at the site and
all around and below the valley up to a reasonable depth is the Lithology, i.e.
types of the rocks that make the area.
Surface and subsurface studies using the conventional and latest techniques of
geological and geophysical investigations are carried out.
Such studies would reveal the type, the composition and textures of the rocks
exposed along the valley floor, in the walls and up to the required depth at the
Rocks are inherently anisotropic materials, showing variation in properties in
Complex litho logy definitely poses challenging design problems.
This involves detailed mapping of planes of weakness like bedding planes, schistosity,
foliation, cleavage, joints, shear zones, faults and fault zones, folding and the associated
While mapping these features, special attention is given to recording their attitude,
spacing and nature.
Shear zones have to be searched, mapped and treated with great caution.
In some cases, these may be developed to such an extent that the rock may necessitate
extensive and intensive rock treatment (e.g. excavation, backfilling and grouting etc.).