Necessity of Site investigation –
1. To determine bearing capacity of soil
2. To select suitable construction techniques
3.To select the type and depth of foundation for given structure
4.To investigate safety of existing structures and to suggest the remedial measures
5. To predict lateral earth pressure against retaining walls & foundation of abutments
6. To establish ground water level and to determine the properties of water.
Necessity of sub-soil exploration -
1. To know stratification below ground surface
2. To determining index properties of soil like bulk density, voids ratio, water content, permeability, bearing capacity, compressibility etc.
3. To determine safe bearing capacity for design of foundation of proposed structure
4. To control the seepage and rise of ground water below surface
5. To decide size , depth and type of foundation for the proposed structure
6. To know grain size distribution by sampling undistributed soil sample and classify soil accordingly
7. To decide suitability of soil for proposed structure.