In a blind zone, the geophone cannot detect the seisdmic refraction.

Exploratory borings in general exploration is carried out by using _______

In the seismic refraction method, the waves sent along the ground surface is picked by _____

_______ sampler is suitable for soft soils.

The soil stabilised with cement is called _____

The depth of exploration for isolated spread footing is _______

Wash boring cannot be used for _____ type of soil strata.

Mud rotary drilling belongs to _____ type of boring method.