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

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

The sampler in standard penetration test has outer diameter of _____ mm.

The commonly used penetration test are ___

Which of the following method is adopted for fast boring?

For sampling saturated cohesion-less soils ___ is inserted.

Mud rotary drilling belongs to _____ type of boring method.

The standard penetration test is given in ________