In this method, hole is drilled by driving a casing about 3 m long and then inserting a hollow drill rod with a chisel shaped chopping bit attached to the bottom of a hollow drill rod at its lower end.The diameter of the bore hole is generally 150 mm to 200 mm. Water is inserted into a hollow drill rod with a higher velocity. The hole is advanced by a combination action of chopping and jetting action, as the drilling bit cut the soil and water mixed with soil converted into slurry ( mud ) rises upward through the annular space between the drill rod and the casing pipe. Slurry is then collected in a tub. Hole is further advanced by continuously raising and dropping the chopping bit and water jetting action till the required depth.
Wash sample collected in the tub represents only type ( color ) of soil because of soil particles break down by chopping action. The main disadvantages of this method is that it can not be used in hard strata and not suitable for extracting good quality of soil samples.