Foundation in black cotton soil (expansive soil)

where we use under reamed pile :

• Underreamed piles are used in espansive soil.
• These pile are researched by RORKEE CBRI (central building research institute in INDIA).
• These type of pile transfer the  building load at a depth through the pile beyond the seasonal zone variation in moisture content.
• Depth is kept about 3.65 meter for black cotten soil.
• Under reamed pile are bored cast in situ piles and have a base like bulb.
• The spacing of piles is kept 1.5 meter to 3.0 meter
•  These piles are connected by the plinth beam at the top. plinth beam is a reinforced concrete beam.
•  Reinforced is also provided  in the uunderreamed pile to absorb the tensile forces which are developed during the swelling  of soil and these forces are commonly called uplift force.
• The other big advantage of providing reinforcemnt in underreamed pile is that during the hot weather soil shrinks and pile acts as column.