I have a 300 sft plot in Gachibowli in Hyderabad. For the past two months, a cavity of 2 feet in diameter has formed. Rainwater is disappearing into this hole. I got this cavity filled up twice but a hole gets created whenever it rains. The bore is ten feet away and has casing upto 60 feet. I recently got the pump cleaned of mud and pebbles because water and soil had submerged the bore due to heavy rains. Now what is this hole that is forming? Is it a sink hole or a crack through which the water is disappearing? I have heard that sink holes do not form in Hyderabad because the terrain is basalt and hard rock. As an immediate solution, I am getting 100 sq feet area around the hole covered with 2X2 feet stones. Please advise.