Coal pillar design and practice concerning quicksand within thick overlying Quaternary sediments

Quaternary sediments,which are super-thick,overlie most coal-bearing formations in Huaibei and Huainan areas.At the bottom of sediments is No.4 water-bearing formation,which immediately overlie coal-bearing formations and threatens safe mining operations.Coal pillars have been designed to prevent water flowing into the faces and improper designs contributed much waste of coal reserve.Investigation of mining engineering conducted in Tongting Mine,Taoyuang Mine and Qidong Mine in Huaibei area justifies the following principle of coal pillar design under super-thick sediments for the sake of mining safety: at early stages focusing on water control,and later shifting to quicksand.