Moreover, A.R. Nadarian investigate the effect of water on the strength properties of claystone backfill. Direct shear tests were carried out on the claystone to obtain strength properties under moisture as placed and saturation condition.The test result show the increased moisture in claystone backfill from moisture content as-placed to saturate condition was reduction in the value of friction angle is responsible for most of shear strength reduction of claystone. Whereas reduction in cohesion was less about 5 kPa