Experimental study on the deterioration law of saturated and dry porous rocks

Abstract

Abstract The coal seam floor is highly susceptible to the formation of hole defects after mining disturbance. And the destabilization of rocks containing hole defects and water saturation can affect the risk of burst water in the floor. Based on this, experimental studies were carried out on saturated and dry three-hole sandstone specimens using conventional triaxial compression experiments. The results show that after saturation with water, the compressive strength of the saturated specimens decreases with the increase of the surrounding pressure compared with the dry specimens. The weakening effect of water on the strength of the porous rock was 20.19% on average. The maximum degradation of compressive strength of saturated specimens is 61.31% greater than that of dry specimens by 50.15%. The weakening effect of water on the three-hole specimens is greater. The fracture damage form formed on the specimen surface under low perimeter pressure (2 ~ 10MPa) is dominated by inclined shear fracture and splitting fracture, which is mainly subjected to compression shear. The saturated and dry three-hole specimens under medium-perimeter pressure (18 ~ 26MPa) indicate that the number of fractures formed is low. The saturated and dry specimens indicate the formation of parallel or coplanar fracture system. The specimens indicate the formation of fractures subject to shear, tension and shear expansion damage. The saturated and dry three-hole specimens under high perimeter pressure (34–42 MPa) form damage damage zones around the holes, which are significantly damaged by tension and expansion. The damage form of the specimen is mainly shear expansion and tension damage.