INVESTIGATION OF THE ROOF PRESPLITTING AND ROCK MASS FILLING APPROACH ON CONTROLLING LARGE DEFORMATIONS AND COAL BUMPS IN DEEP HIGH-STRESS ROADWAYS

Abstract

ROADWAY DEFORMATION AND COAL BUMPS ARE MAJOR CHALLENGES FOR UNDERGROUND ENGINEERING. TAKING THE LU'AN MINING DISTRICT IN SHANXI PROVINCE AS AN EXAMPLE, THE FAILURE MECHANISM OF DEEP HIGH-STRESS ROADWAY WAS STUDIED. NUMERICAL SIMULATIONS AND THE SIMILAR MATERIAL TEST WERE PERFORMED TO INVESTIGATE THE EFFECT OF THE ROOF PRESPLITTING AND ROCK MASS FILLING ON THE STABILITY OF ROADWAY SURROUNDING ROCK. THE CHANGE LAWS AND DISTRIBUTION FEATURES OF STRESS AND PLASTIC ZONE, AND THE FRACTURE CHARACTERISTICS OF ROOF STRATA WERE ANALYZED. UNDER CONDITIONS WHERE THE ROOF WAS NOT PRESPLIT, THE ROADWAY WAS IN A HIGH-STRESS ENVIRONMENT DUE TO THE MASSIVE SUSPENDED ROOF. THE FAILURE PROCESS OF THE HIGH-STRESS ROADWAY BEGAN WITH TENSILE CRACK IN THE SHALLOW ROOF AND THEN EXTENDED TO THE TWO RIBS, RESULTING IN THE YIELD OF A COAL PILLAR. UNDER THE CONDITION THAT THE ROOF WAS PRESPLIT, THE PEAK VALUE OF THE VERTICAL STRESS AT THE COAL PILLAR WAS DECREASED FROM 18.2 TO 9.8 MPA WHILE THAT OF THE VIRGIN COAL RIB WAS DECREASED FROM 15.8 TO 13.5 MPA. BOTH THE SIMILAR MATERIAL TEST AND NUMERICAL RESULTS SHOWED THAT THE ROOF OUTSIDE THE COAL PILLAR (RCP) WAS CUT OFF ALONG THE PRESPLITTING LINES AND WAS FRACTURED INTO DIFFERENT SIZES OF MASSES. THE BROKEN ROCK MASS FILLED IN THE GOAF AND SUPPORTED ON THE OVERLYING STRATA, WHICH REDUCED THE LOAD ON THE COAL PILLAR. THE FIELD MONITORING DATA INDICATED THAT IMPLEMENTING THE ROOF PRESPLITTING AND ROCK MASS FILLING PROCESSES SUCCESSFULLY CONTROLLED LARGE DEFORMATIONS OF THE ROADWAY AND COAL BUMPS, WHICH IMPROVED THE STABILITY OF SURROUNDING ROCK.