Meikuang Anquan (Jul 2024)
Study on anti-impact effect of hydraulic fracturing for long holes in medium and high thick hard roof
Abstract
In view of the insufficient pressure relief effect of thick hard roof of 3106 working face in Menkeqing Coal Mine, the key layer inducing roof shock of 3106 working face was determined by the active strata of micro-seismic high-energy events monitored in the field and theoretical analysis. The long-hole hydraulic fracturing technology was proposed and applied in the field, and the fracturing effect and pressure relief effect were analyzed and evaluated. The results show that the sandstone layer with the average height of 59.33 m and the thickness of 49.95 m from the coal seam is the key layer to induce shock. After hydraulic fracturing, the fracture surface is prefabricated in the key layer, the water content in the fracture increases, the continuity of apparent resistivity is enhanced, and the resistance reduction phenomenon appears. Hydraulic fracturing weakens the integrity and strength of the key layer, and the micro-seismic energy is released into “high frequency and low energy”. The average occurrence density and energy released in long meters of large energy events are reduced by 55% and 79%, respectively. No dynamic phenomena such as large energy mine earthquakes occur in site during mining. The compression step distance of the working face is shortened, the compression strength is reduced, and the dynamic load coefficient decreases significantly and gradually. The slope of surface settlement increases after mining fractured zone in the working face, and the thick hard roof collapses more fully. This study confirmed the effectiveness and feasibility of long-hole hydraulic fracturing technology in anti-impact engineering, and realized the safe mining of working face.
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