IN-SITU MEASUREMENT OF THE EFFECT OF FAULT ACTIVATION AND MINE PRESSURE RESPONSE IN THE FLOOR TO SEAM MINING

To study the water-conducting effect of activated floor faults caused by mining,in-situ stress and water pressure measurement methods were selected. Five boreholes were designed in a typical working face,including within the fault zone,in the hanging wall and footwall of the fault,and in the intact zone. Additional stress and water pressure were monitored during the advancement of the working face. The results show that the variation in additional stress exhibited three stages: a stable and unchanged stage,a slow development stage,and a rapid increase stage,with the maximum value occurring in the intact floor. Water pressure showed the greatest fluctuation and reached the highest value in the intact zone. In the three boreholes near the fault zone,water pressure fluctuated to a certain extent as the working face advanced,but the overall fluctuation was small and the pressure remained very low. This indicates that no signs of fault activation occurred during the mining process of the working face. Through comprehensive comparative analysis,it was found that changes in additional stress and water pressure at the same depth in the fault zone and the intact floor under mining pressure exhibit both correlations and differences. Both parameters showed good consistency within the stress concentration zone prior to mining,but additional stress reflected the manifestation of mining-induced pressure more clearly than water pressure. The variation in water pressure could be divided into two stages,whereas additional stress variation exhibited three stages. To a certain extent,additional stress better reflects the propagation-zone response characteristics of mining-induced pressure in the coal seam floor. These ideas and results can be applied to advance warning of mining above confined aquifers in complex geological structure zones.