Law Study on the Overlying Strata Movement of Top-coal Caving Face Inducing Rock Burst

摘要

By the seismic observation technology, the microseism (MS) effect of the overlying strata movement was observed and the achieved results are as follows. (1) The MS activity is periodic. Before the rock burst happens, the total energy continuously gets larger, and on the day when rock burst happens, the total energy gets up to the largest level, and it drops to an extraordinary low level after the rock burst. (2) Before the rock burst happens, the events firstly get higher and then drop lower. The rock burst happens during the process of events reducing. (3) The average elevation can reflect the development state of the movement of the overlying strata. Before the rock burst happens, the average elevation gets higher stage by stage, and when or pre of the rock burst happens, the elevation gets up to the largest, while it drops abruptly after the rock burst happening. (4) In the MS activity cycle, the spatial distribution of seismcities get higher in elevation and vast in space before rock burst happens. When rock burst happens, it gets up to the peek values and the strata near the working face active strongly. According to the observed results and based on the voussoir beam theory, the bi-directional (up and down wards) movement model of top-coal caving face was promoted. Based on the model the energy and stress sources of rock burst were analyzed. As a result, the rock burst mainly happens during the overlying strata moving downwards, hence it's possible to observe and prevent rock burst by monitoring the upward movement of the overlying strata.