近松散层开采孔隙水压力变化 及其对水砂突涌的前兆意义

 开采沉陷离心模型试验表明，采空区和煤柱上方的黏土层中的孔隙水压力在煤层开采之后，出现积聚和消散现象，超静孔隙水压力增量最大可达垂直自重应力的15%～22%。采动孔隙水压力监测模型的试验表明，采动引起的承压含水层中孔隙水压力的变化特点同煤层开采进度以及顶板周期来压密切相关，煤柱上方含水层中孔隙水压力一般表现为先升高后降低，工作面上方含水层中孔隙水压力变化与开采位置有关，当工作面通过测点下方时，孔隙水压力出现明显的下降，当测点处于采空区中部时，孔隙水压力升高并会保持一段时间。采后顶板下沉期间各测点孔隙水压力均呈下降趋势。突砂模型试验表明，一旦抽冒或形成水砂突涌后，含水层内孔隙水压力表现为剧烈下降并形成瞬时负压，水压下降后随突涌过程发展保持在某稳定水平上，突砂口附近呈现相应的水力坡降。由以上试验结果可知，孔隙水压力可以作为近松散含水层开采溃砂灾害预警和监测的重要前兆信息源。

VARIATION OF PORE WATER PRESSURE AND ITS PRECURSOR SIGNIFICANCE FOR QUICKSAND DISASTERS DUE TO MINING NEAR UNCONSOLIDATED FORMATIONS

The automatic monitoring and predicting system are significant for actively treating quicksand hazards in mining engineering. The centrifugal model tests emphasize the variations of pore water pressure and the concentration and dissipation of the excess pore water pressure in clay layers above the mined-out area and coal pillars，and the maximum excess pore water pressure can be increased by 15%–20% of the vertical dead-weight stress at the monitoring point. A mining-induced pore water pressure simulation experiment shows that the variation of the pore water pressure in a confined aquifer due to mining is closely related to the mining progress and periodic roof pressure. The pore water pressure in the aquifer above the coal pillars generally increases firstly and decreases then during mining. The pore water pressure variation in the aquifer above mined-out area is related to the location of working face，which decreases obviously when working face just passes the said point，and increases for a period of time while the monitoring point lies above the mined-out area. Quicksand model tests show that，when water inrush and quicksand start，instant negative pore water pressure is recorded at first，then the water head stabilizes at a low level for a period of time as the other sensors around the fissure demonstrate a water funnel with certain hydraulic gradient. It can be deduced from these results that the pore water pressures can be of important precursor significance for monitoring and forecasting the quicksand hazards in mines.