地下煤层开采引起的岩层运动是一系列安全和环境问题的根源，研究采动岩层运动规律是安全、高效、绿色开采的重要基础。通过对岩层运动过程的研究，揭示了采动覆岩卸荷膨胀累积效应及其对岩层运动规律的影响机制。研究表明:采动覆岩经历了卸荷膨胀与再压实的动态过程。受关键层结构控制，上覆岩层由下向上成组破断运动，关键层破断前，阻断了上覆载荷向下方岩层的传递，导致其因卸荷而产生膨胀，包括碎胀与弹性膨胀。随着关键层破断高度增加，覆岩卸荷高度同步增大，因卸荷而膨胀的岩层总厚度不断增大;同时卸荷煤岩也受到已破断关键层载荷的压实作用，从而造成覆岩卸荷膨胀总量的不断变化。将这种覆岩卸荷膨胀总量随覆岩卸荷高度动态变化的现象定义为采动覆岩卸荷膨胀累积效应，进而建立了其理论模型，并通过淮北海孜煤矿巨厚火成岩下采煤覆岩裂隙实测进行了验证。结果表明，采动覆岩卸荷膨胀累积效应对采动岩层运动规律产生了重要影响，如影响覆岩关键层下离层量，影响覆岩关键层贯通破断的高度，影响不同开采条件的地表下沉系数等。采动覆岩卸荷膨胀累积效应改变了对离层存在形式的传统认识，该效应的存在导致关键层下最大离层量一般小于采高的10%，覆岩可注浆充填空间并非传统认识上的“离层区”，而主要是注浆充填压力“压实”作用下将覆岩卸荷累积膨胀所转化出的那部分空间，该发现指导了覆岩隔离注浆充填绿色开采技术的创新研发及其在建筑物压煤开采中的成功实践。

Strata movement caused by underground coal mining is the primary cause of a series of safety and envi- ronmental problems. Studying the movement law of mining-induced strata provides an important basis for safe,ef- ficient and green mining. Through studying the process of strata movement,this paper reveals the cumulative effect of overburden strata expansion induced by stress relief and its influence on strata movement. The results show that the overburden strata undergoes a dynamic process of stress relief induced expansion and re-compaction. Under the control of the key strata structure,the overburden strata move in groups from bottom to top. Before a key stra- tum break,the transfer of its overburden load to the underlying strata is blocked,resulting in their expansion,including bulking and elastic expansion. As the breaking height of key strata increases,the unloading height of over- burden increases. At the same time,the unloaded coal and rock strata are also compacted by the load of the bro- ken key layer,which results in the dynamic change of the total amount of overburden unloading expansion. The phenomenon that the total amount of overburden unloading expansion changes with the height of unloading over- burden is defined as the cumulative effect of overburden strata expansion induced by stress relief. A theoretical model was then developed and verified with the measurements of the bedding separation aperture under an ex- tremely thick igneous sill in the Haizi Coal Mine,China. The results also show that this cumulative effect has an important impact on the movement law of mining-induced strata,such as the amount of bedding separation under key strata,the height of interconnected fractured zone of key strata,and the surface subsidence coefficient under different mining conditions. The cumulative effect has changed the traditional understanding of bedding separation by resulting into a small bedding separation aperture that is usually less than 10% of the mining height. The vol- ume of the injectable zone in the overburden was found to be not that of the traditional bedding separation,but the injection-induced volume that was transformed from the expansion zone because of the high injection pressure. This finding has guided the innovation of the green mining technology of isolated overburden grout injection and its successful application in mining under surface infrastructures.

1 概念

2 理论模型

   2.1 模型假设

   2.2 特殊条件模型的建立

   2.3 一般条件模型的建立

3 理论模型的验证

   3.1 计算实例

   3.2 实测验证

4 讨论

5 结论