煤炭地下气化温度场动态扩展对顶板热应力场及稳定性的影响

为探索煤炭地下气化过程中煤层温度场扩展对顶板应力的热影响，利用相似材料制作大尺度顶板模拟内蒙古乌兰察布褐煤层顶板泥质软岩，对煤层温度场动态扩展条件下，顶板应力场扩展过程及顶板稳定性进行实验研究。结果表明，在模型实验中，顶板热应力的最大值可达1.5 MPa。在氧化区培育阶段和气化阶段，煤层温度场沿通道轴向平均扩展速率分别为0.018，0.028 9 m/h，顶板热应力场沿通道轴向扩展速率分别为0.015和0.027 m/h。氧化区培育阶段煤层温度场扩展主方向与裂隙方向一致，煤层温度场动态扩展与顶板热弥散的双重作用使顶板应力场的扩展速率逐渐趋近于煤层温度场扩展速率。同时，泥岩顶板受高温影响在垂直气化通道方向形成稳定的拱形结构，可维持顶板在垂直气化通道方向的区域稳定。

Effect of temperature field dynamic expansion of underground coal gasification on thermal stress field and stability of roof

To explore the thermal effect induced by expansion of temperature field in coal seam on the stress characteristic of roof above the coal seam in underground coal gasification (UCG)，some similar materials were used for making a large scale roof to model the soft roof above the lignite coal seam located in Ulanqab，Inner Mongolia，China.The model test was carried out to investigate the effect of the dynamic expansion of temperature field in coal seam on the thermal stress and stability of roof in underground coal gasification (UCG).The results show that the maximum value of the thermal stress of the roof made by similar materials is 1.5 MPa in the model test.At the two stages of oxidation zone formation and gasification，the average expansion rate of temperature field in coal seam along the axis of the gasification channel are 0.018 m/h and 0.028 9 m/h，respectively，and the expansion rate of thermal stress on roof along the gasification channel are 0.015 m/h and 0.027 m/h，respectively.The expansion direction of temperature field is in consistent with the orientation of the cracks in coal seam at cultivation stage.The phenomenon of heat dispersion of roof induced by the temperature field dynamic expansion of coal seam，that occurs in UCG process，makes the expansion rate of thermal stress of roof gradually approach that of temperature field of coal seam，in the same time，the high temperature can form a regional stable arch structure that maintains the stability of clay roof in a direction perpendicular to the gasification channel.