多关键层结构下不同采厚覆岩移动及围岩响应特征

Movement of overburden with different mining thickness and response characteristics of surrounding rock under multi-key layer structure

针对多关键层结构下煤厚复杂工作面覆岩移动及围岩应力问题,采用RFPA-Strata数值模拟方法研究了多关键层结构下不同采厚关键层破断特征及不同关键层破断前后支承应力响应特征。结果表明:①采高小于2.5 m时仅低位关键层破断且能够形成稳定的砌体梁结构,此时低位关键层能够承载自身及其上方至中位关键层下方岩层重量,煤体仅需承载低位关键层下方软岩重量及附加载荷,煤岩体承载力较好,超前支承应力峰值随采高增加逐渐增大。②采高大于3 m时中位、低位关键层均发生破断,中位关键层破断后形成砌体梁结构,此时中位关键层能够承载自身及其上方至高位关键层下方软岩重量;低位关键层破断后其断裂的岩块未能与前方未完全破断的岩层铰接,低位关键层为悬臂梁结构,此时煤体需承载煤层上方至中位关键层下方岩层重量及附加载荷,超前段煤岩体发生大量剪切破坏导致煤岩体承载力降低,超前支承应力峰值随采高增加逐渐减小。③关键层运动影响支承应力分布特征,关键层完全破断后低位关键层下沉位移量减小,超前支承应力峰值大小及其距煤壁的距离随关键层破断均减小。④采高大于3 m时,低位关键层破断后主要影响超前支承应力峰值点距煤壁距离,峰值大小变化较小;中位关键层层破断后主要影响支承应力峰值大小,峰值点距煤壁距离变化较小。

In view of the problem of overburden movement and surrounding rock stress in complex thick coal working face under the key layer structure,the RFPA-strata numerical simulation method was used to study the fracture characteristics of key layers with different mining thickness and the response characteristics of support stress before and after the failure of different key layers under the multi-key layer structure.The results show that:①when the mining height is less than 2.5 m,only the lower key layer is broken and a stable mason⁃ry beam structure can be formed.At this time,the lower key layer can bear the weight of itself and the weight of the rock layer above and below the middle key layer..The coal body only needs to bear the weight of the soft rock under the lower key layer and the additional load.The bearing capacity of the coal body is good,and the peak value of the advanced bearing stress increases gradually with the increase of mining height.②When the mining height is greater than 3 m,the middle and lower key layers are broken,and the masonry beam structure is formed after the middle key layer is broken.At this time,the middle key layer can bear the weight of itself and the soft rock a⁃bove and below the high key layer;after the low key layer is broken,the broken rock block fails to articulate with the front incomplete bro⁃ken rock layer,and the low key layer is a cantilever structure.At this time,the coal body needs to bear the weight and additional load of the rock layer above the coal seam to the middle key layer.A large number of shear failures occurs in the coal-rock mass in the front sec⁃tion,which leads to the reduction of the bearing capacity of the coal-rock mass,and the peak value of the advanced bearing stress gradu⁃ally decreases with the increase of the mining height.③The movement of the key layer affects the distribution characteristics of the sup⁃porting stress.After the key layer is completely broken,the subsidence displacement of the lower key layer decreases.The peak value of the advanced bearing stress and the distance from the coal wall decrease with the break of the key layer.④When the mining height is greater than 3 m,the fracture of the low key layer mainly affects the distance between the peak point of the advanced bearing stress and the coal wall,and the peak value changes little;the fracture of the middle key layer mainly affects the peak value of the bearing stress,and the distance between the peak point and the coal wall changes are small.