针对薄基岩工作面易发生顶板整体切落压架事故问题，采用理论分析和数值模拟对一般工作面和薄基岩工作面采场覆岩结构失稳致灾机理进行对比研究。建立采场覆岩“宏观-大-小”结构力学模型，确定不同覆岩结构失稳支架临界工作阻力，分析了关键层上覆载荷对关键层破断形式和破断块体稳定性的影响，并通过UDEC数值模拟软件对典型工程地质条件下采场覆岩结构及应力场演化特征进行了模拟验证。研究结果表明：① 一般工作面回采后，采场覆岩中会自下而上依次形成“支架-围岩”小结构、“砌体梁”大结构、“压力拱”宏观结构，小结构的稳定性取决于大结构的稳定性，而大结构的稳定性又取决于宏观结构的稳定性;② 在宏观结构的保护作用下，关键层上覆载荷较小，关键层破断岩块容易形成“砌体梁”平衡结构，作用在支架上的力较小，工作面矿压显现缓和;③ 随着关键层上覆载荷增大，关键层破断步距减小，破断形式由弯拉破断转变为剪切破断;④ 当关键层破断岩块上覆载荷过大，大结构发生失稳，关键层自重及其上覆载荷经垮落带岩层作用在采场支架上，导致小结构失稳，发生压架事故;⑤ 薄基岩工作面采场覆岩中无法形成宏观结构，上覆岩层在承压含水层水压力及自重作用下沿煤壁发生全厚整体切落，易造成工作面压架事故;⑥ 一般厚层坚硬顶板工作面来压步距越大，矿压显现越剧烈，而薄基岩工作面来压步距小，矿压显现反而剧烈。

The powered support jam accidents due to the intact shear fall of all overlying strata occur easily in the longwall working face under thin bedrock.The theoretical analysis and numerical simulation were used to study the difference in the disaster-causing mechanism of overlying strata structure instability between in normal longwall working face and thin bedrock longwall working face.The mechanical model of “macroscopic-big-small” structure were established for overlying strata in longwall mining,the critical support working resistance was defined based on the stability analysis of different overlying strata structures,the impact of pressure above the key stratum on the breaking form and block stability of key stratum was analyzed,and the overlying strata structure and the evolution feature of the stress field were simulated by UDEC numerical simulation software.The results show that ① from bottom to top,the overlying strata are formed by “support and surrounding rocks” small structure,“voussoir beam” big structure and “pressure arch” macroscopic structure in longwall mining under normal working face,the stability of small structure is mainly determined by the stability of big structure,while the stability of big structure is mainly determined by the stability of macroscopic structure.② The breaking block of key stratum is ease to form a “voussoir beam” balance structure due to the lower pressure on the key stratum under the protection of macroscopic structure,so that the support load is lower,and the strata behaviors is easing.③ The breaking interval of key stratum decreases due to the increase of pressure on the key stratum,and the breaking form changes from shear breaking to flexural tensile breaking.④ The big structure is in an unstable state due to the high pressure on the key stratum,which will lead to the small structure instability under a dead load of key stratum and pressure on the key stratum,so that the powered support jam accidents occur.⑤ The macroscopic structure cannot be formed in overlying strata when mining below the thin bedrock,the intact shear fall of all overlying strata takes place due to the hydraulic pressure of unconsolidated confined aquifer and the weight of the overlying strata,which may induce powered support jammed accidents.⑥ The longer the weighting step is,the stronger the strata behaviors for a normal working face with thick and hard roof,while the shorter the weighting step is,the stronger the strata behaviors for a thin bedrock working face.

1 采场覆岩“宏观-大-小”结构模型

2 采场覆岩结构稳定性分析

   2.1 采场覆岩小结构稳定性分析

   2.2 采场覆岩大结构稳定性分析

   2.3 采场覆岩宏观结构稳定性分析

   2.4 采场覆岩结构与“三带”的划分

3 一般工作面覆岩结构数值分析

   3.1 工作面概况

   3.2 数值模拟模型

   3.3 数值模拟结果

4 薄基岩工作面覆岩结构数值分析

   4.1 工作面概况

   4.2 数值模拟模型

   4.3 数值模拟结果分析

5 现场应用

6 结论