浅埋大采高工作面顶板关键层结构稳定性分析

Stability analysis of key stratum structures of large mining height longwall face in shallow coal seam

我国西部浅埋厚煤层普遍采用大采高综采方法回采,大采高综采工作面顶板关键层结构形态及其稳定性对采场矿压及围岩控制具有显著影响。通过建立等效直接顶对采空区充填度的计算模型,将等效直接顶分为'充分充填型'和'一般充填型'。基于物理相似模拟和UDEC数值模拟,分析了大采高采场覆岩单一关键层'高位斜台阶岩梁'结构和双关键层'斜台阶岩梁+砌体梁'结构的稳定性,揭示了单一关键层工作面来压迅猛和双关键层工作面存在大小周期来压的机制,得出工作面支架以等效直接顶静载为基本载荷,以关键层结构失稳动载为附加载荷,给出了工作面支护阻力的计算公式。通过工程实例分析得出,支护阻力随采高、岩层破断角、关键层厚度及关键块长度的增加近似呈线性增大,随关键块回转角的增加近似呈线性减小,采高相同时支护阻力随等效直接顶厚度增加明显增大,等效直接顶静载是大采高支架压力的主要部分,同时验证了支护阻力计算公式的可靠性,表明此计算公式可为类似工作面支架选型及岩层控制提供借鉴。

The fully mechanized mining method with a large mining height is widely applied in shallow thick coal seam of western regions in China,and the key stratum structure and its stability in fully mechanized longwall face with a large mining height have significant impact on the mine pressure and surrounding rock control.A calculation model of the goaf filling degree of the equivalent immediate roof including fully filling and generally filling types was established.Based on physical simulation experiments and UDEC numerical simulation,the stabilities of'high position and oblique step voussior beam'structure of single key stratum and'oblique step voussior beam and voussior beam'structure of double key strata in large mining height longwall face were analyzed,and the pressure mechanisms of the longwall face with single key stratum or double key strata were revealed.A formula for calculating the reasonable support resistance in the longwall face,taking the static load of the equivalent immediate roof and the instability dynamic load of the key stratum structure as the basic load and the additional load respectively,was put forward.An engineering example analysis indicates that the support resistance increases linearly with increasing the mining height,the break angle of the stratum,the thickness of the key stratum and the length of the key block,but decreases linearly with increasing the rotation angle of the key block,and that,when the mining height is the same,the support resistance increases with increasing the thickness of the equivalent immediate roof,and the static load of the equivalent immediate roof contributes mainly to the pressure of the hydraulic support in a large mining height longwall face.The reliability of the calculation formula of the support resistance was verified,and it is shown that the calculation formula can provide a reference for the support selection and ground control in similar longwall faces.