工作面长度对覆岩空间结构演化及大采高采场矿压规律的影响

工作面长度的增加是导致采场矿压强度增加的原因之一。通过相似模拟试验证明了覆岩能破断成梯形台形态，并指出了梯形台形成机制及梯形台的参数计算原理。利用梯形台分析了工作面长度对覆岩破断规律的影响，指出了梯形台与关键层理论的关系。基于薄板理论推导了岩层破断步距的计算公式，分析了工作面长度对梯形台空间结构演化及采场矿压显现特征的影响。结果表明：由于覆岩按梯形台破断，工作面长度较短时，加载层厚度较小，来压强度小。对比研究了赵庄2号井1305大采高工作面（工作面长度为85 m）和1302大采高工作面（工作面长度为180 m）矿压特征。结果表明：1305工作面基于梯形台和薄板理论进行选型计算，支架计算工作阻力为4 738 kN，现场选用额定阻力5 500 kN能够满足顶板控制的要求；1302工作面基于梁理论进行选型计算，支架计算工作阻力为7 623 kN，现场需选用额定阻力7 800 kN才能满足顶板控制的要求。

Effect of mining face length on the evolution of spatial structure of overlying strata and the law of underground pressure in large mining height face

The increased length of mining face is one of the significant factors to increase the underground pressure in longwall (LW) face. The physical model tests showed the fractured shape of overlying stratum exhibited as trapezoid platform structure (TPS) after roof caving. Its forming mechanisms were investigated in detail and the calculation principle of geometric parameters of TPS. The effect of mining face length on the fracturing behaviour of overlying strata was studied according to the TPS, and then the relationship between the TPS and key strata theory was also given. The thin plate theory was applied to calculate roof weighting interval. Then, the influence of mining face length on TPS’s parameters was analysed as well as underground pressure. The results show that due to TPS-shaped fracturing characteristics of overlying strata, the thickness of loading layers and roof weighting intensity decrease with the decrease of mining face length. Field measurements were conducted in LW1305 with the face length of 85 m and in LW1302 with the face length of 180 m in mine No.2 of Zhaozhuang. The measured data show that the resistance of the supports should not be less than 4 738 kN and 7 623 kN in LW1305 and LW1302, respectively, and the roof is maintained well with the resistance of 5 500 kN in LW1305 and 7 800 kN in LW1302.