深部开采隔水关键层在不同高跨比下的力学解对比

Comparison of Mechanical Solutions of Water-Resistant Key Strata in Deep Mining under Different Height-Span Ratios

摘要: 在深部开采防治水实践中，煤层底板不同高跨比的隔水关键层和作用在隔水层的水拉力是决定能否突水的重要因素。将隔水关键层的厚度和跨度比模拟成梁的高跨比，针对不同高跨比下固定梁的力学特点，通过弹性力学和材料力学两种对固定梁的解法分别对其平面关键点的应力进行求解，将两个计算结果与FLAC3D模拟结果进行对比分析，探究浅梁理论是否适合于关键层应力分析，并运用到实际隔水关键层的运用中。研究结果表明：在高跨比不超过0.2为浅梁的情况下时，弹性力学解的正应力解误差在11%~20%左右，材料力学正应力解误差在20%~30%，相比之下弹性力学较为精确，浅梁理论中弹性力学解则更适用于关键层；当高跨比超过0.2时，弹性力学解误差出现“跳跃”现象，材料力学解的误差也逐步递增，隔水关键层不再适用于两者的浅梁理论；而剪切应力解最大误差不超过11.5%，符合工程精度。综上所述，在高跨比不超过0.2情况下建议关键层固定梁的应力分析首选采用弹性力学解的浅梁理论，研究结果为深部高承拉水上安全开采以及矿井突水的监测与临突预测预报等具有重要的理论指导意义。

Abstract: In the practice of water inrush prevention and control in deep mining, the key water-repellent layer with different height-span ratio of coal floor and the water pulling force acting on the wa-ter-repellent layer are important factors to determine whether water inrush can be carried out. In this paper, the thickness and span ratio of the key layer of the water barrier are simulated as the height-to-span ratio of the beam. According to the mechanical characteristics of the fixed beam under different height-span ratios, two solutions of elastic mechanics and material mechanics are used to solve the key points of the fixed beam, to solve the stress of the two calculation results and FLAC3D simulation results, to explore whether the shallow beam theory is suitable for the stress analysis of the key layer, and apply it to the application of the actual water-resistant key layer. The results show that when the height span ratio is less than 0.2 for shallow beams, the normal stress error of elastic mechanics solution is about 11%~20%, and the normal stress error of material mechanics solution is 20%~30%. Comparatively, the elastic mechanics solution is more accurate, and the elastic mechanics solution of shallow beam theory is more suitable for key layers. When the height-span ratio is more than 0.2, the error of elastic mechanical solution appears “jump” phenomenon, and the error of material mechanical solution also increases gradually, and the wa-ter-proof key layer is no longer suitable for the shallow beam theory of both. The maximum error of shear stress solution is less than 11.5%, which is in line with engineering accuracy. To sum up, it is recommended to adopt the shallow beam theory of elastic mechanics solution for stress analysis of fixed beams in key layers under the condition that the height-span ratio is less than 0.2. The research results have important theoretical guiding significance for deep high-supported water mining safety and mine water inrush monitoring and imminent prediction.