考虑有效应力的钻屑量理论分析及试验研究

考虑深部开采条件下水平地应力作用不能忽略,引入有效应力,推导得到新钻屑量公式,分析给出了有效应力与钻屑量间关系,提出了通过有效应力判断钻屑量方法。在此基础上以典型阜新孙家湾矿突出危险煤层为例,利用自主研制的三维应力煤体钻屑量检测试验装置,改变轴压模拟垂直地应力、围压模拟水平地应力、孔隙压模拟瓦斯压力作用,进行了实验室尺度下钻屑法模拟试验,研究了有效应力、煤层深度、瓦斯压力对钻屑量影响规律。研究结果表明:钻屑量与有效应力呈线性递增关系,试验值略大于理论值,平均误差为7.9%,与前人结论一致,验证了新钻屑量公式有效性及三维应力煤体钻屑量检测试验装置可靠性;随着煤层埋藏深度增大,钻屑量越大,钻屑量与煤层深度呈线性递增规律,且钻屑量随钻孔深度增加呈先减小、后递增、最后缓慢递减规律,在钻孔深度12.5 cm处钻屑量最大,表明此处为应力集中区;钻屑量随瓦斯压力增加,呈指数函数递增规律,瓦斯压力越大,孔壁裂纹扩展越明显,说明瓦斯对煤体软化作用越显著。上述研究结论对该矿深部煤与瓦斯突出预测和防治具有重要参考价值。

Theoretical and experimental studies on drilling cutting weight considering effective stress

Considering that the horizontal stress can not be ignored under deep mining, the new formula for drilling cutting weight is derived based on the effective stress. The relationship between the effective stress and the drilling cutting weight is analyzed. The method for judging the drilling cutting weight by the effective stress is put forward. On this basis, by taking the typical high gassy mine of Sunjiawan Coal Mine in Fuxin as an example, using the developed 3D stress test devices for coal drilling cutting weight and changing the axial pressure to simulate the vertical crustal stress, the confining pressure is used to simulate the vertical crustal stress and the pore pressure is used to simulate the gas pressure. Laboratory experiments are carried out to study the effects of the effective stress, coal seam depth and gas pressure on the drilling cutting weight. The results show that the drilling cutting weight increases linearly with the effective stress, and the test values are slightly larger than the theoretical ones, and the average error deviation is 7.9%, which is consistent with the previous conclusions. This verifies the reliability of the new formula for drilling cutting weight and the three-dimensional stress test devices. With the increasing depths, the drilling cutting weight is greater, that is to say, the drilling cutting weight increases linearly with the depth of coal seam. With the increase of drilling depth, the drilling cutting weight firstly decreases and then increases and finally decreases slowly. The location of the maximum amount of drilling cuttings is at the depth of 12.5 cm, which indicates that the place is the stress concentration area. With the increase of gas pressure, the drilling cutting weight increases in the form of exponential function, and it has a significant influence on the shape of the coal wall and the hole. With the increase of gas pressure, the more obvious the crack growth of the hole wall, the more remarkable the softening effect of the coal seam. The conclusions have an important reference value for the prediction and control of coal and gas outburst in coal mines.