基于能量耗散率的钻孔防冲效果评价方法

采用理论分析、实验室试验及数值模拟等手段,研究了从能量角度评价钻孔防治冲击地压效果的方法。钻孔前后应力总量计算表明,钻孔对煤岩体的作用在于"调压",并非仅"卸压"。相对于应力角度,从能量角度评价钻孔防冲效果的过程更为简便。不同矿井煤样单轴加卸载试验发现,采用线弹性体弹性应变能计算公式的计算结果要大于实际值,且冲击倾向性越弱,计算误差越大,提出了基于弹性能量指数的修正公式。钻孔围岩弹性应变能的变化受最大主应力的做功特征主导,围岩应力调整过程中,弹性应变能能否积聚与围岩方位及侧压系数有关。在此基础上,提出钻孔耗能率的概念,可定量评价不同钻孔防冲设计之间的优劣,并通过FLAC3D进行数值模拟实现。以钻孔耗能率为评价指标得出,钻孔防冲效果与钻孔孔径呈幂函数关系,与煤层强度呈负相关。与φ100 mm钻孔相比,φ150 mm钻孔耗能效果是其2.9倍,φ200 mm钻孔耗能效果是其6.5倍。

Evaluation method for rockburst-preventing effects by drilling based on energy-dissipating rate

Evaluation method for rockburst-preventing effect by drilling from the perspective of energy was studied based on theoretical analysis,laboratory tests and numerical simulation.The total amount calculations of stress before and after drilling show that drilling in coal results in “pressure regulation”,not only “pressure relief”.With respect to the perspective of stress,the evaluation from the perspective of energy is easier.Uniaxial loading and unloading tests of coal specimens from different coal mines show that the calculation results using the energy calculation formula for linear elastic materials are greater than the actual value,and the stronger the bursting liability of coal,the smaller the calculation error.Modified formula based on elastic energy index is proposed.The variation characteristics of elastic strain energy in surrounding rock are dominated by the characteristics of doing work by the maximum principal stress.It is related to rock orientation and lateral pressure coefficient whether the elastic strain energy can be accumulated when the stress regulates in surrounding rock.On this basis,the concept of energy dissipation rate for drilling is proposed,which can be used to evaluate different drilling designs,which is realized by numerical simulation through FLAC3D.There is a typical power function relationship between borehole diameter and rockburst-preventing effects,which is negatively correlated with seam strength.Compared with 100 mm borehole,the energy dissipation effort of 150 mm one is 2.9 times more,and 200 mm one is 6.5 times more.