隧道施工期岩爆超前地质预报方法探讨

Discussion on advance geological prediction method of rock burst in deep-buried tunnel construction period

为解决硬质岩隧道高地应力环境下岩爆预测方法少,预测准确度不高的难题,本文通过分析隧道勘察期地应力和施工期岩爆特征,基于沟谷型岩爆首次提出TSP物性参数预测岩爆段落的方法,并形成了一套岩爆分析的全序列预测体系(岩爆环境分析、物探长距离预测、微震监测近距离预警、现场观听),可远、中、近有层次预测岩爆风险。研究成果表明:(1)小于500 m埋深的沟谷型岩爆有沿洞轴向呈“链式”发生的特点,深埋大于800 m的深埋型岩爆具有一定离散性。(2)满足动态弹性模量>70 GPa,静态弹性模量>60 GPa,密度>2800 kg/m^(3),泊松比<0.25,横波波速v S>3200 m/s,纵波波速v P>5500 m/s,发生岩爆可能性更高;(3)掌子面炮孔钻进明显缓慢,少量有堵孔现象,爆落有效进尺小于炮孔深度,人耳偶尔可听到围岩表层有爆裂声,声响剧烈且持续时间长,发生岩爆风险更高;本文研究成果和手段可为类似高地应力环境下岩爆预测和防控提供参考,具有推广意义。

At present,there have been few methods to predict rock burst in hard rock tunnel under high ground stress environment,and the accuracy of conventional prediction methods is not satisfactory.Based on the analysis of the ground stress during tunnel investigation and the characteristics of gully rock burst during construction period,the method of predicting rock burst sections with TSP physical property parameters is proposed in this paper,and a complete series of rock burst prediction system is formed for rock burst analysis,including rock burst environment analysis,long distance prediction of geophysical exploration,micro-seismic monitoring and short-range early warning,on-site listening,which can predict rock burst risks in a hierarchical manner from far,middle and near levels.Through the study,the following conclusions are obtained:(1)The gully type rock burst with a depth of less than 500 m has the characteristics of“chain mode”occurring along the axial direction of the tunnel,and the deep-buried rock burst with a depth of more than 800 m has a certain discreteness;(2)If dynamic elastic modulus>70 GPa,static elastic modulus>60 GPa,density>2800 kg/m^(3),Poisson ratio<0.25,shear wave velocity v S>3200 m/s,P-wave velocity v P>5500 m/s,rock burst is more likely to occur;(3)The drilling of gun holes on the tunnel face is obviously slow,with a small amount of hole blocking phenomenon,and the effective penetration of blasting is less than the depth of the gun hole.The human ear can occasionally hear the cracking sound on the surface of the surrounding rock.If the sound is violent and lasts for a long time,and the risk of rock burst is higher.The research results and methods proposed in this paper can provide reference for rock burst prediction and prevention under similar high ground stress environment,and have popularization significance.