基于矩张量的深埋隧洞岩爆机制分析

Analysis of rockburst mechanism for deep tunnel based on moment tensor

以锦屏二级水电站微震监测数据为基础,将矩张量引入到深埋隧洞岩爆机制分析研究中。对分析过程中遇到的2个关键问题提出了针对性的建议:①隧洞工程为线性工程,传感器布置空间有限,难以形成良性传感器阵列,矩张量分析结果的可靠性受到很大的影响,为此,提出了数值计算过程中的坐标系空间旋转法。该方法按最优路径旋转隧道坐标系,使对于同一个事件的每个传感器,源-传感器射线到新坐标系的3个方向余弦差值在10倍数值范围以内,在数值计算过程中,可以得到较理想的矩张量结果。②针对Ohtsu使用矩张量分解判断岩石破裂类型的方法中,提出的各分量比重计算公式,仅适用于各分量均为受拉的情况。考虑快速掘进条件下隧洞工程受力方向的不确定性,扩展其分量比重计算公式到更一般适用状态。在此基础上,建立了一套完整的岩爆孕育过程矩张量分析方法。利用该方法对锦屏二级水电站典型岩爆微震数据进行分析,结果表明,该方法可以较好地解释岩爆孕育过程岩石破裂演化机制。

Moment tensor method is introduced to analyze rockburst mechanism for deep tunnel,based on microseismic monitoring data of Jinping Ⅱ hydropower station.And some recommendations are proposed for two key issues in the analysis process： ① Restricted by the construction environment in the tunnels,tunnels are excavated in a straight line,and sensors can only be installed at the wall of tunnel or in the shallow boreholes.The calculation reliability of moment tensor is affected greatly on the numerical calculation;the coordinate rotation method is given to improve it.This method rotates the tunnel coordinate system to the new coordinate system,which makes the value of the direction cosine between the source-sensor vector and every coordinate axis less than 10 times,for every waveforms in the event.The ideal results can be got from a large number of moment tensor calculation.② To get rockburst nucleation process,which calculates the moment tensor firstly,and decompose the moment tensor to the components of basic type,judge the rock fracture type based on the rule from the percentage of the components.But the rule proposed by Ohtsu is only applicable to all components by pulling,which is not suitable to tunnels of fast drilling;therefore,one rule is proposed to extend a more generally applicable state.Lastly,the complete method is established which used to research rockburst nucleation process by the moment tensor method.Analyzed microseismic data of Jinping Ⅱ hydropower station before rockburst happened by this method,the results show that the method can explain the evolution of rock failure mechanism better.