岩爆结构面强度的弱化特征

Strength weakening characteristic of rock burst structural planes

  • 摘要: 岩爆破坏以其突发性与瞬间破坏性等特点,在工程中很难予以预防.本研究基于动力学与能量作用原理,通过固有振动频率等振动特征指标实现对边界剪切弹性系数的计算.在物理模型试验中,应用多普勒激光测振仪对岩爆体破坏全过程进行远程振动特征监测.试验得出,结构面强度的非协调弱化效应是岩爆发生的必要条件,结构面弱化的时空差异是发生瞬时性岩爆还是迟滞型岩爆的主要因素.当结构面弱化较慢时,则为迟滞型岩爆,反之,则为瞬时性岩爆.基于固有振动频率可识别岩体结构面的弱化速率,岩爆发生全过程中,结构面的总耗散能仅为赋存弹性能的0.06%,使得几乎所有的弹性动能都将转化为冲击动能,表现为岩爆体以高速的形式弹射出来.基于频率下降速率等监测数据分析,可识别岩爆结构面强度的非协调弱化特征.因此,增加固有振动频率等动力特征监测指标,无疑会进一步提高对岩爆孕育演化特征规律的认识,并在地下空间工程岩爆预警监测方面发挥重大作用.

     

    Abstract: Prediction and prevention of rock burst in project is difficult because of its paroxysm and sudden destructiveness. Determining how to predict the time, place, and intensity of rock burst is one of the main engineering problems that must be solved via geotechnical engineering. Increasing number of experts from the field of underground mining and construction are applying new monitoring techniques and methods to study rock burst for its effective prediction. In the model experiment, the entire process of structuretype rock burst was remotely monitored via the laser Doppler vibrometer. Based on the dynamic theory and energy conservation law; the natural vibration frequency was used to analyze the elastic coefficient of the shear plane. The experimental results show that the incompatible weakness of structural plane is a necessary condition for the occurrence of rock burst, and the spatiotemporal difference of the structural plane strength is the main factor that determines the immediate or the time-delayed rock burst. Slow weakening of the structure causes time-delayed rock burst, whereas rapid weakening causes immediate rock burst. During the whole process of rock burst, the weakening rate of rock mass structure is determined using the natural vibration frequency, and the dissipated energy of the structure occupies merely 0.06% of the rock elastic energy. Thus, most of the elastic energy is released in the form of kinetic energy, and the rock is ejected with high velocity. Furthermore, the incompatible weakening characteristics of rock burst structural planes can be analyzed using the analysis of the frequency decline rate. Therefore, the new monitoring index of dynamic characteristics such as natural vibration frequency improves the understanding of evolution characteristics of rock burst and plays a significant role in the early warning of rock burst in underground engineering.

     

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