不规则震动加载条件下岩石裂纹扩展机理研究

The failure of rock mass during the seismic load, is basically a failure due to the cracking processes, hence needing a thoroughly investigation of the cracking mechanism.Literatures mainly focused on the cracking study under quasi-static loading,while few researches were under seismic. Irregular seismic loading technique is used to load the flaw-contained marble and gypsum specimens vertically in this project. High speed camera technique and sonic velocity continuous monitoring technique are used to observe and monitor the cracking processes. Particle Flow Code (PFC), which is based on the Discrete Element Method (DEM), is adopted to simulate the cracking processes accordingly. The investigation of specimens containing a single flaw will reveal the crack initiation,cease,multiple propagation as well as the tension/shear types under irregular seismic load, which is varied in frequency and amplitude. The investigation of specimens containing two flaws will reveal the coalescence processes as well as the modes of coalescence.The relationship between the cracking processes and the frequency, amplitude and last time of irregular seismic load will be set up. The numerical simulation will reveal the evolution from micro cracks to macro cracks, and the changes of stress and strain in the specimens during the processes of crack initiation,cease and multiple propagation under the irregular seismic load. Finally, the mechanisms of crack initiation,cease,multiple propagation and coalescence under irregular seismic load are fully studied based on the physical tests and PFC simulations.

岩体在震动荷载条件下发生破坏，其根本的内在机制是裂纹扩展问题，需要对其扩展规律及贯通机理进行深入研究。已有裂纹扩展研究集中在准静态荷载条件下，对震动荷载条件却少有开展。本项目拟采用不规则震动加载技术，对含预制裂纹的大理石和石膏试样进行竖向加载，采用高速摄像技术和声波波速连续测量技术，观察和监测裂纹演化过程，并结合颗粒元数值方法，研究裂纹扩展及贯通机理。通过分别对含单条和两条预制裂纹试样的加载研究，揭示在震动频率及周期峰值快速变化的不规则震动加载条件下，新生裂纹的起裂、止裂、多次扩展，裂纹的张拉/剪切类型及扩展后交互贯通过程和贯通模式。建立裂纹扩展贯通过程与不规则震动荷载的频率、峰值序列及持续时间之间的对应关系。通过颗粒元模拟，探讨微裂纹演化为宏观裂纹的过程，揭示裂纹演化过程中的应力应变演化特征。最后综合试验和模拟结果，探索不规则震动加载条件下新生裂纹的起裂、止裂、多次扩展过程和贯通机理。

岩体在震动荷载条件下发生破坏，其根本的内在机制是裂纹扩展问题，需要对其扩展规律及贯通机理进行深入研究。已有裂纹扩展研究集中在准静态荷载条件下，对震动荷载条件却少有开展。本项目拟对含预制裂纹试样进行不规则震动加载，研究裂纹扩展及贯通机理。通过分别对含单条和两条预制裂纹试样加载研究，揭示在震动频率及周期峰值快速变化的不规则震动加载条件下，新生裂纹的起裂、止裂、多次扩展，裂纹的张拉/剪切类型及扩展后交互贯通过程和贯通模式。建立裂纹扩展贯通过程与不规则震动荷载的频率、峰值序列及持续时间之间的对应关系，探索不规则震动加载条件下新生裂纹的起裂、止裂、多次扩展过程和贯通机理。研究结果表明，张拉破坏是震动荷载条件下的主要破裂机制，在震动加载序列中，张拉位移达到最大值处，是裂纹起裂和扩展的时机。如果震动荷载持续反复作用在一个方向上，当第一次加载序列只能使裂纹萌生，后续重复加载序列并不能使裂纹继续扩展。如果改变加载方向，进行不同方向的反复交替加载，在震动波形不变的情况下，会使得初始起裂裂纹继续扩展贯通，从而导致岩石破坏。这一研究结果表明，在主震后不同方向的余震的作用，或地震波反射交替作用下，岩石容易发生破坏。这与大量岩质边坡在震后余震过程中发生失稳破坏的现象一致。为进一步开展地震波作用下岩质边坡、岩体失稳工程引用研究提供了理论基础。