缺陷岩体加速协同化破坏机制及前兆信息辨识

Accelerated synergistic failure mechanism of defected rock mass and precursor information identification

缺陷岩体对地下煤体的安全开采构成威胁,同时对工程长期安全运行带来较大的隐患,分析其破坏前后所展现的物理量变化特征,将为岩体失稳提供前兆辨识信息。以含缺陷单元的石膏组合体为研究对象,研究其破坏-失稳时空演化过程,捕捉和比较失稳前关键时刻对应物理场信息的变化差别,探讨岩体破坏失稳前由独立活动向整体协同化运动的过程。试验结果表明:缺陷组合体完全破坏分为强偏离线性、静态亚失稳和动态亚失稳3个阶段;首先相对强段为承载主体,弱段出现孤立的应变积累区和释放点并作用于强弱接触面;之后弱段积累区迅速增多并扩展和迁移,不同性态岩体呈现应变协同化传递具有单元性和区域性特征;最终应变释放点相互贯通,强弱段相互作用加强使得协同化程度达到最大,成为岩体进入全面失稳快速破坏的标志。为进一步验证上述试验结果的科学性、合理性,以某矿井断层采动涌水为工程背景,制作采场断层模型并进行双向加载试验,研究断层失稳错动引发涌水的过程及触发条件,揭示了断层亚失稳阶段协同化破坏机制。上述试验结果表明缺陷岩体进入亚失稳阶段是协同化破坏开始的标志。

Defected rock mass seriously threatens the safety construction and long-term operation of underground engineering. It is significant to investigate the physical variables before and after the instability, which provides useful information to identify the precursor of rock mass instability failure. This study is to conduct experiments on the gypsum in combination with crack elements, and further to investigate its space-time evolution process of the failure-instability. Before the instability failure, the changes in the corresponding physical field are captured and compared at critical moments. The processes from the independent activity to overall synergistic movement of rock mass are discussed as well. Experimental results indicate that the complete destruction of the crack combination can be divided into three stages： strong deviation from the linear, static sub-instability and dynamic sub-instability. In the non-linear stage, the relatively strong segment become the main bearing body. The isolated strain accumulating area and releasing points appeared firstly in the weak segment, and then acted on the interface between strong and weak segments. Strain accumulating areas in the weak segment rapidly increase, extend and migrate. Different lithologies of rock mass present strain synergistic transmission with unitary and regional characteristics. Finally, strain releasing points are mutually connected. When both the synergistic effect and strain accumulation degree in the strong segment reach their limits, the stage of rapid destruction of rock mass into full instability emerges. A stope fault model is established to further verify that the results are scientific and rational. This model was based on the engineering background of water inrush in a coal mining. The two-axial loading experiment was carried out to investigate the process of water inrush and trigger conditions caused by the fault instability. The mechanism of synergetic failure in the sub-instability stage is revealed. Experimental results indicate that the sub-instability stage of jointed rock mass makes the beginning of synergistic failure.