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受载岩体破坏全过程声波响应特征及工程意义

Acoustic response characteristics and engineering significance of loaded rock during failure process

  • 摘要: 矿井灾害的孕育和发展过程中,常伴随着岩体应力的变化,岩体应力的变化引起岩体发生变形、破坏,从而改变围岩的声学特征,其中岩体的波速变化特征可对煤矿某些地质灾害起到预测预报的作用。通过晋城矿区现场取样,采用岩石力学加载系统和声波测试系统对岩石单轴加载破坏全过程的声波脉冲信号进行实时采集,利用自主开发的脉冲信号初至时间智能处理Pickup程序模块,对测试数据进行处理。研究结果表明:晋城西区和北区煤系地层岩石力学特征和波速变化特征差异较大,西区岩石加载破坏全过程中波速变化经历“上凹-线性增大-突降上升-台阶波动-台阶突降”5个阶段,而北区岩样呈脆性破坏,岩石波速变化缺少台阶波动阶段;岩石受载应力为65.67%σmax~86.75%σmax时,波速出现震荡式降低点,为岩体变形破坏过程中的扩容点;不同区域岩石加载过程中波速增大幅度差异大,岩石加载破坏不同阶段的波速响应机制具有不同的工程意义,可为矿井地质灾害的防治提供参考。

     

    Abstract: During the gestation and development process of mine disasters, the variation of rock mass stress is often accompanied, then causing rock deformation and destruction and the acoustic feature of surrounding rock will be changed. Wave velocity variation characteristics of rock could have an effect on geological disaster forecast. The rock samples derive from Jincheng coal mine area. This paper collects acoustic wave pulse signal through rock mechanics loading system and acoustic wave test system under single axle load failure process, picks the first arrival time of pulse signal and deal with the test data by using the self-developing “pickup module”. The research results show that the rock mechanics characteristics and wave velocity variation characteristics of coal measure strata have large difference in different area, wave velocity variation can be divided into 5 stages, that is “upper concave-linear increase-sudden drop and rise-level fluctuations-step drop”, during loading process, brittle rock is short of level fluctuations stage. Wave velocity appears drop point of shock type when the load is (65.67%-86.75%)σmax. The drop point of wave velocity also is the volumetric dilatancy point during rock deformation and fracture process. The increase amplitude of wave velocity has large difference during loading process for the rock in different area. The wave velocity responding mechanism of different stages has different engineering significance during load process, which can provide references for the geological disasters prevention of coal mine.

     

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