煤系典型岩石受载全过程光-电-声波多参数响应特征

Characterization and analysis of optical-electrical-acoustic multi-parameter response of the whole process of loading typical rocks in coal measure formation

  • 摘要: 【目的】 岩石在载荷作用下的变形与断裂会引起潜在参数信息的变化,通过参数的动态捕捉可表征裂隙生成、扩展、闭合过程,是一种岩石健康评价的重要方法。【方法】 基于搭建的多参数测试系统,开展单轴加载条件下岩石试件的分布式光纤应变、电极电流、纵波波速的同步采集,进一步构建强度-参数特征关系图谱以及参数层析成像结果,精细描述了砂岩、灰岩、泥岩三类典型岩石受载全过程多参数的时空演化特征。【结果和结论】 试验结果表明:时间-压力曲线和多参数响应曲线具有较好的一致性,螺旋布设的分布式光纤应变在试件的原生孔隙压缩和线弹性阶段表现为缓慢、稳定的增长,在裂隙生成、扩展阶段表现为突然、快速的增长。试验中,砂岩、灰岩、泥岩的临破裂分布式光纤应变值为933×10-6,401×10-6 和 3790×10-6;电极电流在原生孔隙压缩和线弹性阶段变化微小,在裂隙生成、扩展阶段明显地降低、裂隙闭合时有一定回升;在原生孔隙压缩、线弹性、破裂阶段,砂岩的纵波波速平均值分别为4.38、 4.39、 1.26 km/s,灰岩的纵波波速平均值分别为4.83、 4.93、 3.10 km/s,泥岩的纵波波速平均值分别为3.65、 3.57、 1.71 km/s。通过获得的岩石受载全过程能量值,构建了损伤变量D来评价岩石试件的损伤演化程度,砂岩的D值经历了缓增-降低-突增3个阶段,灰岩的D值经历了缓慢增大-快增-停滞-突增4个阶段,泥岩的D值经历了缓慢增大-快增-突增3个阶段。基于分布式光纤应变测试结果,探究了不同岩性岩石试件的破裂模式,为载荷下次生裂隙生成、扩展以及潜在破裂面位置预测提供支持。

     

    Abstract: The deformation and fracture of rock under loading will cause changes in potential parameter information, and the dynamic capture of parameters can characterize the process of fissure generation, expansion, and closure, which is an important method for rock health evaluation. The article is based on the construction of a multi parameter testing system, which achieves synchronous collection of distributed fiber optic strain, electrode current, and longitudinal wave velocity of rock specimens under uniaxial loading conditions. Furthermore, a strength parameter characteristic relationship graph and parameter tomography imaging results are constructed to finely describe the spatiotemporal evolution characteristics of three typical rock types under full loading with multiple parameters. The experimental results show that there is good consistency between the time pressure curve and the multi parameter response curve. The distributed fiber optic strain with spiral arrangement shows a slow and stable growth during the primary pore compression and linear elasticity stage of the specimen, and a sudden and rapid growth during the crack generation and expansion stage. In this experiment, the distributed fiber optic strain values of sandstone, limestone, and mudstone under imminent fracture were 933×10-6, 401×10-6, and 3790×10-6, respectively; The electrode current changes slightly during the compression and linear elasticity stages of the primary pores, but significantly decreases during the generation and expansion stages of cracks, and rebounds to a certain extent during crack closure; In the primary pore compression, linear elasticity, and rupture stages, the average longitudinal wave velocities of sandstone are 4.38 km/s, 4.39 km/s, and 1.26 km/s, respectively. The average longitudinal wave velocities of limestone are 4.83 km/s, 4.93 km/s, and 3.10 km/s, respectively. The average longitudinal wave velocities of mudstone are 3.65 km/s, 3.57 km/s, and 1.71 km/s. The energy value of the entire process of rock loading was solved, and a damage variable D was constructed to evaluate the degree of damage evolution of rock specimens. The D value of sandstone went through three stages: gradual increase, decrease, and sudden increase. The D value of limestone went through four stages: slow increase, rapid increase, stagnation, and sudden increase. The D value of mudstone went through three stages: slow increase, rapid increase, and sudden increase. Based on the results of distributed fiber optic strain testing, the fracture modes of rock specimens with different rock types were explored, providing assistance for the generation and propagation of cracks under load, as well as the prediction of potential fracture surface positions.

     

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