气液复合加载的岩爆模型试验研究

Model tests on rock burst using gas-liquid composite loading

针对现有岩爆模型试验设备及方法存在的不足,采用自主研发的气液复合型岩爆模型试验装置,进行不同应力梯度下的大尺寸岩爆模型试验。通过对试件宏观破坏现象、内部变形规律及声发射特征参数的分析,研究岩爆发生、发展过程及破坏机制。结果表明:岩爆的发生与荷载梯度、能量的集聚程度和破坏时能量的释放速率密切相关,模型荷载梯度差值不一导致局部应力集中程度不同,影响试件破坏前期能量的耗散与集聚及岩爆时刻能量的释放速率,竖向破坏荷载梯度差值越大,局部应力集中程度越高,能量释放速率越快,转化为动能的能量越多,岩爆现象越易发生。模型试件破坏时,顶部竖向最大荷载值θ_σ处于与单轴抗压强度R比值为0.5~0.7范围,梯度荷载条件下,动静组合加载是试件破坏荷载降低的主要原因,其试验方法符合工程岩体的实际受荷。

To overcome the deficiency of the existing test devices and methods for rock burst modeling, a gas-liquid composite loading test device was developed to conduct the large size rock burst modeling under different stress gradients. In this paper, the occurrence, development processes and failure mechanism of the rock burst were studied through the analysis of the macroscopic failure features, interior deformation characteristics and the acoustic emission characteristic parameters of the sample. The results show that the occurrence of rock burst is closely related to the stress gradient, the energy concentration degree and the energy release rate during the rock burst processes. The differences of load gradient difference in the model test lead to the different concentration degree of internal stresses. These differences also influence the energy dissipation and agglomeration of the specimen in the early stage and the energy release rate at the moment of rock burst. If the difference of the vertical fracturing load gradient becomes greater, the degree of the local stress concentration becomes higher and the energy release rate will be faster. At the same time, the energy converted into the kinetic energy will increase and the probability of rock burst will be larger. When the specimen is broken, the ratio of the maximum vertical loadσθ on the top to the uniaxial compressive strength R is 0.5-0.7. Under the gradient loading condition, the static and dynamic composite loading is the main reason for the reduction of the failure load capacity of the specimen.