Research On Similar Material Model Test And Numerical Simulation For Columnar Jointed Rock Mass

Rock is a kind of discontinuity, heterogeneity, anisotropy and nonlinear natural geological body, being rich in discontinuities that include fissures, fractures, joints, faults, bedding planes, shear zones and dykes. These discontinuities have an important effect on stress distribution in space and the failure mode of rock mass. Among them, the columnar jointed rock masses are enrich in joints, and cracks, and its mechanical properties are particularly special. Nowadays, many hydropower stations in southwest reveal a lot of columnar jointed rock masses, prone to relaxation and cracking during excavation, and engineering mechanics properties of columnar jointed rock mass are more and more valued by water conservancy project. Based on the indoor model test and numerical simulation method, This article studies the failure mechanism, the deformation and strength characteristics, and mechanical parameters for the columnar jointed rock mass. This paper mainly focuses on the following aspects:(1) According to the similarity principle and structure characteristics and mechanical properties of columnar jointed basalt, the parameters’s similarity ratio of the model test is derived. Based on the research status and the advantages and disadvantages of similar materials, appropriate similar material is selected to simulate brittle basalt rock. Develop scheme, and through the test of mechanical properties for model specimens, the best similarity ratio is selected for the subsequent production of jointed specimens, which is close to the physical and mechanical parameters of basalt.(2) No columnar joints, different column sections and different dip angle model specimens are made. The size of the artifical jointed rock mass specimen is 100×100×100 mm3. After the uniaxial compression test, that columnar joint, column shape and dip angle influence on the mechanical properties of specimens will be analysed. The deformation, strength, failure mechanism of the columnar jointed specimen, and failure form of joint are summarized.(3) The similar material model specimens with different dip angles are subjected to uniaxial compression by discrete element numerical simulation software 3DEC. Deformation, strength, failure mode and stress-strain curves of numerical simulation are compared with the model test. The results of numerical simulation will verify the conclusions of laboratory tests, and summarize the laws of mechanical properties of columnar jointed rock mass.(4) Adopting non-continuum mechanics numerical calculation analysis methods, in Baihetan Hydropower Station Diversion Tunnel as an example, the failure mechanism under excavation unloading of cavern with columnar jointed surrounding rock mass is studied. The failure characteristics of structure-stress control and anisotropic relaxation deformation mechanism for columnar rock mass have been analyzed. The phenomena, including that the roof arch collapsed and columnar joints of sidewall relaxed on the left bank diversion cave, have been explanated.