Study On Mechanical Characteristics And Evolution Of Mechanical Parameters Of Hard And Brittle Basalt

With the deepening of the construction and research work of the Baihetan Hydropower Station in Jinsha River,the general understanding of hard and brittle rocks in the early stage of engineering and academia is not enough to reasonably explain the complex failure mode of the hard-brittle basalt in Baihetan,and may even affect the construction and operation safety of the giant underground caverns of Baihetan hydropower stations,therefore,it is very urgent to fully understand the mechanical properties,deformation laws and failure characteristics of basalt under different conditions,and reveal its inherent damage mechanism.The main research work and results of this paper are as follows:(1)The cryptocrystalline basalt and almond-shaped basalt from Baihetan were selected as research objects,and the uniaxial compression and conventional triaxial compression tests of standard samples were carried out,and acoustic emission monitoring was carried out simultaneously,combined with electron microscopy scanning of damaged specimen sections.The rupture development process and failure mode of hard brittle basalt under different confining pressures are analyzed,and the failure mechanism of tension-tensile shear composite under hard pressure of hard brittle basalt is revealed.(2)The characteristic stress of basalt is calculated by using the crack volumetric strain model of hard brittle rock,and systematic study on the intensity evolution of cryptocrystalline and almond-like basalt under loading conditions,and the linear Mohr-Coulomb criterion and nonlinearity are used respectively.The linear Mohr-Coulomb criterion and the nonlinear Hoek-Brown criterion are used to fit the test results,and the mechanical parameters of basalt are obtained.The mechanical parameters are discussed to reveal the inherent failure mechanism of hard brittle basalt during loading.The quantitative analysis of the cryptocrystalline and almond-like basalt brittleness was carried out,and the different failure modes of cryptocrystalline and almond-shaped basalt were explained from the perspective of brittleness.(3)The triaxial cyclic loading and unloading test of cryptocrystalline basalt and almond basalt was carried out.By defining the plastic internal variable,the evolution law of elastic parameters and strength parameters of basalt with the plasticity of the sample was established,and the evolution expression of each parameter was established.Through the FLAC3 D numerical value,the characteristics of the plastic zone of the surrounding rock during the excavation of Baihetan underground powerhouse are analyzed.