Particle DEM Simulation For Rock Tests Of Direct Tension And Compression

In rock engineering, many machanics parameters and the constitutive relation of rock are obtained by compression test. In traditional research, rock is thought to be endured compressive stress rather than tensile stress. According to study results nowadays, the tensile strength is obtained by split tests in laboratory experiment. However, the defect of split tests leads to significant errors between measured tensile strength and the real one. Consequently, only the direct tension experiment can reflect the true tensile characteristics correctly. With the construction of tremendous rock engineering, researchers devote themselves to the study of triaxial compression experiment, and make many achievements in this felid. Many of their investigations focus on exploring rock’s macroscopic mechanical properties. Nevertheless, the intrinsic mechanical properties of rock can only be acquired by the method which combines the microscopic analysis and the macro mechanical behavior. And the numerical methods have advantage over any others in the researches.In order to avoid the defect caused by FEM which regard the rock as continuous and homogeneous medium in the study of rock compression-tension mechanical properties, a numerical method was applied to simulate the rock tension-compression experiment. This method, granular distinct element method, is a sufficient way to solve non-continuum mechanical problems. With this method, this paper can analyze the failure and deformation mechanism from a micro perspective. In order to achievement the purpose of replacing the laboratory experiments with numerical simulation completely or partially, this paper makes use of Particle Flow Code PFC2D to investigate these issues as follows:(1) This investigation introduced construction method of particle flow model, by creating the biaxial compression model. The rock macro mechanical behavior was investigated by changing the value of micro-properties between each particle. And then this paper summarized the corresponding relation between micro-properties between particles in particle flow model and rock micro-properties.(2) By creating uniaxial compression particle flow model of sandstone and simulating the experimental results, this paper calibrated the micro-properties between particles which can reflect the real properties of sandstone. Simulated stress-strain curves, failure mode, and crack initiation mode were analyzed, and the deformation and failure mechanism of brittle material rock were investigated too. The direct tensile model of sandstone was created by using the calibrating results of micro-properties. On the basis of simulation model, the stress-strain curves and failure mode were also studied.(3) In this paper, the marble experimental results were adopted to calibrate the biaxial compression particle flow model. And then the particle micro-properties was acquired which can reflect the properties of marble. This paper verified the accuracy of simulation results for marble laboratory experiment by studying the stress-strain curves and strength characteristics which were obtained by triaxial compression simulation in three different ambient pressure. This paper also investigated the relation between the crack initiation and the deformation failure mode by analysing the relation of simulation results.