Microstructure Research On Basic Mechanical Properties Of Clay

Unlike metal and other solid materials, soil has a very complex property. The main reason causing the complex characteristic of deformation of soil is its miro-structure. The research of soil structure can be started from microcosmic form of soil. Attention should be paid to not only the geometric features, but also the mechanical characteristic of soil particles. Most of the soil experiments can only do research on the macro mechanical property of soil, while research on micro mechanism is inadequate. As a special kind of discrete element method, article flow theory and numerical method has a unique advantage in the research on microcosmic mechanism of macroscopical mechanical features of soil. With this technology, this article will investigate the microcosmic mechanism , in view of basic micro mechanics of clay. Specific studies include:(1)to use particle flow software (Particle Flow Code in 2 Dimension) to investigate technology of making clay samples, of which are composed of flat or needle-like clay particles, and conduct an initial simulation;(2)to use particle flow software to conduct compression test on simulated soil samples, to study the changes of micro-structure of clay during the compression process.(3) to use particle flow software to conduct shearing test on simulated soil samples, to study the internal force distribution of clay, how the particles are arranged, and the cohesion are destroyed ,during the shearing process.(4) to use particle flow software to shear the simulated soil samples from different direction, and investigate how the micro-structure of clay affects its mechanical anisotropy.After these work, the main conclusions are obtained as follows:(1) The e-p curves and k₀ curves obtained from simulated compression tests are fundamentally the same as the ones obtained from actual compression tests.(2) The Clay particles' initial arrangement has an obvious directing property, In the compression process the arrangement of particles obviously concentrated to the level direction. During the process, internal forces of soil samples are increasing gradually and have a uniform distribution. And internal force is mainly side-to-side contact and transferred. In the compression process, the bonding between the particles is gradually and uniformly broken.(3)In the shearing process with the increase of confining pressure, the largest axial stress also increase. With the existence of cohesion, the stress-strain curve has no longer a peak, and cohesion is broken gradually but not uniformly during shearing process. In the shearing process the arrangement of particles concentrated from vertical direction to the level direction, and internal forces increased gradually, which has a vertical crack-distribution.(4) Clay is anisotropic in all directions. The level modulus of elasticity is significantly less than the vertical one. When there is a cohesive force between the particles, the anisotropy of soil sample reduces obviously.