Numerical Simulation Of The Microstructure Of Gravel- Mixed Clay

Gravel-mixed clay is a coarse and fine particles of mixed complexes, being widely used as a king of engineering material. Its mechanical properties are controled by microscopic structure of gravel-mixed clay, in order to reflect the microstructure of gravel-mixed clay to reveal the microstructure affects the mechanical traits more precisely. Through laboratory experiments, microscopic structure of image analysis, simulation, parameter sensitivity analysis, the mechanical properties of gravel-mixed clay, micro structural features influence the mechanism of mechanical behaviors were studied. Details are as follows:(1) With researching on gravel-mixed clay by indoor experimental, through changing amounts of gravel, gravel-mixed clay samples were studied by consolidated undrained triaxial tests, the study results showed that:when the confining pressure is low, with gravel containing low amounts (0%-20%) the strength of gravel-mixed clay declined slightly, the figure of pore water pressure ascends while the amounts of gravel increase. when the amount of gravel reach 20%, the strength of gravel-mixed clay ascends and pore water pressure reduces while the amounts of gravel increase. In high confining pressure, with the amounts of gravel increasing, gravel-mixed clay strength increase. With the amounts of gravel increasing, internal friction angle increases.(2) The samples of gravel-mixed clay were scaned by CT. Studies show that:when the amount of gravel is 20%, gravel grains in the soil in the form of suspension. When the amount of gravel reach 40% or 60%, gravel grains are close in the spatial distribution. The clay between the gravel particles is more dense than the other. This helps the transfer of the force, forming the force transmission skeleton with the gravel grains together. The voids generally exist on the contact surface of gravel and clay in gravel-mixed clay. Pore counts and the volume increase in gravel-mixed clay, while the amounts of gravel increase.Based on two-dimensional images from CT scans, we achieved a three-dimensional reconstruction.(3) The constitutive model based on 3D reconstruction of selected adapted, using the finite element software ABAQUS, numerical simulation of microscopic structure of gravel-mixed clay and compare the shear strength, pore water pressure of pure clay and gravel-mixed clay under different confining pressures, verified by numerical simulation:under the low confining pressure, the gravel grains is for suspension in the gravel-mixed clay, the mechanical properties are controled by clay. Under the high confining pressure, intergranular porosity being compacted in a high pressure process of consolidation and coupled with hardening of clay, the greater confining pressure makes the clay more dense between the gravel grains, the greater rigidity of the skeleton, so undrained strength of the gravel-mixed clay rises with the amounts of gravel increasing. Under the low confining pressure, with gravel containing low amounts, the effective stress of clay far away from gravel grains dechines with the amounts of gravel increasing. Under the high confining pressure, clay far away from gravel grains is compressed and become dense, the figure of pore water pressure reduces, while the amounts of gravel increase.