Numerical Simulation Of Desiccation Cracking In The Cross Section Of Clay Soil

In nature,the desiccation cracking in the cross section of clay is an important factor leading to the gradual failure of soil dam,soil slope and clay liner.Early in the 1960s,many people/researchers did a lot of research on clay drying and cracking.However,the dry shrinkage cracking mechanism of clay is still in the stage of qualitative analysis and theoretical assumptions.The research on the changing law of the key physical and mechanical parameters of the soil in the process of dry shrinkage cracking is insufficient.But now,with the development of technology,a new numerical analysis method,discrete element method,is applied to the complex and changeable geotechnical mechanics.The current numerical simulation mainly focuses on the evolution of surface cracks,instead of vertical shrinkage cracking process.These simulations usually do not consider the humidity migration and stress coupling.Based on the discrete element analysis software PFC,this research sets up a moisture diffusion model,and makes it available to do a two dimensional simulate of moisture-stress interaction.By changing different parameters,this paper analyzes the change of the internal stress and how the mechanical properties and soil-water characteristics influences the process of water loss and cracking during the process of dehydration and shrinkage cracking.The main conclusions are:a)Preliminary derived the correspondence between the parameters of thermal conductivity theory and percolation theory.It laid the foundation for simulation of seepage in soil using the PFC thermal module.b)Based on previous research,a two dimensional simulating method considering moisture-stress interaction is established.c)In the simulation results,the relationship between the water content and the cracking depth fits well.d)By analyzing the relationship between the horizontal force and the time of the particles near the crack,it is found that when the crack tip breaks,the force of the particles is not necessarily the largest at the same surface.The force may be related to stress concentration.e)Through force analysis of the particles on the crack surface,it is found that when the surface of the soil cracks,the force of the particles are larger.With the expansion of cracks,the force of the particles on the internal crack surface of the soil is decreasing and gradually tends to be gentle.This may be related to stress concentration.In the same way,when the cracks expand downward,the change in water content at the crack tip is also decreasing.That means,when the interior of the soil cracks,the change of water content is less than that when the soil surface cracks.f)Through analysis of changes of various parameters in fracture morphology over time,analysis of the change of water content on the upper and lower surface of soil at one time,andanalysis of influence of various parameters on cracking depth over time,it is found that the expansion rate of soil,the characteristics of soil and water properties play a major role in the vertical cracking of clay.The second important factors are mechanical properties of soil indicators.Finally,the macro-microscopic properties of the cohesive soil are considered together to provide a series of crack prevention measures for cohesive soil slopes.