Experimental And Numerical Study On The Hydromechanical Behavior Of Mudstone Subjected To Cyclic Hydration And Dehydration

Many structures of underground engineering are constructured in mudstone formation.Due to having clay minerals,mudstone exhibits a notable coupled hydro-mechanical behavior,particually swelling.In this paper,we will study the hydromehcanical behavior of the mudstone combining different macro-microscopic experimental and numerical methods to reveal the mechanisms of deformation and damage during drying and wetting.The main work is summaried as follows:(1)Develepment of a specific setup to follow the weight of the mudstone samples,the effect of cyclic hydration and dehydraiton on the soil water content curve will be analysied and quantified;the cyclic number of hydration and dehydraiton on the SWCC is notable and the latter will be fitted using the V-G model;the quantitifed anlaysis will be carried out;(2)Propose of a two-dimensional diffusion model to describe the hydration of the mudstone and characterization of the diffusion coefficition;the diffusion coefficient increases with the increase of relative humidity(RH)when RH is at low level,and it redecreases when RH reaches 98%;combining with NMR and MIP techniques,the water distribution and pore size of the mudstone will be analysied;(3)The deformation of the mudstone at multiscales will be identified combining ESEM and DIC techniques.The cyclic hydration and dehydration tests have carried out to investigate the cyclic number and hydric gradient on the hydric deformation and structure.The results show that the hydric deformation of the mudstone strongly depends on the hydric gradient and cyclic number of hydration and dehydration;(4)The hydric deformation of the studied mudstone exhibits notable heterogeneous,nonlinear and anisotropic and irreversible.The mechanisms of the heterogeneous,nonlinear and anisotropic deformation of the mudstone will be revealed by analyzing the microstructure change and component;(5)Using finite element method,the hydric deformation will be simulated.It is found the internal stress concentration will be created during during hydration and dehydration and it is due to the imcompatible deformation of the different components and such stress is the origine of the damage of the mudstone.