Experimental Study On Water Retetion Characteristics And Pore Size Distribution Of Complete-intense Weathering Mudstone

Unsaturated soil is widely distributed in the earths surface,and its performance is in a variety of forms.The internal micro structure of the soil is more complex,and its material performance has inextricably relationship with the stability of its material properties for engineering mechanics and reliability engineering practice.Along with the rapid development of the society,the proportion of unsaturated soil application in engineering practice is more and more,and the engineering problems are more and more obvious.It shows the important influence on slope stability,geological disasters,and the treatment of contaminants and the development of new energy especially.Themacroscopic features of unsaturated soils are closely related to the physical state of unsaturated soils of microscopic structure,and the internal transfer of liquid and gas-liquid interface.In another words,the content of water and the form and the existence of water has a direct effect on the unsaturated soil.So the study of hydraulic properties of unsaturated soil is the foundation on the study of unsaturated soil.In this paper,a series of water retention and mechanical behaviour tests and mercury intrusion porosimetry(MIP)on unsaturated compacted and undisturbed complete-intense weathering mudstone specimens,were performed to investigate effect of the specimens preparation on water retention behavior,pore-size distribution and its mechanical behaviour.And based on the results of the MIP tests experienced two different suctions,a method for predicting the water retention curve is proposed.(1)The pressure plate method,filter paper method and vapor equilibrium technique with saturated salt solution are used to investigate the soil-water characteristics.The soil water content,saturation and void ratio decrease with the increase of suction,and the specimens shrinkage and dry density increased.In the high suction stage,the pore ratio has little effect on the soil water characteristic curve,which is expressed by suction and water content.But,In the low suction stage,the pore ratio has effect on the soil water characteristic curve.There is little difference between the undisturbed and the compacted samples in water retention capacity,but the undisturbed samples have better water retention capacity in the suction stage of 0.1-1MPa.(2)Mercury intrusion porosimetry was carried out on undisturbed samples and compacted samples of complete-intense weathering mudstone under different suction conditions.With the increase of suction,the relatively large pores of the soil first contract,and then the smaller pores shrink.For compacted samples,the saturated specimen exhibits a unimodal pore size distribution,and the specimen experienced 38MPa suction has a double-porosity microstructure.And the undisturbed natural specimens exhibit a unimodal pore-size distribution.(3)Based on the results of the mercury intrusion porosimetry tests in 3 different suctions,a method for predicting the water retention curve of undisturbed specimens during drying is proposed,and the predicted results are compared with the measured values.Finally,select the respective section of the suction range integration into the full suction range of water retention curve,making the prediction more accurate.(4)The soil water characteristic curves under different dry densities were measured.And Based on the theory of Young-Laplace equation,boundary capillary water and adsorbed water in the dry density-water content.