Study On Soil Water Characteristic Curves Under Dry-wet Cycles And True Triaxial Conditions

Two experimental methods are used to study the soil water characteristic curve of unsaturated remolded loess in this paper.Firstly,dry-wet cycle tests were carried out on the unsaturated consolidation apparatus of the unsaturated loess under different matrix suction paths,and the variation of SWCC under different matric suction paths was analyzed,the influence of dry-wet cycles on the pore distribution of unsaturated remolded loess is studied from the microscopic point of view;In addition,the unsaturated true triaxial apparatus was used to carry out the equal b shear dehumidification test on the unsaturated remolded loess,and the variation law of the soil water characteristic curve and the deformation characteristics of the soil under the complex stress condition are analyzed.The existing formula of the soil water characteristic curve is deduced under the true triaxial stress condition,which is related to the ratio of the middle principal stress b is obtained,The variation law of formula parameters under different ratio of intermediate principal stress is studied,the variation of formula parameters under different medium stress parameters is studied.The results are as follow:(1)The variation law of soil water characteristic curve is different under different suction control paths.Under the condition of drainage,the SWCC of dry-wet cycles with air pressure gradient gradually moves downward with the increase of dry-wet cycle times,while the SWCC of dry-wet cycle with air pressure unchanged and pore water pressure gradient gradually rises with the increase of dry-wet cycle times.The air-water movement state is different under different conditions,and the water holding capacity of the former decreases,while that of the latter increases.From the microscopic point of view after the control of air pressure increasing and decreasing of dry-wet cycles and control of pore water pressure increasing and decreasing of dry-wet cycles will not affect the internal pore distribution of the sample.(2)The formula of soil water characteristic curve based on conventional triaxial stress with four variables of net mean stress,generalized shear stress,water content,matrix suction is obtained,which is related to medium stress parameters,net small stress and the difference between large stress and small stress.In the formula,the parameter 1 increase with medium stress parameters increase,the parameter m decrease with medium stress parameters increase,the parameter n decrease with medium stress parameters increase,and the parameter 1 increase with net small principal stress increase,the parameter m decrease with net small principal stress increase,the parameter n decrease with net small principal stress increase.(3)In the process of shear dehumidification of unsaturated remolded loess,under the complex conditions of matric suction、net mean stress and shear stress,the volume strain and volume strain increase,while the void ratio and water content decrease.