Experimental Study On Permeability Of Fine-grained Soil Under Different Stress States

Fine-grained soil is widely distributed in nature,and it is the basic material for buildings such as dikes,dams,foundations,and slopes.Generally speaking,due to the difference in particle composition,fine-grained soil exhibits different permeability characteristics,especially under certain stress,its permeability no longer conforms to Darcy's law.Existing specifications give the method of soil permeability test,but do not consider the effect of stress state on soil permeability coefficient.In this paper,the triaxial compression penetration tester is used to conduct the soil permeability coefficient test under different stress states,and to study the permeability of fine-grained soil.The experiment considered the effects of confining pressure,stress level and soil compaction on the permeability of fine-grained soil.With the help of ABAQUS finite element software,the numerical simulation study of the triaxial compression penetration test is carried out,and the comparative analysis is carried out.The main research work is as follows:Two soil materials,silt and clay,were selected and subjected to triaxial compression penetration test under different stress states.First of all,considering the permeability change of fine-grained soil under constant pressure,it is found that the permeability of fine-grained soil decreases approximately linearly with the increase of confining pressure,and the permeability coefficient of silt and clay changes when the confining pressure changes from 100 k Pa to 300 k Pa The declines were 76.8% and 72.2%,respectively.What's more,the permeability of fine-grained soil was investigated under different stress levels,and it was found that with the increase of stress level,the permeability of finegrained soil would change first and then rise.Silt permeability tends to be minimum when the stress level S=0.5,and the clay permeability tends to be minimum when the stress level S ?(0.7,0.8).Furthermore,Triaxial permeability tests were carried out under two compaction degrees of silt and clay,and the results showed that the permeability of the soil with larger compaction degree was relatively less affected by external stress.Last but not the least,in order to quantitatively describe the relationship between permeability coefficient and stress state,an empirical formula considering the permeability coefficient between stress states was established.With the help of ABAQUS finite element software,based on the fluid-solid coupling theory,the numerical simulation of the triaxial compression permeability test of finegrained soil was carried out.According to the calculation results of soil stress,displacement and pore water pressure,the changes of soil stress field and seepage field are analyzed,and the results show that the simulation results are basically consistent with the experimental results.