Numerical Simulation Of Electric Field On The Pore Structure And Its Change Of Saturated Sand

The liquefaction of saturated sand is caused by particle migration and pore structure change,which leads to the decrease of soil strength or even loss of stability,and will bring catastrophic damage to the site,such as slope sliding,uneven settlement and large deformation.In view of the above sand liquefaction problem,it is proposed to explore from the perspective of pore structure change,and analyze the change of pore structure of saturated sand from the perspective of electric field change,so as to provide theoretical basis for the electrical test of sand liquefaction.Based on the support of the National Natural Science Foundation of China ’ Study on the pore reconstruction mechanism of saturated sand in the whole process of vibration liquefaction ’(project approval No.51978317),this thesis simplifies the saturated sand in the state of two-phase loose particle accumulation into a particle body composed of multiple equal-diameter circular particles and pore water,and carries out the numerical simulation of the electric field under the change of pore structure of saturated sand.Combined with the electrical test of the circular particle model,the electrical test results are compared with the numerical simulation results.The main research contents and conclusions are as follows :(1)The two pore structure parameters of particle porosity and particle spacing are proposed to quantitatively characterize the change process of pore structure,that is,the homogenization process of pore distribution is the process of increasing the average of particle porosity or decreasing the standard deviation,and increasing the average of particle spacing or decreasing the standard deviation.(2)The numerical simulation of the electric field with holes is carried out by COMSOL finite element software,and the finite element analysis method of electric field is proposed.Taking the single particle model as an example,the influence of different particle sizes and positions on the electric field is discussed,and the relationship between the transverse and longitudinal resistivity and different particle sizes and positions is obtained,which provides technical support for the subsequent electric field numerical simulation of the pore structure change process of saturated sand.(3)The numerical simulation of the electric field under the change of the pore structure of the particles after simplifying the saturated sand is carried out.It is found that when the pore distribution gradually tends to be uniform,the bending degree of the electric field streamline is lower and lower,that is,the length of the electric field streamline is shorter and shorter.At this time,the transverse and longitudinal tortuosity is also smaller and smaller,indicating that the pore distribution homogenization process is a process of decreasing tortuosity.(4)The electrical measurement test of the simplified circular particle model of saturated sand was carried out,and compared with the numerical simulation results,the variation law of electric field in the process of pore structure change was obtained.The conclusion shows that the transverse resistivity,longitudinal resistivity and average structural factor all show a decreasing trend in the process of pore structure homogenization,which is caused by the rearrangement of particles and the smoother pores between particles in the process of pore distribution homogenization.(5)By analyzing the error rate of the electrical test results and the numerical simulation results,it is concluded that under the four different particle sizes,when the seven pore distribution states gradually tend to be uniform,the error rates of the simulated values of the transverse resistivity,the longitudinal resistivity and the average structural factor are smaller than the experimental values.The rationality and accuracy of the numerical simulation results are further verified,which provides a basis for studying the change law of pore structure in the whole process of saturated sand liquefaction.