Study On The Evolution Of Subgrade Soil Resistivity Under Vibration Load

Intelligent compaction technology,as an emerging technology,has begun to be applied in roadbed construction and has brought great convenience to construction.However,research and practice have shown that due to the influence of moisture content,there are differences between intelligent compaction test values and traditional quality control indicators in evaluating the quality of roadbed compaction,which in turn affects the further promotion and application of intelligent compaction technology as a quality control method.Therefore,real-time testing of moisture content is of great significance for improving the accuracy of intelligent compaction testing.Therefore,this article uses the resistivity method to achieve real-time detection of soil moisture content,and studies the changes in soil settlement and resistivity under different soil moisture content and excitation forces.The numerical simulation obtained the variation of resistivity with water content and porosity,as well as the relationship between resistivity,water content,and porosity under different excitation forces.Establish a vibration wheel soil model to analyze the distribution of vertical compressive stress inside the soil under static pressure and rolling pressure of the vibration wheel,as well as the variation of soil surface resistivity during the two processes.The results will provide a theoretical basis and testing method for moisture content testing in the intelligent compaction process,thereby providing support for improving the accuracy of intelligent compaction control.The main research content and achievements completed are as follows:(1)By combining the effective stress principle of unsaturated soil,Richards seepage equation,and the extended Archie equation,the bi-directional coupling equations of soil moisture field,stress field,and electric field in the process of roadbed compaction are obtained.Conducting indoor experiments and establishing the same theoretical model based on the fluid solid electrical coupling equation as the experiment,it was found that there was no significant difference between the calculated simulation results and the experimental test results,reflecting the good consistency of the test model.(2)In order to analyze the evolution of the resistivity of the roadbed soil under strong and weak vibrations,as well as high and low frequencies,a cross-sectional model of the roadbed is established.By analyzing the resistivity of the roadbed under different vibration loads,it is found that under the same moisture content,the soil resistivity rapidly decreases at the moment of loading,and then shows a stable fluctuation state.When the amplitude of the excitation force is constant,as the soil moisture content increases,the resistivity will decrease;When the amplitude of the excitation force increases and the moisture content of the soil is constant,the resistivity of the soil will decrease,and the fluctuation amplitude of the resistivity will increase.(3)In order to analyze the changes in the electric field of the roadbed under vibration loads,based on the established cross-sectional model of the roadbed,the cloud map changes during compaction can be obtained.It can be seen that the voltage equipotential lines of the soil near the test electrode are dense,and the voltage equipotential lines far from the electrode are sparse.The electric field in soil is affected by the magnitude of the excitation force.Under the same soil moisture content,the soil resistivity and influence range under larger excitation forces are smaller than those under smaller excitation forces.(4)Study the changes in soil resistivity under the vibration wheel during the process of vibration compaction of roadbed.Based on the vibration wheel soil model,calculate the resistivity change of the vibration wheel rolling compaction for 5 seconds.The results show that the resistivity of four types of soil with different moisture contents shows a V-shaped distribution under the static pressure of the vibration wheel,and the resistivity is the lowest at the intersection of the vibration wheel and the soil.During compaction,there will be a small amount of soil accumulation at the edge of the vibrating wheel,where the resistivity will suddenly increase.During vibration compaction,there was no sudden increase in soil resistivity at the edge of the vibration wheel,indicating that the vibration wheel compacted the soil without significant changes in soil porosity and good compaction quality.