Study On Resistivity Variation Characteristics Of Saturated Sand Under Impact Loading

Sand liquefaction is a common seismic phenomenon,and sand liquefaction causes serious changes and deformation of soil structure and properties after saturated sand is shaken,which is also an important cause of serious damage and deformation of buildings and other infrastructure,and also shows that the influence of load on sand liquefaction behavior is significant.At present,the mechanism of vibration liquefaction of saturated sand soil cannot be comprehensively and accurately explained,and there are still certain shortcomings in the liquefaction behavior of some load vibration of non-cohesive soil.Based on the above deficiencies of sand liquefaction behavior,this thesis carried out a pore reconstruction test study on saturated sand in the whole process of vibration liquefaction,combined with resistivity testing technology and self-developed test equipment to test and study the resistivity change characteristics of saturated sand liquefaction under impact load,analyzed the change law of resistivity of saturated sand under different load amplitudes,and the influence of different load amplitudes on the development law of pore water pressure of saturated sand,and explored the pore reconstruction phenomenon during the liquefaction of saturated sand.The relationship between resistivity and pore water pressure of saturated sand with different particle sizes under impact loading conditions was studied.The main research contents and conclusions of this thesis are as follows:1.The experimental test of the resistivity test method of saturated sand was carried out,and the influence of solution saturation and Na Cl solution concentration on the resistance of sand with different particle sizes was analyzed,and the relationship between resistivity and these influencing factors was established.2.In order to more accurately test the resistivity change law of saturated sand under impact load,the self-developed rotary switching electrode scanning device was tested and evaluated in detail,which made sufficient data guarantee for the subsequent saturated sand resistivity test test.3.Based on the impact device independently designed by the research group,the experimental study of the resistivity change characteristics of saturated sand under impact load conditions was carried out.The test shows that the magnitude of the load amplitude affects the change of resistivity of saturated sand,the larger the load amplitude,the greater the initial and final change of resistivity of saturated sand,the sudden drop of resistivity of saturated sand before and after each impact is also increasing,and the steep drop time of resistivity of saturated sand with fine particles is longer than that of coarse-grained saturated sand.4.The pore reconstruction phenomenon of saturated sand under impact load was explored,the pore water pressure change law of saturated sand under different load amplitudes was experimentally analyzed,the change law of superstatic pore water pressure during liquefaction of saturated sand was explored,and the change law of pore water pressure and resistivity of saturated sand with different load amplitudes and different particle sizes was analyzed.The total time for the growth and dissipation of pore water pressure in coarse-grained saturated soil was significantly less than that of fine-grained saturated soil.The resistivity development of saturated sand is negatively correlated with pore water pressure,and while pore water pressure increases,the resistivity of saturated sand decreases,and when the pore water pressure dissipates,the resistivity of saturated sand begins to rise.As the load amplitude and the number of load impacts increase,so does the compactness of saturated sand.