Study On Resistivity Variation Characteristics Of Different Grade Saturated Sand During Liquefaction Process

The liquefaction of sand caused by dynamic loads such as earthquakes with short but high strength has caused serious damage to human society.In addition to the intensity of the earthquake,the soil conditions of the earthquake site,such as relative density,particle group and clay content,are also important factors affecting the liquefaction behavior of saturated sand,and the liquefaction behavior and liquefaction resistance of grade pairing have a significant impact.However,the influence of the liquefaction behavior of the stage pairing is controversial and needs to be further studied,and the non-destructive testing of the specimen is also an important aspect.Based on the above problems,this thesis introduces electrical measurement technology,using the property of resistivity to react to the pore structure of saturated sand,first study and analyze the resistivity law of different graded saturated sand in the static state,and on this basis,the resistivity change characteristics of different graded saturated sand in the process of impact liquefaction are studied,and at the same time,combined with the superstatic pore pressure in the liquefaction process,the influence of pore structure change during the liquefaction of different grades of saturated sand is analyzed through the change characteristics of resistivity.The following are the main work and conclusions of this article:(1)The alternatance test of resistivity of saturated sand with different grades in the static state was carried out by alternating current square wave,and the test results showed that for saturated sand of the same gradation,the greater the relative density,the greater the resistivity of saturated sand.When the relative density is constant,only one type of saturated sand containing one particle group,the smaller the particle group,the smaller the saturated sand resistivity,containing two different particle groups of saturated sand,with the increase of fine sand content,the resistance of saturated sand first increases and then decreases.(2)For saturated sand of different grades,after the impact load,the superstatic pore pressure increases rapidly to the peak,but there are also differences,and the resistivity is obviously different.For saturated sand containing only one particle group,the smaller the particle group,the longer the superstatic pore pressure increase of saturated sand,the smaller the sudden increase in superstatic pore pressure,the longer the resistivity dip time,and the smaller the sudden drop amount.With the increase of fine sand content,the sudden increase time of superstatic pore pressure first increases and then decreases,the sudden increase of superstatic pore pressure first decreases and then increases,the resistivity dip time increases first and then decreases,and the resistivity dip decreases first and then increases,with the fine sand content being 40% as the turning point.(3)For saturated sand containing only one particle group,in the process of superstatic pore pressure dissipation,the smaller the particle group,the longer and slower the time and speed of pore pressure dissipation,0.25-0.5mm and 0.1-0.25 mm saturated sand in the process of superstatic pore pressure dissipation appear pore pressure stabilization stage,the smaller the particle group,the longer the pore pressure stabilization and drop time;the smaller the particle group,the greater the increase in resistivity of saturated sand.For saturated sand with coarse and fine particle groups,the time of dissipation of superstatic pore pressure increased overall,while in saturated sand with a fine sand content of 40%,the dissipation time of pore pressure became shorter.With the increase of fine sand content,the amount of resistivity of saturated sand first decreases and then increases,with the fine sand content being 40% as the turning point.(4)During the liquefaction process,the resistivity of saturated sand has a significant correlation with the change of superstatic pore pressure,and after the destruction of saturated sand,the superstatic pore water pressure is instantaneously generated,and the resistivity also decreases,and the time when the resistivity reaches the trough slightly lags behind the time when the superstatic pore pressure reaches the peak.(5)The change law of resistivity basically reflects the pore reconstruction phenomenon in the whole process of liquefaction of saturated sand.