Effects Of Different Soil Layer Conditions On The Impact Liquefaction Response Of Saturated Sandact Load

As a country with frequent earthquakes,the problem of sand liquefaction caused by earthquakes has always been one of the hot issues in the field of geotechnical engineering.The excess pore water pressure will be generated in soil under vibration load,and the development of excess pore water pressure will be influenced by different soil conditions in the actual stratum.Based on the self-developed liquefaction dynamic test system,this paper conducts liquefaction tests on saturated sand with different soil layers by using shock type vibration load.Shock type vibration load is a type of earthquake action,which is relatively simple and can clearly reflect the response law and mechanism of soil liquefaction under vibration load.This paper mainly analyzes the dynamic pore pressure development law,water film phenomenon and settlement change law of saturated sand under different soil layer conditions after impact liquefaction.At the same time,it carries out theoretical derivation of water film formation conditions,time history change of water film thickness and soil layer settlement,and compares the theoretical calculation results with the experimental results.The main research contents and conclusions of the full paper are as follows:1、Based on the law of conservation of energy,a dynamic test system for liquefaction was developed.The test principle of the system and each component of the test equipment are explained in detail.2、The impact liquefaction characteristics of saturated sand were studied considering the soil layer number and sandwich type.The results show that when there is a weakly permeable interlayer,there will be an obviously non-uniform distribution of "water film" at the interlayer,which experiences a rapid formation,gradual development,and then a slow dissipation process after impact.The dynamic pore pressure of soil increases rapidly within a very short time after the impact.The whole development process presents transient response and steady response stage,in which the steady response stage goes through slow decline and fast decline.With weakly permeable interlayer,the steady-state response process lasts for a long time,which is obviously affected by the permeability coefficient of weak permeable layer.With the rapid increase of dynamic pore pressure,the settlement rate increases obviously,and the settlement amount accounts for 90% of the total settlement amount when the dynamic pore pressure is at a higher level.3、Based on the experimental results of one-dimensional impact liquefaction of saturated sand,the macroscopic phenomena such as water film and sedimentation during impact liquefaction of saturated sand containing sandwich were analyzed and deduced theoretically.According to the derived results,the corresponding calculation program is compiled,and the time-history results of water film thickness and sedimentation are compared with the experimental results,which verifies the reliability of the experimental analysis in this paper.