Study On Sand Liquefaction Reinforced By Encapsulated Stone Columns

Sand liquefaction is a common form of earthquake secondary disasters.Most of them are accompanied by sand blasting on the ground,road cracking,and damage to the foundations of houses.This undoubtedly brings a severe blow to people’s lives.Therefore,it is a great significance to research on the reinforced sand liquefaction in order to reduce the casualties and property damage caused by earthquake..At present,the method of liquefaction of sand reinforced by loose material piles is common,and traditional stone columns are used more frequently.They have the effects of drainage reinforcement and weaken deformation,and simplify the construction method to some extent.However,in the rapid development process of stone columns,its inadequacies are increasingly emerging: its own cohesion is weak,and the foundation soil around the piles is required to provide a certain constraint,which causes stone columns under the action of seismic shearing to deform earlily and eventually cause the bearing capacity of the foundation to be destroyed.Therefore,in order to change this shortcoming of the stone columns,it was decided to wrap a layer of geosynthetic material around the stone columns,combining the drainage reinforcement effect of the stone columns itself with the tensile strength and corrosion resistance of the wrap material,and thus get a new type of pile-Encapsulated Stone Columns.And then carried out research on its liquefaction of reinforced sand.Based on the shaking table test,the paper studies the sand liquefaction of single and group encapsulated stone columns.In the first place,a single pile of encapsulated stone columns is the main research object,compared with the test of a single pile of stone column and unreinforced model foundation,the inherent characteristics of single pile of encapsulated stone columns are preliminarily discussed and verified.Subsequently,the experimental research on sand liquefaction by group piles was carried out,and the liquefaction mechanism of sand reinforced with group piles of encapsulated stone columns was analyzed.The research shows that under the same experimental conditions,compared with the unconsolidated model foundation and the single-piled stone columns model foundation,a single pile of encapsulated stone columns can form a more smooth drainage channel,and the reinforced model foundation drainage increased,the foundation settlement reduced.And the maximum value of pore water pressure is significantly reduced,and all the liquefaction of the middle and lower layer foundations does not occur,that is,the single pile of encapsulated stone columns presents a more excellent drainage reinforcement effect.Compared with the group pile of encapsulated stone columns reinforcement,the pile group gravel pile reinforcement and unreinforced model foundation,the total settlement of the group pile of encapsulated stone columns reinforcement model foundation is reduced by 50%,and compared with the unreinforced foundation is reduced by 31.8%.The drainage volume was 33.3% higher than the unreinforced foundation,and 16.6% higher than that of the stone columns.In addition,the peak value of the excess static pore pressure of the encapsulated stone columns shows a trend of increasing first and then falling instantly.The pore pressure ratio also increases first and then drops below 1.0,and the drainage reinforcement effect of the encapsulated stone columns is further discovered.Within the allowable depth range,it increases with the deepening of soil foundation depth,showing a vertical increasing effect.Therefore,studies have shown that the effect of sand liquefaction by single piles or group piles of encapsulated stone columns is better than that of stone columns.