Study Of Model Test And Numerical Simulation Of Geosynthetic Encased Stone Columns Reinforcing Silty Clay Ground

Soft soil is widely distributed in China.With the further development of highways,highways will inevitably pass through soft soil areas.Due to the low bearing capacity of soft soil and high groundwater level,it is often difficult to bear the load of pavement,which is prone to large settlement.To overcome this problem,soft soil foundation reinforcement is often required.Vibration sinking pipe gravel pile(hereinafter referred to as the traditional gravel pile)is widely used in engineering because of its convenience,fast construction speed and low cost.However,the reinforcement effect of gravel pile on soft soil foundation is limited and the settlement cannot be effectively controlled.In order to improve the above defects of traditional gravel pile,researchers put forward the concept of wrapped gravel pile.However,at present,the research on the wrapped gravel pile mostly focuses on the tensile strength and length of the wrapped material,and the in-depth study of the gravel material of the pile body is less.Most studies are based on static load,and the bearing characteristics of wrapped gravel pile under dynamic load are less considered.Therefore,based on model experiment and numerical simulation method,this paper studies the gravel material of wrapped gravel pile and the bearing characteristics under dynamic load.The main conclusions are as follows:(1)Compared with the traditional gravel pile,the wrapped gravel pile has larger stiffness,better reinforcement effect,and smaller settlement under the same load;(2)The gravel gradation affects the settlement of the composite foundation by affecting the compactness of the pile.The better the gradation,the smaller the settlement of the composite foundation;(3)In a certain range of particle size,under the same gradation,the larger the gravel particle size,the less the contact point between the gravel,the smaller the overall deformation of the gravel pile,the higher the bearing capacity;(4)The load distribution in the composite foundation of wrapped gravel pile under cyclic loading also follows the principle that the greater the stiffness,the greater the bearing capacity.Under cyclic loading,the settlement of composite foundation wrapped with gravel piles developed rapidly at the beginning of loading,and then stabilized;(5)The modulus of gravel,the internal friction angle of gravel and the stiffness of geogrid are important factors affecting the settlement of composite foundation.With the increase of pilesoil modulus ratio,the internal friction angle of gravel and the stiffness of geogrid,the settlement of composite foundation gradually decreases.Increasing the internal friction angle of gravel can effectively increase the pile-soil stress ratio and improve the pile stress transfer efficiency.With the increase of geogrid stiffness,the settlement of composite foundation gradually decreases,but when the stiffness is greater than a certain value,the effect is weakened.