| Soft soil refers to a soft soil layer with high water content,large void ratio,high compressibility and poor water permeability.Due to the low strength of the soft soil layer and the poor engineering geological conditions,when constructing urban projects such as industrial buildings or civil buildings on soft soil foundations,engineering problems such as foundation instability or excessive settlement are likely to occur.How to ensure the stability of buildings on soft soil foundations has always been an extremely important issue because of the success or failure of the entire project.There are many ways to deal with soft soil foundations.The most common practice in recent years is to lay a layer of sand on the surface of soft soil.This is a simple,fast and economical approach.However,with the construction of urban projects more and more,the sand source is gradually scarce.If the geogrid can be used to complete the reinforcement of soft soil foundation in the absence of sand source,this will certainly reduce the engineering cost to a certain extent.In this paper,the soft soil foundation is taken as the research background,and the soft soil foundation treated by geogrid reinforced sand cushion is taken as the research content.The FLAC 3D finite difference software is used to simulate the sand cushion under the different reinforcement parameters.The influence of work traits provides a valuable reference for the design and engineering application of geogrid reinforced sand cushion.In this paper,the static load numerical model of reinforced sand foundation is established by FLAC 3D,and compared with the existing indoor model test results to verify the rationality of the parameters selection.Secondly,by optimizing the choice of reinforcement,cushion thickness,reinforced materials,number of reinforced layers,first layer reinforcementspacing and rib placement position,the sand cushion is placed under the soft soil with different reinforcement parameters.The numerical simulation of the foundation,by analyzing the load-settlement curve,the bearing ratio BCR and the reinforced cushion,the vertical stress of the geogrid,and the displacement cloud map,the evolution law of the bearing characteristics of the reinforced cushion soft soil foundation is obtained.Finally,the influence of the sand cushion under the single-layer reinforced mode on the bearing capacity of soft soils with different stiffness is analyzed.Research indicates:(1)Adding a certain thickness of sand cushion on the soft soil foundation can effectively improve the bearing capacity of the foundation and reduce the compression deformation of the foundation.The reasonable cushion thickness can effectively reduce the settlement of the soft soil foundation.Under the same load conditions,the deformation modulus of the reinforced sand cushion is larger than that of the plain cushion,and the deformation modulus of the thinner cushion will be greatly improved after the reinforcement.(2)The reinforcement effect of the geogrid only begins to work after the load reaches a certain value,and the reinforcement effect becomes more obvious as the load increases.Under the same conditions,the reinforcement effect of the three-way geogrid is better than that of the two-way geogrid.(3)Within the effective reinforcement depth range,changing the number of reinforcement layers and the arrangement position of the geogrid has a great influence on the bearing capacity of the reinforced sand cushion.As the number of layers of the laying grid increases,the range of stress concentration areas and the amount of settlement of the reinforced cushion layer are reduced.(4)The deformation modulus of the reinforced sand cushion increases with the decrease of the thickness of the cushion,the increase of the number of geogrid layers and the upward displacement of the arrangement position of the reinforcement.(5)Under the same load,the lower the stiffness of the weak underlying layer,the lower the bearing capacity of the corresponding foundation.The stiffness of the weak lower layer is larger,and a layer of biaxial geogrid and a layer of triaxial geogrid are added to the sandcushion,and the final settlement is not much different.In practical applications,it is necessary to comprehensively consider the economic benefits and carrying capacity issues and make rational selection. |
