Research On Performance Of Composite Foundation Of Granular Piles Based On Sponge City Concept

It was imperative to enhance the city's own rainwater consumption function and speeded up the solution of the urban rainy season.Based on the concept of “sponge city”,this paper studied the influence of rainfall infiltration process on the engineering characteristics of composite foundation of granular material piles through theoretical analysis and finite element simulation combined with unsaturated soil foundation with groundwater.Firstly,the theoretical analysis of the rainfall infiltration process was carried out,and the influence of rainfall infiltration on the mechanical parameters of the soil layer was discussed.The reinforcement mechanism of the composite foundation of the granular material pile was systematically analyzed.The similarity between the seepage principle and the seepage of the bulk material pile was compared.Combined with the classical theoretical formula of soil mechanics,the characteristics of the composite foundations of natural foundation and granular material piles were analyzed under rainfall conditions.The results showed that soil weight,cohesion,internal friction angle and elastic modulus after rainfall the change had a greater impact on the properties of the foundation.After rainfall infiltration,the groundwater level was increased,the vertical effective stress of the soil above the groundwater level was increased,and the vertical effective stress of the soil below the groundwater level was decreased.The composite foundation of granular material could significantly reduce the settlement of foundation and improve the bearing capacity of foundation.Secondly,the ABAQUS software was used to study the fluid-solid coupling effect of the example.The displacement field,stress field,pore pressure field and seepage field at different rainfall moments were compared and analyzed.The results showed that the finite element analysis considered the coupling of multiple parameters before and after rainfall.The simulation results of the stress distribution and settlement of the soil was more accurate than the theoretical calculation,more in line with the actual situation.It could be seen from the seepage field that the rainwater around the composite foundation after the rainfall infiltration converges to the pile with large permeability coefficient,and the existence of the pile accelerated the infiltration rate of the rainwater and was introduced into the deeper soil layer through the pile.From the distribution of the pore pressure field of the foundation soil,it could be known from the calculation that the composite foundation of the granular material could significantly increase the infiltration of rainwater,and could effectively introduce more rainwater into the deeper soil layer to protect the water source effect.Finally,simulation analysis of the project to be built was carried out,and the application effect of the composite foundation of the bulk material pile in the sponge city was checked.The results showed that the composite foundation of granular material pile had the dual functions of bearing and water guiding,which was suitable for the construction of sponge city.