Influence Of Rainfall Infiltration On Artificial Fill Foundation Treated With Lime-soil Compaction Piles In Mountainous Area

In the north,central and western regions of China,where the groundwater level is usually deep and the rainfall is low,unsaturated soil is the main building and engineering site.With the improvement of people's living standard,villa area tend to appear in the mountainous areas with beautiful natural scenery.Due to the complex topography and landform conditions in the mountainous area and the distribution of multiple gullies and steep ridges,it is often necessary to fill a large area in civil engineering construction.When these shallow foundation buildings are built on the artificially filled collapsible foundation with high compressibility,special treatment is needed for the artificial filled ground,and the common method is the lime soil compaction pile method.Due to the heterogeneity of the artificial filled foundation,there will be a certain degree of uneven foundation settlement along the direction of the conversion surface of the excavation and filling,which will bring some hidden dangers to the overall safety of the building.Because of the large green area,it is easy for the rain water to infiltrate into the foundation soil layer under the basement of the building after the occasional heavy rainfall.Additional settlement occurs when the soil is deformed by humidification,this will exacerbate the phenomenon of uneven settlement of the building,when the differential settlement value reaches a certain limit will cause cracks,subsidence and other security problems.This paper is based on the practical project of Xingyang city,henan province,in view of the lime soil compaction pile composite foundation,the two-dimensional finite element model is established.Under the condition of rainfall,first of all,using MATLAB to make research of two-dimensional rainfall infiltration process,then using GeoStudio to calculate the seepage field under the fluid-solid coupling condition.The development and change of water content and pore water pressure of heterogeneous artificial fill foundation under rainfall condition were obtained.Based on the calculation results of the seepage field,the additional settlement caused by the humidification deformation of soil under the combined load of force and water is calculated by numerical simulation and the advanced layered summation method.Analysis results show that permeability of artificial filled soil decreased significantly after dealed with lime-soil compaction pile,and the water-resistance effect is obvious.However,when rainwater infiltrates into the soil layer interface,due to the poor permeability of the lower soil mass,the rainwater on the interface appears the phenomenon of reverse accumulation,and the path of rainwater infiltration changes greatly.The water content of local soil increases rapidly under the action of water infiltration,which leads to a sharp change in its strength and deformation parameters.The uneven settlement of buildings is aggravated due to the uneven degree of soil deformation.When the differential settlement of soil is too large,it will cause the cracking of filled wall and indoor floor.This paper studies the influence of rainfall infiltration on seepage field and stress field of heterogeneous artificial fill foundation,and provides qualitative and quantitative analysis and discussion,which can provide certain calculation basis for predicting the uneven settlement of buildings in engineering practice.