Experimental Study On The Deformation And Subsidence Characteristics Of Saturated-unsaturated Silt Soil Foundation

Above the water table is the non-saturated soil, while below it is saturated. Thisfoundation is usually called saturated-unsaturated soil foundation. Foundation subsidencewill result in many engineering disasters, such as, the tilting and even collapse of houses,collapse of the road foundation, dam, etc. Calculation and prediction methods of saturatedsoil subsidence deformation has matured. Many scholars are studying the calculation andprediction methods of unsaturated soil foundation subsidence. While the research of thesaturated-unsaturated soil foundation is still in its infancy. Therefore, it is crucial toaccurately calculate and predict saturated-unsaturated soil foundation subsidencedeformation.On the newly subsided silt, and focusing on the saturated-unsaturated foundation, thisessay mainly researches the influence of the moisture content on the silt shear strength andcompressive modulus as well as the saturated part of the saturated and unsaturated and thedeformation characteristics of the unsaturated part. With the experiment results, this essaybuilt up the numerical simulation of saturated-unsaturated foundation subsidencedeformation based on fluid--structure interaction theory and gives a detailed analysis andresearch on the pore water migration mechanism in the process of the subsidence of theunderwater.The main research achievements are as follows:(1) It systematically summarized the research status of the saturated and unsaturatedfoundation subsidence deformation home and abroad. And it also analyzed the principle ofeffective stress of the saturated and unsaturated soil, the realization process of the seepageprinciple in software as well as the coupling process of seepage and stress field.(2) Direct shear test under different moisture conditions shows that the recentShanghai deposited silt cohesion c value and soil moisture values is in a linear relationship;when the value of the friction angle φ in the moisture content is less than9%, the φ willdecrease rapidly with the increase of moisture content; when the moisture content is more than9%, φ will increase slowly with the increase of moisture content.(3) According to the experiment of silt consolidation under conditions of different initialmoisture content and different dry density, the smaller the dry density the soil, the smallerinfluence of the moisture content to the compression modulus.(4)According to the indoor model experiment of the saturated-unsaturated foundation,computation of the subsidence deformation can neither take no consideration of theunsaturated part, nor regard the unsaturated soil as saturated part. If not, there will be greaterror. The comparison of the two model experiments shows that under different loads,when thickness of saturated and unsaturated layer is certain, the amount of compression ofthe unsaturated and that of saturated has a corresponding proportional relationship.(5)Numerical simulation of saturated-unsaturated foundation subsidence deformationwas built up based on the theory of fluid-structure interaction by using Geo-Studio. Andthe accuracy and liability of the simulation was tested by comparing the actual projectwith the monitoring data.