Study On The Suction In Saturated Clay Foundation

In recent years,uplift foundation is widely used as the anchorage schemes of upper structure.In the clay subsoil,structure inevitably bears the adhesion,which determines the uplift structure stability and hoisting equipment selection,from sediments in the process of uplift or pullout.The uplift bearing capacity of pile foundation and bucket foundation is important to stable structure.On the other hand,the uplift bearing capacity needs to be overcome as resistance in the process of pile pulling and salvage.However,it is usually studied as a whole by experiments and the influence factors and the interaction of negative pore pressure and adhesion are not studied completely.Therefore,the influence factors of uplift speed and overburden load on suction are studied by model test in order to determine the value and development rule of negative pore pressure and adhesion.And on this basis,this paper combines mono-hull model tests with simulation analysis to obtain some conclusions and achievements as following:(1)Test results show that the distributions of pore water pressure of soils below the center of circular foundation under compressing and pulling load conform the calculated results of additional stress.The suction increases with the increase of uplift speed and the increasing rate decreases when uplift speed exceeds certain value.The negative pore pressure develops with the displacement of soils.Both suction and negative pore pressure increase with time and adhesion increases first and then decrease with time.(2)Based on mono-hull model test,the 3D pullout model is established in soft clay.The model takes Mises yield criteria,and considers using cohesive model between soil and structure.The FEA shows the simulated pore water pressure is consistent with the test,which verifies cohesive model can reflect the contact deformation characteristics between soil and structure.(3)By the FEA,it proves that adhesion properties between soil and structure determine the negative pore pressure and suction of soil upon foundation in the process of pullout.