Triaxial Test Study On Consolidation And Unloading Strength Behavior Of Hangzhou Silt

There are a large number of deep silt layers in Hangzhou area,which are characterized by low standard penetration number,low bearing capacity of foundation and poor foundation in typical plain area.Therefore,the strength and deformation parameters of silt under different stress states,especially under unloading conditions,must be clearly and accurately understood when construction of similar foundation pit and tunnel works is carried out in silt layers.Although many scholars have done a lot of research on the mechanical properties of silt,the research on strength,deformation and constitutive model of Hangzhou silt under unloading condition is not deep enough.In this paper,indoor triaxial apparatus is used to study the consolidation and undrained triaxial shear tests of remolded silt in Hangzhou under triaxial loading and unloading.The Cambridge model parameters in the constitutive model of Hangzhou silt and the strength and deformation law of Hangzhou silt under unloading conditions are obtained.Finally,the deformation modulus is studied and a deformation modulus is obtained.Fitting formulas of modulus to void ratio,over consolidation ratio and confining pressure.The main work carried out in this paper is as follows:1.The research status of deformation strength and Cambridge model of regional saturated silt at home and abroad is discussed and analyzed,and the mechanical properties of silt under different stress states are summarized by scholars at home and abroad.2.Design the triaxial loading-unloading isotropic consolidation test of remolded silt in Hangzhou and the triaxial consolidation undrained shear test scheme under unloading.Through laboratory tests and triaxial loading-unloading isobaric consolidation tests of remolded silt in Hangzhou,the parameters of Cambridge model of Hangzhou silt are obtained.3.Triaxial consolidated undrained shear tests on remolded silt in Hangzhou were carried out under unloading condition.Firstly,cohesion and internal friction angle under normal condition?OCR=1?were obtained.According to the test results,the last parameter M in the Cam-clay of Hangzhou silt was obtained.The influence of unloading condition on remolded silt in Hangzhou was studied by triaxial consolidated undrained shear tests under unloading condition.Stress-strain curve,pore pressure curve and finite stress path curve of the soil under unloading condition.The laws between strength and unloading,pore pressure and unloading,effective stress path and unloading of Hangzhou silt under unloading are obtained.4.On the basis of triaxial loading-unloading isobaric consolidation and unloading triaxial consolidation undrained shear tests,the stress-strain curves are analyzed and processed uniformly,and the laws of cohesion and internal friction angle of Hangzhou silt under unloading are obtained.5.Deformation parameters in Hangzhou area are studied,focusing on deformation modulus E₅₀.On the basis of laboratory tests,the relationship between deformation modulus and over-consolidation ratio,confining pressure and void ratio is fitted,and a formula for calculating deformation modulus suitable for Hangzhou area is proposed.The above results have certain reference significance for the verification,application and popularization of Cam-clay parameters,strength and calculated deformation modulus of Hangzhou silt under unloading condition.In addition,a formula for calculating the deformation modulus of Hangzhou silt is put forward through laboratory tests,which has certain practical and guiding value for determining the deformation and settlement of Hangzhou silt under unloading condition in practical engineering.