Variation Of Sensitivity With Stress Level Under Different Consolidation Stress Paths

The sensitivity framework is the main theoretical framework to quantify the effect of soil structure on the mechanical behaviour of natural sedimentary clays.However,because this framework is built under the one-dimensional consolidation condition,there are often outstanding contradictions between the framework and the actual engineering situations.How to quantify the mechanical consequences of soil structure under different loading conditions has become an imperative problem in theoretical research and foundation engineering.In this thesis,the existing sensitivity framework and its references are extended to triaxial axisymmetric conditions by using laboratory tests and theoretical analysis methods.A stress sensitivity change model is established to describe the variation of sensitivity with respect to stress level.And then through qualitative analysis and case calculation,the influence of different references on sensitivity relationship is investigated,considering the effect of initial water content and consolidation stress path.The main conclusions and contributions are highlighted as follows:(1)A series of compression tests under different consolidation stress paths were performed on reconstituted clays,base on which the intrinsic compression line under triaxial axisymmetric conditions is clarified to be unique.Moreover an empirical approach of determining the intrinsic compression parameters that depend on the consolidation stress path,the initial water content and the liquid limit was developed.(2)By analyzing the undrained soil strength data in the literature,it was clarified that the undrained strength of reconstituted clay under different consolidation stress paths is in a oneto-one correspondence with the void ratio at the end of consolidation,and the intrinsic undrained strength line under triaxial axisymmetric conditions was proposed.It was concluded that using the reference of different consolidation stress paths should get a stable strength sensitivity.(3)Base on analyzing the results of compression tests under different consolidation stress paths on undisturbed and reconstituted clays,it is found that the volumetric strain increases with the increase of deviatoric stress(q)under the same mean effective stress in the normal consolidation state.(4)The definition of stress sensitivity was extended to current stress level state under triaxial axisymmetric conditions.Then a stress sensitivity change model was proposed by introducing the Liu-Carter Model into the stress sensitivity framework.The simulation results indicated the influence of consolidation stress paths on the change law of stress sensitivity.(5)Base on qualitative analysis and case calculation,it was verified that strength sensitivity remains the same when using different reference frames.Meanwhile,the influence of different references on the relationship between stress sensitivity and strength sensitivity was clarified.