Experimental Study On Yield The Strength Sensitivity Of Natural Sedimentary Soil With Stress Level

The strength and compression characteristics of the natural sedimentary soil are different from those of the remolded soil,and the soil sensitivity evaluation system is an important theory to reflect the influence of soil structure.Through the cone and unconfined compression test,one-dimensional KO consolidation test and triaxial consolidation test,this dissertation studies the variation of the traditional sensitivity,stress sensitivity and strength sensitivity of natural sedimentary soil,and discusses the relationship between the strength properties and the compression yield of the natural sedimentary soil under different stress levels.The main contents and results are as follows:(1)Through unconfined compression test and cone test,it is concluded that the traditional sensitivity of natural sedimentary soil under non stress level has no definite corresponding relationship with soil water content;the sensitivity of natural sedimentary soil from structural formation is different from the sensitivity reflected by the remolded soil which is preformed by precompression.The double logarithm method is used.The relationship between the undrained strength of the remolded soil and the normalized water content obtained by the unconfined compression test and the cone test was analyzed,and the results were found to be in accordance with the predicted results proposed by Hong.(2)When the consolidation stress is small,the undrained strength of the natural sedimentary soil changes little.When the consolidation stress is exceeded,the undrained strength is in line with the original point with the increase of the consolidation stress,and the mechanical properties of the remolded soil are the same as the natural sedimentary soil.The compression yield and strength yield of the remolded precompression soil are caused by the over consolidation effect.But the natural sedimentary soil is due to the structure of the soil itself,the undrained strength of the soil increases gradually with the decrease of the water content after consolidation,and the strength of the natural sedimentary soil is gradually close to the remolded soil after the yield of the natural sedimentary soil,and by comparing the curves of one-dimensional compression void ratio and triaxial undrained strength with stress level.The vertical effective stress corresponding to the inflection point of compression curve and KO consolidation strength curve is basically the same.but The vertical effective stress corresponding to the inflection point of isotropic consolidation strength curve is small.It shows that the one dimensional consolidation shear stress accelerates the yield of the soil.(3)Through the indoor triaxial consolidation undrained test,it is found that when the yield stress corresponds to the consolidation rate,there is an inflection point near the water content.And the natural strength curve ISuL is introduced.It is found that the pore index of the natural sedimentary soil decreases linearly with the increase of undrained strength and is gradually close to ISuL under the different stress levels.The curves of the remolded preloading soil and the ISuL curve coincide,which is related to the initial water content of the remolded soil,the traditional sensitivity can be used as the strength sensitivity under the stress free level,while the strength sensitivity is the yield law of natural sedimentary soil structure with stress level.In the vicinity of the corresponding consolidation yield stress,the sensitivity of soil stress increases first and then decreases gradually.The intensity sensitivity of isotropic consolidation increases first and then decreases with the increase of consolidation stress.The corresponding intensity sensitivity in K0 consolidation is fluctuated near the consolidation yield stress and decreases gradually,and the stress sensitivity and the intensity sensitivity tend to decrease as a whole.