Study On The Cumulative Deformation Characteristics Of Overconsolidation Soft Clay Under Three Dimensional Stress State

The cyclic vertical and cyclic horizontal normal stress of soil element change with the same phase,and the amplitude is different under traffic loading.This study useed the GDS true triaxial apparatus carried out a series of undrained cyclic.true triaxial tests on overconsolidated Wenzhou clay under the coupling of cyclic major and intermediate principal stresses.This can simulate the coupling of cyclic vertical normal stresses and cyclic horizontal normal stresses parallel to the driving direction induced by traffic loading.The main contents and results are as follows:(1)A series of static experiments with different over consolidation ratio,OCR,and coefficient of intermediate principal stress,b,have been taken.The effects of OCR and b on the curves of strain-stress,excess pore pressure,the relationship between major and intermediate principal stress and effective stress paths were studied respectively.(2)The coefficient of cyclic intermediate principal stress,bcyclic,is defined.A series of experiments considered the cyclic stress ratio,CSR,on overconsolidated clay under the coupling of cyclic major and intermediate principal stresses have been taken.The effects of bcyclic and CSR on dynamic pore pressure,major principal strain,intermediate principal strain,cures for coupling relationship of major principal strain and intermediate principal strain,hysteresis loop,effective stresses paths and modulus of resilience strain were studied respectively.(3)Further study the effects for the coupling of bcyclic,CSR and number of cycles,N,on permanent major principal strain and permanent intermediate principal strain.The quantitative formula of permanent major principal strain considering the bcyclic,is obtained.The parameter of this formula is defined.It is found that the rule of permanent intermediate principal stress considering the bcyclic,and obtain the critical coefficient of cyclic.intermediate principal stress(4)An.empirical prediction model of permanent major principal strain considering both bcyclic,CSR and N under three-dimensional stress state is proposed.