Experimental Study On Static And Dynamic Characteristics Of Overconsolidation Saturated Soft Clay Under Long Term Loading

Thick soft clay layers are widely distributed in the southeast of China.A lot of projects,such as railways,airport runways,motorways have been or will be constructed on the soft clay subgrade.These projects are not only subjected to the static load of embankment but also the effect of the long-term cyclic load of traffic loading,which leads to large ground deformation and strength degradation of the sub-grade clays.Hence,it is necessary to develop practical Post-construction settlement control technology for the soft clay sub-grade.In this study,a series of compression test and dynamic experimental studies are conducted on natural and overconsolidation Wenzhou soft clay through WG-2A double low pressure oedometer system and GDS triaxial apparatus(Cyclic stress?Cyclic stress?Cyclic pore pressure and Permanent strain included).In order to find a more practical model of dynamic settlement by study the effect of over consolidation ratio and cyclic loading with stages on soft clay.The main contents are as follows:(1)According to the compression and consolidation of soft clay subgrade,natural and overconsolidation tests on secondary consolidation specimens have been conducted.In this section,the relationship of consolidation deformation and preconsolidation pressure of soft clay and secondary consolidation coefficient and over consolidation ratio are researched.A formula for secondary consolidation deformation of soft clay is established.(2)Cyclic triaxial tests have been conducted to study the long-term cyclic behavior of soft clay induced by traffic loading.The effect of over consolidation ratio on stress-strain,pore pressure evolution,stress-strain hysteresis loops are investigated.In order to predict the settlement of soft clay under traffic loading,the permanent strain equation under different influence of the over consolidation ratio is established,and the rationality of the equation is verified by comparing with the measured value.(3)Experimental study of triaxial test cyclic loading by stages under drained condition have been conducted.The development characteristics of axial strain and pore pressure were obtained.Stress-strain hysteresis loop development under stages of intermittent cyclic loading,modulus development with different over consolidation ratio and cycle stress ratio,the ratio of the strain accumulation without cyclic loading to the total strain accumulation by all stages are investigated.These conclusions can be used to guide the engineering practice.