Consolidation Test And Numerical Simulation Of Remolded Saturated Loess Considering The Rheological Property

Loess is a special kind of quaternary sediment,which is widely distributed in China,especially in western area.In recent years,with the deepening of the western development,there are more and more embankments of highways and railway,airport,and large-scale dam constructions,in which a large number of high-fill projects are involved.Therefore,it has an important guiding significance for the practical construction project to study the relevant physical and mechanical characteristics of loess,especially the strength and deformation characteristics of remolded loess over time.Through the 1-D consolidation test of the saturated remolded loess under continuous loading and unloading,the deformation characteristics and the cumulative effect of deformation after cyclic loading of loess are analyzed.According to the laboratory test,a related numerical model is established by ABAQUS,and the s imulation results are compared with the test results to verify the rationality of the numerical model.Based on the existing model,the numerical models of the different constant stress and strain rates consolidation test under the condition of single-stage loading and multi-stage of loading and unloading are established;the variations of effective stress,pore water pressure and pore ratio with time,and the pore-water pressure distribution along soil depth under different loading conditions are analyzed and compared.According to the laboratory 1-D consolidation test and the finite element analysis,the main conclusions can be obtained as follows:(1)Instantaneous deformation emerges after loading or unloading,which accounts for a large proportion in the total deformation of the soil sample under certain stress level.However,the rebound deformation of the specimen is much smaller than the compression deformation when loading and unloading same amount to a same level,which indicates that the plastic deformation accounts for most of the total deformation of the specimen.The attenuated creep deformation occurs during long time loading stage;in the process of unloading,obvious viscous deformation can be observed under the low stress level.(2)ABAQUS is used to simulate the 1-D consolidation test.The rationality of the boundary conditions and the boundary surface model used in the numerical model are verified.Therefore,the overall condition of deformation of the saturated remolded loess during the loading process can be approximately simulated.However,the calculated rebound deformation in the simulation is much smaller than the real deformation,which indicates that the parameter related to rebound deformation estimated by the confined compression test is small.(3)The greater the stress-rate is,the faster the effective stress increases,but the final effective stress is smaller when the stress finally reaches to a fixed value.The final effective stresses of different stress-rate models vary greatly.(4)The greater the stress rate,the faster the pore water pressure increases and the larger the final pore water pressure amplitude.When the stress rate is smaller,the pore water pressure increased to a peak value and begins to drop;and the smaller the stress rate is,the earlier the pore water pressure begins to drop.The void ratio decreases rapidly at the early stage and then gradually slows down.The larger the stress rate is,the faster the void ratio decreases,and the larger the final void ratio is,which indicates that the vertical deformation of the specimen is smaller.(5)The larger the loading rate,the greater the deviation between the effective stress and the total stress.The effective stress does not decrease instantly with the decrease of total stress,but shows a certain lag,and the greater the stress rate,the more obvious the lag effect.At the unloading phase,the smaller the stress rate,the faster the pore water pressure decreases.Negative pore water pressure emerged at the bottom of sample at the end of unloading stage,and the value become larger with the increase of loading rate.(6)In constant strain rate model,the vertical effective stress increases slowly in the first half period but accelerates in later period.When the time reaches 60% of the total time,the stress is only about 20% of the final stress in each group.(7)When the strain rate is higher,the pore water pressure increases faster,and the final value is larger.In the early loading stage,there is little difference between the pore water pressures along the depth direction,and the pore water pressure isochrones are approximately parallel.