Deformation Behavior And Its Time Effect Of Embankment Widening Of Expressway On Soft Foundation

In the background of an increasing demand for expressway widening projects and inadeuqence of study on widening embankments on soft ground, supported by the Zhengjiang Segment of Shanghai-Nanjing Expressway Widening Project, analysis of the deformation behavior of widening embankment founded on soft ground is demonstrated by in-situ and laboratory tests, numerial simulation, monitoring verification.By in-situ tests and laboratory tests, the physical and mechanical properties of soils under old and new embankment are comparatively studied. The results indicate that for the uncertainty of soil properties, exploring sampling and tests, quantitative assessment for the difference of physical and mechanical properties between the soils under the new and old embankments is difficult, and then the difference is hard to be taken into account for the design value of soil parameters.With numerical simulation, the stress distribution and deformation processes of the soft ground are studied with consideration of different widening heights, widths, parameters of ground soils, pavement loads, embankment construction velocity, the results reveal that the maximum vertical additional stress and shear stress, maximum settlements and horizontal displacements are lowly influenced by the widening height and width, while highly by the Es; normal construction rate change has little impact on the stress distribution and deformation of soft ground after the embankment is finished.By numerical simulation and monitoring verification, the influence of pile length, pile distance, pile lateral friction force, geogrid and construction rate on the widening embankment founded on soft ground treated with Cement Deep Mixing(CDM) piles of is analyzed, the results indicates that: pile length and distance are the most significant influent factors to the deformation controlling; due to the decrease of pile lateral friction force, the accumulated settlements of widening embankment is mostly influenced, and then the post-construction settlements and post-construction differential settlements; geogrid laid over the soft ground treated with piles and pile caps has not distinct improvement on differential settlements; the embankment construction rate has influence on settlement rate but little on accumulated settlements. According to the above-mentioned results, an optimized treatment scheme for widening embankment on soft foundation is advanced and adopted. The settlement monitoring results show that the numerical calculation results almost accord with the actual settlements and the settlements indexes can meet the requests of deformation controlling standards.Some one-dimensional consolidation creep tests lasting for nearly one year are performed for simulating the course of embankment construction loading, the creep rate of muddy silty clay is found to have a feature of "steady-small accumulating-more steady", and that if the ultimate load is the same and the lasting time is long enough, the accumulated deformation and creep law of soil samples with different loading process have almost the same tendency. Considering the creep properties with Strain Hardening Creep Law, the deformation of widened embankment during construction and service is numerically simulated and verified by monitoring data, the results indicate that the calculating deformation with creep consideration can match the monitoring deformation better than that without creep consideration. Settlements prediction for typical embankment section shows that the proportion of creep settlement to total settlement rises with the time increasing, at the end of 30a, calculating settlement with creep consideration is nearly 10% larger than that without creep consideration, but the post-construction settlements and differential post-construction settlements can still meet the controlling standards.Combining ways of experiments on ground soil and filling soil, in-situ monitoring, modifying controlling indexes for embankment construction and deformation, analysis of pavement crack investigation and precaution, a composite method is advanced for construction and deformation controlling during express way widening.