Study On Deformation Characteristics Of Embankment Of Overly Wet Soil In Reconstruction And Extension Of Old Road In Seasonal Frozen Area

Due to the influence of environmental factors in the seasonal freezing zone,the roadbed will inevitably produce post-construction settlement deformation.This problem of uneven deformation becomes more prominent in the road widening and reconstruction project on the roadbed of excessively wet soil.In order to understand the characteristics and laws of deformation of over-wet soil subgrade in various time periods,the effects of freezing-thawing cycles on shear-resistance and compression-resistance of over-wet soils were studied,and the sub-humidified soil subgrade in the reconstruction and expansion project of Harbin-Heihe Class I Highway was selected.The deformation monitoring analysis was conducted.Based on the indoor test and outdoor monitoring data,an equal ratio finite element model was established to simulate and predict the deformation of the subgrade in the test section.The results show that the higher the moisture content of the wet soil is,the smaller the shear strength,the smaller the internal friction angle and the cohesive force,and the more easily the lateral deformation of the soil.The higher the moisture content,the higher the compressibility of the soil.With the increase of the load,the water content has less and less influence on compressibility.There is a linear relationship between the initial porosity ratio and the compression coefficient.The more dense the soil mass of the wet soil is,the harder it is to compress,and it is more difficult to complete the heavy-duty compaction standard for the construction.After freeze-thaw cycles,the soil structure changes,and the vertical polygonal cracks generated form a lattice structure on the shear surface,which increases the internal friction angle of the soil and makes the lateral deformation surface of the soil move down.With the increase in the number of freeze-thaw cycles,the compression coefficient and vertical permeability coefficient of over-wet soil increased,and did not increase after four cycles of freeze-thaw cycles.This indicates that the soil is vertical after many freeze-thaw cycles.The deformation tends to be more stable.From the on-site monitoring data,it is found that the temperature-dependent curve at each depth of the roadbed is approximately sinusoidal;the lateral deformation at the foot of the slope grows faster when the frozen soil melts,and the maximum value appears near the frost line.The measured settlement at the road shoulder of the over-wet soil section is greater than that at the central separation zone,and is greatly affected by the groundwater level.Due to the widening of one side of the reconstruction and expansion project,the soil layer deep in one side of the central separation zone has been stabilized for a long time due to consolidation,so the delamination settlement is mainly concentrated in the new paving basement.The layered settlement of the new and old roadbed is not The phenomenon of synchronization tends to cause uneven settlement in the lateral direction of the road.The section of over-wet soil treated with sand-changing improved the temperature-humidity balance of the subgrade of the over-wet soil,reduced the overall moisture content of the subgrade,and the section settlement was smaller,and the horizontal displacement location was more concentrated and stable.Through software simulation,it was found that there is uneven settlement between the central divider and the shoulder,and the greater the settlement is,the closer to the shoulder.The amount of subgrade settlement of the over-wet soil treated by changing sand is smaller,and the sand changing method has certain effect on controlling subgrade settlement and uneven settlement on the cross-section.