| ABSTRACT:The subgrade of heavy-haul rail road and bridge transition section is prone to differential settlement,resulting in irregular lines and affecting traffic safety;In the collapsible loess area,due to the special nature of the foundation soil,the problem of uneven settlement is more serious.This paper studies the engineering characteristics of the loess in road and bridge transition section through the indoor geotechnical test,and based on the characteristics of the loess,we use the lime soil Pile composite foundation and improved subgrade packing to control the settlement.A three-dimensional finite element model of road-bridge transition section is established to analyze the effect of settlement control,and the settlement control method is optimized and analyzed.In this paper,through the indoor soil test,composite foundation on-site testing,finite element numerical simulation and other research methods,the main conclusions are as follows:(1)The failure intensity of loess is positively correlated with the compaction degree,and it is negatively correlated with the water content,and the change is obvious.The relationship between The shear strength parameters and compaction degree and moisture content of the loess can be fitted with a power finger function,and the sensitivity for the moisture content and the degree of compaction is very strong.(2)In the engineering scheme,the bearing capacity of foundation,compaction coefficient of pile body,soil compacting coefficient and collapsibility coefficient all meet the requirements.The lime-soil compaction pile composite foundation is an effective method to process the collapsible loess foundation.The compaction performance and compressive strength of lime-improved loess are greatly improved,and the compression coefficient and the sedimentation coefficient are significantly reduced,which can meet the subgrade design standards as the roadbed fill.(3)The numerical simulation results show that the two treatment measures are both effective to control the settlement of the transition section of the road and bridge in the collapsible loess area.The optimization of the packing grade of the subgrade structure shows that the packing level of the trapezoidal transition section has the most obvious effect on the settlement control.In the foundation,the pile length,pile diameter and pile spacing of the lime soil pile have influence on the settlement value,and the influence of the pile length is the most obvious.In the longitudinal section of the transitional section,to change the length of the lime-soil compacted pile can further reduce the settlement of the roadbed at the station,and expand the settlement range. |
