Reasearch On Static And Dynamic Characteristics Of Road-culvert Transition Section Newly Constructed With Foamed Light Soil In Road Under-crossing Existing Railway

Using high quality and light weight materials for the filling of subgrade behind the abutment is regarded as an active method to solve the problem of transition section irregularity,which has been widely concerned in recent years.In view of the good engineering characteristics and the excellent performance in highway-bridge transition section of foamed light soil,it is of great importance to introduce it into the transition section of the railway field.Due to the particularity of railway lines,the research and application technology of foamed light soil in highway can only serve as a reference,and it is not enough to support its popularization in the railway field.Therefore,based on the Technology Research and Development Program of China Railway Wuhan Group Co.,Ltd(Grant No.17G01),this paper studies the applicability of foamed light soil in railway transition section by numerical analysis,material test,long-term stability monitoring and dynamic test.The main researches are as follows:(1)In view of the engineering defects that the through cracks and the structural brittle failure are easily produced in the foamed light soil due to the stiffness difference or uneven deformation in the highway and bridge transitional section,basalt fiber filament and fiber mesh were used to improve ductility of foamed light soil.It is found that the fiber filament can improve the mechanical strength index to a certain extent,but it can not change the failure mode of brittle failure,the fiber mesh can greatly improve the toughness of the material and resist the extension of cracks from the lower part to the upper part.It is recommended that fiber mesh should be laid in the top and bottom of the foamed light soil structure layer in the structural design.(2)Aiming at the problem of settlement deformation and stiffness matching between rigid structure and foamed light soil subgrade,a numerical analysis model is established.The influence of construction on the existing structures under different backfill materials and transition section structure is compared and analyzed.Based on the results of numerical analysis,it is recommended that the density of foamed light soil should be 700kg/m~3,and the structure should be constructed as inverted trapezoid with a longitudinal gradient of 1:2between the transition section and the existing embankment.(3)In order to verify the applicability of foamed light soil in the transition section of the railway,the static and dynamic monitoring test was carried out.The results show that the application of foamed light soil in the transition section subgrade backfill can solve many engineering and technical problems,the settlement of the transition section is effectively controlled and the dynamic response transit evenly,in addition,the construction is convenient and has no impact on the existing railway operation.In short,foamed light soil has good application potential in railway transition section engineering.