Research On The Working Characteristics Of Lower Partition Slab-Pile Composite Foundation Of Bridge End In Soft Soil Area

The problem of the bridge end bump on soft soil foundations has extremely adverse effects on the normal operation of highway bridges.This paper takes the problem of the bridge end bump of a constructed bridge in the soft soil area of Wenzhou as a background,a new method of using lower partition slab-pile composite foundation to deal with the differential settlement between road and bridge is proposed.The pile-slab composite foundation can improves the foundation bearing capacity and reduces settlement,and makes a coordinated transition of settlement according to the rule by variable stiffness pile arrangement design.This paper monitors the treatment effect of the lower diaphragm-pile composite foundation relying on the project site,and analyzes the force characteristics of the pile and slab through finite element simulation,and the long-term settlement prediction based on the creep effect of soft soil.The main results are as follows:(1)By monitoring the settlement,soil pressure,and pillow beam reinforcement stress of the bridge end section,it is found that as the distance from the bridge end increases and time develops,the settlement gradually increases,the soil pressure gradually increases,and the sleeper beam stress gradually decreases.During 200 days of highway operation,the settlements at 5m,10m,and 15m away from the bridge end were 6mm,15mm,and 18mm,respectively,indicating that the lower partition slabpile composite foundation can not only effectively reduce the settlement,but also make the settlement transition coordinated.(2)Through the force analysis of the lower partition slab-pile composite foundation through finite element modeling,it is found that the force of the piles is good,and the lateral friction resistance of the two rows of piles is distributed in a "single peak" shape,but the side friction resistance of the first row of piles is greater than that of the second row of piles.The overall force of the lower partition slab is better,and the stress concentration level at the fixed end of the slab is only 1/3 of that of the deep-seated concrete slab method.It shows that the pile-slab composite foundation structure is more stable and can better handle the upper load.(3)By considering the creep effect of soft soil in the deep and thick soft soil area,analyze the parameters of the soft soil creep model of the lower partition slab-pile composite foundation,and understand the selection of the parameters of the soft soil creep model through sensitivity analysis.Considering that parameter changes have a greater impact on the long-term settlement,the parameters of the creep model are inversely calibrated by Monte Carlo method and response surface method.The results show that the response surface method can calibrate the parameters faster and more accurately.Based on the calibrated parameters,the longterm settlement prediction of the bridge end subgrade is carried out,the results show that the maximum settlement after ten years is 36.36mm,and the longitudinal slope of 6m before the bridge end section is 0.31%.Based on the conclusions obtained from the above research,the lower diaphragm-pile composite foundation can provide references for future bridge end subgrade design and maintenance projects.Effective control of post-construction settlement can reduce maintenance costs and improve the quality of transportation construction services,which has good economic and social benefits.