Deformation Monitoring Of High-Speed Railway Bridge Foundation Overlying Mined-Out Area

In recent years, with the continuous construction of high-speed railway, many railway lines cross coalmines and the goaf. The presence of goaf roadway is bound to have a certain impact on the deformation of the bridge foundation of high-speed railway. Therefore, it is necessary to research the deformation of high-speed railway bridge foundation overlying the goaf roadway.In this thesis, based on the number59pier and the number62pier, the regularity of the settlement deformation and the load transfer of the two piers under the influence of the upper load is studied by field monitoring.At the same time, based on the settlement and deformation of bridge, exponential curve method is used to analysis and predict settlement and deformation of bridge cushion cap, and discuss the effect on the stability of mined out area by using pile groups foundation and cushion cap’s reinforcement measures. The specific contents and the achievements of the research are as follows:(1)The pile’s axial force of the bridge gradually decreases from the top of the pile to the bottom. At the same section of the piles, the axial force of the piles enlarges with the increment of load. The axial force of the piles which go through the goaf roadway is a certain value in the roadway.(2)The skin friction of piles is first increment and then turns to decrease. At the same section of the piles, It enlarges with the increment of load; the skin friction of piles which go through the goaf roadway is zero.(3)At the beginning of loading, stresses of both soil among piles and pile top will increase rapidly for a while. But with the increasing of the load, the increase of stress of soil among piles is reduced and the increase of stress of pile top is enlarged. The sharing ratio of the pilel load, the sharing ratio of the pile skin friction and the pile-soil stress ratio increases with the increment of load.(4)The settlement of the cap and the soil among piles increases with the increment of load. The settlement at the roof of the goaf roadway increases as the increment of load. The soil settlement above the goaf roadway is greater than that of other places. The settlement of parts of the cap located on the goaf roadway is greater than that of other parts of the cap.(5)The bridge foundation post construction settlement and the final settlement meet the requirements of specification and design by using pile groups foundation and cushion cap’s reinforcement measures. Therefore, this reinforcement measures are effective to enhance stability of mined out area.