The Influence Of Construction Of Bridge Pile Of Highway Foundation In The Karst Area On Adjacent Existing Railway Roadbed And Security Control Technology

The complexity of karst geological conditions makes construction of pile foundation of bridge have a great effect on stability of the adjacent railway bed. Therefore, it is necessary to launch some research that construction of pile foundation of bridge make effect on stability of the adjacent railway bed.The project made the field monitoring for pile foundation construction in the karst region near the bridge of Beijing-Guangzhou railway according to Zhao Hua expressway construction, combining with finite element numerical simulation, and, the safety control technology of design and construction of bridge pile foundation in karst area is studied. The main results are as follows:1. The measured data obtained by field:(1) Beijing-Guangzhou railway bed in the area of construction of pile foundation in the karst area had no deep horizontal displacement and deep horizontal displacement. Beijing-Guangzhou railway subgrade was stable during the time of construction of pile foundation of bridge;(2) No significant changes occurred in underground water level, and producing no significant hydraulic gradient threatening the stability of the rock. And the greater the size of cave, the increase faster in amplitude2. The calculation through the finite element numerical simulation:(1) with the increasing in the relative density of the slurry, the maximum horizontal displacement and settlement of subgrade showed a decreasing trend under certain circumstances between pile hole and roadbed distance. Both of them are to be gentle from behind the relative density 1.35;(2) with the increasing of the size of the cave, the maximum horizontal displacement and settlement of subgrade showed an increasing trend. And the greater the size of cave, the increase faster in amplitude(3) The fluence of pile hole cave in the upper position have a great effect on the subgrade than in the pile hole bottom position under certain circumstances between pile hole and roadbed distance;(4) The closer the distance between the pile hole and the roadbed is, the relatively larger the impact is. When the distance is more than 6~8m(about3~ 4D), the influence of pile foundation construction on the adjacent embankment gradually tends to be balance, and the impact is relatively small.3. The results of numerical simulation and field monitoring results reflect the same law. Consequently, proving the reliability of the numerical simulation calculation, and could provides certain reference for bridge pile foundation in karst area, avoiding to estimate the influence of adjacent structures by empirical methods.4. The safety control technology of design and construction of bridge pile foundation in karst area is studied, in order to reducing the influence on adjacent to the existing railway subgrade, filling the difficulties of current design and construction of pile foundation in karst area.