Study On Vertical Bearing Capacity And Settlement Of Bridge Pile Foundation Passes Through Multi-Karst-Caves

The engineering geological conditions of karst region is very complex. The existence of karst cave has a major impact on working properties of bridge pile foundation. This thesis is rely on the Zhua longyan Bridge project in Yibin-Xuyong expressway. The K59+059 to K59+125 section of Zhua longyan bridge project is a district of Karst grown. Karst cave in this area is multilayer. Part of the karst has been filled Some of the pile foundations under the column pier penetrate through multi-karst-caves.The vertical bearing mechanism of pile foundation in karst area is used to study on the analyze and calculate methods of vertical bearing capacity and settlement deformation of bridge pile foundation,which penetrates through the multi-karst-caves.The research achievements are mainly as followed.Firstly,author analyzed and discussed the side resistance and tip resistance distribution law of socketed piles in karst area.The derived formula of vertical bearing capacity of pile foundation can be obtained in consideration of the thickness of roof of concealed karst cave.Secondly,author proved the vertical bearing capacity calculation formula of pile foundation when it penetrates through the multi-karst-caves,according to settlement of pile top in base of the load transfer method.Thirdly,author discussedand analyzed the influence of height,breadth,quantity and vertical relative distance of karst cave on working properties of pile foundation,such as pile displacement,distribution of side resistance and tip resistance,according to the numerical simulation.The results show that the height,quantity and vertical relative distance of karst cave have a major impact on working properties of pile foundation,but we can find that the effect of the breadth of karst cave to be small or non-existence.At the same time,simulation analysis on the pile displacement and force distribution of group piles under the column pier in practical engineering is to be done.Finally,according to practical engineering of Zhua Longyan Bridge,the difference of ultimate vertical bearing capacity of single pile,deduced from theoretical calculating methods and numerical computation method less than 15%.Meanwhile,the P-s curve,deduced from these two methods is similar.This research result of vertical bearing capacity and settlement deformation of bridge pile foundation,penetrate through the multilayer karst cave can serve as reference for design and construction projects related to karst caves.