The Bearing Character of Bridge Piles in Karst Areas

This paper covers a project that conducted methods of self-balanced pile tests with three-dimensional numerical simulation analysis on effects of karst caves on the load capacity of bridge foundations located at hidden caves. Taking Nanpanjiang Bridge in Yunnan as a case study, it carried out static loading tests on No.1 Pier, No.2 pier and No.1 pile which foundations are free from caves. Then it adopted the finite element method to establish a cave-rock-pile foundation three-dimensional analysis model for systematically analyzing effects of top plates with different thickness and caves with different sizes and locations under different working conditions on the loading capacity of bridge foundations. Furthermore, soils having four different conditions surrounding piles under each working condition were also considered and analyzed. It was found that the distance between roof of the cave and pile tip was the main factor affecting the loading capacity of the pile foundation. The research results were successfully applied in evaluating loading the capacity of a pile foundation in Nanpanjiang Bridge in Yunnan. Thus, the research results improved utilization and reliability of roof of karst caves in highway construction.