Experimental Study On The Vertical Bearing Capacity Of Bridge Pile In Mul Ti-layer Karst Area

With the vigorous development of the highway in our country, a large number of highway under construction have to cross the karst area, the complex and changeable karst area bring much difficulty to the construction of bridge pile foundation. There have been much research for the influence of karst on pile foundation and the stability of cave, but most of existing researches only take the effects of single cave on pile foundation to consideration. The load-bearing characteristics of piles which pass through multi-layer karst area have not been paid enough attention, and the current specification also failed to provide effective design method. Therefore, the research of bearing characteristic of bridge pile foundation in multi-layer karst area is meaningful to actual engineering.This thesis takes the project of natural science foundation of Hunan Province, "The research for disaster effect physics modal and its application on bridges and tunnels foundations in mountainous highway" (No.14JJ2105), as background. The similar principle and similar material are applied in the indoor test research of the load-bearing capacity of bridge pile foundation in multi-layer karst area. Finally, the load- settlement curve, axial force distribution and side friction on pile are obtained through the results of modal test, and the distribution regularities are compared to the load-bearing characteristic of pile foundation in single karst region or common karst region. The influence of the amount of caves on vertical load-bearing characteristic of pile foundations is analyzed.This thesis is mainly about modal test research and finite element numerical simulation analysis, and an universal finite element software is used to simulate the piles in karst area with different amount of caves and calculate the load capacity. Numeric simulation results and modal test results are comparatively validated. The bearing capacity of pile in conditions of different karst cave radius, different relative height between karst caves, and different karst height are analyzed by the finite element software, at last the influence of cave parameters on bearing properties is explored and summarized.