Study On Vertical Load Transfer Mechanics And Bearing Capacity Of Rock-socketed Piles

The rock-socketed piles are one of the most used foundations in constructions of bridges, ports and buildings in our country. How to rationally determine the vertical load-bearing capacity of rock-socketed piles is one of the most important questions in engineering. Considering the characters of the rock strength in three-dimension stress state, the load-bearing mechanics and the methods of determining the vertical load-bearing capacity of rock-socketed piles have been deeply system studied, that has important signification in theory and engineering.Firstly, through deeply discussing of the load-bearing mechanics of rock-socketed piles and every calculating mode and effecting factors of the side friction resistance and the end resistance of piles, the actual methods of determination the vertical load-bearing capacity of rock-socketed piles were analyzed. Aimed at the defect of the actual methods which do not consider the stress distributing in the rock mass at the end of rock-socketed pile or the thickness of the terrance, using Timoshenko elastic theory deduces the stress distributing in the rock mass. Combining with the modified Drucker-Prager failure criterion which derived from three-dimension stress rock constitutive model, a new method for determining the vertical load-bearing capacity of rock-socketed piles was put forward, which can consider the effect on the rock strength by the second principle stress and the third principle stress. Corresponding calculating program was compiled using MATLAB and applied to an engineering example of rock-socketed piles bridge foundation in Tan-Shao expressway. The result shows that this method was feasible and correct and can explicitly show the whole terrance failure process as the load added. Finally, the terrance at the end of the pile was sorted 72 classes including different three kind of rocks, different four kind of spans and different six kind of thicknesses. Every instance was elastic-plastic analyzed by Marc software, the vertical load-bearing capacity of rock-socketed piles was determined by double standards of the plastic area distribution and the displacement of the pile bottom. Base on calculating results, three terrance failure modes are put forward. Compared with the usual punching shear failure, shear failure and flexural failure, that can more clearly reflect the terrance failure characters and process. Furthermore, investigated the affections of the vertical load-bearing capacity of rock-socketed pile effected by the three factors of rock...