STATIC LOADING STUDY OF BEARING CAPABILITY BEHAVIOR OF ROCK- SOCKET PILE IN RED BEDS SOFT ROCK |IN XIANG-LIOU BASIN

The red beds soft rock of the age from Cretaceous to Eogene is widespread in Xiang-Liou Basin. It is a kind of soft rock with the features of weak diagenetic process and susceptible to weathering and can easily be disingtegrated. The practical working conditions of rock-socket pile in the soft rock is different from those in the《Technical Code for Building Pile Foundations》(JGJ94-94). The vertical static load test is adopted to investigate 4 large-diameter rock-socket pile in the rock. The variation of axis force in each pile is measured by sliding micrometer and strain gauges. Hence, the bearing capacity behavior, load transfer mechanism, the lateral friction and end bearing are researched in this paper. According to the test results, the load transfer performance of rock-socket pile is similar to that of end-bearing friction pile, the Q-s curves are slowly varying. The pile length, covering and soil around pile are all important to the load transfer mechanism and action of lateral friction. For the natural structure of the red soft rock, the critical displacements of piles are 2~6 mm and the tested result is much higher than those recommended by the Specifications, which indicates that the shaft resistance is strengthened. As the result, the bearing capacity of rock-socket pile in the soft rock is very good, while the lateral friction and end bearing cannot display simultaneously. The study results show that the design standards should be controlled by the strength and the deformation of pile foundation, and the parameter used in design should accord with the load transfer law of pile.