풍화된 암반에 근입된 현장타설말뚝의 하중전이 기구

Abstract

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of the rock socketed pile should be will known. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanisms of drilled shaft socketed into weathered rock was investigated. For that, 5 cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the field test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The side shear resistance of the pile in moderately weathered rock reached to yielding point at a few millimeter displacements, and after that, the rate of resistance increment dramatically decreased. However, that in the highly/completely weathered rock did not show the obivious yielding point, and gradually increased showing the hyperbolic pattern until with the relatively high displacement(>10 mm). The end bearing-displacement curves showed linear increase at least until with the base displacement of approximately 10 mm, regardless rock mass conditions.