Study of Model Experiments on Uplift Piles in Clay under Oblique Loads

YANG Ming-hui, YANG Xue-wen, ZHAO Ming-hua


 Laboratory model tests on steel piles embedded in cohesive soil were carried out to study the transformation law in relation to ultimate uplift capacity and displacement patterns of uplift piles subjected to oblique loads. The test results show that the side of the pile near the oblique load is always under pressure, while the other side is in tension all the time, which differs from the uplift pile subjected to vertical loads. After reaching the ultimate capacity, soil in some depth is cracked only around the side close to oblique load. The failure surface occurs below the top of the pile. The failure area on the earth surface is distributed as a fan, whose range becomes larger with the increasing inclination of loads. Meanwhile, the ultimate capacity of piles increases with the increase of the inclination angle. On this basis, the calculation model of uplift piles subjected to oblique loads and the formula of failure surface around the pile were established based on the failure mode. Moreover, according to the analysis on the equilibrium conditions of the soil element, a formula for estimating the oblique capacity of uplift piles in clay soil subjected to oblique loads was also proposed. The predictions agree well with the test results so that the formula can be used in practical engineering.



Keywords: clay,  oblique loads,  uplift piles,  laboratory tests,  ultimate capacity

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