Performance of laterally loaded piles in improved coal ash deposit

A series of pile load tests was conducted at a fossil fuel power plant in Taiwan to evaluate the performance of piles in a coal ash deposit that were improved using gravel compaction. The data from lateral load tests on two large-sized reinforced concrete piles were analyzed in this study. The original penetration resistance of the coal ash layer was low, but it increased after the ground improvement. Based on the load-defection curves of the test piles, the complete relationships of equivalent subgrade reaction coefficient kh with lateral displacement were derived and compared with those suggested by the Architectural Institute of Japan (AIJ) and the Japan Road Association (JRA). A composite SPT-N value was adopted to include the contribution of the gravel piles. It was found that the JRA equation using the composite SPT-N value fitted well with the relationships. Moreover, the experimental pile response and p-y curves were deduced using the inclinometer slope data. The relationships of the secant kh of the p-y curves vs. the normalized lateral displacement were further compiled and compared with those predicted by the JRA method. It was shown that the predicted curves using the composite SPT-N values also agreed well with the experimental relationships. Through a comparison of the profiles of the soil reaction with some existing lateral limiting soil pressure formulas, it was found that Prasad and Chari's method was able to yield predictions close to the ultimate soil reaction.