IN-SITU TEST AND ANALYSIS ON MECHANICAL CHARACTERISTICS OF PILES IN SANDS

Large number of engineering practice shows that there are thick sand layers in the foundation along the middle and lower reaches of the Yangtze River, China. The sand layers are good bearing stratum for pile foundations. In the area, the sands are at shallow depths, have big thicknesses, and include silt and silt clay. As the depth increases, the sands become dense. The experimental results of the driven piles indicate that the status of the density of sands has great influence on the construction of the performed piles. The pile-driving operation is easier in the loose or slightly dense sands than in the medium or very dense sands. In this paper, large scale static load tests are carried out for three piles of a power station. The characteristics of the pile settlement with load variation are studied. The axial force and side resistance of the piles are calculated at the same time. The designed diameter of the three piles is 800mm, and their length is 47.2m. The grade of the concrete is C35.Nine soil layers are passed through by the pile body. The results of static loading tests indicate that the relation of the load(Q) and settlement(s) is nonlinear. The Q-s curves can be divided into three stages including the elastic, elastic-plastic and overall damage. The frictional resistance of the sands under 15m depth is much bigger than the silt clay or the muddy soil. The results indicate that the bearing capacities of the piles are all more than 4800kN.It will be provided as reference for future design and research.