Abstract:

It is a new idea to adopt pile-net composite foundation for circular coal yard in fossil power plants, while not only certain soil strength is required to bear the upper load, but also the influence of soil deformation in load area on ring foundation shall be taken into account. Through prototype test and study on pile-net composite foundation of circular coal yard, this paper gives an introduction to that how to test stress and strain of pile, soil and cushion under large-area load. During the process, two loading and testing schemes were designed, while two layers of geogrids were arranged in test zone 1 and no geogrids in test zone 2. Based on the test results of two test zones, the paper investigates the depth and range of influence of large-area load on soil deformation inside and outside the load area, and analyzes the variation principle of vertical and lateral stress of cushion and soil in different elevations. Then combining with the change of pile axial force of middle pile and boarder pile in load area, the negative friction of upper soil is calculated. According to the stress of cushion and soil near the cap table, the pile-soil load sharing ratio and stress ratio are computed. Therefore the effects of geogrids on stress and strain of soil inside and outside the load area are deduced to provide objective technical parameters and suggestions on the design and construction of pile-net composite foundation of circular coal yard.

Key words: PHC pile, geogrids, pile-net composite foundation, pile-soil stress ratio, circular coal yard