圆形煤场中桩-网复合地基原体试验研究

在大型圆形煤场中采用桩-网复合地基是火电厂地基方案设计的新思路,该方案不仅要考虑地基土层的强度满足上部荷载的要求,还需要考虑堆载区内土体的变形对环基的影响。通过对圆形煤场中桩-网复合地基原体试验研究,介绍了在大面积堆载下如何进行桩、土及垫层中应力与应变的测试,设计了2套堆载与测试方案,在试验1区铺设了2层土工格栅,而在试验2区未铺设土工格栅。根据在2个试验区所获得的测试成果,研究了大面积堆载对堆载区内外土体变形的影响深度与范围,对比分析了不同高程处垫层与土体的竖向及侧向应力随深度的变化规律,结合堆载区中桩与边桩的桩身轴力变化,计算出上部桩侧土体对桩所产生的负摩阻力,并依据承台顶面附近测得的垫层与土层的应力,计算出桩土分担荷载的比例,以及桩土应力比的大小与变化规律。在此基础上得到土工格栅对大面积堆载区内外土体应变与应力的影响程度,从而可以为大型圆形煤场桩-网复合地基方案的设计与施工提供客观的技术参数与建议。

Prototype testing study of pile-net composite foundation of circular coal yard

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.