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目前对于湿陷性较弱或无湿陷性的Q2离石黄土层上桩基性能的研究非常匮乏。为确定超大厚度黄土地区Q2离石黄土层上的桩基承载力,进行现场单桩静载荷试验。在试桩桩身布置混凝土应变计和钢筋应力计,桩端布置土压力盒,对试桩进行现场内力测试。研究结果表明:(1)桩身轴力和桩侧摩阻力两者随桩身范围内的分布规律不仅与桩顶荷载的大小有关,而且与桩周土的性质有关。(2)当桩顶荷载Pt与桩顶加载极限值Pu之比小于0.80(Pt/Pu<0.80)时,桩顶沉降主要是由桩身弹性压缩引起的;当Pt/Pu≥0.80时,在计算桩身沉降量时应考虑桩端土体的沉降量Sb。(3)规范简化法中对综合系数的取值偏大,建议取=0.44作为本地区同类型桩的计算参数。从简化法和线性法出发,提出一种利用桩身压缩量来预估单桩沉降的新方法。
At present, the research on pile foundation of Q2 limestone loess with weak collapsible or non-collapsibility is very scarce. In order to determine the bearing capacity of pile foundation on Q2 limestone loess layer in super thick loess area, the static load test of single pile on site was carried out. Concrete strain gauges and steel bar stress gauges are arranged on the test pile body, soil pressure boxes are arranged on the pile end, and the internal force test of the test pile is conducted. The results show that: (1) The distribution of both the axial force of the pile body and the frictional resistance of the pile body with the pile body is not only related to the load of the pile head, but also to the nature of the soil around the pile. (2) When the ratio of pile top load Pt to pile top load limit Pu is less than 0.80 (Pt / Pu <0.80), settlement of pile top is mainly caused by elastic compression of pile body. When Pt / Pu≥0.80, When calculating the settlement of pile body, the settlement of pile-soil body should be considered. (3) In the standard simplification method, the value of the comprehensive coefficient is too large, it is recommended to take 0.44 as the calculation parameter of the same type of pile in this area. Based on the simplified method and the linear method, a new method of estimating pile settlement by using the amount of pile compression is proposed.