大型格池桩筏基础共同作用的试验研究

In-situ Testing and Research of Large Square Pond's Piles-raft Foundation Under Cooperation of Ground and Structure

结合南京市城北污水处理厂曝气沉淀池地基及基础工程设计,对格池闭水载荷试验过程中桩筏基础的变形、筏板底土压力分布、桩顶荷载受力分布及桩与筏板的荷载分担测试方法与结果进行分析和研究,探讨了曝气沉淀池在实际运行工况时,桩筏基础与地基共同作用的机理和变化规律。试验结果表明：大面积筏板后浇带部分筏板在受力转变过程中,对桩筏基础的沉降值影响甚微;在桩径相同时,可通过调整不同区域内的桩长来优化桩基承载力的设计;两相邻格池,当一池为卸载（排水）,另一池为加载（注水）时,卸载一侧的桩顶反力会达到最大值;扣除水浮力的影响,当桩距径比s/d=3.8-4.5时,筏板分担荷载平均比值：满池工况为9.0%,空池工况为11.3%;桩筏基础最大沉降量及最大差异沉降量均远小于设计值和允许值,对类似工程设计取s/d=5.0-6.0,筏基可承担15%-20%的荷载,经济效益会非常显著。

Based on the foundation design of the North Nanjing sewerage farm, the pile-raft foundation＇s transform, the distribution of soil pressure under the raft and pile load are measured during the water loading test. The sharing in upper loading of piles and raft is analyzed, and also the measuring method is discussed. The mechanism and changing disciplinarian of pile-raft foundation and ground＇ s cooperation under real conditions are introduced and discussed. The test results indicate that the raft post-casting belt has less influence on the raft＇s settlements. Adjusting piles＇ length when the piles＇ diameters are all the same can optimize the bearing capacity of pile. Under the condition that one pond is being pouring in and the neighboring pond is being pumping out, the piles＇ reaction of the neighboring pond can reach the maximum. The sharing percent of raft is about 9% （pond full） and 11.3% （pond empty） under the condition that the ratio s/d of space between piles and pile＇ s diameter is about 3.8 - 4.5. The test results indicate that the measured settlement and non-uniform settlement are far below the designed value and the admitted value. The ratio s/d can get 5 - 6 in the future that the sharing percent of raft will get 15% - 20%, which can get remarkable benefit.