【摘要】 针对当前规范法支盘桩极限承载力计算结果偏于保守、经济性不足的问题，依托中江高速改扩建项目对3根不同桩长和支盘组合的支盘桩进行了破坏性静载试验和理论研究。首先，通过分析试桩荷载-沉降曲线和桩体内力数据，研究了支盘桩桩体破坏以及荷载传递特征。其次，以Meyerhof基础极限承载力理论为基础推导适用于支盘桩的极限承载力模型，并引入投影面积比和截面突变系数以考虑分支承载力。最后，将理论模型计算和试验结果进行对比验证了理论可行性。结果表明：依据现有规范设计的3根试桩安全系数分别为2.8,3.0,3.0,可知支盘桩安全系数较大，有待进一步研究；由分支和支盘组成的支盘桩，盘体作为主要的承载部件，载分担比例最高，六分支承载能力仅约为等直径盘体的50%,并且桩端对总承载力的贡献度很小；短桩相对于长桩直杆段占比小，分支和支盘承载占比更大；支盘各部分的承载力发挥与桩长、分支/支盘设置以及支盘埋深密切相关；依据Meyerhof深基础端承力理论提出的支盘桩极限承载力通用计算方法可以考虑埋深、土体等参数对支盘承载性能的影响；理论和实测值的比较发现所提方法具有较高的计算精度；分支/支盘极限承载力的计算误差小于17%,支盘桩极限承载力计算误差小于13%,满足工程需求。更多还原

【Abstract】 Due to the current issues about conservative and insufficient economic calculation results of the ultimate bearing capacity of squeezed branch piles, the destructive static load test and theoretical research are conducted on 3 squeezed branch piles with different pile lengths and combinations of branches and plates based on Zhongshan-Jiangmen expressway renovation and expansion project. First, by analyzing the load settlement curve and internal force data of the test pile, the failure and load transfer characteristics of the support plate pile are studied. Second, based on Meyerhof’s theory of ultimate bearing capacity, a model for the ultimate bearing capacity of squeezed branch pile is derived, and the projection area ratio and section mutation coefficient are introduced to consider the branch bearing capacity. Finally, the theoretical feasibility is verified by comparing the theoretical model calculations with experimental results.The result shows that(1) the safety coefficients of the 3 test piles designed according to the existing specifications are 2.8, 3.0, and 3.0 respectively, and it can be concluded that the safety coefficient of the support plate pile is relatively high and further research is needed;(2) the squeezed branch pile composed of branches and branches has the highest load-sharing ratio as the main bearing component, with the six branches having a load-bearing capacity of only about 50% of the same diameter disk, and the contribution of the pile end to the total load-bearing capacity is small;(3) short piles have smaller proportion of straight rod segments compared to long piles, while branches and support plates have a larger proportion of bearing capacity;(4) the bearing capacity of each part of the support plate is closely related to the pile length, branch/support plate setting, and support plate burial depth;(5) the general calculation method for the ultimate bearing capacity of branch pile based on Meyerhof’s deep foundation end bearing theory can consider the influence of parameters such as burial depth and soil mass on the bearing performance of branch piles;(6) the comparison between theoretical and measured values reveals that the proposed method has high computational accuracy;(7) the calculation error of the ultimate bearing capacity of the branch/support plate is less than 17%, and the calculation error of the ultimate bearing capacity of the support plate pile is less than 13%, meeting the engineering requirements.更多还原