海上淤泥区斜拉桥超长桩基自平衡法承载力试验研究

针对大型铁路、公路建设过程中对基础结构承载力的严格要求，为了探讨采用自平衡试桩法对承载大吨位、超长的灌注桩进行单桩竖向承载力检测的可行性，以 G228 国道浙江三门园里至宁海一市段跨海大桥工程为依托，计算了海上淤泥区超长桩竖向极限承载力。以旗门港特大桥、海游港特大桥的四个测试桩为典型案例，运用自平衡检测结果且结合相关规范，根据实测值绘制出上下桩段的Q-s 曲线、s-lgt 曲线和 s-lgQ 曲线，分析其上下桩段的极限承载力变化，并且根据等效转换原理作出桩顶加载 Q-s 曲线图，确定桩顶在极限荷载下的位移。结果表明: 采用自平衡法进行检测并建立加载曲线分析，成功解决了海上淤泥区斜拉桥超长桩极限承载力研究问题。进行研究的四个主墩测试桩在等效桩顶加载下，极限承载力均未超过设计容许承载力，最大位移分别为 16. 45 mm、16. 14 mm、10. 08 mm 和 8. 18 mm，满足施工要求。自平衡法技术在 G228 国道三门园里至宁海一市段跨海大桥施工中的成功运用可供同类工程施工参考。

Self-balancing method-based experimental study on bearing capacity of super-long pile foundation for cable-stayed bridge in marine silt area

Aiming at the strict requirements for the bearing capacity of foundation structures during the constructions of largescale railway and highway，the vertical ultimate bearing capacity of the super-long pile in the marine silt area is calculated in accordance with the construction project of the sea-crossing bridge for the Sanmenyuanli－-Ninghaiyishi section of G228 National Highway in Zhejiang Province，so as to discuss the feasibility of detecting the vertical bearing capacity of single pile for the large tonnage and super-long cast-in-place pile through the self-balancing test pile method． By taking four test piles of both Qimengang Super-large Bridge and Haiyougang Super-large Bridge as the typical cases，the Q-s curve，s-lgt curve，and s-lgQ curve of the upper and lower pile sections are drawn according to the measured values through applying the self-balancing test results and combining with the relevant specifications，and then the changes of the ultimate bearing capacities of the upper and lower sections of them are analyzed，while a Q-s curve diagram of the pile top loading is made in accordance with the equivalent conversion principle for determining the pile top displacement under the ultimate load． The result shows that the problem of the study on the ultimate bearing capacity of the super-long pile for the cable-stayed bridge in marine silt area is successfully solved through making detection with self-balancing method and establishing loading curve for the relevant analysis． The ultimate bearing capacities of all the four main pier test piles for the study are not over the design allowable bearing capacity with the maximum displacement values of 16. 45 mm，16. 14 mm，10. 08 mm and 8. 18 mm respectively，thus the relevant construction requirements are satisfied． The successful application of the self-balancing method to the construction of the sea-crossing bridge for the Sanmenyuanli－-Ninghaiyishi section of G228 National Highway can provide references for the construction of the similar project concerned．