摘要
针对喀斯特地区输电线路工程中普遍存在的上覆厚土层(4~7m)、下卧中等风化及以上岩石的特殊地基条件,提出一种短桩锚杆复合基础。为了揭示复合基础的承载机制,建立相应的工程设计方法,推动这种新型基础在工程中的应用,选取位于广东阳春典型喀斯特地区的上覆粉质黏土、下卧微风化石灰岩的地基作为试验现场,依据我国110~1 000 kV电压等级输电杆塔承受的上拔荷载,设计出6个不同入土深度、不同锚筋数量的1∶1全尺寸短桩和复合基础,通过开展现场抗拔承载特性试验,获得试验基础的荷载位移曲线、抗拔承载力、地基破坏模式等规律,进一步揭示复合基础的抗拔承载机制;结合现场试验结果与理论分析,提出复合基础的失效是由其下部锚杆基础破坏时对应的上拔位移所控制,在此基础上建立复合基础抗拔承载力的计算公式,并给出复合基础失效位移以及承载力分配系数的确定方法。通过与现场试验结果的对比,验证所给方法的正确性,为该类新型基础在工程中的推广应用提了理论依据。
In this paper,a composite foundation combining short pile and anchor was proposed for the complex foundation conditions with overlying thick soil layer(4–7 m) and underlying moderately weathered rock in the Karst area for overhead transmission line project. In order to reveal the bearing mechanism of the composite foundation and to establish the corresponding design method to facilitate the better application to projects,the foundation with overlying silty clay and underlying weakly weathered limestone at the typical Karst area of Yangchuan in Guangdong province was selected as the site of field test. Six full-size foundations(1∶1) with different embedded depths and different anchor numbers were designed according to the uplift load on the tower hanging the transmission line of 110–1 000 kV voltage in China. The load-displacement curves,ultimate uplift bearing capacities and foundation failure modes of the tested foundations were obtained in the pull-out tests on the site. It was concluded from the test results and theoretical analysis that the failure of the composite foundation is controlled by the ultimate uplift displacement when the anchor appears damaged. On this basis,a formula for calculating the uplift bearing capacity of the composite foundation was established,and the methods to determine the failure displacement and the allocation coefficients of bearing capacity of the composite foundation were proposed respectively. The correctness of the methods was verified by comparing with the field test results.
引文
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