【作者】 李好；

【导师】 周绪红； 吴则尧；

【作者基本信息】 湖南大学 ， 建筑与土木工程， 2004， 硕士

【摘要】 近年来，随着城市建设的快速发展，高层建筑的大量兴建与城市地下空间的开发利用，必将带来大规模基坑工程的开挖和支护。本文首先对国内外大量的与基坑支护相关的土压力计算基本理论和传统的支护结构设计方法进行了综合分析和评价。针对长沙市某深基坑工程，作者编制了弹塑性有限元程序进行分析。在程序中，土体采用弹塑性的Druck-Prager本构模型，护坡桩和土体都采用平面应变四结点等参单元进行网格划分，在桩和土体之间引入Goodman接触单元，对于锚杆，采用杆单元进行模拟，利用改进的“空气单元法”模拟基坑的分布开挖。对比有限元程序计算所得的位移值和实测结果，两者较吻合，验证了程序的适用性。 有限元计算结果表明，该工程的护坡桩的下部水平位移比上部水平位移大，由于桩的埋深只有1.2m，在实际工程中要特别注意“踢脚”现象；基坑坑底的隆起随着距开挖面的距离越远，隆起量也越大，最大隆起量发生在基坑的中部；基坑周围的地表沉降，在基坑顶部最大，离基坑顶部越远，沉降越小；锚杆的轴力分布为两端小，中部大；随着基坑的开挖，锚杆承受的拉力越来越大且锚杆轴力峰值有向锚杆末端偏移的趋势。最大值为197kN，小于设计抗拔力330kN。 该基坑支护综合考虑了土质条件、施工方法、周围环境等因素，方案选择安全可靠，取得了明显的社会效益和经济效益。更多还原

【Abstract】 In the recent years, along with the high-speed development of city construction, a great number of high-rises are constructed together with the exploitation of the underground structure, which surely brings large-scale excavation and support of the foundation pit project. In this dissertation, a large quantity of the fundamental theories about the earth pressure calculation and the traditional design methods applied to the protection of the foundation pit are comprehensively analyzed and evaluated. Aiming at a deep foundation pit in Changsha, the author has written a elastic-plastic finite element program, in which a constitutive model of "Druck-Prager" is used for soil. A method employing the "Goodman" joint element to describe the frictional behavior between soil and pile which are divided into 4-noded plane strain isoparametric elements, is proposed. The anchor is divided into bar element. In this program, the modified "void element" method is adopted to simulate the excavation of the foundation pit. The results from the comparison between calculated values and field results show that the method of elastic-plastic finite element analysis is practical.The calculated results of the numerical model show that the horizontal displacement of the lower pile is larger than that of the upper. Because the embedded depth of the pile is only 1.2 meter, the "kick foot" phenomenon should be emphasized in the practice. The blowups of the pit bottom increases with the longer distance from the wall, reaching its maximum value in the middle of the pit. The most dramatic settlement happens in the upmost edge of the pit, decreasing with the increasing distance from the edge of the pit. The anchor tension increases with the excavation depth, and the peak value of the tension tends to move towards the end of the anchor. The allowable anchor capacity of 330 kN is larger than the maximum load of 197 kN.The soil condition, construction method and the surrounding are considered synthetically for compare and selection of the plan. The selected plan assures the deep foundation pit is safe and reliable. Obvious social and economical benefits have been obtained.更多还原