【作者】 曲力群；

【导师】 罗书学；

【作者基本信息】 西南交通大学 ， 岩土工程， 2002， 硕士

【摘要】 高层建筑的日益发展给岩土工程界不断带来新的挑战，深基坑支护工程就是其中的一个方面。基坑支护工程的优劣，直接影响到工程的造价和施工的进度，因而受到广泛的重视。 基坑支护结构的种类有很多，排桩支护结构是最常见的一种。在当前的设计与施工中，桩顶圈梁的作用未引起足够的重视，普遍将其视为安全储备，而将排桩与圈梁的整体支护结构视为悬臂梁来计算的，这样的计算结果显然过于保守不尽合理。本文所开展的试验研究工作即是针对基坑支护结构中圈梁的刚度对整体支护结构的性状影响。 本文试验是以尼龙棒模拟支护桩，以扁钢模拟桩项圈梁，采用砂土填筑地基，通过变换圈梁的截面尺寸及堆载进行了八组试验。试验结果表明，圈梁和排桩的协同作用使得桩身内力与变位明显不同于无圈梁情况。圈梁与桩的刚度比为2～3为最佳，有圈梁时桩的入土深度可以考虑占总桩长的30％，但需要根据具体的土层性质和桩的类型斟酌而定。本文编制的计算程序对于试验分析和工程设计有重要参考价值，解决了许多复杂的计算问题。 圈梁可以有效地控制桩顶位移，可以起到维持基坑周围建筑物稳定的作用。圈梁的抗弯刚度与桩的刚度比对桩身弯矩特别是坑底附近的最大弯矩值也有很大影响。坑底以上桩侧土压力采用梯形分布模式，计算结果与砂土地基的矩形分布实测土压力符合较好。 笔者认为，今后应在以下方面做进一步的探讨与研究工作。全面考虑影响排桩—圈梁整体支护结构协同作用的各种因素，加强各种工况的模拟与研究，以求得到整体支护结构的最佳效果；需要不断改进测试和分析的方法，获得真实可靠的试验数据，提高分析结果的可靠性；改善对周围地面变形计算方法的精确度，保证基坑周围建筑物的安全；考虑基坑支护框架结构的“空间效应”，做出更加符合基坑空间型体的模型。更多还原

【Abstract】 New challenges have constantly been turned up by the development of tall buildings in the field of civil engineering. One of them is the retaining and protecting engineering for deep excavation. Now people have laid stress on the quality of retaining and protecting engineering because it has influenced the cost of engineering and process of construction.It has many types of the retaining and protecting engineering for excavation. Piles in row are one of the most common retaining and protecting structures. The affect of top ring beam has not been thought highly at presenti which has been regarded as the safety measure. The whole retaining and protecting structure of piles in row and top ring beam is calculated by the method of cantilever beam, and the result is not reasonable obviously. It is the effect of ring beam in retaining and protecting mechanics properties for excavation that this paper focuses on.In this paper, there are eight groups tests. It is on condition of the retaining and protecting piles imitated by nylon sticks, the top ring beam imitated by steel board, the foundation wadded by sandy soil, and the sectional size and extra load changed. The test result makes known that ring beam and piles in row working as a whole is different from the state having no ring beam. It is best that the stiffness ratio of ring beam to pile is 2 to 3. We think over burying depth of piles is 30% of the whole length when ring beam existing. But it is necessary to decide according to the quality of soil layers and types of piles. The computer program of this paper has the important reference value on test analysis and engineering design. It resolves many complicated questions of calculating.Ring beam may control the top displacement of piles validly. It has affect on keeping buildings stabling around foundation pit. The stiffness ratio of ring beam to pile affects the maximum value of moment near the bottom of excavated pit. The earth pressure over the pit bottom calculated by the trapezoid mode, and the result is better according with the rectangle mode of sandy foundation.The author proposes making further research work in the followingrespects. It will has well-considered factors on the common affect of piles in row and ring beam whole retaining and protecting structure. We need the best results through enhancing imitating and researching the various situations. It should improve the methods of measure and analysis for enhancing the reliability. It will find the accurate calculating method on deflection of soil body so as to ensure the safety of buildings near the pit. Considering the space effect of retaining and protecting frame structure, it will has a space model fitting excavated pit.更多还原