【作者】 谷淡平；

【导师】 熊智彪；

【作者基本信息】 南华大学 ， 结构工程， 2010， 硕士

【摘要】 随着城市地下空间的发展,大量深基坑不断涌现。SMW工法作为一种新型的基坑支护结构,由于其特殊的优点而被广泛应用,但是SMW工法支护形式的桩土共同作用机理仍不明确,因此对SMW工法进行研究具有重要的现实意义。文章针对SMW工法支护形式,采用了模型试验研究以及三维有限元数值模拟分析,对其桩土共同作用进行了研究,主要成果如下:1、对试验模型在不同开挖工况下桩顶位移、桩侧土压力以及桩身应力进行了测试。位移测试表明:支护结构变形过程可以分为初始阶段、稳定阶段、位移剧增阶段及破坏四个阶段;联系其嵌固深度得出了该悬臂支护合理的嵌固比λ=0.66;同时位移数据与时间的关系,说明软土基坑支护结构的变形时间效应显著。2、运用能量法对水泥土横向作用进行研究,研究表明水泥土墙高与基坑边长的比值对该作用影响巨大,且进一步得出了考虑水泥土横向联系的桩顶最大位移值的解析解。3、从土压力沿深度的分布、随开挖工况的变化、与朗肯极限土压力的比较以及极限土压力与位移关系四个方面来讨论土压力测试结果。得出了试验墙背土压力在深度上为梯形分布;被动土压力小于朗肯被动土压力,计算时建议取其1/3-2/3;主动土压力比朗肯主动土压力稍大;同时得出了本试验的主动极限土压力的所需桩顶位移值及位移速率。4、桩身应力应变实测值与不考虑水泥土作用的桩身应变计算值对比,从而得出水泥土对桩身刚度的贡献,建议在SMW工法支护结构设计时可以适当的考虑水泥土贡献。5、运用MIDAS/GTS对试验的进行数值计算,将计算结果与试验实测结果进行对比分析。更多还原

【Abstract】 With the development of urban construction, lots of deep foundation pits have come forth continuously. As a new support structure for foundation pit, SMW engineering method is widely used due to its especial advantages, but the mechanism of pile-soil interaction of SMW engineering method is still unclear, so it is of great practical significance to study SMW method.According to the support of SMW engineering method, the mechanism of its pile-soil interaction is studied by model test study and three-dimensional FEM in this paper. The specific contents include the following works:1. The displacement of piles top, the lateral earth pressure and pile stress of the test model are tested under different excavation situation. The results of displacement mesurement show that the deformation process of support structure can be devided into four phases, that is, original phase, stabilization phase, displacement leap phase and breakage phase. By combining with its mbeded depth, the reasonable embed ratio of the cantilever retaining can be obtained, and its value is 0.66. In addition, the relationship between displacement and time shows that the deformation of the support structure for soft soil foundation pit is significant.2. The transverse action of cement soil is studied by energy method. The results show that the ratio of the height of cement-soil wall to the side length of foundation pit has significant influence on the effect, and the analytical solution of the maximum displacement value of pile top in view of lateral Contact relation is obtained.3.The test results are discussed in terms of the distributing of earth pressure, the variety with excavation situation, comparing with Rankine limit earth pressure, along with the relationship between earth limited pressure and displacement. The results show that the distribution of earth pressure in depth for the test wall is trapezoidal. The factual passive earth pressure is less than the Rankine passive earth pressure, the suggested value is 1/3 to 2/3 of its value, while the active earth pressure is a little more than Rankine active earth pressure. Also the needed value of the displacement and its rate of pit top for active limited earth pressure for the model test are obtained.4. Comparing the measured stress and strain of pile to the calculated values without regard to the work of cement soil, the contribution of cement soil to the rigidity of pile body can be seen, is important, its contribution can be considered in appropriate extent. A suggestion is that of a appropriate contribution of cement soil can be considered in the designing of support structure by SMW engineering method.5. The test is numerically calculated by MIDAS/GTS. In addition, the comparison of calculated results and measuring results are conducted.更多还原