非等长双排桩在成都膨胀土基坑工程中的应用研究

发布时间：2018-01-07 19:22

本文关键词：非等长双排桩在成都膨胀土基坑工程中的应用研究　出处：《成都理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着成都地区深大基坑的增多,施工场地小及红线距离近等问题逐渐明显,对基坑变形的控制也提出了更高的要求。由于成都东郊膨胀土地区土层含有大量的高岭土,遇水软化后,锚杆、锚索杆件不能通过土体的侧向摩擦力为基坑支护结构提出足够的锚固力,致使该地区的基坑常常出现垮塌的险情,给人民的生命及财产安全造成巨大的影响。因此,如何解决好膨胀土地区城市建设项目中的基坑支护及环境效应问题成为岩土工程的热点与难点,技术安全、经济合理的基坑支护结构体系是基坑工程的一个发展方向及研究重点。双排桩支护结构由于具有整体高度大、侧向位移小、不需要设置支撑、施工方便、速度快、不需要工作面等优点,目前广泛应用于边坡加固、边坡抗滑、基坑支护等工程中。但是,双排桩的作用机理及受力特性目前还不清楚,双排桩的设计理论不成熟,主要依靠工程经验。本文在总结前人研究的基础上,以成都膨胀土地区东方华大广场基坑工程为背景,对地基岩土体的物理力学参数特征进行研究,并结合大型有限元分析软件MIDAS-GTS对双排桩支护结构的受力性状包括双排桩的排拒、后排桩桩距、桩身刚度、嵌固深度、土体性质和前后桩长不等的情况进行建模分析,研究双排桩的最优设计参数,提出了非等长双排桩在成都膨胀土基坑工程中的应用,最后以典型工程为例,对支护结构进行模拟计算,并结合监测数据验证了方案的合理性,为非等长双排桩支护结构在以后膨胀土基坑中的应用提供工程经验,减少膨胀土地区工程造价,并为进一步的优化设计提供理论支持。本文研究的主要成果有:(1)对研究区膨胀土的物理力学参数特征进行研究发现,未遇水软化段土体强度是遇水段强度的2倍左右;膨胀土强度参数粘聚力c和含水率呈线性关系。(2)通过对双排桩不同的排拒、后排桩桩距、桩身刚度、嵌固深度、土体性质和前后桩长不等的情况进行建模分析发现:(1)前后桩长不等情况下,后排桩的桩长变化比前排桩更能影响支护结构的位移和内力,且后排桩桩长增加到一定值时,对支护结构的影响较小,此时的后排桩长度为最优长度,能体现出该支护设计的经济性。(2)土层粘聚力对支护结构的位移影响较大,内力影响较小;内摩擦角对支护结构的位移和内力都有较大影响。(3)排拒适当增加,支护结构的位移会减小,且随着排拒的增大,位移的减小幅度在不断减小,当排距增加达到一定值以后,排距变化对支护结构的位移影响较小,并且前排桩弯矩逐渐上升,后排桩弯矩则逐渐下降。(3)对成都东郊龙泉驿地区的工程实例进行数值模拟分析,比较计算值与实测值二者之间的差异。同时根据桩身应力、冠梁应力及桩后土压力的变化,分析膨胀土地区非等长双排桩支护结构的受力形状。为非等长双排桩支护结构在以后膨胀土基坑中的应用提供工程经验,并为进一步的优化设计提供理论支持,同时为该地区同类基坑工程支护设计提供借鉴。
[Abstract]:With the increase of the deep foundation pit in Chengdu area, small construction site and the red line near the problem gradually, also put forward higher requirements to control the deformation of foundation pit. Due to the eastern suburbs of Chengdu expansive soil area the soil contains a large amount of kaolin, water softening, bolt, anchor rod not by lateral friction of soil for foundation pit the supporting structure of anchoring force enough, resulting in the area of the foundation pit often collapse danger, causing huge influence to people's life and property security. Therefore, how to solve the city construction projects in the area of soil excavation and environmental effect of expansion has become the focus and difficulty of geotechnical engineering technology, safety, economy the reasonable foundation pit support structure system is a key development direction of foundation pit engineering and research of double row pile retaining structure as a whole big height, the lateral displacement is small, do not need to. The support, construction is convenient, fast, no need to face and other advantages, is widely used in slope reinforcement, landslide, engineering foundation pit supporting. However, the mechanism of double row pile and stress characteristic is unclear, the design theory of double row piles is not mature, depend on engineering experience. In this paper, on the basis of previous studies, using Chengdu expansive soil foundation pit engineering large square east China as the background, study the characteristics of physical and mechanical parameters of rock soil, and combined with the finite element analysis software MIDAS-GTS on the double row piles supporting structure stress characters including double row piles and rejection of the rear pile spacing. The pile stiffness, embedded depth, and soil properties before and after pile length ranging from the modeling analysis, the optimal design parameters of double row pile, put forward the non isometric double row piles in Chengdu expansive soil foundation pit engineering application, and finally to A typical project as an example, to simulate the supporting structure, and combining with the monitoring data to verify the rationality and non isometric double row piles supporting structure in the foundation pit after the expansion application provides engineering experience, reduce the area of expansive soil engineering cost, and provides theoretical support for the optimization design of the main results of this paper further. Study: (1) the study area expansion characteristics of soil physical and mechanical parameters were found in water softening water soil strength is about 2 times the strength of expansive soil; strength parameters cohesion c and moisture content showed a linear relationship. (2) based on the double row piles different rejection. The rear pile spacing, pile rigidity, embedded depth, and soil properties before and after pile length ranging from the modeling analysis found that: (1) before and after pile length ranging from under the condition of back pile length changes than the front pile can influence the displacement of supporting structure and internal Force, and the rear pile length increases to a certain value, the effect of supporting structure is small, the length of back row pile for the time optimal length, can reflect the supporting design of economy. (2) soil cohesion larger influence on displacement of supporting structure, the internal force influence is small; the internal friction angle of displacement and the internal force of supporting structure are affected. (3) rejection increased appropriately, the displacement of supporting structure will decrease, and with the increasing of rejection, the decrease in displacement decreases when the row spacing increase reaches a certain value, the row spacing changes on the supporting structure of the displacement effect the front and rear pile bending moment increased gradually, the pile bending moment decreased gradually. (3) based on the numerical simulation of the eastern suburbs of Chengdu Longquanyi area project, compare the difference between the two calculated values and measured values. At the same time according to the change of pile stress, stress and soil pressure of pile cap beam, divided Non isometric double row piles supporting structure stress analysis for land area expansion. The shape of unequal length double row piles supporting structure in the foundation pit after the expansion application provides engineering experience, and provide theoretical support for further optimization design, and provide reference for the design of similar foundation pit support in this area.

【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU753

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