桩锚—土钉复合支护基坑的变形与稳定性研究

发布时间：2018-03-23 14:35

本文选题：复合土钉墙　切入点：变形　出处：《西南交通大学》2017年硕士论文

【摘要】：土钉+预应力锚索+搅拌桩复合基坑支护结构在工程中得到了广泛应用,但是现阶段关于该结构工作特性的研究成果还较少,导致理论明显滞后于工程实践。针对这一现状,本文结合工程实例,采用 Midas/GTS(Geotechnical and Tunnel Analysis System)有限元分析程序对该类型复合土钉支护结构的工作性状进行了详细分析,得到的研究成果及结论如下:1.通过对基坑变形的监测数据与Midas/GTS有限元程序计算结果比较分析,结果表明,该有限元程序能较好地模拟基坑的工作性状。2.加入搅拌桩后,支护结构的受力变形性状发生了明显变化,复合结构的变形形态与桩锚式支护结构相似,其侧向变形呈中间大、上下两端较小的变化规律,且最大值约在0.75倍开挖深度处,土钉的轴力呈沿长度方向递减的变化趋势。3.按照轴力的不同分布形态,可以将土钉分为轴力递增型、弓形及轴力递减型三种。轴力递增型土钉主要分布在基坑的上部,其轴力沿土钉长度方向递增;轴力呈弓形的土钉主要分布在基坑的中部,其轴力为中间最大,两端较小;轴力递减型土钉主要分布在基坑的下部,其轴力在土钉与搅拌桩接触的部位最大,往后逐渐减小。4.施加预应力能有效控制基坑的侧向变形,且预应力施加在基坑的侧向变形最大值对应的部位时,对变形的限制效果最好。5.在基坑的稳定性计算中,其稳定性系数取基坑强度折减计算不收敛对应的强度折减系数存在不合理之处,取基坑强度折减系数与侧向变形关系曲线中拐点对应的折减系数作为基坑的稳定性系数更为合理。6.影响支护结构稳定性的因素包括土钉的长度、坑底超挖深度、搅拌桩的直径及嵌固深度等,其中,基坑下部土钉的长度是影响基坑稳定性的关键因素。
[Abstract]:Soil nailing prestressed anchor cable mixing pile composite foundation pit support structure has been widely used in engineering, but at present, there are few research results on the working characteristics of the structure, which leads to the theory obviously lagging behind the engineering practice. In this paper, the working behavior of this type of composite soil nailing support structure is analyzed in detail by using Midas/GTS(Geotechnical and Tunnel Analysis system finite element analysis program combined with an engineering example. The research results and conclusions are as follows: 1.Through comparing the monitoring data of foundation pit deformation with the results of Midas/GTS finite element program, the results show that the finite element program can simulate the working behavior of foundation pit. The deformation behavior of the supporting structure has changed obviously. The deformation pattern of the composite structure is similar to that of the pile-anchor support structure. The lateral deformation of the composite structure is large in the middle, the upper and lower ends are smaller, and the maximum value is about 0.75 times of the excavation depth. The axial force of soil nailing tends to decrease in the direction of length. According to the different distribution form of axial force, the soil nailing can be divided into three types: axial force increasing type, arch type and axial force decreasing type. The axial force increasing type soil nailing mainly distributes in the upper part of foundation pit. The axial force increases gradually along the length of the soil nailing, the axial force of the soil nailing with bow shape is mainly distributed in the middle of the foundation pit, the axial force is the largest in the middle and the two ends are small, and the decreasing axial force is mainly distributed in the lower part of the foundation pit. The axial force is the largest in the contact part between soil nailing and mixing pile, and then gradually decreases .4.When the application of prestress can effectively control the lateral deformation of foundation pit, and the prestress is applied to the position corresponding to the maximum lateral deformation of foundation pit, In the calculation of the stability of foundation pit, the stability coefficient is taken from the strength reduction calculation of foundation pit, and the strength reduction coefficient corresponding to the convergence of the strength reduction calculation of foundation pit is unreasonable. It is more reasonable to take the reduction coefficient corresponding to the inflexion point in the curve of strength reduction and lateral deformation of foundation pit as the stability coefficient of foundation pit. The factors affecting the stability of supporting structure include the length of soil nailing, the depth of overdigging at the bottom of the pit. Among them, the length of soil nailing at the bottom of the foundation pit is the key factor affecting the stability of the foundation pit.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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