京张城际铁路八达岭地下车站大断面隧道开挖与支护技术研究

发布时间：2018-05-28 05:27

本文选题：大断面隧道 + 拓扑优化　；参考：《北京交通大学》2017年硕士论文

【摘要】：自中国第一条高速铁路(京津城际铁路)建成以来,高速铁路在中国迅速发展,列车在穿越隧道时,考虑到空气动力学问题,隧道的断面通常较大,在围岩条件一般时,大断面隧道的开挖会对周围岩体造成很大扰动,如何保证大断面隧道围岩的稳定性和衬砌结构的安全性是目前需要克服的重要工程难题。本文以国内第一座修建于山岭中的深埋地下火车站(京张城际铁路八达岭地下车站)为依托,综合使用多种研究手段,对车站大跨段开挖中的关键技术问题进行研究。从围岩变形、围岩应力与塑性区、衬砌应力等角度对施工方案进行研究,评选最优方案。利用ABAQUS的拓扑优化功能,以应变能作为目标函数,计算大跨段型钢的最优结构。通过对不同长度、预应力、刚度的锚杆锚索对于围岩变形影响的研究,得到初支中锚杆锚索支护参数的确定原则。取得以下主要成果:(1)在设计单位提出预留核心土法和预留中岩柱法的基础上,作者个人提出三台阶七步法的方案,并对三种开挖方案进行研究,选取最优方案。研究发现,三台阶七步法在控制围岩稳定和保证结构安全两方面都有不足,此方案可以排除。预留核心土法虽然最终拱顶沉降要大于预留中岩柱法,但是此方案的拱顶沉降在开挖各阶段缓慢发展,预留中岩柱法在破除上部岩柱时,拱顶沉降迅速增大,因此在控制围岩稳定性方面,预留核心土法要优于预留中岩柱法。在保证结构安全方面,预留中岩柱法的优势明显,初衬的最大拉应力明显小于预留核心土法,可以确保初衬不会受拉破坏,只要能够保证破除上部岩柱时支护及时,将会对围岩产生最小扰动。综合比较,预留中岩柱法最优。(2)对大跨段锚索长度、刚度、预应力的不同对围岩变形影响的研究可知,锚索的长度对于控制围岩的变形起到了关键作用。有锚索情况下,锚杆的轴力明显减小,而锚索自身长度的增加也使不同位置锚索的轴力分布更加均衡,从而在有效控制围岩变形的前提下避免自身受拉破坏。锚索的预应力和刚度的增加虽然可更好地控制围岩变形,但是效果并不显著,在设计时对这两个支护参数的选取主要考虑满足锚索抗拉强度的要求。(3)利用ABAQUS拓扑优化功能,对四分之一圆环型钢进行优化,计算所得优化结果符合“两头大中间小”的规律,在此基础上对八达岭地下车站大跨段的型钢结构进行优化,对优化后的结构进行分析,得到了“强化拱脚拱腰”的型钢截面尺寸方案,以保证拱脚拱腰初支的刚度。
[Abstract]:Since the establishment of the first high-speed railway in China (Beijing-Tianjin Intercity Railway), the high-speed railway has developed rapidly in China. When the train passes through the tunnel, considering the aerodynamic problems, the section of the tunnel is usually large, and when the surrounding rock conditions are normal, The excavation of large section tunnel will cause great disturbance to surrounding rock mass. How to ensure the stability of surrounding rock and the safety of lining structure of large section tunnel is an important engineering problem to be overcome at present. Based on the first underground railway station (Badaling Underground Station of Beijing-Zhangzhou-Intercity Railway) built in the mountains in China, this paper studies the key technical problems in the excavation of the long span section of the station by using a variety of research methods. The construction scheme is studied from the angles of surrounding rock deformation, surrounding rock stress and plastic zone, lining stress and so on. The optimal structure of long span section steel is calculated by using the topological optimization function of ABAQUS and the strain energy as the objective function. By studying the influence of anchoring cables of different lengths, prestress and stiffness on the deformation of surrounding rock, the principle of determining the supporting parameters of anchor cables in initial support is obtained. The main achievements are as follows: 1) on the basis of reserving core soil method and reserving middle rock column method, the author puts forward a three-step seven-step method, and studies three kinds of excavation schemes, and selects the optimal scheme. It is found that the three-step and seven-step method has shortcomings in controlling the stability of surrounding rock and ensuring the safety of the structure, and this scheme can be eliminated. Although the final dome settlement of the reserved core soil method is greater than that of the reserved middle rock column method, the dome settlement of this scheme develops slowly in each stage of excavation. When the upper rock column is broken by the reserved middle rock column method, the dome settlement increases rapidly. Therefore, in the aspect of controlling the stability of surrounding rock, the reserved core soil method is better than the reserved medium rock column method. In the aspect of ensuring structural safety, the method of reserving middle rock column has obvious advantages, and the maximum tensile stress of initial lining is obviously smaller than that of reserved core soil method, which can ensure that the initial lining will not be damaged by tension, so long as it can ensure that the support is timely when the upper rock column is broken. There will be a minimal disturbance to the surrounding rock. By comprehensive comparison, the study on the influence of the length, stiffness and prestress of anchor cable on the deformation of surrounding rock shows that the length of anchor cable plays a key role in controlling the deformation of surrounding rock. In the case of anchor cable, the axial force of the anchor rod decreases obviously, and the increase of the length of the anchor cable makes the axial force distribution of the anchor cable in different positions more balanced, thus avoiding the tensile damage under the premise of effectively controlling the deformation of surrounding rock. Although the increase of prestress and stiffness of anchor cable can better control the deformation of surrounding rock, the effect is not obvious. The selection of these two supporting parameters mainly considers to meet the requirements of tensile strength of anchor cable in design. On the basis of the optimization of 1/4 ring section steel, the optimized results accord with the law of "two ends, middle and small". On this basis, the section steel structure of the large span section of Badaling underground station is optimized, and the optimized structure is analyzed. The section size scheme of "strengthening arch waist" is obtained to ensure the stiffness of arch waist initial support.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.4

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