摘要
长锚杆对隧道围岩的作用研究与数值模拟变形控制研究具有现实的工程应用价值。锚杆设置等加固措施的主要目的是增强围岩薄弱层面的抗剪性能,延缓或抑制层间错动,提高结构的稳定性和安全性。但在支护工程过程中,还普遍存在三个问题：一是支护结构的安全系数过大,过于保守,造成资源及经济上的浪费；二是支护结构安全系数偏小,起不到良好的支护效果,且不安全；三是缺乏研究数据,没有规律对支护技术提供参考。因此,使得本论文的研究有了重要的意义。
本文分别对锚固设计方法和有限元法进行了详细的阐述,在此基础上设计了长锚杆控制的对比工况以及详细描述了长锚杆的施作工艺,并讨论了围绕隧道支护开展模拟的力学模型的选用,应用大型通用有限元分析软件ANSYS进行长锚杆控制围岩变形的数值模拟仿真研究。
本文采用基于岩石力学方法的围岩—结构模型进行内力和变形分析,同时可得出围岩开挖后的应力状态、洞周变形以及锚杆轴力等,从而可判断锚杆支护参数的选择是否合理,能否满足围岩开挖后洞室是稳定的,以确保隧道及地下工程施工安全进行。根据本文依托的实际工程的工程概况,建立和其相对应的隧道纵断面模型,分别进行锚杆长度对比工况模拟研究。锚杆长度分别为4m、6m、8m,对三种工况下数值模拟所取得的结果进行比较分析。
通过ANSYS对三种工况的数值模拟,得到：27根4m锚杆控制拱顶最大变形量为28.02cm,27根6m锚杆控制拱顶最大变形量为24cm,18根8m锚杆控制拱顶最大变形量为18.33cm,可见,18根8m锚杆控制变形最有效：并得到锚杆水平布置时,部分锚杆轴力呈单峰变化规律。同时,对不同埋深及围岩下三种工况的支护效果进行模拟,得到8m锚杆的支护效果均优于4m锚杆和6m锚杆的支护效果。
通过理论的研究和模拟数据的对比分析,针对具体地形以及隧道围岩的力学性质等因素优化锚杆设置,对于软弱围岩隧道,长锚杆的设置对围岩的加固效果优于普通锚杆设置,为实际的支护工程以及今后进一步的支护研究提供参考数据,具有实际工程应用价值。
Study on controlling the surrounding rock deformation of tunnel by long bolt and controlling the deformation by numerical simulation has real values in engineering applications. The main purpose of anchor settings and other reinforcement methods is to strengthen the weak levels of sheer rock performance, delay or inhibit the dislocation between layers to improve the structure stability and security. However, there are still three questions in support engineering processes:First, if the supporting structure of the safety factor is too large, will resulting in waste of resources and the money; Second, if the supporting structure of the safety factor is too small, would not achieve good supporting effect and security; Third, lack of relevant research data and no law to provide reference for technical support increasing the difficulties in support engineering process. Thus, the study of this paper is important.
This paper described in detail both in anchorage design method and the finite element method, based on that, designed comparison of the condition controlling by long bolt and described the process facilities of long bolt in detail. Also discussed the selection of the mechanical model in tunnel support simulation, use the large general-purpose finite element analysis software ANSYS to simulation of the deformation in controlling the surrounding rock deformation of tunnel by long bolt.
This method is based on rock mechanics, analysis the internal force and deformation by surrounding rock-structure model, and can obtain the stress state of rock after excavation and the deformation hole surrounding and the bolt axial force, which can determine the parameters of bolting choice is reasonable and the rock excavation in the tunnel is stable, and ensure the tunnel and underground construction are safety. This paper established the vertical section of the tunnel model based on the actual engineering project survey, simulates and analysis the bolt length. Three conditions of simulation results were compared, there bolt lengths are 4m,6m and 8m.
Numerical simulation the three conditions by ANSYS, maximum deformation of the vault controlling by 274m bolts is 28.02cm, maximum deformation of the vault controlling by 276m bolts is 24cm, maximum deformation of the vault controlling by 188m bolts is 18.33cm, controlling by 18.8m bolt is the most effective method; simulation also shown, when the bolts are arrangement horizontally, some bolt's axial force variation of a single peak. Meanwhile, at different levels of depth and rock, simulating the effect of the supporting of three conditions, and the supporting effect of 8m bolt is better than the supporting effect of 4m and 6m anchor bolt.
Through theoretical research and comparative analysis of simulation data, arrangement the bolt for the specific terrain and mechanical properties of surrounding rock, for soft rock tunnel reinforcement, long bolt is better than the ordinary bolt, and the reference data for the actual support engineering and further research in future is valuable for practical engineering applications.
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