富水弱胶结粉细砂层隧道双侧壁施工工法及数值模拟分析

发布时间：2018-03-06 00:22

本文选题：富水弱胶结砂层　切入点：双侧壁导坑法　出处：《兰州交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：需要大力发展交通工程的中国西北地区广泛分布着富水弱胶结砂层，在这种典型软岩地层中修建大断面隧道工程的难度比较大、安全风险高，严重制约着我国西北地区交通工程的发展。如何在此类软弱围岩地质条件下，安全、高效的修建高质量隧道，是当前隧道工程界面临的重要课题之一。本文依托在建的兰渝铁路桃树坪隧道工程，研究探讨了富水弱胶结粉细砂层隧道双侧壁导坑施工工法及其辅助施工措施等关键技术；对隧道施工过程中的相关应力项目进行了监测和分析；采用有限元软件对隧道施工过程进行了模拟，研究分析了围岩变形规律、支护结构应力分布特征及其变化规律，并结合监测结果综合评价了现行施工方法、支护参数的可行性和支护结构的安全性。综合以上内容的研究分析，得出了以下主要研究成果：（1）在此类特殊富水软岩地层中修建隧道等地下工程时，施工技术的关键在于以降水为前提，超前注浆加固为保障，大断面划分成小断面（双侧壁工法），快挖、快支、快封闭为组织原则，这样才能有效的控制围岩的变形，确保隧道施工安全、高效的推进。（2）通过对围岩压力、接触压力、二衬钢筋内力的监测和分析，可以看出各监测点的围岩压力、接触压力以及二衬钢筋内力等均呈现出了不规律波动变化的特性，受各部开挖、临时支撑的拆除影响较大，出现长时间波动情况，，在监测3到5个月后都呈现出了收敛趋势，基本稳定，数值均在允许范围之内，支护结构处于安全状态。（3）通过对隧道施工过程进行数值模拟分析，可以看出在此类地层中修建隧道时，围岩易被扰动，扰动范围大，变形速度快，变形时间长，隧道贯通后竖直和水平位移最大值分别为23.6mm和11.2mm；鉴于双侧壁导坑法施工的不对称性，支护结构的受力表现出了不对称性，隧道贯通后初期支护结构的第1和第3主应力最大值分别达到了1.4MPa和-21.7MPa，支护结构受力处于正常状态。（4）拆除临时支撑是双侧壁导坑法施工比较关键的一道工序，在拆除临时支撑时，对围岩的位移及支护结构的受力都会产生重要的影响，围岩位移和支护结构的应力都会发生突变，突变值较大；研究断面的支护结构应力最大突变值达到了7.4MPa，占到了最大值的37.7%。因此要尽量分段、小范围、小震动拆除，避免对围岩造成较大扰动，并且要加强该段围岩量测频率，发现变形过大时，尽早采取措施，加强支护，控制该部位受力状态的恶化及变形的扩大。
[Abstract]:In northwest China, where traffic engineering needs to be vigorously developed, there are widely water-rich and weak-cemented sand beds. It is difficult to build large section tunnels in this typical soft rock formation, and the safety risks are high. The development of traffic engineering in northwest China is seriously restricted. How to build high quality tunnel safely and efficiently under the geological condition of soft surrounding rock is one of the important problems facing the tunnel engineering field at present. Based on the Taoshuping tunnel project of the Lanzhou-Chongqing railway, this paper discusses the construction method of double-sidewall diversion pit and its auxiliary construction measures for the tunnel with rich water and weak cemented fine sand layer. The related stress items in tunnel construction are monitored and analyzed, the tunnel construction process is simulated by finite element software, the surrounding rock deformation law, the stress distribution characteristics of supporting structure and its variation law are studied and analyzed. Combined with the monitoring results, comprehensive evaluation of the current construction methods, the feasibility of supporting parameters and the safety of the support structure. Based on the above research and analysis, the following main research results are obtained:. 1) in the construction of tunnels and other underground projects in this kind of special water-rich soft rock strata, the key point of construction technology is to take precipitation as the premise and advance grouting reinforcement as the guarantee, and the large sections are divided into small sections (double side wall construction method, quick excavation, quick branch, etc.). Fast closure is the principle of organization so that the deformation of surrounding rock can be controlled effectively and the tunnel construction is safe and efficient. 2) through the monitoring and analysis of surrounding rock pressure, contact pressure and internal force of second lining steel bar, it can be seen that the surrounding rock pressure, contact pressure and internal force of the second lining steel bar all show irregular fluctuation characteristics, and are excavated by each part. The removal of temporary braces has a great influence on the removal of temporary braces and has a long period of fluctuation. After monitoring for 3 to 5 months, the temporary bracing shows a convergent trend, which is basically stable, and the values are all within the allowable range, and the supporting structure is in a safe state. 3) through the numerical simulation analysis of tunnel construction process, it can be seen that the surrounding rock is easily disturbed, the disturbance range is large, the deformation speed is fast, and the deformation time is long when the tunnel is built in this kind of stratum. The maximum values of vertical and horizontal displacement after tunnel opening are 23.6mm and 11.2mm respectively. The maximum of the first and third principal stresses of the primary support structure of the tunnel is up to 1.4 MPA and -21.7 MPA, respectively, and the force of the supporting structure is in the normal state. The removal of temporary bracing is a key procedure in the construction of double-side wall diversion pit method. When the temporary support is removed, it will have an important impact on the displacement of surrounding rock and the force on the supporting structure. The displacement of surrounding rock and the stress of supporting structure will both change, and the catastrophe value will be larger. The maximum abrupt value of stress of supporting structure in the research section has reached 7.4 MPA, accounting for 37.7% of the maximum value. In order to avoid the disturbance to the surrounding rock, and to strengthen the measuring frequency of the surrounding rock, when the deformation is too large, measures should be taken as soon as possible to strengthen the support, to control the deterioration of the stress state and the expansion of the deformation.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.4

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