第三系砂泥岩地层隧道施工安全及对策研究

发布时间：2018-09-12 12:14

【摘要】：随着国家经济的发展和社会的进步,公路铁路建设方兴未艾,于是穿越第三系砂泥岩地层的隧道数量急剧增加,其长度、断面面积和埋深也越来越大,隧道施工安全问题越来越突出。不论对国家还是企业,施工安全始终是至关重要的。砂泥岩地层隧道的施工安全问题是国内外隧道施工安全方面一直关注的热门问题,目前整体研究水平尚不能满足施工需要。当前我国在建的砂泥岩地层隧道很多,有利于积极开展其施工安全及对策的研究和总结工作。本文依托牡绥线双丰隧道这一工程实例,分析预判了可能有安全隐患的地段;利用迈达斯GTS有限元分析软件进行施工模拟,比较分析了不同条件下,隧道可能出现的安全隐患并给出了应该注意的应对方法。主要得到下列结论:(1)通过对砂泥岩地质状况下隧道施工过程的模拟,结果表明:①三台阶法开挖时,围岩第一主应力最大值为-0.61MPa,围岩第三主应力最大值为-1.26MPa;采用CD法开挖时,围岩第一主应力最大值为-0.52MPa,围岩第三主应力最大值为-1.05MPa;采用三台阶七步开挖法时,围岩第一主应力最大值出为-0.34MPa,围岩第三主应力最大值为-0.68MPa。②三台阶法开挖时,结构沿X方向上的最大位移为18.5cm,沿Y方向的最大沉降量和隆起量分别为16.2cm和19.0cm;采用CD法开挖时,结构沿X方向上的最大位移为15.9cm,沿Y方向的最大沉降量和隆起量为11.4cm和14.2cm;采用三台阶七步开挖法时,结构沿X方向上的最大位移为8.6cm,沿Y方向的最大沉降量和隆起量为8.1cm和8.7cm。(2)拱腰、拱脚在围岩水平荷载作用下发生较大的挤出变形,而拱部则在围岩竖向荷载作用下发生沉降变形。因此,可以通过增强锁脚措施等手段来控制围岩的水平位移和竖向沉降,从而确保施工安全。(3)隧道右侧的围岩压力基本上都大于左侧,表现出了不对称;山体的侧向压力很大,施工时应予以高度重视;各测点的围压都有增大趋势。(4)钢拱架当前最大应力发生在右侧拱腰处,为-400.32MPa,左右侧测量值不对称,说明隧道可能受到偏压影响,施工中应重视。当钢拱架闭合时,各观测点的应力进一步的优化,不对称性逐渐减小,偏压影响逐渐减小,各点趋于稳定。(5)初支和二衬间接触压力初期增加较大,主要是因为前方掌子面的开挖对其有较大的扰动;随后因为混凝土的收缩徐变而使接触压力减小;随着二次衬砌的完成,逐渐趋于稳定。(6)混凝土应力多处于受压状态,前期的波动变化主要由于混凝土硬化的强度变化造成的;随后出现混凝土应力逐渐缓慢减小的现象,主要是因为二次衬砌施作完成形成一个整体共同受力。(7)二次衬砌钢筋受力状态不同,内层钢筋多处于受拉状态,外层钢筋多处于受压状态,前期的小幅度变化主要跟混凝土硬化受力不均匀有关;随后由于二衬施作完成,钢筋受力逐渐增大,二次衬砌开始承受围岩变形。
[Abstract]:With the development of national economy and the progress of society, the construction of highway and railway is in the ascendant, so the number of tunnels passing through the Tertiary sand and mudstone strata increases sharply, and its length, cross-section area and buried depth are also increasing. Tunnel construction safety problem is more and more prominent. Whether to the country or the enterprise, the construction safety is always vital. The safety of tunnel construction in sand and mudstone strata is a hot issue in tunnel construction safety both at home and abroad. At present, the overall research level can not meet the construction needs. There are a lot of sand and mudstone stratum tunnels under construction in our country at present, which is helpful to carry out the research and summary of its construction safety and countermeasures. Based on the engineering example of Shuangfeng Tunnel in Musui Line, this paper analyzes and predicts the potential safety hazards, and uses Midas GTS finite element analysis software to carry out the construction simulation, and compares and analyzes the different conditions. The potential safety risks of the tunnel and the countermeasures that should be paid attention to are given. The main conclusions are as follows: (1) through the simulation of tunnel construction process under sand and mudstone geological conditions, the results show that when the first principal stress of surrounding rock is -0.61MPa, the maximum of the third principal stress of surrounding rock is -1.26MPa when the first principal stress of surrounding rock is excavated by using the CD method, The maximum value of the first principal stress of surrounding rock is -0.52MPa, the maximum of the third principal stress of surrounding rock is -1.05MPa, and the maximum value of the first principal stress of surrounding rock is -0.34MPa, and the maximum value of the third principal stress of surrounding rock is -0.68MPa.2 when the three-step excavation method is adopted. The maximum displacement along X direction is 18.5 cm, and the maximum settlement and uplift along Y direction are 16.2cm and 19.0cmrespectively. The maximum displacement along X direction is 15.9 cm, and the maximum settlement and uplift along Y direction are 11.4cm and 14.2 cm. The maximum displacement along X direction is 8.6 cm, and the maximum settlement and uplift along Y direction are 8.1cm and 8.7 cm 路(2) arch. However, the arch is subjected to settlement deformation under the vertical load of surrounding rock. Therefore, the horizontal displacement and vertical settlement of surrounding rock can be controlled by means of strengthening foot locking measures to ensure the safety of construction. (3) the surrounding rock pressure on the right side of the tunnel is basically larger than that on the left side, showing asymmetry, and the lateral pressure of the mountain body is very large. The confining pressure of each measuring point has an increasing tendency. (4) the current maximum stress of steel arch frame occurs at the right arch waist, which is -400.32 MPa, and the measured value of the left and right side is asymmetric, which indicates that the tunnel may be affected by bias pressure, which should be paid attention to in construction. When the steel arch frame is closed, the stress of each observation point is further optimized, the asymmetry decreases gradually, the influence of bias decreases gradually, and the points tend to be stable. (5) the initial contact pressure between the initial support and the second liner increases greatly. The main reason is that the excavation of the front face has a great disturbance to it; then the contact pressure decreases because of the shrinkage and creep of concrete; with the completion of the secondary lining, the contact pressure tends to stabilize gradually. (6) the concrete stress is mostly in the state of compression. The fluctuation in the early stage is mainly caused by the change of the strength of concrete hardening, and then the concrete stress decreases slowly. The main reason is that the secondary lining is completed to form a common force. (7) the secondary lining steel bars are in different stress states, the inner steel bars are mostly in the tensile state, and the outer steel bars are mostly in the state of compression. The small change in the early stage is mainly related to the uneven hardening force of the concrete, and then due to the completion of the second lining, the stress of the reinforcement gradually increases, and the secondary lining begins to bear the deformation of surrounding rock.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U455

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