【作者】 郑强；

【导师】 林从谋；

【作者基本信息】 华侨大学 ， 结构工程， 2011， 硕士

【摘要】 随着我国隧道建设快速发展,大断面小净距隧道将日益增多,新奥法应用于大断面隧道尤其2扩4大断面小净距隧道的设计、施工仍然处于探索和验证阶段。由于大断面小净距隧道结构型式的特殊性和新颖性,其在施工过程中与既有隧道相互影响难以把握,边施工边通车,且隧道断面大、扁平率低,施工工序复杂,中间岩柱的受力复杂,围岩稳定性差,而施工方法是影响隧道围岩稳定的重要因素之一,合理的施工方法可以充分利用围岩的自承作用,在最小的支护条件下,得到满足围岩稳定要求。因此,研究2扩4各种施工方法中围岩稳定性和力学响应,这有助于今后类似2扩4大断面隧道合理设计和安全施工提供具有价值的参考。本论文在岩石力学基本原理和新奥法基本思想指导下,以扩建大帽山公路隧道为依托,对大断面隧道不同扩挖大小、不同开挖顺序和不同开挖进尺的CD法施工的力学特征共计6种工况进行了数值模拟,并结合现场监控量测,分析了CD法扩挖时隧道施工各阶段的应力场、位移场、锚喷支护力学特征的动态演化规律、塑性区的分布规律及对既有隧道的影响,取得以下一些主要成果:1、软弱围岩洞口段地表沉降槽出现形成两头小,中间大的倒马鞍形的沉降曲线,在既有隧道正上方出现一个微小的沉降槽;地表的总位移量主要是由于上半断面的开挖引起,周边收敛变形和拱顶下沉有振荡特征,洞壁围岩并不是一直朝净空移动。2、大断面隧道围岩强度发挥明显区域形态类似于蝴蝶翅膀,右拱肩围岩强度发挥区域与临近隧道相互贯通,围岩的应力变化主要集中在隧道结构较近的区域;围岩掌子面塑性区深度为0-5m,各导坑台阶塑性区与掌子面塑性区相互连通,连通区域可能形成与隧道纵向呈45°的塑性滑动面。中间岩柱右拱腰位置的位移变化最为剧烈,是最易失稳破坏点。3、隧道初期支护处于压应力状态,右拱腰也出现应力集中,其相应应力值为1.61MPa,但未超过混凝土抗压允许值16.7Mpa;锚杆的轴力特征是不断变化的,洞周围岩内锚杆的轴力分布极不均匀,拱脚的位置锚杆处于受压状态,其最大压力为43.46KN,其余部位的锚杆处于受拉状态,其最大拉力为167.98KN。4、新建隧道的开挖对既有隧道横断面产生不均匀沉降和不同程度的变形,拱脚、拱腰、拱顶等部位的最终沉降不等且依次减小,左侧的变形相对右侧较大,整个断面呈现明显的偏压状态。新建隧道的开挖对既有隧道的最大拉应力增量为0.25MPa,略小于拉应力增量弱影响阏值(0.3MPa),受新建隧道施工的轻微影响;最大压应力为-0.82MPa,小于弱影响压应力增量值(1.OMPa ),因此既有隧道是安全的。5、分析比较6种不同工法的地表沉降、拱顶位移、支护结构内力分布和围岩塑性区范围分布的优劣,CD法ACBD顺序循环进尺1m的开挖方式是最为适合大帽山隧道软弱围岩扩挖施工的方案。更多还原

【Abstract】 With the rapid development of tunnel construction, small interval tunnel of large span will increase, and new Austrian tunneling method which applied to small interval and large Tunnel’s design and construction especially 2 expanded 4 is still in the exploration and validation phase.Because structure type of small interval tunnel of large span has specificity and novelty,and it’s construction process and the existing tunnel interaction is difficult to grasp, Also,because of it’s construction side of the opening of the tunnel,the large flat rate, complicated construction process ,the middle pillar of the complex stress and so on, however, construction of the tunnel is an important factor in stability of surrounding rock, Reasonable construction method can take full advantage of the self-supporting effect of rock, rock stability requirements are met in the smallest support condition. Therefore, the study of various construction methods 2 expand 4 in the expansion of stability and mechanical response of rock, which help reasonably tunnel design and construction of the similar to the tunnel 2 extend 4,provide valuable safety information.In this thesis,base on the expansion of Da Mao Shan Tunnel and the basic principles of rock mechanics as well as the thought of new Austrian tunneling method, six different excavation conditions execute numerical simulation in CD construction method of different sizes, different sequence and different footage , combined with on-site monitoring and measurement, the distribution of the dynamic evolution such as various stages of tunnel stress field, displacement field, mechanical characteristics of shotcrete support,also, the distribution of plastic zone and the impact on the existing tunnel aboat have studied,made the following major achievements:1.Settlement curve on the soft rock entrance of the surface appear two side small, big in the middle and has a tiny settlement trough above the existing tunnel,the total displacement of the surface was mainly due to the half section excavation,deformation of the surrounding convergence and crown settlement have oscillation, also,not the wall rock has been moving towards the clearance.2.The shape of rock strength to play was similar to butterfly wings region, The shape of rock strength to play is Interconnected with the adjacent tunnel,rock stress mainly in the area close to the tunnel structure; plastic depth of rock tunnel is 0-5m, the divisions plastic zone and the tunnel face connected with each other, and connected region may be formed with the tunnel 45°vertical plastic sliding surface. the right position of the middle pillar of the displacement has Great changes ,which are the most unstable failure point3.Initial support is in the compressive stress state, the right waist has stress concentration which the corresponding stress is 1.61MPa, but not exceeding the value of concrete compressive strength allows 16.7Mpa; characteristics of Anchor axial force is constantly changing,Distribution of bolt axial force around Rock is very uneven,the position of the foot is in compression, the maximum pressure 43.46KN, the remaining parts is in tension, the maximum pulling force of 167.98KN. 4.Excavation of the new tunnel will impact on the existing tunnel which produce differential settlement and varying degrees of deformation,the final settlement on Arch, arch back, vault is not equal and in turn reduce, the deformation on right side is larger than left, therefore,the entire section shown clear bias state.The increments of maximum tensile stress which new tunnel excavation impact on the existing tunnel is 0.25MPa, slightly less than the tensile stress of weak value of shut (0.3MPa) by the minor impact of the new tunnel; the maximum compressive stressis -0.82MPa , less than the incremental value of the weak impact of stress (1.0MPa), so both the tunnel is safe.5.Merits of 6 different construction method of surface settlement and crown displacement and the force distribution of support structure as well as the distribution of the plastic zone are analysid and compared,and draw CD method of ACBD sequence and footage 1m excavation is the most suitable for Da Mao Shan construction plan on soft rock更多还原