【作者】 蔚立元；

【导师】 李术才；

【作者基本信息】 山东大学 ， 岩土工程， 2010， 博士

【摘要】 自从1843年英国工程师布鲁内尔使用盾构机建成第一条水下隧道—穿越泰晤士河的人行隧道以来,水下隧道逐渐为人类接受,并且由于不破坏航运、能全天候通车、引线短、拆迁少以及能一洞多用等优点,在最近几十年来蓬勃发展,成为和桥梁并举的穿越江河湖海的交通方式。我国从1970年穿越黄浦江的打浦路过江隧道建成后,四十年来有几十条水下隧道已经建成或在规划中。水下隧道与一般山岭隧道最主要、最显著的区别是：存在上覆水体以及纵断面曲线是倒人字坡,而这两点都和覆盖层这个关键因素有着紧密的联系。水下隧道覆盖层是指隧道拱顶与水体下地表之间的岩土体,对于钻爆法和盾构法修建的水下隧道而言,它既是上覆水体的渗流途径、隧道的防突水屏障和稳定性支撑结构,又是纵断面设计中的决定因素,所以覆盖层厚度即隧道埋置深度是水下隧道设计施工的重要参数和关键指标,影响水下隧道造价和安全。本文主要从以下五个方面进行了水下隧道围岩稳定性分析和合理覆盖层厚度确定等方面的工作。(1)从弹性问题复势理论的的基本方程出发,借助Verruijt提供的保角映射函数和基本解法求解“含圆孔半平面弹性体在地表边界上受任意分布荷载”的问题,并把这种解法应用到水下隧道围岩应力、位移的分析中。(2)制作了由高强PVC板和型钢组成的试验架,开发了光纤监测系统和渗流量计量器,并研制了新型固流耦合相似材料,在此基础上以青岛胶州湾海底隧道为工程背景进行了流固耦合模型试验。试验过程中记录了渗流量和关键点的位移、应力及渗透压力等多元信息,并与FLAC3D的计算结果进行了对比分析。(3)基于Thorne和Souley的研究成果,构建了能反映体积压缩状态下损伤发展并关联渗透率的爆破损伤模型,并将其嵌入FLAC3D软件中的应力硬化-软化模型中。(4)以青岛胶州湾海底隧道为研究对象,由位于断层破碎带f3-1中的典型断面ZK5+607的几何参数和地质资料构建三维数值计算模型,借助FLAC3D先后从洞室开挖效应和爆破振动响应两个方面研究了水下小净距隧道的施工相互影响。(5)详细阐述了确定覆盖层厚度中的工程类比法如深浅埋隧道分界法、普氏压力拱法、挪威海底隧道建设经验法、日本最小涌水量法、国内顶水采煤法及最小位移法等,并讨论了它们各自的应用途径；进一步归纳出了简单实用的经验公式,并进行了适用性评价。最后提出了确定水下隧道合理覆盖层厚度和纵断面设计线路的方法体系,并以胶州湾海底隧道为工程背景进行了运用。经过上述分析,得到的研究成果如下：1、中线左右两倍洞跨、底板以下两倍洞跨到地表范围内围岩应力集中现象明显,位移受隧道开挖影响明显,覆盖层尤其应给予重点关注；隧道中线两侧2倍洞跨范围内,沉降槽比较陡峭,然后逐渐平滑,最后趋近于水平。2、地层沉陷结果具有明显的分层传递性,即沉降变形由地表到拱顶传递,变化逐渐减弱；洞周点垂直位移随距地表距离增加而逐渐减小。3、随着开挖进行,覆盖层竖向位移逐步增加,32.1m水深时开挖后关键点A的位移大约为10.0mm；应力场二次调整,拱顶正上方竖向压应力逐渐减小,并且出现水平拉应力区；渗压场剧烈变化,超孔隙水压力逐渐消散。随着水位的提升,覆盖层位移大幅增加,92.1m水深时的位移大约是32.1m时的两倍多；拉应力数值增加、区域扩大；最终渗压场明显变化；隧道涌水量剧烈增大,92.1m水位时的涌水量至少是32.1m时的两倍多。4、大多数现有爆破损伤模型是基于张拉体积应变的拉仲损伤判断准则建立的,但是在体积压缩状态下损伤已经开始发生、积累,并且会导致渗透率的增大。5、小净距隧道实际施工时应该使各掌子面有一定的空间间距,并且各施工步之间要有时间间隔：围岩自稳能力允许时要尽量采用全断面开挖,尽量采用小进尺；在相互影响较大的断面,服务隧道的拱部、仰拱和先行开挖主隧道的内边墙是现场施工和监测工作中应注意的部位。6、钻爆法施工时炮眼装药不耦合系数一定要严格控制,必要时可以通过现场试验来确定；可以施作中空眼以降低爆破振动强度；爆破施工覆盖层的影响范围在15m之内：在施工中应注意加强监控量测并推迟二次衬砌的施作；施工洞的拱部、先行洞的迎爆面边墙是爆破振速峰值最大的部位,对这些位置要加强监测；施工洞的拱部出现了严重的应力集中现象和拉应力区,施工中可用超前小导管进行预加固。7、在上覆土层较薄或基岩基本裸露时,可用最小涌水量法拟合公式计算的覆盖层厚度值作为选线的参考；挪威海底隧道建设经验方法确定的覆盖层厚度偏于保守,且没有考虑开挖面积的影响；合理覆盖层厚度不仅与上覆水体深度、岩体特性和开挖面积有关,而且还与围岩分层情况有关,最小位移法回归公式的计算值可以作为覆盖层厚度的下限值。8、提出了确定水下隧道合理覆盖层厚度和纵断面设计线路的方法体系。更多还原

【Abstract】 The first underwater pedestrian tunnel that lies through the River Thames Since was built using the shield methed by the British engineer, Brunel, in 1843. From then on, the underwater tunnel has got gradual acceptance of human. Because of none-destroying the shipping, all-weather traffic, short lead, less demolition, multi-hole and so on, the underwater tunnel as a traffic mode which can cross rivers, lakes and straits has become as important as bridges in recent decades. In China, The first underwater tunnel, Dapu tunnel, spans the Huangpu River and was built in 1970. Since then, dozens of underwater tunnels have been built or in planning.The most important and significant differences between underwater tunnels and general mountain tunnels are the presence of overlying water and the inverted longitudinal slope. These two points are closely associated with the overburden layer, a key factor of underwater tunnels. The overburden of underwater tunnel is rock-soil mass between the vault and ground surface. The overburden is not only the percolation path, prevention barrier of water inrush and support structure of stability, but also the key factor of profile design for underwater tunnels which are built with drilling-blasting method or shield methed. So the depth of overburden is an important parameter and key indicator in design and construction of underwater tunnels. Furthmore, the overburden depth restricts construction cost and safety.The core content of this dissertation is study on stability of surrounding rocks and selection of overburden thickness for underwater tunnels. The study is primarily expanded from the following five aspects.(1) Using the conformal mapping function and basic solution provided by Verruijt, the classical problem of an elastic half plane with a circular cavity, loaded arbitrarily on the surface boundary is solved. Then stress and displacement analysis of surrounding rocks of underwater tunnels is performed with this method.(2) Based on the analysis on similarity theory of solid-fluid coupling, the new analogous material for solid-fluid coupling has been found. Extensible 3D test bench and optical fiber monitoring system are developed. Then fluid-solid coupling model test are performed for the Kiaochow Bay Subsea Tunnel. The evolution mechanism of overburden has been analyzed by the monitoring results of multi-field information. The results from model test and numerical calculation are comparatively analysed eventually.(3) An new rock blasting damage constitutive model which can represent damage development under volume compression state is established based on research results of Thorne and Souley, and this model contacts permeability with volumetric strain. In order to be applied in engineering practice, the new constitutive model is embed in strain-hardening/softening model of FLAC3D.(4) The section ZK5+607 of the Kiaochow Bay Subsea Tunnel which is located in the fault f3-1 is chosen as typical cross section, and a three-dimensional model for numerical analysis is established according to geometrical parameters and geological information.of the typical cross section. It is studied use FLAC3D that construction interaction of little distance parallel subsea tunnels owing to excavation effect and blasting vibration influence.(5) Engineering analogy methods used for selecting overburden thickness, for example method from domestic standards, pressure arch theory method, domestic experiences from mining under waterbody, Japanese minimum leakage method, Norwegian subsea tunnel construction experience, minimum displacement method and so on, are expatiated detailed. Then, simple and practical empirical formula are induced. Fitness evaluations are given finally,Through the above analysis, the research results are listed as follows:1. Surrounding rock that lies less twice the tunnel span apart from midline, and from twice the tunnel span bellow floor to ground surface, especially the overburden, has apparent deformation and stress concentration. Additionally, In this region settling tank vary from steep to smooth while the distance to tunnel midline increases.2. Ground subsidence results have obvious layered transmission, ie settlement change gradually weakened from the surface to the vault; and vertical displacement of surrounding rock decreases while the distance to surfaee increases.3. The vertical displacement of covering layer gradually increase with the excavation. The displacement of key point A is about 10.0mm after total excavation under 32.1m water head. Because of the second adjustment of stress field, the vertical stress of rockmass just above the vault decreases, and horizontal tensile stress zone appears. Dramatic changes occur in seepage pressure field, excess pore water pressure dissipates gradually. As the upgrade of water level, displacement of overburden increase substantially, the values of 92.1m water depth are more than twice times of that of 32.1m. tensile stress values increase, and the region expand. Final seepage pressure field changes obviously. Water inflow dramatic increase, the value of 92.1m water depth is at least more than twice times of that of 32.1m.4. Most of the existing blasting damage models are established by stretching damage criterion based on the tensile volumetric strain, but the damage has occurred and accumulated under volume compression state. In addition this will lead to increase of permeability.5. When the little distance parallel underwater tunnels are constructed, the working faces of different tunnels should have some spacing, and there should be time interval between different construction steps. The full-face excavation type and short footage should be chosen firstly if the self-stability of surrounding rock is allowable. In the section of significant mutual influence, arch and invert of service tunnel and the inner wall of constructed tunnel should be concerned in construction and spot measure.6. The charge decouple coefficient of blast holes should be controled strictly when drill and blast construction method is adopted, and it can be determined through the field test if necessary. Hollow holes can be Excavated to Reduce the intensity of blasting vibration. The influence scope of rock overburden under explosive load is within 15m. Spot monitoring measurement should be strengthened and concrete linings should be postponed. The maximal peak values of vibration velocity occur on arch parts of excavating tunnel and walls facing the blasting side of constructed tunnels, while stress concentrations and tension stresses appear at arch parts of excavating tunnel. So the support system shoud be reinforced at these positions.7. Japanese minimum leakage method can be used to choose overburden thickness when overlaying soil layer is quite thin or bedrock is basically exposed. Overburden thickness determined by norwegian subsea tunnel construction experience is rather conservative, and this method does not consider the impact of excavation area. Reasonable Overburden thickness is related with not only the overlying water depth, Rock properties and excavation area, but also the situations of surrounding layer. The calculational value gained from the minimal distance method regression formula can be used as the lower limit.for overburden thickness.8. The method system for selecting rational overburden thickness and determining lognitudinal section line is put forward.更多还原