长江近入海口复杂地质条件下隧道工程风险评价

发布时间：2018-08-07 18:11

【摘要】：近年来,我国隧道及地下工程建设数量不断上升,工程建设的难度持续增加,规模也越来越庞大。但是隧道工程因为所处地质条件的不明确和隐蔽性,与之而来的问题就是建设过程中存在很多风险。这不仅会造成生命和财产的损失,还会造成一定的社会影响。在隧道项目的规划和实施阶段,利用合适的方法对隧道风险分析,不仅可以确定工程建设的风险程度,还可以预判可能产生的风险事故,从而方便我们采取一定的风险控制措施,从而有效减少风险事故造成的损失。本文针对长江近入海口复杂地质条件下的隧道工程进行风险评价。主要以常熟电厂输水盾构隧道为例,针对其复杂的地质水文条件,通过风险因素的分析与稳定性风险分析,提出符合工程实际的方法进行风险评价。主要研究内容及成果如下：(1)结合工程区地质条件和水文条件,分别从隧道特征、管片特征、围岩特征,对常熟电厂输水隧道风险因素进行分析。按照已有的理论,对隧道建设过程中各方面的稳定性判断,并得到了一些结论：底部承压含水层水压较大,如果防水措施不当,在施工过程中承压含水层会造成流土等地质灾害；而且第⑤层土含有沼气、朽木和腐殖质,会对施工过程产生影响。(2)工程场区处于长江与徐六泾河交界处,河流作用会对埋置于河床底部的隧道产生影响。因受到潮流和径流的双重作用,通过分析河床在落潮期间处于冲刷状态。但落潮流所处长江主泓位置位于长江深槽处,距离隧道仍有800m左右,而且深槽坡度只有10%；加之近年来,长江中下游地区水库和护岸工程建设,使得徐六泾河段处于相对稳定的状态,所以在隧道使用期内河势的变化并不会对隧道稳定性产生影响。(3)通过数值模拟的方式分析了隧道开挖对周围土体的扰动,并对其进行风险分析,得出结论认为隧道埋置深度的增加有利于稳定,但是当隧道处于④⑤层土中时,处于最不利情况。还通过建立涌水模型,利用蒙特卡罗来模拟分析隧道涌水与潮位变化的关系,得出了隧道涌水主要受底部承压含水层控制,需要在施工过程中做好防水措施。(4)结合工程实际,提出分区段对隧道风险评价。按地质条件的变化对隧道进行区段划分,建立分区风险评价体系。采用综合风险指数评价方法对隧道风险评价,并对各区段风险因素的重要程度分析。通过本文提出的风险评价体系进行计算,最后得出D段和E段处于中等风险等级,尤其是E段风险指数接近较高风险等级。另外B段和C段处于风险较低等级,A段风险指数最小。分析各段所处的风险等级,提出切合工程实际的防渗,防沼气等风险控制措施,目的在于降低风险,减少损失。
[Abstract]:In recent years, the quantity of tunnel and underground engineering in our country has been increasing, and the difficulty and scale of construction have been increasing. However, due to the uncertainty and concealment of the geological conditions, the problem of tunnel engineering is that there are many risks in the process of construction. This will not only cause loss of life and property, but also a certain social impact. In the planning and implementation stage of the tunnel project, using the appropriate method to analyze the tunnel risk can not only determine the risk degree of the project construction, but also predict the possible risk accident. Therefore, it is convenient for us to take certain risk control measures, thus effectively reducing the loss caused by risk accidents. This paper evaluates the risk of tunnel engineering near the estuary of Yangtze River. Taking the shield tunnel of Changshu Power Plant as an example, according to the complex geological and hydrological conditions, the risk assessment method is put forward by analyzing the risk factors and stability risk. The main research contents and results are as follows: (1) combined with the geological and hydrological conditions of the engineering area, the risk factors of the water conveyance tunnel in Changshu Power Plant are analyzed from the tunnel characteristics, segment characteristics and surrounding rock characteristics respectively. According to the existing theory, the stability of all aspects in the tunnel construction is judged, and some conclusions are drawn: the water pressure of the bottom confined aquifer is high, if the waterproof measures are not appropriate, During the construction process, the confined aquifer will cause geological hazards such as flowing soil, and the fifth layer of soil contains biogas, dead wood and humus, which will have an impact on the construction process. (2) the engineering site is located at the junction of the Yangtze River and the Xuliujing River. The action of the river affects the tunnel buried at the bottom of the river bed. Because of the dual effect of tidal current and runoff, the river bed is scoured during the period of falling tide. However, the main Yangtze River current is located at the deep trough of the Yangtze River, which is still about 800 meters from the tunnel, and the slope of the deep channel is only 10. In addition, in recent years, reservoirs and bank protection projects have been built in the middle and lower reaches of the Yangtze River. The Xuliujing River section is in a relatively stable state, so the variation of the river potential in the tunnel will not affect the tunnel stability. (3) the disturbance of the tunnel excavation to the surrounding soil is analyzed by numerical simulation. It is concluded that the increase of the buried depth of the tunnel is beneficial to stability, but the tunnel is in the most disadvantageous situation when it is in 45 layers of soil. Through the establishment of water gushing model and the simulation analysis of the relationship between tunnel gushing and tidal level change by Monte Carlo, it is concluded that tunnel gushing is mainly controlled by the bottom confined aquifer, which requires good waterproof measures in the construction process. (4) combined with the engineering practice, it is necessary to do a good job in waterproof measures. The risk assessment of tunnel is proposed. According to the change of geological conditions, the section of tunnel is divided and the risk assessment system is established. The comprehensive risk index evaluation method is used to evaluate the tunnel risk, and the importance of risk factors in each section is analyzed. Through the calculation of the risk evaluation system proposed in this paper, it is concluded that D and E are in the middle risk grade, especially the risk index of E is close to the higher risk grade. In addition, B and C are at the lowest risk level and A risk index is the lowest. This paper analyzes the risk grade in each section, and puts forward some risk control measures, such as seepage control and biogas control, which are suitable for engineering practice, in order to reduce the risk and reduce the loss.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U452.11

【参考文献】