【作者】 汪魁；

【导师】 赵明阶；

【作者基本信息】 重庆交通大学 ， 岩土工程， 2010， 硕士

【摘要】 虽然水工隧洞堵头的工程量一般不大,但作为水利水电工程的主要控制条件之一,其工期要求都比较紧迫。封堵工作是否能够顺利、及时地完成,对整个后期的工程进度有着极其重要的意义。目前,《水工隧洞设计规范》(SL279——2002)对封堵体设计只给出了一般原则,实际已建工程中都是各自制定设计原则和选取参数,还没有统一的标准。由于堵头对枢纽运行安全极其重要和设计原则不尽合理等多种原因,导致多数堵头设计长度偏于安全,使得本来已是相对短暂的工期更趋紧张,也不必要地增加了工程造价。因此,通过全面分析堵头的力学效应,建立堵头设计的优化方法具有一定的理论意义和工程实用价值。本文在总结国内外导流隧洞封堵设计一般原则的基础上,对堵头设计和稳定性校核进行了深入的理论探讨,并结合金家坝水电枢纽工程,对施工导流洞围岩的渗流场和应力场进行三维有限元数值模拟,研究基于流固耦合模型的堵头的力学效应。主要内容包括:1.)通过对已建水工隧洞堵头设计原则及设计方法的分析,总结现行堵头设计方法存在的问题,分析影响堵头设计及稳定性的因素;2.)结合金家坝水电枢纽工程,利用大型通用有限元软件ANSYS10.0建立施工导流洞封堵影响区域的围岩和堵头的三维弹塑性有限元模型,研究应力场下围岩和堵头的变形和稳定性;3.)结合金家坝水电枢纽工程,运用三维有限元方法建立堵头运行期导流洞影响区域的渗流场模型,分析渗流场对围岩变形的影响,建立围岩渗流场和应力场的耦合模型;4.)通过分析基于流固耦合模型下围岩的变形,研究堵头和围岩的相互作用以及堵头在挡水过程的力学效应,并利用弹塑性力学方法对堵头进行分析,对堵头设计的主要因素进行定量分析,最终提出堵头设计的优化方法。通过以上工作,总结出的结论和工程经验主要有:1.)堵头总体上呈受压状态,而且拉压应力均较小,不会超过堵头混凝土本身的强度;2.)堵水压力主要由堵头与围岩的粘聚力和接触面的摩擦作用共同承担,且摩擦力的发挥从上游端到下游端逐渐减弱;3.)在堵头尾部由于隧洞内无水压力形成临空面,而堵头本身的弹性变形挤压尾部围岩,形成局部围岩塑性区;4.)考虑围岩附加弹性抗力对堵头侧向约束的有利影响,可以对堵头常规设计方法进行修正,修正的堵头抗滑稳定计算公式在一定程度上能够提高堵头的抗滑稳定性;5.)围岩弹性模量的提高有利于堵头的抗滑稳定,因此,封堵段隧洞的开挖不仅要考虑堵头体型特点,而且要考虑堵头的稳定性,避免在复杂断面形状及地质条件的隧洞进行封堵;6.)提高堵头混凝土的强度等级并不能提高堵头的抗滑稳定性,而堵头混凝土本身的强度已经足够大,因此,提高堵头混凝土的强度等级对于堵头工程的安全性来说没有实际作用;7.)将堵头设计成上游断面大,下游断面下的楔形体是保证围岩发挥附加弹性抗力的必要条件,但是,楔形体的楔角应适当,实际工程中应综合考虑堵头的长度及断面大小选取合理的楔角,楔角并非越大越好。更多还原

【Abstract】 Although the amount of hydraulic tunnel plug works in general little, but as one of the the main control of the conditions, the demands of their schedule are more urgent. There is an extremely important meaning for the the construction of the latter part of the project whether completed the plug work smooth and timely. At present,《Specification for design of hydraulic tunnel》(SL279—2002)gives only general principles for the design of plug, however, there wasn’t one certain principles for the construction projects,and in fact, they developed their own design principles and selected parameters for one project. As the plug is very important for the safe of the hydro project and the design principles is not quite rational and any other reasons, the length of some plugs is too large to wasting, not only make the already relatively short duration lasted more tension, but also increased the project cost unnecessarily. Therefore, there are some theoretical significance and practical value in engineering for establishing the optimization method of plug design of plug by the analysis of the mechanical effect of the plug comprehensively.In this paper, based on the general principles of design of the hydraulic tunnel plug at home and abroad, firstly, with the JingJia dam’s hydro diversion tunnel project, simulated diversion tunnel’s rock mass and plug’s stress field and rock mass’s three-dimensional seepage field by finite element method using ANSYS10.0 software, and researthed the force characteristics of the rock mass and the plug based on the coupling of the seepage field and stress field. Secondly, enduced the correction formula of design of plug to consider the rock’s additional flexibility resistance by theoretical analysis. The main contents are as follows:1.) Based on analysis of the principles for some hydraulic tunnel’s plugs, summarized the problems of the current design method of plug and the factors that affect the stability of the plug;2.) With the JingJia dam’s hydro diversion tunnel project, established the three-dimensional elastic-plastic finite element model of the surrounding rock and pug of the diversion tunnel using ANSYS10.0 software, and researched the deformation and stability of the surrounding rock and the plug under the stress field;3.) With the JingJia dam’s hydro diversion tunnel project, established the three-dimensional seepage field model of the the impact of regional of surrounding rock in the Diversion tunnel plug running period. Analysed the the surrounding rock deformation by the influence of the seepage field,and then established the coupled model of seepage field and stress field;4.) By researthed the force characteristics of the rock mass and the plug based on the coupling of the seepage field and stress field, enduced the correction formula of design of plug to consider the rock’s additional flexibility resistance by elastic-plastic theoretical analysis.Through the above work, summarized the main conclusions and engineering experience are as follows:1.) In general, the plug was under pressure,and the tension and compression stresses are smaller and no more than the strength of plug concrete itself.;2.) Water pressure mainly beared by the friction on Contact surface of the plug and surrounding rock,and the friction gradually weakened from the upstream to downstream;3.) The tail of plug formated local plastic zone because of formed the invading surface as no water pressure inside the tunnel and the rock beared the elastic deformation of the plug itself;4.) Consider the beneficial effects by the additional elastic resistance of the surrounding rock, we can amend the plug’s conventional design methods,and the optimization of the formula can improve the stability against sliding plug to a certain extent;5.) Improved the rock elastic modulus is conducive to the stability against sliding of the plug, therefore, tunnel excavation should not only consider the characteristics of plug size but also to take into account the stability of the plug, to avoid to block the tunnel in the complicated cross-section shape and geological conditions;6.) It can not improve the stability of the plug by improving the strength level of concrete of plug, and the plug itself was too safe, therefore, there was no practical effect by improving the plug concrete’s strength grade for the safety of the plug;7.) To play the beneficial effects of the additional elastic resistance of the surrounding rock fully, the plug should be designed into the upstream section of large and small, wedge-shaped body of the downstream section, but the wedge angle of wedge-shaped body size should be appropriate, not the bigger the better.更多还原