引汉济渭深埋隧洞衬砌外水荷载应对措施减载规律及应用研究

发布时间：2018-08-24 08:15

【摘要】：引汉济渭引水隧洞穿过秦岭，开挖距离长，围岩地质构造复杂多变，地下水水位高，在这种情况下隧洞开挖和衬砌过程中产生高渗压和高地应力问题，渗流场与应力场间的耦合作用不容忽视。在耦合作用情况下，衬砌上外水荷载的作用不再是单纯是水压力，还需要考虑围岩渗透变形作用；相应地，外水荷载应对措施的减载规律有了新变化。本文采用考虑渗透体积力和渗透系数动态演化方程的流固耦合控制方程，考虑围岩衬砌的联合承载作用而将其作为整体结构进行建模分析，应用有限元软件ABAQUS对开挖与衬砌灌浆等施工工序进行仿真模拟，对外水荷载在衬砌上的作用机理和堵排水措施减载规律以及应用情况进行了研究。首先建立围岩-衬砌整体结构的二维有限元模型，确定边界条件和模型参数，对开挖-衬砌过程进行模拟。基于流固耦合的原理，分析这一过程中围岩-衬砌结构-水相互作用机理。其次在原有模型基础上，增加灌浆堵水和排水管排水的模拟，通过对灌浆圈渗透参数和排水管长度、数量、布置位置等方案减载效果的对比，分析基于上述响应机理下堵排水措施的减载规律。最后基于动态施工的理念，建立三维有限元模型，反映隧洞施工中空间和时间特征，分析开挖时掌子面、未衬砌围岩、已衬砌围岩三者相互影响的动态过程，为引汉济渭隧洞工程提供应力场和渗流场的动态预测计算结果。通过研究，本文得出结论如下：一、围岩与衬砌结构作为整体联合承载时，在渗流场-应力场耦合作用下，围岩中的渗流体积力同样会间接作用于衬砌结构；在衬砌施工过程中，过大的涌水进入衬砌浇筑模板，带走未凝结的材料，形成结构的缺陷从而改变衬砌结构的渗流特性，导致衬砌上应力的不利分布，这是由地下水渗流产生，在应对衬砌高外水荷载时应该考虑这两种作用的存在。二、为减小对工程区环境影响，灌浆圈渗透系数建议取表层围岩的1/40。灌浆圈与衬砌渗透系数比值小于1时，灌浆措施减载效率扩大2倍，但会增大围岩对衬砌挤压应力1.04倍，应提高其刚度或设置预留变形和柔性垫层。在多排水管布置时顶部排水管的减载作用最大，但是它的减载效果又取决于灌浆圈与衬砌渗透系数比值，，在0.2~1.6之间时效果最佳并且可以将之伸入灌浆圈进一步减载，但是大于5时反而会增大衬砌上应力。衬砌浇筑时模板内防排水和使用防水添加剂是防治渗透破坏的有效措施。三、建立的三维模型为动态施工提供了实时仿真模拟，保障工程设计和施工的安全合理。同时为考虑材料属性的各向异性和空间变异性，有限元计算模型需要结合现场监测，实时进行地下水分布调查、围岩参数反演和室内材料试验。监测、反演、试验、仿真模拟四者相互结合。
[Abstract]:When the diversion tunnel from Han to Jiwei passes through the Qinling Mountains, the excavation distance is long, the surrounding rock geological structure is complex and changeable, and the groundwater level is high. In this case, the problems of high seepage pressure and high ground stress occur during the excavation and lining of the tunnel. The coupling effect between seepage field and stress field can not be ignored. In the case of coupling, the effect of external water load on lining is no longer simply water pressure, but also need to consider the seepage deformation of surrounding rock; accordingly, the law of load reduction of external water load response measures has new changes. In this paper, the fluid-solid coupling governing equation considering the dynamic evolution equation of permeability volume force and permeability coefficient is used to model and analyze the surrounding rock lining as a whole structure. The finite element software ABAQUS is used to simulate the construction processes such as excavation and lining grouting. The mechanism of external water load acting on the lining, the law of load reduction of plugging and drainage measures and its application are studied. Firstly, a two-dimensional finite element model of surrounding rock lining structure is established, boundary conditions and model parameters are determined, and the excavation lining process is simulated. Based on the principle of fluid-solid coupling, the mechanism of wall rock-lining structure-water interaction in this process is analyzed. Secondly, on the basis of the original model, the simulation of grouting water shutoff and drainage pipe is added, and the load reduction effect of grouting ring seepage parameters and drainage pipe length, quantity, layout and so on is compared. Based on the response mechanism mentioned above, the law of load reduction of water plugging and drainage measures is analyzed. Finally, based on the concept of dynamic construction, a three-dimensional finite element model is established to reflect the spatial and temporal characteristics of tunnel construction. The dynamic prediction results of stress field and seepage field are provided for the diversion of Hanji-Wei tunnel. The conclusions of this paper are as follows: first, when the surrounding rock and lining structure are combined as a whole, under the coupling of seepage field and stress field, the seepage volume force in the surrounding rock will also act indirectly on the lining structure; In the course of lining construction, excessive water gushing into the lining pouring formwork, taking away uncondensed materials, forming structural defects, thus changing the seepage characteristics of the lining structure, leading to the unfavorable distribution of the lining stress, which is caused by groundwater seepage. The existence of these two functions should be considered in response to high external water loads of lining. Second, in order to reduce the environmental impact on the engineering area, the permeability coefficient of grouting ring is suggested to take 1 / 40 of the surrounding rock surface. If the ratio of grouting ring to lining permeability coefficient is less than 1, the load reduction efficiency of grouting measures will increase by 2 times, but the extrusion stress of surrounding rock to lining will increase by 1.04 times, so the stiffness of grouting ring and lining should be increased or reserved deformation and flexible cushion should be set up. The load reduction effect of the top drain pipe is the greatest when the multi-drain pipe is arranged, but its load reduction effect depends on the ratio of the grouting ring to the lining permeability coefficient, and the effect is the best when the ratio of grouting ring to lining permeability coefficient is between 0.21,6 and can be further reduced by extending it into the grouting ring. But more than 5 will increase the stress on the lining. Waterproof drainage and waterproof additive are effective measures to prevent seepage damage. 3. The three-dimensional model provides real-time simulation for dynamic construction, and ensures the safety and reasonableness of engineering design and construction. In order to consider the anisotropy and spatial variability of material properties, the finite element model should be combined with field monitoring, real-time investigation of groundwater distribution, parameter inversion of surrounding rock and laboratory material test. Monitoring, inversion, testing, simulation of the four combined.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV672;TV31

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