小浪底无粘结环锚预应力混凝土衬砌结构应力状态及安全评价分析

发布时间：2018-08-30 19:09

【摘要】：无粘结环锚预应力混凝土衬砌结构是应用在水工隧洞中的一种新型结构形式，该结构主要适用于衬砌围岩地质条件较差，衬砌中的水压力较大，以及衬砌产生开裂之后水渗入围岩导致周围建筑物失稳的水工隧洞结构中。作为一种新型的结构形式，无粘结预应力混凝土衬砌具有其特殊的优点：衬砌中钢绞线采用双圈环绕的形式，使衬砌中的压应力分布更加均匀，锚索的沿程预应力损失更小，与有粘结衬砌相比有效预压应力增大，因此衬砌的厚度可以适当减小，这样就能够节省材料，减小开挖量，降低施工的难度和工程造价，有效的加快施工进度。鉴于无粘结环锚预应力混凝土衬砌具有的优势，这种结构在我国水工隧洞中有着广阔的应用前景。黄河小浪底排沙洞是我国第一例采用无粘结双圈环绕预应力混凝土衬砌这种结构形式的水工隧洞。在施工阶段，小浪底排沙洞中埋设了混凝土应变计、钢筋计、无应力计、锚索测力计、渗压计和测缝计等154支观测仪器。小浪底排沙洞从1997年施工，1999年投入运行，使用至今已十几年。在此期间，排沙洞经历了各种设计工况的考验。工程中所埋设的观测仪器积累了数万组观测数据。本文对这些采集的数据进行了系统的整理分析，以了解小浪底工程排沙洞在施工与运行过程中混凝土衬砌应力、应变发展变化的规律，从而判断结构是否合理和安全。本文应用ANSYS有限元分析软件对小浪底排沙洞进行建模分析，分别对锚索张拉阶段的施工期和加水压后的运行期的衬砌应力状态进行分析，并将结果与监测数据进行对比，看出两者具有很好的一致性。结果表明，在整个衬砌结构中，锚具槽部位的受力状态是最复杂的，最大最小环向应力均出现在锚具槽附近，轴向和径向还出现了较小的拉应力。针对在小浪底排沙洞衬砌施工和运行过程中暴露出的问题，尤其是锚具槽部位的漏油等现象，本文对小浪底排沙洞环锚预应力混凝土衬砌的结构设计方案、预应力筋的布置以及锚具槽的布置等内容进行优化设计，，并采用有限元软件模拟分析。研究结果表明：优化后的结构薄弱区范围明显减小，锚具槽附近的应力分布更均匀，具有明显的经济效益，对于今后的工程具有一定的参考价值。根据实测数据和模拟结果对整个无粘结预应力排沙隧洞段的安全使用状态进行评价分析，采用定性与定量结合的方法，并主要通过锚索测力计的监测数据、渗压计的监测数据、衬砌混凝土的应力状态这三个指标进行安全评价分析。结果表明，通过安全评价，认为排沙洞能保证正常使用，不会出现开裂和渗漏。文中建立的小浪底排沙洞施工和运行过程中的安全状态预警预报系统，可以对今后类似工程的设计优化和这种新型结构的推广使用提供依据。
[Abstract]:The unbonded ring anchor prestressed concrete lining structure is a new type of structure used in hydraulic tunnel. The structure is mainly suitable for the poor geological conditions of the surrounding rock of the lining and the high water pressure in the lining. And the structure of hydraulic tunnel where water seeps into surrounding rock and causes instability of surrounding buildings after cracking of lining. As a new type of structure, unbonded prestressed concrete lining has its special advantages: the steel strand in the lining is surrounded by double loops, which makes the distribution of compressive stress in the lining more uniform and the loss of prestress along the cable less. Compared with the bonded lining, the effective precompression stress increases, so the thickness of the lining can be reduced appropriately, which can save the material, reduce the amount of excavation, reduce the difficulty of construction and project cost, and effectively accelerate the construction progress. In view of the advantages of unbonded ring anchor prestressed concrete lining, this kind of structure has a broad application prospect in hydraulic tunnels in China. Xiaolangdi sand discharge tunnel of the Yellow River is the first hydraulic tunnel in China with unbonded double-ring surrounding prestressed concrete lining. In the construction stage, 154 observation instruments, such as concrete strain gauge, steel bar meter, non-stress gauge, anchor cable dynamometer, pressure gauge and joint gauge, are embedded in the Xiaolangdi sand discharge tunnel. Xiaolangdi sand drainage tunnel was constructed in 1997 and put into operation in 1999. It has been used for more than ten years. During this period, the sand drainage tunnel has experienced the test of various design conditions. The observation instruments embedded in the project have accumulated tens of thousands of observation data. In this paper, the collected data are systematically analyzed in order to understand the development and variation of concrete lining stress and strain during the construction and operation of the sand drain tunnel of Xiaolangdi Project, and to judge whether the structure is reasonable and safe. In this paper, ANSYS finite element analysis software is used to model and analyze the sand discharge tunnel in Xiaolangdi. The stress state of lining during the construction period of the tension stage of the anchor cable and the running period after adding water pressure are analyzed respectively, and the results are compared with the monitoring data. We can see that there is a good consistency between the two. The results show that the stress state of the slot is the most complex in the whole lining structure, the maximum and minimum circumferential stress appear near the Anchorage slot, and the axial and radial tensile stresses are smaller. In view of the problems exposed during the construction and operation of the Xiaolangdi sand drainage tunnel, especially the leakage of the Anchorage slot, the structural design scheme of the prestressed concrete lining for the ring anchor of the Xiaolangdi sand drain tunnel is presented in this paper. The layout of prestressing tendons and the arrangement of anchors are optimized, and the finite element software is used to simulate the design. The results show that the weak area of the optimized structure is obviously reduced, the stress distribution near the Anchorage slot is more uniform, and it has obvious economic benefit, which has certain reference value for the future engineering. According to the measured data and simulation results, the safe operation state of the whole unbonded prestressed sand discharge tunnel is evaluated and analyzed. The qualitative and quantitative methods are adopted, and the monitoring data of the anchor cable dynamometer and the osmotic pressure meter are mainly used. The stress state of lining concrete is evaluated and analyzed. The results show that, through safety evaluation, it is considered that sand drainage holes can be used normally without cracking and leakage. The early warning and prediction system of the safety state in the construction and operation of Xiaolangdi sand drainage tunnel can provide the basis for the design optimization of similar projects and the popularization and application of this new structure in the future.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV332

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