高碾压混凝土拱坝地震破坏机理模型试验研究

发布时间：2018-07-29 09:08

【摘要】：随着我国水利事业的蓬勃发展,一大批拱坝已经或正在建设,拱坝的抗震安全显得尤为重要。强震作用下,高碾压混凝土拱坝的破坏机理极其复杂,影响因素众多。尽管目前数值模拟成为研究高坝强震破坏机理的主要途径,但是动力模型试验仍不失为一种重要方法,且我国《水电工程水工建筑物抗震设计规范》(NB 35047-2015)规定当设计烈度为Ⅷ度及以上且高度超过150m的甲类工程大坝,宜进行动力模型试验。高坝动力模型试验的仿真材料、模型技术以及测试方法等仍不够完善,尤其是在强震作用下拱坝结构缝的非线性行为、水平薄弱层的影响、大坝-库水相互作用等方面仍然存在诸多挑战。本文为了探究拱坝强震下结构缝、水平薄弱层以及坝库相互作用,进行了一系列的试验研究,具体包括模型材料试验研究、损伤监测技术方法研究、振动台破坏试验以及数值仿真等。主要研究内容如下：(1)研制了一种具有高密度、低弹模、低抗拉强度且脆性良好的高坝模型材料。针对不同应变速率下模型材料单轴拉伸与压缩本构关系进行了一系列试验研究,得到了模型材料在动力作用下的应力一应变曲线方程,以及极限强度、峰值应力处应变、弹性模量、泊松比和吸能能力与应变速率的关系,且与原型材料的率相关性进行对比,为高坝动力模型试验再现原型拱坝的破坏机理提供材料依据,并为数值研究提供材料参数(本文第二章)。(2)发展了一种高拱坝动力模型试验的损伤监测方法,用以实现对高坝模型动态应力以及结构损伤的监测。模型试验前先利用正压电效应在不同加载速率下进行了传感器标定试验;采用均方根指数定义损伤指数,通过预试验来验证损伤监测方法的有效性。在此基础上,把分布式传感器网络嵌入高坝模型内部,构造路径-时程损伤指数矩阵来表征模型的损伤位置和损伤过程,通过模型试验验证了此方法的可行性。此方法与传统高坝模型测试方法互相补充,提高拱坝动力模型试验测试精度,揭示模型损伤破坏规律(本文第三章)。(3)在模型材料研究与损伤监测技术研究的基础上,通过高坝动力模型破坏试验,分步骤地研究结构缝以及水平薄弱层对拱坝地震破坏机理以及失效模式的影响。模型的建立基于弹性力-重力相似准则,相似关系设计时考虑了原模型材料力学特性率敏感性。模型横缝模拟考虑键槽影响,诱导缝模拟基于断裂力学理论,同时进行含薄弱层的模型材料动态劈拉试验。结果表明,结构缝能够在地震中释放坝体内部应力,提高拱坝整体超载能力；薄弱层的存在没有显著降低坝体整体超载能力,主要影响为拱向约束减弱后,梁向位置进入悬臂梁加载模式后的失效模式。试验成果丰富了高拱坝动力模型试验的研究内容,为优化拱坝抗震设计、评估拱坝抗震安全提供科学依据(本文第四、五章)。(4)以天然水模拟库水,利用拱坝动力模型试验方法研究了库水作用下拱坝动力响应与失效模式。将试验结果与不考虑库水影响的试验进行对比,发现库水使拱坝处于预压状态,充分发挥拱坝耐压的受力特点,较之空库状态更有利于坝体安全。考虑到相似关系要求和实际条件,通过数值分析方法研究了模型库水密度对试验结果的影响。数值模型坝体的非线性本构选用混凝土损伤力学模型,材料参数通过力学性能试验获得,结构缝的模拟采用内聚力单元,通过空库试验结果校核数值模型。数值结果表明,不同库水密度主要对坝体上游面拉主应力分布有影响,对失效模式的影响可以忽略。目前还没有找到更加经济实用且满足相似关系的液体时,天然水模拟库水不失为一种有效的办法(本文第六章)。
[Abstract]:With the vigorous development of water conservancy in China, a large number of arch dams have been or are being built, and the seismic safety of arch dams is particularly important. Under strong earthquakes, the failure mechanism of high RCC arch dam is extremely complex and many factors affect it. Although numerical simulation has become the main way to study the mechanism of high dam strong earthquake damage, the dynamic model The test is still an important method, and the code for seismic design of hydraulic engineering of Hydropower Engineering (NB 35047-2015) stipulates that the dynamic model test should be carried out when the design of a class a dam with a degree of VIII and above and higher than 150m. The imitation real material, the model technology and the testing method of the dynamic model test of the high dam are still not enough. It is perfect, especially for the nonlinear behavior of arch dam structure joint under strong earthquake, the influence of the horizontal weak layer, the interaction of dam and reservoir water, and so on. In this paper, a series of experimental studies are carried out to explore the structural seams, the horizontal weak layers and the dam bank interaction under the strong earthquake of the arch dam, including the model material test. Research, damage monitoring technique, vibration table failure test and numerical simulation. The main contents are as follows: (1) a high density, low elastic modulus, low tensile strength and good brittleness of high dam model materials are developed. A series of tests on the constitutive relation of the uniaxial tension and compression of the model materials under different strain rates are carried out. The stress-strain curve equation of the model material under dynamic action, and the relationship between the ultimate strength, the strain of the peak stress, the modulus of elasticity, the modulus of elasticity, the Poisson's ratio, the energy absorption capacity and the strain rate are obtained, and the correlation between the strain rate and the prototype material is compared, which provides the material for the failure mechanism of the arch dam in the dynamic force model test of the high dam. Material parameters are provided and material parameters are provided for Numerical Research (second chapter). (2) a damage monitoring method for dynamic model test of high arch dam is developed to monitor dynamic stress and structural damage of high dam model. Before the model test, the positive piezoelectric effect is used to calibrate the sensor under the same loading rate. The damage index is defined by the root mean square index, and the effectiveness of the damage monitoring method is verified by pre test. On this basis, the distributed sensor network is embedded into the high dam model and the path time history damage index matrix is constructed to characterize the damage location and damage process of the model, and the feasibility of this method is verified by the model test. It is complementary to the traditional high dam model testing method, to improve the test precision of dynamic model test of arch dam and to reveal the law of damage and damage of the model (third chapter). (3) on the basis of the research of the model material research and damage monitoring technology, the structural seams and the horizontal weak layers are studied step by step through the failure test of the dynamic model of the high dam. The mechanism of earthquake damage and the effect of failure mode. The model is based on the elastic force gravity similarity criterion, and the sensitivity of the original model material mechanical characteristic is considered when the similarity relation is designed. The model transverse joint simulation considers the keyway, the induced seam simulation is based on the fracture mechanics theory, and the dynamic splitting test of the model material containing the weak layer is carried out at the same time. The results show that the structural joints can release the internal stress of the dam in the earthquake and improve the overall overload capacity of the arch dam. The existence of the weak layer does not significantly reduce the overloading capacity of the whole dam, and the main effect is the failure mode after the arch constraint is weakened and the beam position enters the cantilever beam loading mode. The test results enrich the dynamic model test of the high arch dam. The research content of the study provides a scientific basis for optimizing the seismic design of arch dams and evaluating the seismic safety of arch dams (fourth, fifth chapters). (4) using natural water to simulate the reservoir water, the dynamic response and failure modes of arch dams under the action of reservoir water are studied by using the dynamic model test method of arch dam. The present reservoir water makes the arch dam in preloading state, giving full play to the stress characteristics of the arch dam, which is more beneficial to the dam safety than that of the empty reservoir. Considering the similar relationship requirements and the actual conditions, the influence of the water density of the model reservoir on the test results is studied by the numerical analysis method. The nonlinear constitutive model of the numerical model dam is selected to select the concrete damage force. The material parameters are obtained by the mechanical performance test. The cohesion unit is simulated by the cohesive unit, and the numerical model is checked by the results of the empty reservoir test. The numerical results show that the water density of the different reservoirs is mainly influenced by the distribution of the main stress in the upper reaches of the dam, and the effect on the failure mode can be ignored. When using liquids that satisfy similar relations, natural water simulation is an effective method (the sixth chapter).
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV642.4

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