极端荷载作用下混凝土重力坝的动态响应行为和损伤机理

发布时间：2018-01-22 22:22

本文关键词： 混凝土重力坝动态响应损伤机理地震荷载爆炸冲击荷载失效模式损伤累积破坏　出处：《天津大学》2014年博士论文　论文类型：学位论文

【摘要】：随着坝工技术的发展，一大批100m~300m级的高坝建设进入快速发展阶段。在一般状态下，大坝正常的安全运行可以得到保障。然而我国高坝建设主要位于西南强震区域，由于地震动的不确定性，超过设计地震的地震动是存在并可能发生，当发生超设计地震时，大坝可能遭受破坏，抗震安全问题十分突出；同时高坝由于其显著的政治经济效益，无疑成为局部战争和恐怖爆炸袭击的重点攻击对象，大坝一旦失事，后果不堪设想。因此，对突发极端荷载作用下的大坝动态响应行为和损伤机理进行研究，评价高坝的抗震及抗爆安全性，是关系我国社会经济发展全局的防灾减灾重大工作中的重要内容，也是我国水利工程建设中必须面对的前沿性关键技术问题和重要战略课题。由于失事后果严重，突发极端荷载下的高混凝土坝安全及防护问题值得关注。对于混凝土重力坝而言，可能引发大坝灾变的极端荷载主要包括：强地震荷载和爆炸荷载。为了揭示强震及突发性爆炸冲击荷载下大坝的动态响应行为和损伤破坏机理，本文（1）从强震作用下混凝土重力坝的动态响应行为、断裂破坏过程、潜在失效模式及极限抗震能力评价方法；初始裂缝、强震持时、主余震地震序列、近断层地震动对大坝抗震性能的影响等方面，系统地研究了强震作用下混凝土重力坝的动态响应及损伤机理；（2）并从炸药在不同介质的爆炸过程、冲击波传播特性、边界效应；水下和空中爆炸冲击下的大坝毁伤特性；水下爆炸冲击下的大坝破坏效应、抗爆性能及损伤预测等方面，系统研究了爆炸冲击荷载下混凝土重力坝的动力行为和毁伤机理。主要创新工作内容如下：（1）探讨了大坝强震断裂破坏过程，概化出强震潜在失效模式基于扩展有限元基本理论，研究了强震荷载作用下混凝土重力坝的动态响应行为、渐进失效过程以及裂缝张开闭合行为，验证了该方法在分析混凝土重力坝地震破坏过程的可行性，并讨论了网格尺寸效应；分析了混凝土重力坝在不同水平地震作用下的动力渐进破坏过程、破坏形态和开裂破坏位置，概化出强震作用下混凝土重力坝的潜在失效模式，得到了混凝土重力坝的抗震薄弱部位。（2）建立了含初始裂缝的地震开裂模型，提出了极限抗震能力评价方法建立了含初始裂缝的混凝土重力坝地震开裂模型，探讨了初始裂缝对混凝土重力坝起裂时刻、开裂破坏过程、破坏模式、裂缝开展深度、及抗震性能的影响；从基于性能的抗震设防标准及理论出发，针对混凝土重力坝的结构特点，提出了混凝土重力坝极限抗震能力评价方法，该方法首先基于性能的地震破坏评价模型，初步评估大坝的极限抗震能力，同时根据大坝开裂破坏模式、抗滑稳定及坝基塑性区发展范围等方面进一步综合评价坝体-坝基系统的极限抗震能力。（3）建立了损伤累积破坏指标，系统讨论了强震对大坝抗震性能的影响利用能考虑混凝土软化并可反映实际损伤耗散能的混凝土损伤塑性模型，根据混凝土重力坝损伤开裂发展特征，建立了大坝局部和整体损伤累积破坏指标；基于能量持时的基本定义，对不同实测地震动的强震持时进行了预测，探讨了强震持时对混凝土重力坝损伤累积破坏的影响；建立了主余震地震序列的构造方法，通过将实测主震地震动和余震地震动前后连接起来形成了本文所采用的主余震地震序列，定量揭示余震作用对混凝土重力坝累积破坏的影响；采用Lagrangian算法建立了大坝-库水-地基系统的动力耦合模型，对比分析了近断层和远断层地震动作用下的混凝土重力坝动力响应行为和损伤累积破坏效应。（4）建立了水下爆炸气穴模型，探讨了不同边界条件下的冲击波传播机制建立了近边界面水下爆炸气穴效应模型，并验证了气穴模型的有效性；研究了自由面、结构面背水及结构面背空气对水下爆炸冲击波传播特性的影响；揭示了冲击波与自由面反射的稀疏波相互作用以及冲击波与结构面的动态相互作用过程；分析了入射冲击波与反射冲击波的叠加效应，以及由此导致的水面切断效应及气穴现象；探讨了冲击波在不同介质中的透射和反射机理，对比解析了冲击波在结构背水和背空气下的传播机制。（5）提出了大坝抗爆高效数值计算方法，分析了爆炸冲击下大坝毁伤特性建立了基于Lagrangian和Eulerian耦合方法的爆炸冲击荷载下混凝土重力坝全耦合模型，提出了适应大规模和高度非线性问题的高效数值计算方法；考虑爆炸作用下混凝土的高应变率效应、冲击波与结构的动态相互作用以及结构的动态响应等复杂问题，通过与已有的试验成果进行对比，，验证耦合模型的可靠性；研究了起爆介质对冲击波压力峰值、冲量、传播速度的影响；对比分析了水下和空中爆炸下大坝动态响应行为和毁伤特性。（6）探讨了大坝抗爆性能，首次提出了水下爆炸冲击下大坝损伤预测模型探讨了水下爆炸冲击荷载下混凝土重力坝的动态响应行为和破坏效应，分析了近大坝水下爆炸冲击波的传播特性；研究了起爆距离、炸药量、起爆深度及库前水位对混凝土重力坝破坏效应和抗爆性能的影响，获得了水下爆炸冲击下混凝土重力坝的毁伤机理、破坏模式及抗爆薄弱部位，并得到了预警放水的有效人防措施；根据水下爆炸冲击下混凝土重力坝的损伤破坏特征，建议了混凝土重力坝的损伤破坏等级分类，识别对重力坝破坏状态最具影响的因子，首次提出了水下爆炸冲击下混凝土重力坝损伤预测模型，划分了相应于不同破坏等级的重力坝损伤预测关键曲线，得到了水下爆炸冲击荷载下的混凝土重力坝安全起爆距离。
[Abstract]:With the development of dam construction technology, a large number of 100m~300m grade high dam construction has entered a rapid development stage. In general condition, the normal operation of the dam safety can be guaranteed. However, the construction of high dam in China are mainly located in the southwest region of strong earthquake ground motion, because of the uncertainty over the design of the ground motion is present and may occur when when the earthquake occurred over the design, the dam may suffer damage, seismic safety problem is very prominent; at the same time the dam because of its significant political and economic benefits, will undoubtedly become the explosion of local wars and terrorist attacks as key attack on the dam, once the accident, the consequences be unbearable to contemplate. Therefore, research on dam dynamic sudden extreme loads and response behavior the damage mechanism, seismic evaluation and anti explosion safety of high dams, disaster prevention and mitigation in China is the relationship between the development of economy and society in the important work of major In the construction of water conservancy projects in China, it is also an important and important strategic issue which must be faced with in the construction of water conservancy projects in China.
Because of the serious consequences of accident, safety and protection problem of high concrete dam burst under extreme load of concern. For the concrete gravity dam, the extreme load may lead to dam disaster include: strong earthquake and explosion load. In order to reveal the behavior and damage mechanism of dynamic response under the load of Dam Earthquake and sudden explosion, this paper (1) from the dynamic response behavior of concrete gravity dam under strong earthquake, the fracture failure process, failure mode and ultimate seismic capacity evaluation method; initial crack, strong motion duration, major aftershock, influence of near fault ground motions on the seismic performance of the dam and other aspects, systematically studied the dynamic response and damage mechanism of concrete gravity dam under the action of strong earthquakes; (2) and from the explosion of explosives in different medium, shock wave propagation characteristics, boundary effect; underwater and air explosion The damage characteristics of the dam under impact and the damage effect, blast resistance and damage prediction under the impact of underwater explosion are systematically studied. The dynamic behavior and damage mechanism of the concrete gravity dam under blast loading are systematically studied.
(1) to investigate the dam strong earthquake rupture process, generalizes the earthquake potential failure mode
Expansion based on the theory of finite element, studied the dynamic response behavior of concrete gravity dam under strong loading conditions, progressive failure process and the crack opening closing behavior, the validation of the method in the feasibility analysis of earthquake damage process of concrete gravity dam, the effect of mesh size are discussed; dynamic analysis of concrete gravity dam under different earthquake hazard levels of progressive failure process failure mode and crack position, generalizes the concrete gravity dam under strong earthquake. The potential failure mode of the concrete gravity dam of the weak parts.
(2) an earthquake crack model with initial cracks is established, and the evaluation method of ultimate aseismic ability is proposed.
A gravity dam model with initial cracking of concrete cracks, discusses the initial cracking time of concrete gravity dam, failure process, failure mode, crack depth, effect and seismic performance; from the performance of anti-seismic standards and theory which based on the structure characteristics of the concrete gravity dam, put forward seismic performance evaluation concrete gravity limit method, the method based on the performance of the seismic damage assessment model, a preliminary assessment of seismic capacity limit of the dam, at the same time according to the dam cracking failure mode, anti seismic capacity limit sliding stability and development of dam foundation plastic range and further comprehensive evaluation of dam foundation system.
(3) the damage cumulative damage index is established, and the influence of strong earthquake on the seismic performance of the dam is systematically discussed.
By considering concrete softening and can reflect the concrete damage plasticity model actual damage dissipation, damage and cracking of concrete gravity dam according to the characteristics of development, establish local and global damage dam cumulative damage index; the basic definition of duration based on different measured ground motion duration of earthquake forecast, discusses the influence of strong shock when the damage cumulative damage of concrete gravity dam; establish the structural methods of major aftershock, the measured ground motion and mainshock aftershock and link up to form the main aftershock earthquake sequences are used in this paper, the quantitative effect of aftershocks reveal the impact of cumulative damage of concrete gravity dam is established; the dynamic coupling model of dam water - foundation system using Lagrangian algorithm, comparison and analysis of near fault and far fault ground motion of concrete gravity dam under the action of moving Force response behavior and damage cumulative damage effect.
(4) the cavitation model of underwater explosion is established, and the mechanism of shock wave propagation under different boundary conditions is discussed.
The cavitation effect model established near edge interface of underwater explosion, and verifies the validity of the cavitation model; on the free surface, affecting the structure surface water and surface structure of air blast wave propagation characteristics of underwater; reveals the sparse wave and free surface reflection shock interaction and interaction process the shock wave and the dynamic structure; analysis of the incident wave and the reflected shock wave superposition effect, and the resulting water cut effect and cavitation; discusses the shock wave in different media transmission and reflection mechanism, the contrastive analysis of the propagation mechanism of shock wave in the structure of water and air back back.
(5) a numerical calculation method for the high efficiency of the dam is put forward, and the damage characteristics of the dam under the explosion impact are analyzed.
The establishment of the concrete gravity dam full coupling model of blast load coupling and method of Lagrangian based on Eulerian, is proposed to meet the large-scale and highly efficient numerical calculation method considering nonlinear problems; high strain rate effect of concrete under explosion, shock wave and the dynamic interaction between the structure and the structural dynamic response and other complex issues, comparison through the test results and the reliability of the coupling model is verified; the initiation medium impulse pressure of shock wave peak, influence propagation velocity; comparative analysis of the dynamic response of the dam under explosion behavior and damage characteristics of water and air.
(6) the anti explosion performance of the dam is discussed, and the dam damage prediction model under underwater explosion shock is proposed for the first time.
To explore the underwater explosion shock load of concrete gravity dam under the dynamic response and damage effect, analysis of the propagation characteristics in the dam of the underwater explosion shock wave; study initiation distance, quantity of explosive, detonation depth and effect of water level on the library before the concrete gravity dam failure effect and anti explosion performance, the damage mechanism of concrete gravity dam water blast, failure modes and blast resistant weak parts, and the effective measures of water air defense warning; according to the failure characteristics of concrete gravity dam damage to underwater explosion, proposed concrete gravity dam damage classification, the most influential factor of dam damage identification, is proposed for the first time prediction model of underwater explosion under the impact of concrete gravity dam, corresponding to different damage level of the gravity dam damage prediction curve has been divided, underwater explosion The safety initiation distance of the concrete gravity dam under the blast impact load.

【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】：TV642.3

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