灾变条件下高拱坝整体失效分析的理论与方法

THEORY AND METHODS OF HIGH ARCH DAM'S ENTIRE FAILURE UNDER DISASTER CONDITIONS

为了发展国民经济,充分利用水资源和水能资源,我国在建和拟建的十多座高拱坝高度在200m以上,达到300m量级,无论是建设规模还是建设难度均为世界之最,存在不少具有挑战性的科学技术问题。它们大多建于西部高山峡谷地区,地形地质条件复杂、环境恶劣、地震烈度高,严重威胁高拱坝的安全。因此,高拱坝在灾变条件下的破坏机制和安全评估一直是坝工专家高度关注的问题。高拱坝的整体破坏机制和相应的分析方法是拱坝安全性研究的主要内容之一,但至今对整体破坏的力学机制没有统一的认识,也没有一个具有力学理论基础的可行方法。该文简略介绍拱坝现行的安全性校核方法,指出存在的问题。根据力学系统的稳定性理论,揭示了高拱坝整体破坏的本质是稳定性问题。基于其破坏过程中荷载位移曲线的特征,论证了高拱坝的失稳破坏是一种由于材料非线性引起的、始于强度破坏的物理不稳定现象,失稳形式为极值点失稳。展示了拱坝整体稳定性的一些分析方法,指出基于弹塑性渐进分析的间接法是目前进行拱坝整体稳定性的可行方法,并通过物理模型试验验证了数值模拟的正确性;同时,也指出该方法并非直接从力学系统稳定性理论导出,科学的分析方法与失稳破坏判据应通过物理扰动方程的研究得到。揭示了非线性对拱坝极限承载能力的影响,理想弹塑性本构和几何线性处理均会高估拱坝的极限承载能力,偏于不安全。给出应用突变理论确定大坝极限承载能力的条件。提出确定极限承载能力的最大弹性变形能判据。

In order to develop national and civil economy, make full use of water resources and hydropower resources, more than a dozen of over 200 meter-high and even 300-meter high arch dams are being building and will be built in China, both whose scale and difficulties of construction are the greatest in the world, and many challenging scientific and technological problems come along as well. Most of these high arch dams are built in western alpine and gorge region where topographic and geologic conditions are very complex, with bad environment and high seismic intensity. All these threaten safety of high arch dams seriously. Thus, failure mechanism and safety assessment of high arch dam under disaster conditions has always been a highly concerned issue to dam experts. The global failure mechanism and analysis methods of high arch dam accordingly are the main content of safety research for arch dam, however, there is no uniform understanding of mechanics mechanism of global failure and feasible methods based on mechanics theory. In this paper the current safety assessment methods are introduced briefly and the open problems are pointed out. According to stability theory of a mechanics system, it is demonstrated that the essence of the global failure＇ of a high arch dam is stability issue.According to the features of the load-displacement curve in its failure progress, failure of a high arch dam belongs to the physical instability problem caused by non-linear material, started in local strength damage, which is the extreme point destabilization. Some analysis methods of the global stability for a high arch dam are presented, in which the Indirect Method based on elastic-plastic progressive analysis is considered to be a feasible method at the present time to study the global stability of the high arch dam, which is verified by physical model test. However, the Indirect Method is not derived directly from stability theory of a mechanics system, and the scientific analysis method and the destabilization criterion should be obtained from the physical disturbance equations. And the effect of the non-linearity on the ultimate bearing capability （UBC） of a high arch dam is shown, the perfect elastic-plastic constitutive relationship and geometric non-linearity make the capability to be overestimated, which is unsafe. Moreover, to determine the UBC of a dam, the criterion based on maximum elastic strain energy and the condition based