Effect of cycling temperature on propagation of tensile fatigue cracks in concrete mass dams

循环温度对混凝土大坝拉伸疲劳裂纹扩展的影响

• 批准号: 543903-2019
• 负责人: Svecova, Dagmar
• 金额: $ 5.8万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Collaborative Research and Development Grants
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=720822
• 关键词: Effect; cycling; temperature; propagation; tensile

A stability review of monolithic concrete dams in Manitoba discovered that if a crack was initiated by cyclic thermal stress, the subsequent increase in internal water pressure via the crack would cause the crack to propagate leading to increased risk of instability of the structure. Manitoba Hydro initiated a project to review, research and test to ensure the tensile strength of the concrete, particularly at construction joints, can continue to be relied on to provide the cohesion necessary for safety against sliding failure. Research and testing of concrete is required to evaluate strength deterioration due to thermal cycling. The finite element analysis (FEA) performed as part of the stability review shows that the seasonal warming and cooling of the mass concrete structure generates an annual cycle of differential movement causing the stress in the upstream face of the dam to shift between tension and compression. The risk to the dam stability from crack propagation initiated by these temperature cycles and subsequent tensile fatigue in mass concrete are not well understood. This project will help to estimate the rate of crack growth under thermal cycling. The objective of this study is to investigate the impact of the temperature fluctuations and resulting cyclic tensile and compressive stresses on the long-term durability of concrete, and the impact on the durability of the construction joints. This study will train nine HQP, three each at the Master's and Bachelor's level, one Ph.D. student and two post-doctoral fellows. This research will enable Manitoba Hydro and other dam owners to assess the safety of these structures against possible instability due to cracking. The results will inform the ongoing Manitoba Hydro dam safety program through better understanding of threats to stability as well as modifications to monitoring and surveillance, if required.

对曼尼托巴省单块混凝土大坝的稳定性评估发现，如果裂缝是由循环热应力引起的，随后通过裂缝的内部水压的增加将导致裂缝扩展，从而增加结构不稳定的风险。马尼托巴水电公司启动了一个项目来审查、研究和测试，以确保混凝土的抗拉强度，特别是在施工接缝处，可以继续提供必要的凝聚力，以防止滑动破坏的安全。为了评估热循环引起的混凝土强度退化，需要对混凝土进行研究和试验。作为稳定性评估的一部分进行的有限元分析（FEA）表明，大体积混凝土结构的季节性增温和降温产生了一个年度周期的微分运动，导致大坝上游面的应力在拉压之间转换。由这些温度循环和随后的大体积混凝土拉伸疲劳引起的裂缝扩展对大坝稳定性的风险尚未得到很好的理解。这个项目将有助于估计热循环下的裂纹扩展速率。本研究的目的是探讨温度波动和由此产生的循环拉压应力对混凝土长期耐久性的影响，以及对施工缝耐久性的影响。本研究将培养9名HQP，其中硕士和学士各3名，博士生1名，博士后2名。这项研究将使曼尼托巴水电公司和其他水坝所有者能够评估这些结构的安全性，防止可能因开裂而不稳定。研究结果将为正在进行的曼尼托巴水电站安全项目提供信息，帮助他们更好地了解大坝稳定性面临的威胁，并在必要时对监测和监视进行修改。