Stand-up Time of Jointed Rock Masses in Underground Excavations

支撑时间是指开挖后无支撑隧道在坍塌前保持稳定的时间。在地下采矿和土木隧道施工中，巷道掘进工作面附近岩石支护系统的设计和安装与站场时间密切相关。如果能准确地估算出开挖时间，就有可能优化开挖周期，大大提高隧道的推进速度。遗憾的是，目前估计站立时间的方法仍然基于Bieniawski在1976年提出的方法，这表明站立时间预测存在很大的不确定性。本研究面临的挑战是更好地了解岩体的行为，并提供解决方案，以更准确地评估在岩体中开挖的隧道的直立时间。基于提高岩石力学和采矿科学知识的需要，我们建议研究时变岩石破坏现象，了解影响站起时间的机制，建立时变岩石破坏模型并使用实验室和现场数据验证该模型，研究岩石支护如何提高站起时间，并将结果应用于地下开采。将采用的方法是结合实验和现场观测以及使用先进数值工具的数值模拟的应用。计算节理岩体中开挖隧道的站起时间，开发考虑开挖跨度、岩体质量、覆盖层深度、开挖形状等因素的站起时间估算新图表。许多矿山在开挖周期结垢后立即使用喷射混凝土。本研究将定量研究喷射混凝土对提高直立时间的影响。本研究的研究结果有助于更好地理解岩石随时间变化的基本问题，并为采矿和民用隧道行业提供更准确地估计站立时间的工具。这项调查的潜在成本效益是显著的，因为它为加拿大矿业公司提供了一个有用的工具，以做出与隧道开发中的岩石支护相关的重要决策，从而提高安全性和生产力。

Stand-up time is the time that an un-supported tunnel would remain stable after excavation before it collapses. In underground mining and civil tunneling, the stand-up time is closely related to design and installation of rock support systems near tunnel advancing faces. If the stand-up time can be assessed accurately, it is then possible to optimize the excavation cycle and increase the tunnel advance rate considerably. Unfortunately, the current method of estimating stand-up time is still based on the method proposed by Bieniawski in 1976, which shows a large uncertainty in stand-up time prediction.The challenge in this research is to better understand the behaviour of rock mass and provide solutions to assess stand-up time of tunnels excavated in rock masses more accurately. Based on the need to advance knowledge in rock mechanics and mining science, we propose to study the phenomenon of time-dependent rock failure, understand the mechanisms that govern stand-up time, develop a time-dependent rock failure model and verify the model using laboratory and field data, study how rock support enhances stand-up time, and apply the result to underground mining. The approach to be adopted is a combined application of experimental and field observations and numerical modeling using advanced numerical tools. Stand-up time of tunnels excavated in jointed rock masses will be calculated and new charts for stand-up time estimation considering factors such as excavation span, rock mass quality, overburden depth, and excavation shape will be developed. Many mines apply shotcrete immediately after scaling in an excavation cycle. The effect of shotcrete on stand-up time enhancement will be studied quantitatively in this study.The research findings from this study can contribute to a better understanding of the fundamental problem of time-dependent behaviour of rocks and provide a tool for the mining and civil tunneling industries to estimate stand-up time more accurately. The potential cost-benefits of this investigation are significant because it provides Canadian mining companies a useful tool to make important decisions related to rock support in tunnel development so as to improve safety and productivity.