State of the Art: Rock Tunnelingby Edward J. Cording,
Abstract: In the past twenty years, improvements have been made in the quality of geotechnical information on tunnel projects. Even with good exploratory information, it remains difficult to predict the effect of rock conditions on support and lining behavior, particularly for deep rock tunnels. With the advent of tunnel boring machines, rates of advance have increased dramatically. They have been increasingly used in difficult ground conditions where rock stability around the machine must be controlled to maintain advance rates. Large underground chambers, both deep and shallow, are being excavated in difficult ground conditions, taking advantage of the ability to stabilize the openings with tied-back and continuous supports. Many more construction tools and procedures are available, and there is a growing understanding of the conditions in which their use is appropriate. The evaluation of performance is important for understanding the often subtle rock behavior effecting tunnel excavation and support. Index properties can be correlated with performance if the mechanisms controlling behavior are understood. Two contrasting groups of case histories in which field measurements were carried out are summarized: small, deep tunnels in highly stressed ground, and large chambers at shallow depth.
Subject Headings: Tunnels | Rocks | Construction equipment | Information management | Excavation | Case studies | Linings
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