Soft ground tunneling in the vicinity of existing structures is a major challenge to tunneling engineers. Tunneling works cause inevitable ground movements that may lead to unrecoverable damages to adjacent structures. Tunneling rates significantly affect such risks. However, a guideline that determines appropriate tunneling rates and accounts for the effects of tunneling on the structures existing in the vicinity is not available. Tunneling records in terms of TBM advance speed (AS), utilization factor (U), and advance rate (AR) for tunnels constructed without causing significant risks on the existing structures are presented in the paper. These records are discussed for different types of existing structures. Ranges of these records for tunneling without causing detrimental effects on different types existing structures are recommended. Useful observations are also made on the variation of these records with the ground type and composition and the precautions to be adopted to mitigate the tunneling risks on existing structures. |
