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DTIC ADA092013: Tunnel Boring Machine Technology for a Deeply Based Missile System. Volume II. State-of-the-Art Review.

Technical feasibility and cost studies were made for a deep-based missile (DBM) tunnel system (Mesa concept) by means of tunnel boring machines (TBMs), along with designing an egress machine for post-attack tunneling through approximately 2,500 feet of probably unstable rock to the rubble zone. Currently, available designs of TBMs are readily adaptable for the conventional excavation in geologic environment considered suitable for DBM siting. Most, if not all, of the tunnel sections in the rocks of anticipated structure and strength will require support varying from simple rock bolting to concrete segments. Current (1979) costs for similar tunnels (Chicago) vary from $600 to $800 per linear foot of tunnel, while the estimated costs for the DBM tunnels average as high as $1,600 per foot because of the greater depths, weaker rock, longer tunnels, possible remoteness geographically, and other related factors. Two concepts for egress machines have been proposed by the Robbins and Jarva companies. The details of use of geotechnical data are given in Appendix A and were qualitatively for estimates of support requirements and costs. The only calculation that could be made based upon avail

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