Generally speaking, the pilot heading is aways used for geological exploration, speeding up the construction, improving the draining and Ventilation condition, promoting efficiency of residue transporting. When tunneling on high ground stress soft rock region, the pilot heading will play a more important role. Lan yu line Mu Zhai ling tunnel main passes through the region of carbonaceous slate. Due to the high ground stresses, the primary reinforcement system underwent large deformation, evenmore the lining is cracked. Through excaving the pilot heading, can relief the stress. Then enlarg the pilot heading to main tunnel, the deformation of primary support will be reduced, and the tunnel will be stable. Compare the "pilot and enlarging" excavation method with bench excavation method on surrounding rock deformation. As the result, the "pilot and enlarging" excavation method is effective for control of the deformation of the tunnel.
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