Field monitor and research of optimizing design on deep buried road tunnel in loosen and fractured layer

In order to probe into the properties of deep buried road tunnel in loosen and fractured layer, the group have monitored some items, including ground surface settlement, net space convergence, and stress of steel arch centering, strain of steel arch centering. Based on the monitoring results, we point out that the best time of influence sphere of time and space during tunnel excavation under this geology conditions, and analyse the stress properties of surrounding rock and supporting system. The analysis results provide basis for optimizing design, and the optimized supporting parameters meet the requirement of stress according to theoretical calculation. The conclusion can serve as example to other projects in design, construction and monitor under similar condition.