Risk Assessment And Control In Construction Progress Of Shallow Buried And Soft Rock Tunnel Beneath Existing Highway

In order to evaluate the construction risk of shallow buried and soft rock tunnels beneath existing highway, the efficacy coefficient method is used to prevent safety accidents. The surface settlement, vault settlement, peripheral convergence, rock quality designation, groundwater observation, working face observation, primary support structure observation, and pavement observation are selected as evaluation indexes. The risk assessment model of tunnel's construction based on the efficacy coefficient method was established. Then the model is applied to the Diantou tunnel of Dali-Yongsheng highway in Yunnan Province. The results show that the construction risk of the left tunnel is extremely high and the warning level is serious warning. By comparison, the risk grade of the right tunnel construction is relatively lower and the warning level is moderate warning. The existing construction measures cannot meet the safety requirements for the crossing section and need to be adjusted in time. Through comprehensive analysis, some measures such as closing partial lane, reinforcing working face, strengthening the primary support, adjusting the advanced support plan, closing primary support in time and speeding up the construction of second lining, are used in construction. These measures avoid the occurrence of tunnel disasters, and ensure the safety and success of the tunnel's construction.