On the morning of May 22, the right tube of the Baowukou Tunnel under the Linjian 3 Contract of Zhejiang Jiaogong Road & Bridge Construction, a subsidiary of Zhejiang Communications Group, was successfully holed through, marking a breakthrough in the project's construction. It is the first tunnel in this contract section to be completed and the first long tunnel over 2,000 meters to be holed through along the entire Linjian project line.

The Baowukou Tunnel is a separated tunnel, with the right tube 2,207 meters long; construction began on March 31, 2020. The tunnel was excavated from both ends. At the entrance end, the geological rock strata are weak and fractured and change frequently, and the terrain is steep; there is a 16-meter height difference between the portal and the existing Provincial Road 208, making excavation extremely difficult and posing high safety risks. At the exit end, there were problems such as the difficulty of relocating high-voltage transmission towers.

Under heavy pressure, in order to achieve early holing-through of the tunnel, the Linjian 3 Contract took multiple measures: first, it held several safety and technical briefing meetings, carefully prepared construction plans, and strictly followed the principles of "advance pipe forepoling, short advance, weak blasting, strong support, early sealing, and frequent measurement" for construction in Grade V surrounding rock sections; second, in response to the excessive height difference at the tunnel entrance, the project carefully calculated the slope and built a safe construction access road by filling 30,000 cubic meters of slag; third, wet-mix shotcrete technology was used during construction to accelerate the cycle of initial tunnel support while improving the quality of the wet-mix shotcrete and reducing safety risks; fourth, several SCORE meetings were held to pool the strength and wisdom of the workforce and provide strong support for the construction of the Baowukou Tunnel.

The Baowukou Tunnel is a key controlling project of the Linjian 3 Contract, and the expected goal of "zero accidents" was successfully achieved. Next, the Linjian 3 Contract will continue to maintain the good momentum, further strengthen management while ensuring construction quality, and ensure that the left tube of the tunnel is holed through in mid-June, accelerating toward building a quality project.