The structure of the Hsuehshan Tunnel is generally sound and does not pose any threat to motorists, according to the preliminary report of a special taskforce commissioned by the Ministry of Transportation and Communications (MOTC).
The taskforce, led by Yang Yeong-bin (
The taskforce's main objective yesterday was to determine whether the tunnel structure is safe, Yang said.
However, the taskforce has yet to identify the cause of water leaks in the tunnel, he added.
Yang said at a press conference yesterday evening that the rock in which the tunnel was bored could bear a tremendous amount of weight from above.
The water leaks occur in the concrete lining between the tunnel's inner wall and a waterproofing membrane, he said.
The lining is comprised mainly of concrete and steel.
Yang said that the concrete lining would not collapse, and any deformation or displacement in its structure would only become apparent with long-term monitoring.
The tunnel's waterproofing membrane should function as a conduit to drain off underground water and reduce the water pressure, he said.
The Taiwan Area National Expressway Engineering Bureau will have to use more than just grouting to fix the water leak, with different methods being applied under different circumstances, he added.
"You cannot use some back-country method to fix a five-star construction," he said while commenting on the measures that the bureau has already taken.
Yang suggested that cross-sectional scanners be installed to monitor any abnormality in the concrete lining.
He also advised the bureau to purchase vehicles specifically used for tunnel maintenance.
For the next phase of its investigation, Yang said that the institute would invite experts from Japan and Austria specializing in the so-called New Austrian Tunneling Method to make first-hand observations about the tunnel.
The New Austrian Tunneling Method utilizes the stress of surrounding rocks to stabilize a tunnel's structure.
The taskforce will turn in a comprehensive report on the status of the tunnel in three months. It will only complete the report after it has incorporated the foreign experts' evaluations, he said.
Yang gave the assurance that the taskforce would execute its duties in a fair and transparent manner, and that no conclusion would be drawn until all taskforce members were in agreement.
The team was first briefed by the bureau yesterday morning, following which it conducted a field trip inside the tunnel in the afternoon.
Reports compiled by the construction crews working on the Hsuehshan Tunnel showed that water leaks had been detected in 18 places before the official launch of the tunnel.
Another 18 places in the tunnel were found to have water leaks after the tunnel was opened to the public.