Widening cracks hold up southern tunnel construction

A number of cracks have been found in the tunnel sections pre-constructed for part of a tunnel project running under the Saigon River in Ho Chi Minh City, raising the concerns of authorities and stakeholders involved.

The Thu Thiem Tunnel, part of the East-West Highway project linking District 1 in HCMC downtown with District 2 in the Thu Thiem peninsula, is projected to be 1.5 kilometers long, with a 370-meter section running under the Saigon River.

Four tunnel sections – each measuring nine meters high, 33 meters wide and 92 meters long – developed a series of cracks even prior to their completion in June.

The sections were built in Dong Nai Province but had not yet been transported to HCMC.

In a report to the State Inspection Committee for Construction Projects (SICCP) on July 31, the management unit of the East-West Highway and HCMC water environment project said the cracks need repairing before the sections can be brought to HCMC.

In a previous report in May, SICCP had sounded an alarm on the issue, announcing that fissures had appeared in all four tunnel sections.

Some cracks, with dimensions of one-millimeter wide and two to three meters long, far exceeded the criteria previously outlined by the package’s contractor, Japan’s Obayashi Corporation.

Inspectors said the cracks had absorbed rain water, which would weaken the loading capacity and stability of the whole tunnel structure.

SICCP said it had requested repair work for the cracks in November 2007, but the project’s management unit and the contractor didn’t deem it necessary to find a solution.

Vice Director of the East-West Highway and HCMC water environment project, Dao Xuan Ngoc, had said the cracks were only “hairlines” and would automatically disappear after the assembly of the tunnel sections.

Another inspection of the tunnel ramps part, which was also contracted to be built by the Obayashi Corporation, uncovered a sinking foundation.

Subsidence was happening at the rate of 10 millimeters per month, according to a report submitted by the project’s management unit on August 8.

Solutions at odds

In a note to SICCP, the management unit of the East-West Highway and HCMC water environment project cited a host of proposed solutions from the contractor and consulting agencies to fix the cracks.

Obayashi Corporation said fissures whose widths were under 0.1 millimeters were unnecessary to repair.

For cracks whose widths were larger than 0.1 millimeters, the company suggested using a special glue to fix them.

The contractor claims that repairs could be either implemented before or after applying stretching cables to reinforce the tunnel sections, as this process would not exacerbate the width of the cracks.

But Japanese firm Pacific Consultants International (PCI) disagreed with Obayashi’s proposals, saying the contractor had failed to account for several factors, including the lifespan of tunnel sections, when drafting solutions to mend the cracks.

The consulting agency proposed that cracks should be glued prior to stretching the cables, to be followed by a welding together of the crevices after the cables are stretched.

The project’s management unit concurred with PCI’s suggestions and noted that the contractor has to be fully responsible for the tunnel’s quality and progress based on contract clauses, in addition to covering repair and consultancy costs.

Earlier, the management unit had also enlisted the Quality Assurance and Testing Center 3 (Quatest 3) to review the cracks and give advice in its capacity of an independent consultant, but Obayashi had refused to pay any relevant consultancy fees to Quatest 3.