Engineering aftershocks of the 1999 "Chi-Chi" earthquake that devastated central Taiwan first hindered progress. Then, as resulting seismic design uncertainties were being resolved last year, the disease SARS afflicted the island, spurring a mass exodus of migrant labor.
|TAIWAN TRAINS High-speed rail line stretches 345 km. (Photo courtesy of Taiwan High-Speed Rail Corporation)|
Dave Herron, project manager of a consortium responsible for 37 kilometers of the high-speed line near Taichung, says that his team is now finishing up, having recently ended work ahead of schedule. Other joint ventures along the route are also completing the nearly 350-km of infrastructure. With civil work now ending, "progress has been tremendous," says Nita Ing, chairwoman and chief executive officer of the Taiwan High-Speed Railway Corp. As mechanized track installation gains momentum. equipping and commissioning railroad systems this year and next remain "a very big challenge," she adds.
With most of its population concentrated along the coast between Taipei and Kaoshiung, Taiwan seems well-suited for high-speed trains. When completed in late 2005, the line will shuttle trains at 300 km per hour along a continuous stretch of development between the islands north and south extremities.
Conceived in the 1980s, the project took off as a 35-year build-operate-transfer contract awarded to THSRC in 1997. Among THSRCs five core members is Continental Engineering Corp., Taipei, Taiwans largest private-sector contractor.
From Ground Up
Starting "from zero," THSRC created a company in the first six months after winning its contract and built on that over two years, says Continental Engineering executive Chao-Yi Chia. "At the very beginning, some people thought it was Mission Impossible," he says.
THSRC secured initial financing in early 2000 and awarded 12 civil contracts, together worth some $6 billion. THSRC chose fixed-price, lump-sum, design-build contracts for better efficiency, says S.C. Lin, the companys assistant vice president for civil construction management. Traditionally, design was done "very conservatively and very expensively," he explains. Click here to view chart
Only the lines stations are being built according to the owners designs. Here, THSRC eschewed design-build to control the architecture, says T.C. Kao, vice president for buildings. Work on six new stations and two upgrades, costing $600 million, began in May 2002. They are due to open in October 2005, with another four after 2007.
For the civil work, all 12 consortiums are dominated by Asian contractors. Germanys Bilfinger + Berger Bau AG and Hochtief AG are among the few non-regional major firms, providing experience that even the largest local firms lacked, says Cheng-Hsiung Kang, a senior executive of Continental Engineering.
BREAKTHROUGH Tunneling on the rail line usually encountered sands and clays. (Photo courtesy of Taiwan |
High-Speed Rail Corporation)
Continental is Bilfinger + Bergers equal partner in the projects BBCE joint venture, which has two adjacent contracts near Taichung covering 80 km and worth about $1.1 billion. The team has built 66 km of viaduct, and drove the 7.4-km-long Paghuashan tunnel.
BBCE this January handed over its last section to the tracklayers some two months ahead of schedule, says former project co-director Stefan Roth. That, however, was a deadline extended early on to accommodate a lengthy engineering debate triggered by the 1999 Richter 7.3 Chi-Chi earthquake, which killed some 2,000 people.
Stunned by that devastation, the interior ministry altered earthquake zoning and changed seismic design criteria for all public works, says THSRCs Lin. "We sent a letter to all contractors...that was really a shocksome had already started design [and] the [original] code was already conservative." BBCEs design had reached an advanced stage, says Roth. "That was destroyed by the new earthquake zoning," he says.
The new seismic criteria, which varied depending on ground conditions, were extremely complicated, says Herron, BBCE project manager on one contract for 24 km of viaduct and seven tunnels. One example of the seismic changes was a 25% increase in skin friction safety factoring for piles under compression.
Adding up the cost of all proposed changes along the route resulted in a potentially ruinous 30 to 40% cost hike, says Lin. But a subsequent review rescued the project. Essentially, it found the original criteria to be adequate. But by September 2000, when the government reverted to them, "we had wasted about five months," he says.
BBCE and the owner agreed on acceleration measures and payments, but not on the effect on quantities used or their costs, says Roth. The whole earthquake review "influenced our design approach," he says. "What is being provided is on the [conservative] side." Herron adds that BBCE and the owner have reached accord on all payments.
Acknowledging the effect on schedules, THSRC issued time extensions. Herrons contract received an extra two months and more resources, including a third precast concrete production line at the site.
LAUNCHING Steelwork launchers placed |
800-tonne girders for much of the rail viaduct.
(Photo courtesy of Taiwan High-Speed
Of the roughly 345-km railroad, nearly 40 km is tunneled, while over 250 km is on viaducts and bridges that avoid disrupting highways and communities. For most of the viaducts, "you had a choice...of using full span precast concrete or casting on a normal shoring system," says Herron. "Segmental construction was not allowed for high-speed rail."
Because the southern section needed to be completed earlier for train tests, its contractors opted for conventional cast-in-place decks on traveling formwork, says Lin. Some 10% of other viaducts were cast on props. Balanced cantilever, deck launching and steelwork bridges were used over sites such as rivers.
Nearly two-thirds of the viaduct was built with full-span precast box girders, adds Lin. Steelwork launchers advancing onto waiting piers place the 800-tonne girders. One of five contractors used its launcher to deliver girders, while the others moved them on wheeled vehicles. BBCE is now trying to sell its three 40-wheel, 200-tonne transporters.
BBCEs choice of full span precasting "meant we could concentrate our resources in one area and limit the work being done in the-right-of way primarily to substructure,"says Herron. "And it reduces the work force."
Designed by a team of Bilfinger engineers in Germany and U.K.-based FaberMaunsell Ltd., BBCEs section of viaduct typically comprises post-tensioned girders up to 35 m long, 6 m wide and more than 3 m deep with 13-m-wide top slabs. The supporting piers vary in thickness and are generally 6 m tall.
BBCEs two contracts started in April 2001 with foundation work. Pad foundations occur mainly in the rocky northern region. Sands and clays in a high water table further south are more prone to liquefaction in earthquakes, requiring piles.
Working in gravel with cobbles in places, the contractor used hydraulic rigs to drive 2,400 partially cased piles, with excavations supported by polymer fluid. In easier sands and clays, a fleet of reverse circulation rigs drove some 5,000 piles. Generally, viaduct piers are supported by four 2-m-dia piles some 60 m deep.
Pier work followed closely behind piling, and BBCE crews cast and placed the first of nearly 700 whole-span girders in October 2001 after six months setting up the three production lines. The yards gantry cranes placed the first girder. Later, spans were erected with a single advancing launcher until last August.
Apart from a minor collapse, tunneling on BBCEs stretch of railroad was uneventful, Herron says. The twin-track tunnels typically have horseshoe-shaped profiles with 130-sq-m excavated faces. They were excavated and temporarily supported with arches and spray concrete, followed by cast-in-place reinforced lining.
At the 7.4-km Paghuashan tunnel, Herrons team excavated four faces through variable clay and sand. They achieved an average of 6.5 m per day, peaking at 14.2 m, says tunnel manager Frank Hemmert. "The original design showed a lot of rock bolts. We found they were not needed," he says. With the ground almost self-supporting, "we redesigned everything."
In contrast, the 4.3-km Hukou tunnel, about 70 km from Taipei, has collapsed twice. The tunnel is part of a design-build contract for 18.4 km of line, held by a joint venture led by Daiho Corp., Tokyo, with Taiwanese firms Chiu Tai General Contractor Co. Ltd. and Kou Kai Construction Co. Ltd.
Trouble started after the heading had broken through between two faces near the north portal in August 2002, says THSRCs Lin. After the 50-m obstruction was excavated that October, a 250-m-long collapse occurred near the tunnels mid-point. "We cant identify the cause," says Lin. But "we knew this was the most difficult tunnel" due to the wet, weak sands.
Slow and Deliberate
|VIABLE VIADUCTS Viaducts built by launching of precast girders aimed to minimize disruption to local communities and wildlife. (Photo courtesy of Taiwan High-Speed Rail Corporation)|
While such construction snags have been rare, bureaucracy has been rampant. For the 12 engineering teams, waiting for their designs to be checked and ensuring uniformity has been "a tedious process," says Herron. "In the early stages, when everybody was getting to grips with the design criteria...there were times we thought it would be impossible."
For each contract, there is an independent team checking all plans in detail. A higher-level team, reporting to the owner, audits the process by reviewing sample designs. If all goes well, the client issues a "statement of no objection," allowing construction to proceed. But the process was so slow that the "final statement of no objection was achieved after all the spans were installed," says Herron.
Worried about delays, BBCEs team and other consortiums short-circuited the checking system. "The penalties on the project are so high that you cannot be late. And the indications were [that] you would not get extensions of time due to the approvals process," says Herron. So rather than wait for the owners green light, BBCE kept building on the basis of its detailed checkers approvals.
"The risk was...to build something that could have ended in a big dispute," says Roth. But "we always worked on the safe side" and never as far as the critical design, adds his co-director, Cheng-Hsiung Kang. There was not any construction on BBCEs contracts that needed retrofitting or remediation, says Herron.
THSRCs Lin agrees that the approval process was "too complicated," blaming it on the BOT procurement method. But "its still much faster than if wed been working for a government agency,"notes Roth. "The push is there....They wanted it finished."
The checking woes diminished over time, but then SARS erupted, terrifying the Thai workers that account for most of BBCEs payroll. "We lost about 20% of our workers," says Herron. Many declined to renew their visas and went home to avoid exposure to SARS.
A strict disinfecting regimen and twice-a-day health checks seemed to reassure many workers. "You had to have full monitoring in place to make sure you didnt get SARS. That would have been a catastrophe. We would have been shut down," says Herron. By increasing the number of subcontractors and raising overtime, "we just had to manage."
Nevertheless, construction dust is now finally settling. "We never expected that we could complete [the project] so soon," reflects a relieved Herron.y putting most of its new high-speed railroad on viaducts, Taiwan is avoiding many construction pitfalls along the route through the urbanized corridor that stretches across the islands western coast. Production line techniques for thousands of 800-tonne girders further eliminated snagsbut not SARS and seismic events that harried the $15-billion, three-year-old construction project.