Viaduct section of the Hong Kong to Macau Bridge passes load testing
Following the announcement of the complete connection of Hong Kong-Zhuhai-Macau Bridge, Hong Kong Link Road on May 18, 2017, the Highways Department has now announced that the road surfacing works and road facilities of the about 9.4 km long viaducts, 1 km long Scenic Hill Tunnel, and 1.6 km long at-grade roads along the east coast of the airport were successfully completed. The remaining works in progress mainly include the final installation and testing of the Traffic Control and Surveillance System, as well as the final work of some ancillary facilities.
To construct the Hong Kong Link Road in close proximity to one of the busiest airports in the world, the Hong Kong International Airport, the engineering team encountered various challenges during both the design and construction stages. Under the tight airport height restriction, the construction of the viaduct section required the use of a massive straddle carrier to construct the long-span bridge of more than 180m in length, in order that the viaduct could pass over the northern shore of Lantau and thus avoid touching the land in vicinity of the Sha Lo Wan archaeological site of high conservation value. Furthermore, large precast modules, including marine concrete pile cap shells and precast pre-stressed concrete piers that was the first of its kind in Hong Kong, were extensively adopted to reduce the environmental impact due to marine in-situ concreting work.
The construction of the Scenic Hill Tunnel was the most difficult and challenging construction works in this project. The Scenic Hill Tunnel comprises two tunnel tubes of about 1 km in length running in parallel, passing underneath Scenic Hill, Airport Road and the Airport Express Line and connecting at-grade roads through the new reclamation area. Four different tunnel construction methods were adopted to cope with the different technical difficulties. They comprise the drill and blast method through Scenic Hill, the mined method underneath the Airport Road section, the box jacking of tunnel segments underneath the Airport Express Line and the cut and cover method at the reclamation area. As the tunnel had to pass underneath the operating the Airport Express Line, the engineering team adopted the box jacking method that was the first time in Hong Kong, to build two large vehicular tunnel tubes.
The gigantic tunnel segments were pushed forward underneath the Airport Express Line by several series of hydraulic jacks controlled by a precision computerized system. The normal and safe operation of the railway was maintained during the construction period. The engineering technology and construction requirements are very stringent and have caused significant difficulties.
With the unremitting effort of the engineering team, the site difficulties and challenges faced during the construction of both viaduct and tunnel sections were resolved one by one for the successful completion of the works.
In addition, the load test and the associated analysis of the Hong Kong Link Road viaduct section have also been completed. The viaduct section is about 9.4 km long from the HKSAR boundary to Scenic Hill on the Airport Island. The load test commenced on the viaduct section in mid-October 2017 and was carried out on all 230 spans of the 19 bridge structures. The analysis indicated that all the bridge structures of the viaduct complied with the requirement for the designed loading capacity.
The Director of Highways, Mr Daniel Chung, visited the site on January 11 to witness the load test on the last bridge span and receive a briefing by the testing team. Mr Chung expressed his heartfelt thanks to the testing team for arranging and conducting the test days and nights, so that the load test for all 230 spans could be successfully completed within about three months. The testing team explained that the load test was conducted using a convoy of vehicles with a total weight of 380 tonnes (comprising a loaded tractor and trailer with a total weight of about 200 tonnes and six loaded trucks of about 30 tonnes each).
After the convoy of vehicles was stationed at each bridge span of the viaduct, the vertical deflection of the viaduct was measured to assess whether the bridge structures all complied with the requirement for the designed loading capacity.