Contract No. HY/98/01 Improvement to Road – Tai Lam Section

CLIENT HKSAR

ENGINEER Maunsell Consultants Asia Ltd.

CONTRACTOR Build King Group

CONTRACT VALUE HK$268 million

CONSTRUCTION PERIOD September 1998 to May 2001

MAJOR QUANTITIES : 4 lane carriageway together with hard shoulder 3.0km Construction of reinforce fill retaining wall 1.2km Permanent Rockfall Fence 1.7km Rock excavation 57000m³

This project is to provide a climbing lane and hard shoulder to the existing Eastbound Carriageway of Tuen Mun Road Tai Lam Section and will in addition improve the slopes above Tuen Mun Road.

The works to be executed under this project include:  Construction of a verge, hard shoulder, climbing lane and reconstruction of the existing carriageway of the Tuen Mun Road eastbound carriageway at Tai Lam  Construction of Reinforced Fill Retaining Walls in the existing median of Tuen Mun Road.  Cutting back existing slopes (Slopes TL/S1 & TL/S4) on the north side of Tuen Mun Road to the east of Brother’s Bridge and at the eastern end of the Tai Lam Portion.  Excavation of existing slope (the South Rock Knob) on the south side of Tuen Mun Road to the east of Brother’s Bridge to enable Tuen Mun Road to be temporarily diverted away from the north-slope excavation.  Construction of rockfall fences on the slopes above Tuen Mun Road.  Site Investigation and slope improvement works to the existing waterworks catchments fill slopes and boulder removed and/or stabilization works at Sam Shing Hui, and Tai Lam.  Replacement of the existing Tuen Mun Road median barrier with concrete profile barrier at Ting Kau Portion.  Maintenance works to existing slopes, retaining wall and road within the site limits.

HIGHLIGHTS :

The major challenge of the project is the cutting back of the slope, in rock, above the live traffic of Tuen Mun Road at the slope toe. In order to proceed with the excavation safely, the South Rock Knob was excavated, both the eastbound and west bound traffic were then temporarily diverted away from the north slope. The construction of the reinforced fill retaining wall along the existing median was also proceeded in advance of any works at the northern slopes so that an additional traffic lane was provided for the temporary diversion of the traffic away from the northern slope. Temporary roadside rock fall fence was then erected at the slope toe with sand cushion behind to catch any blocks of rock that become detached and fall down the slope during excavation.

Another main feature of the project is the construction of the Reinforced Fill Retaining Wall at the Central Median for an extra traffic lane on top. This includes excavation at the existing slope of the Central median while temporarily supporting the existing eastbound carriageway (generally with pipe piles), erect precast concrete panels on the concrete footings and backfilling with selected fill materials sandwiched with galvanized steel reinforcing strips in layers. A temporary steel access bridge was constructed from the works area off , spanning across both the West bound carriageway of Tuen Mun Road and Castle Peak Road for the transportation of materials and plants to and from the site.

Throughout the project, the 3 lanes traffic along the eastbound carriageway of Tuen Mun Road has to be maintained at all time. A complicated traffic diversion scheme has been adopted for the full depth carriageway reconstruction to maintain the traffic flow.