's road engineering fea Quality control testing In construction is essenti Interior design: Manila Hotel's rebirth

-Ait HK'S FIRST HIGH-CAPACITY RURAL

TUEN MUN is one of the three new towns being developed in Hong Kong's . It is 17 km west of another new town and 32 km by existing roads from the commercial heart of the territory Tsim Sha Tsui, . By 1986 will have nearly half-a-million people. From the early planning stages of the new town, it was clear that the existing tortuous Castle Peak Rd would prove an inadequate link between Tsuen Wan and Tuen Mun. A high-capacity road link was con• sidered an essential prerequisite to the development of Tuen Mun. The Hong Kong Government commissioned a firm of consultants to prepare a report on a new road between the two towns and, follow• ing its acceptance, to design and supervise construction. Tuen Mun Rd, as it is now called, is Hong Kong's first high-capacity, limited- access rural highway. It is being constructed in two stages.

First carriageway Construction of the US$57.1 Mun Rd will form part of Route 2 Aerial view of Tuen Mun Rd which million initial stage commenced in which will provide continuous dual- links with Tsuen Wan New Town. It is Hong October, 1974, and involved com• carriageway travel from Tuen Mun Kong's first high-capacity, limited- pletion of the first carriageway of to Kowloon. access road and, when completed in what will eventually be a dual, During the initial site reconnais• 1980, it will form part of Route 2 three-lane road some 17 km long. sance for the design of Tuen Mun which will provide continuous dual- carriageway travel from Tuen Mun Also included was the formation Rd, records were made of topo• to Kowloon. (Hong Kong Public works for the second carriageway graphical and surface geological Works Department photograph). over about 7.3 km of its length and features, drainage systems and land the complete construction of the use. This was augmented by stereo• proximately 100 m intervals along two intermediate interchanges. scopic study of available aerial the road alignment. Construction of the US$17.8 photographs. The information ob• Tests were carried out on the million second stage will commence tained was used for planning the soil samples recovered to classify soon after the first carriageway is detailed ground investigation. them and to determine their streng• opened to traffic this month (May, Some 170 boreholes were locat• th, consolidation and permeability 1978). ed at probable bridge foundation characteristics. In addition, surveys When completed in 1980, Tuen sites, in Tai Lam Bay and at ap- were made of the jointing visible in

ASIAN BUILDING & CONSTRUCTION, MAY 1978 the rock outcrops and of the occur• investigation was augmented as part from aerial photography under• rence of groundwater. of the construction work. taken in 1963. A flying height of Although for most of its length The Crown Lands and Survey 549 m and photographic scale of Tuen Mun Rd is aligned through Office of the Public Works Depart• 1/3 600 had been used. granite rock and its overlying de• ment have established a fully co• Information from the aerial sur• composed mantle, the eastern 2 km ordinated survey network including vey was verified and the maps up• lies on decomposed volcanic rock. triangulation stations, traverse sta• dated by a limited ground survey The most prominent rock outcrop• tions and bench marks covering the undertaken by the Highways ping occurs at Brothers Point where whole of Hong Kong. A detailed Office, PWD.

TUEN MUN ROAD extensive adverse sheet joints were survey based on aerial photography For construction purposes, sur• observed. at a scale of 1/1 200 now covers vey stations were established along Results of the investigations most of the land area of the New the route to enable the road and its were used in the design of cuttings Territories. This survey scale was structures to be set out. Accurate

1.50 m 1.50 m 10.05 m 2.50 m 10.05 m 1.50 m

TUEN MUN ROAD CARRIAGEWAY CROSS SECTION

and embankments, structural used for preliminary alignment and survey was particularly important foundations, marine works and the engineering studies of Tuen Mun for Tuen Mun Rd as considerable carriageway pavement. The rock Rd. lengths of the road are situated in level determined from the bore• For the detailed design work relatively inaccessible hillside with, holes was also used for providing that followed, plans at the larger in places, heavy vegetation. setting out information for the cut• scale of 1/500 were considered es• Because of the topography tings. sential. These were prepared by a through which Tuen Mun Rd Subsequent to commencing private firm in 1973 by machine passes, a particular effort was made work on site, the pre-tender ground plotting to 2 m contour intervals to minimise the cost of earthworks.

12 ASIAN BUILDING & CONSTRUCTION, MAY 1978 CONSTRUCTION

The time involved in testing the various detailed vertical and hori• zontal alignments to determine the most economical design was con• siderably reduced by the consul• tant's extensive use of computer programmes. By the use of computer facilities a complete set of 1/250 scale machine-drawn cross-sections at 20 m intervals along the road was pre• pared. The chosen alignment of the EMBANKMENT 17 km road meets standards shown SLOPE in Table 1 (pg. 14). At its eastern end (see map), the chosen route of the Tuen Mun Rd connects with the Castle Peak Rd at a signal-controlled junction. When the Tsuen Wan By-pass is construct•

ed, this connection will become one SAFETY FENCE of the slip roads in a three-level interchange. CARRIAGEWAY EDGE COVERED DRAINAGE CHANNEL The road climbs to a high point

SUB-SOIL DRAIN

CARRIAGEWAY SURFACE AND SUB-SURFACE

built on the waterfront. An inter• .. Because of the massive rock change with Castle Peak Rd serves formation at Brothers Point, at the the traffic needs of this developing eastern side of Tai Lam Bay, the YOKES village. Tuen Mun Rd passes the new road has been constructed village on a high-level viaduct be• close to the shoreline with the fore climbing for an another 2 km existing Castle Peak Rd being re• PLATFORM through sparsely populated aligned on reclamation. Tuen Mun countryside. Rd descends rapidly to this shore• line before crossing the bay on a causeway with a bridge built to JACKING RODS allow for the discharge from Tai Lam Chung Reservoir. The enclosed area of the bay is expected to be reclaimed eventually. A second CONCRETE DISCHARGED intermediate interchange is located ON TO PLATFORM COLUMN SLIPFORMING at the western side of the bay and near giving a panoramic provides access to nearby villages view of the harbour and islands. and the Lok On Pal desalter. The natural slope of the ground in The chosen route cuts inland this area is very steep, so the road is and follows a succession of ridges carried on a viaduct constructed HANGING and cultivated valleys for the next 3 SCAFFOLD' just below an existing catchwater. km. The road then runs through The road crosses two deep valleys broken land separating army bar• before it descends to . racks from their training grounds to Sham Tseng is a large village the north. At its western end, Tuen separated from the sea by Castle Mun Rd connects directly into the Peak Rd with a bakery, chemical centre of Tuen Mun over a reclaim• works, brewery and textile factory ELEVATION ed section of the Castle Peak Bay.

ASIAN BUILDING & CONSTRUCTION, MAY 1978 Table 1 - Alignment standards Tuen Mun Rd will have two when the final stage of the road is Minimum sight distance three-lane carriageways separated completed the maximum climbing for stopping 90 m by a central reserve and bounded gradient will be 6%. Minimum (absolute) by relatively narrow verges and The road pavement has generally horizontal curve radius 130 m Minimum vertical crest curve radius 1 000 m Minimum vertical sag curve radius 2 000 m Maximum gradients: The Sham Tseng Viaduct (left) Ascending 6% during construction. Descending 8.3% (Hong Kong Public Superelevation: absolute Works Department maximum photograph). A view of the Telford Absolute maximum 10% Bridge (below). In Desirable maximum 7% all, 10 road bridges, three footbridges and 15 Table 2 - Tuen Mun Rd box culverts have been constructed carriagev^ay along the Tuen Mun Cross section Rd. (Scott Wilson Kirkpatrick & Part• Three-lane carriageway ners photograph). width (normal) 10.05 m Three-lane carriageway width (on sharp curves) 10.95 m Hard strip 1.50 m Verge to embankment width 1.50 m hard strips. Until the second been formed with 250 mm of Verge to cut width carriageway is opened, the first crushed stone sub-base, 150 mm of (minimum) 1.20 m carriageway will carry two-way bituminous macadam base and 100 Minimum clearance to traffic. Details of the carriageway mm of asphaltic concrete surfacing. bridge piers 1.00 m cross section are given in Table 2. Where formation is rock, the sub- Minimum headroom 5.10 m In designing the road the nature base has been omitted. Almost Central reserve width of the terrain dictated the use of 125 000 tonne of sub-base and (minimum) relatively steep gradients. However 135 000 tonne of bituminous sur• facing have been used. Hong Kong's average annual rainfall is about 2 200 mm, most of which is concentrated in the sum• mer months. The wettest month on average is June with a normal rain• fall of about 400 mm although monthly falls in excess of 800 mm have been recorded. The highway drainage systems have to cope with the resulting intense run-off. The return period for the design storm used in calculating the capa• city of all drainage systems for Tuen Mun Rd was 50 years with checks at 1 in 200 years for carriageway drainage. Because of the generally steep nature of the ground, many drain• age structures have to withstand high velocities and erosive bed- loads. Concrete lined cut-off channels

14 ASIAN BUILDING & CONSTRUCTION. MAY 1978 CONSTRUCTION

The Bridge (Scott Wilson Kirkpatrick & Partners photograph).

are constructed above all cuttings and elsewhere to lead water to the main watercourses which are taken under the road in culverts. The smaller culverts, up to 1.5 m diameter, but of a minimum size of 900 mm diameter to allow easy access for maintenance, were de• signed as precast concrete pipes with flexible joints to allow for differential settlement. These joints also allow the pipes to be laid with slight changes in vertical alignment to suit the split carriageway design. Because of problems in the sup• ply of precast pipes of the required strength early in the construction period, the contractor was, how• ever, allowed to build a few culverts using cast in-situ RC. The larger culverts carrying main streams under the road have been built as single or multi-cell rein• forced concrete boxes, each cell drains of up to 900 mm diameter. carriageway drainage. Water is col• being up to 2.5 m square. Water falling on the face of the cut lected from the Tuen Mun Rd Watercourses, intercepted by the slopes is led away by channels on carriageway by continuous covered road in cuttings, are carried down each berm while the grassed fill channels set flush with the carriage• the cutting faces in stone-lined step• slopes are protected from scour by way. Because of this deep concrete ped channels into catchpits from chevron drains. channel, subsoil drains have had to which they are directed into pipe Positive systems are used for all be located under the carriageway rather than in the verge. The carriageways of the diverted and realigned sections of Castle Peak Rd are drained by gullies set below kerbed carriageway edges. In all, 10 road bridges, three footbridges, 12 underpasses and 15 box culverts have been constructed. Most of the road bridges had to be built at relatively inaccessible locations and so lightweight, pre- tensioned concrete beams were chosen. These are supported on columns founded on spread foot• ings, prestressed concrete piles or hand-dug caissons. Because of the topography, several of the columns are very high, with the tallest at Tsing Lung Tau being 33 m high. A notable aspect of the construction of these tall columns has been the

A footbridge on the Tuen Mun Rd. (Scott Wilson Kirkpatrick & Partners photograph).

ASIAN BUILDING & CONSTRUCTION, MAY 1978 contractor's use of the slipforming were needed to cross Tai Lam and que reduces overbreak during blast• technique. Castle Peak Bays and to realign a ing, increases the stability of the As access was easier at Sham section of Castle Peak Rd. slope and gives the exposed rock Tseng, longer and heavier post- Cut slopes in soft material are face a smooth appearance with the tensioned beams were chosen for SHAM TSENG the viaduct. The span of 32 m for VIADUCT this viaduct was dictated by the width of the nullah flowing through CROSS the village. Construction of the via- SECTION

TING KAU I VIADUCT duct required relocation of a sub• stantial section of the old village, CROSS -CONCRETE PILES I and new housing has been provided SECTION II I I I \ 6 nearby. Underpasses and footbridges // M li ll \ have been provided to connect generally flatter near Tsuen Wan pre-splitting drill holes remaining as Castle Peak Rd to developments than along the remainder of the a feature. located north of Tuen Mun Rd. The route because of the finer-grained Embankments have been com• underpasses have been designed as soil in the Tsuen Wan area. Hori• pacted with side slopes of 1 on 1.5. in-situ RC box structures. The foot• zontal drains and rockfill buttresses The slopes are protected with grass bridges have been designed to suit have been provided at the base of and chevron-pattern channels. Step• the terrain: one is an in-situ con• some of these slopes to improve ped carriageways have been con• crete-arch structure and the other stability. structed over a length of some 4.5 two have in-situ prestressed con• About half the material excavat• km to reduce the size of embank• crete decks. ed has been hard and so several of ments in side-long ground and to Difficult topography along the the slopes have been cut to a near help to blend the road into the road's alignment has required both vertical angle where rock is expos• landscape. major earth and marine works. It ed. These slopes have been stabilised Little dredging was required for has been necessary to form cut using rock bolts and anchors, con• the realignment of Castle Peak Rd slopes up to 70 m high and fill crete buttresses, and construction but some 700 000 m^ of mud had slopes as much as 40 m deep in of horizontal drains. Many of the to be removed from Tai Lam Bay. order to fit the road into the hilly rock slopes were formed using the The dredged channel has been back• terrain. Considerable marine works pre-splitting technique. Thistechni- filled with suitable material. The

16 ASIAN BUILDING & CONSTRUCTION, MAY 1978 CONSTRUCTION

road carriageway is constructed on intervals by emergency/maintenance checks along the road and will be fill bounded on exposed faces by crossings. observing the motorists closely. rock mounds with wave wall blocks No pedestrian access is allowed Development of Tuen Mun Rd providing additional protection on to Tuen Mun Rd and vehicles are has been the responsibility of the the seaward side. only permitted to gain access to the Highways Office and Tuen Mun The final section passing across road at interchanges. The speed New Town Development Office, Castle Peak Bay was formed by limit on the road is 64 km/h (40 Public Works Department, Hong pumping marine sand directly on mph); police will operate radar Kong. • top of the original seabed and then constructing an earthfill embank• TUEN MUN RD-STAGE I ment on this sand blanket. Several systems aiding traffic Project data: Link road contract tender operation and safety have been in• sum HK$23 730 702 corporated in the design of the Length of road 17.0 km Sham Tseng Viaduct contract road. Earthworks tender sum HK$17 559 024 Steel barriers are included in the excavation 5 700 000 m^ Main contract tender central reserve and on embankment Fill 4 500 000 m^ sum HK$222 246 768 verges. The complete length of the Pipe and box culverts Consultants: Scott Wilson road will be lit and directional - length 5.0 km Kirkpatrick & Partners, Consult• traffic signs will be illuminated. Underpasses 12 No. ing engineers. Hong Kong Emergency telephones will be in• Prestressed - beam road Contractors: Kumagai Gumi stalled on both sides of the road at bridges 9 No. (1.5 km) (Hong Kong) Ltd (main and a spacing of 500 m. Along side-by- In-situ road Sham Tseng Viaduct contracts); side sections of dual carriageway, bridge 1 No. (0.1 km) Hsin Chong Construction Co. the central reserve will be broken at Footbridges 3 No. Ltd (link road contract) Skinplate is beautiful, functional and tough! What is Skinplate?

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ASIAN BUILDING & CONSTRUCTION, MAY 1978 1