76
CHE TUBE: HOW SAFE
A go-ahead is expected within a few weeks on Hongkong's $10,000 million mass-transit
system. Presumably the government will have investigated the tube's safety aspects before it gives approval. But how safe is 'safe'? How will pre-war buildings on less-than-substantial foundations fare with an underground system beneath them? Is our soil too soft? What about typhoons? Here, Mazy Lui
discusses these questions
with two University of Hongkong men, one a geologist, the other a civil engineer.
on
Ha government green light expected next month
the month on the proposed underground railway, disquiet among a small segment of Hongkong's geologists has not been dispersed on a number of points.
the colony at large the dream of a mass transit system is So overpowering that few questions are asked whether the tube will add to Hongkong's accident-inducing
factors.
"Flooding
can.
in sonte ways, affect the tube, but I'm sure it can be catered for in drainage design," he said. "It's only during construction that water is a problem, but it will be eliminated by the lining after construction," he said.
Or Peng pointed out that most land along the waterfront was reclaimed land. "The 'fill materials' may be anything from large boulders to garbage. That means the construction equipment will have to be able to adapt to changing soil conditions," he said.
"AS
the geological structure of the island sustain such a massive project? Will it affect the foundation of high-rise buildings? Or be #thegen? Or cili par in a
aus of soft soitt
Vanappell be given, vie will probably
Drilling
far as engineering is concerned, I don't see any difficulty in drilling, except that different excavation methods will be needed to
X. the fee digner of petituation, that it had viewed all aspects of the scheme before taking the decision. Apart from the question of raising $10,000 million for it. the next over-riding matter is that of public safely.
Since August, soil loses have
been partied
by 2 consuttant engineering firm on behalf of the Public Works Department. "Sections
of the projected route are being drilled, and the soil collected and analysed.
So da, according to de firm, there has been no indication to say that the tube is not feasible.
However, amid the excitement created among engineering, banking and business cæcles - with visions of potential profits there remains some underlying lear that perhaps Though emphasis is placed on the question of public safety. These fears were emphasised in
nurt
talks a Blangkong Standard reporter had with a civil engineer and a geologist, not involved with the survey. Both said that construction and
maintenance of the tube was, of course, possible ~ but because of the Colony's geological structure, would իր Construction complicated because of the variations in soll and rock properties.
Buildings
Also there is bound to be some
effrel on buildings which d 12417 have drep pillug Whether it will weaken the foundations to an extent that will pose a security risk during A typhoon is something that needs detailed study.
"The May showity the projected route reveals that most parts will be built along the waterfront, where water content is relatively high", says Dr CJ. Peng, Senior Lecturer of Geography and Geology Department, University of Hongkong.
He explained that large amounts of water had to be pumped out. "But drilling of soft soil
is easier than of hard rocks, so excavation won't be very hard," he said.
One main defect is that during ruiny seasons or floods, when the soil is saturated with water, a "cave in" muy occur, possibly resulting in a collapse.
To remedy this, he suggested lining the tube walls with heavy concrete, supporting. the tube with timber or steel and proper drainage.
Dr Peter Lumbs, reader in civil
engineering at the university, shared this opinion.
abiat serben gergitimatevan," Da Lalkas vaid. Certain sections of the tube wit Še i solid greùnd, Ph example, in the Western
District.
Excavation of hard rock will be
WILL IT BE?
TSUEN WAN WEST
TSUEN WAN
more expensive and difficult. "But the merit is that it can support itself and resist in collapse, especially ipneous reeks," Dr Peng said. In Hongkong. 70 per cent of the land area is covered with hard rocks, such as granite and volcanic rocks, which are hard, compact and dense. The voft rocks consist of sedimentary rocks, such as
Al sandstone and shale. paddy fields, reclaimed land ami waterfront land stand on soil.
Roth lecturers believe that typhoons won't affect the tube, as it is constructed underground.
"We can see from the projected plan that no region along the
will be close Ioute
to The landslide arcus, so i don't think landslides will act as hindranco either," Dr Lunbr sick.
Yet,
both expressed worry about the foundations of buildings.
"The subway may affect the old buildings which Jinvo 'shallow' foundations: There should not be any adverse elicets on the recently-built
with building
deep Foundations." Pr Lambs
said.
and
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Dr Peng said he thought two types of buildings nicht be affected il buildings. standing on reclaimed and low-lying ground; pre-war buchtings with shabow foundations. Concluding. Dr Lumby said: "There will be no major technical problems Ja building the tube, and no problem at #l in maintenance, ONIC 11's finished." There are of course, problems the authorities are aware of. But the public, especially those people who live on shallower-piled buildings above the tube roule, have the right to an assuranen that the risks are within bounds. Government officials explain that there is no sizeable danger. It would mean that more money would have to be spent in some parts to eliminate risks,
Mr David Butler, Consultant
Engineer of Scott Wilsh Kirkpatrick und Partners. which is carrying out the soil tests, said: "Yes, the tube may have some effect on buildings with El shallow foundation.
"But I am sure with careful and proper constructing inethods, it can be remedied. Landslidus, floods and typhoons won't affect the tube," he said.
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MASS TRANSIT, ROUTES
1.1
Map showing the pt credules or the mass transit scheme.
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