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Hong Kong Builder
A view of the interior of the completed structure.
The buildings are founded almost entirely on solid bedrock, but at one end of the site which occupies land reclaimed in 1929 it was necessary to drive concrete piles as the rock was too deep below the surface to be reached by solid foundations.
Owing to the sandy nature of the soil and its proxi- mity to the waterfront, it was found necessary to sink hollow reinforced concrete caissons for the deeper foundations in order to keep the water out during con- struction. A considerable amount of underground con- struction was required for the circulating water intake and discharge. A deep screen house was constructed inside a sheet pile coffer-dam to a depth of 10'0" below lowest water level and from this a twin reinforced culvert 6'0" square leads the water throughout the length of the station. The lower part of the foundations for the future turbines was constructed in order to reduce disturbance to running machinery when new extensions had to be installed. One of the major points of interest in this building is that all the concrete was vibrated into its final form, a process which was then new to Hong Kong.
General Contractor's Experiences.
During the course of construction of the Power Station the Contractors had many unique experiences.
The building is partly on rock and partly on "Franki”
piles. At one corner, solid rock was six inches below the surface of the ground and at the diagonally opposite corner the piles were carried to a depth of over 40 feet. But hard ground did not follow a uniform slope and boulders were often encountered. At one spot where a group of four piles were to be driven to take a footing about 5 ft. square, three were taken down to about 23 feet, but the driving tube for the fourth pile struck solid rock at 13 ft. A jackhammer was let down into the piling tube and after drilling about 12" a charge was fired shattering the rock. This enabled piling to be continued to a satisfactory depth.
In many places, owing to the depth to which excava- tion was required to be. taken, blasting through solid rock to 22 ft, below ground was necessary.
This was some 11 ft, below low water. Timber shuttering was out of the question not only because the timber was destroyed by the shattered rock but also because of the difficulty in controlling seepage of sea water through the tissues in the rock. Reinforced caissons were constructed and
The Dispensary
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The Doctor's Room