BENCH MARK SERVICE
S a new service for private archi. tects, engineers and surveyors, copies of the index plan and bench mark cards, showing the positions of level reference points in the Colony, are now available for sale at the Crown Lands and Survey Office of the Public Works Department,
There are three plans showing the positions of the bench marks (level reference points) on Hong Kong Island, in Kowloon and New Kow. loon and the New Territories. They are sold at $2 a copy.
A bench mark card bearing a small photograph is also available to give the exact position and level of the bench marks. At present this service applies to Hong Kong Island only but will be extended to Kowloon and the New Territories in due course. Copies of these cards com.
L SOIL TEST (from Page 72)
'sive strength and the trench depth as
already described.
It is recommended that three or four penetrations be made on a trench wall to get an average unconfined compres- J sive strength of the soil. Accurate 1 testing involves brushing away or cut- ting away material which has been disturbed by the trenching equipment This exposes the natural soil for A
plete with photographs can be bought at $2 each.
The system of establishing bench marks began in 1866 when H.M. Surveying Vessel "Rifleman" set a copper bolt in a store-house wall in the old Naval Dockyard to serve as a starting point for all levelling in the Colony.
It became known as "Rifleman's Bolt" and was 17.833 feet above a level regarded in 1866 as the lowest possible tide in Hong Kong Harbour. This level was later known as the "Colony Principal DatumTM “P.D.**
ог
The bolt was removed when the naval authorities handed over the old store-house to Government. It will be inserted in the recently com- pleted Naval Block,
realistic test. The formula shown above includes a safety factor.
Anyone working regularly with soils knows their variable nature. Soils, therefore, must be treated with care and caution. Where the soil structure changes rapidly, or where unstable con- ditions appear to exist in trenching work, the services of experienced soils and foundation engineers should be used as a final check on the safety of the soil.
Principal Datum is about four feet below the mean sea level. In Hong Kong, heights and levels for roads, drains, waterworks. buildings and other development all refer to P.D.
To assist surveyors, engineers and architects, bench marks have been established all over the Colony. These marks consist of a metal bracket fixed either to solid rock or to a wall and are given reference numbers for identification purposes.
The extension of the levelling system from "Rifleman's Bolt" pre- sented special problems due to the long stretches of water that had to be crossed from the island to the mainland by way of Lei Yue Mun. This was carried out in 1933.
In recent months, the system was extended to Lantau Island by way of Green Island, Gau Yi Chau, Hei Ling Chau and Silvermine Bay.
CORRECTION
THE whole of the Hong Kong City Hall project was designed and supervised by the Architectural Office of the Hong Kong Public Works Department. In our report on the completed building this was, by a regretted oversight, never clearly stated. The architects and others engaged in the resign and building of the City Hall are all members of the Public Works Department.
F
ARTISTIC WORKS
RAOUL BIGAZZI
UNION HOUSE
MARBLES
MOSAICS
ORNAMENTAL TERRAZZO TILES
STAINED GLASS
TELEPIIONE: 25177
BRONZES
WROUGHT IRON
THE HONG KONG & FAR EAST BUILDER-VOLUME 17, NUMBER 1
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