LAND, PUBLIC WORKS AND UTILITIES
geotechnical constraints that could significantly affect the costs or timely implementation of the new airport and related projects.
The Geotechnical Information Unit (GIU), which houses the largest collection of data on ground conditions in Hong Kong, continues to serve as an important reference centre for geotechnical information in its much enlarged premises in the new Civil Engineering Building in Ho Man Tin. The GIU has served more than 2 400 users during the year.
The office's work on the use of underground space continued in 1991. Detailed feasibility studies for a government warehouse at Siu Sai Wan and for a refuse transfer station at Mount Davis were completed, the latter project being taken forward by the Environmental Protection Department for construction scheduled in 1993. Geoguide 4: Guide to Cavern Engineering and a Code of Practice on Fire Engineering for Caverns, which are aimed at providing guidance on design and construction of caverns, are being drafted. The office also continued to carry out preliminary engineering geological studies for cavern projects and arrangements were completed for including underground space in the government town planning system.
The Marine Geotechnology Section provided advice and carried out research and development work on the marine geotechnical aspects of Port and Airport Development Strategy projects, notably on the properties of hydraulic fills.
A report on a review of earthquake data for the Hong Kong Region was published in August 1991 and a programme has been set up to disseminate technical data and research information through the publication of a series of reports. A review of Geoguide 1: Guide to Retaining Structure Design was completed and a comprehensively revised edition will be ready for issue in 1992. New guidance documents on piling, blasting and the use of filters are being prepared.
Considerable quantities of concrete are required each year by the construction industry. The stone processing industry in Hong Kong produces coarse and fine aggregates primarily to suit the needs of the ready-mixed concrete suppliers. In 1991, Hong Kong's total con- sumption of sand and aggregates exceeded 19 million tonnes, of which 17 million were used in concrete production. Around four million tonnes of cement were also consumed. This is equivalent to an annual consumption of almost two cubic metres of concrete per head of population. Around half the territory's demand for aggregates is met locally, the balance is imported from China. The local quarries are supervised by the GEO. Plans are advanced for the implementation of the new landscape rehabilitation policies at urban quarries. During 1991, the government closed its last remaining direct labour quarry at Mount Butler on Hong Kong Island. The government has now withdrawn totally from the pro- duction of processed stone and the manufacture of bituminous materials by direct labour.
The new purpose-built Public Works Central Laboratory at Kowloon Bay was officially opened by the Director of Civil Engineering in July 1991. The six Public Works Laboratories together employ over 150 staff, of whom 10 are professionals and 140 are of technical and clerical grades. Over 310 000 tests on various construction materials were carried out during 1991. The laboratories are accredited under the Hong Kong Laboratory Accreditation Scheme (HOKLAS) to carry out calibration services, as well as tests on such construction materials as concrete, steel, aggregates, cement and pulverised fuel ash. Among the innovative features to be found in the Central Laboratory are the soil triaxial testing systems which can be operated fully automatically, with all of the data being logged directly into a computer.
217