No-dig technology in Hong Kong

Hong Kong is a heavily urbanised city. The small amount of space available in Hong Kong and the high population in Hong Kong necessitate engineering solutions which are often unique and complex. Due to the need for development, underground services including water supply pipelines have to be laid under roads which are already loaded with heavy traffic. Road openings in these roads will lead to traffic conjestion and consequently a chaotic condition. To avoid road openings, a technique known as no-dig technology has been gaining grounds in Hong Kong. There are many variations of this technique. However, a common form of this technique is to push a steel pipe, (a cylindrical thin shell structure), section by section, under a road by strong hydraulic jacks. In this method the need for road opening is dispensed with and there is no need to be concerned with traffic jams, traffic diversion and the provision of temporary structures. Although this method appears to be an ideal method for laying underground utilities in Hong Kong, the cost and the lack of knowledge have deterred such application here. In this paper, the advantages and disadvantages of the use of such thin shell underground structures are discussed.