Metros under construction around the world

Many cities are tackling their urban congestion problems by utilising underground space and developing or expanding underground railways or metros. This paper presents metro projects currently being constructed in four major world cities: Los Angeles, Copenhagen, Bangkok and Toronto. An overview of each project is presented together with illustrations of the tunnelling process and station development. The major design issues common to all the projects were settlement and groundwater control. Other issues specific to particular projects, such as earthquake allowance or maintenance of traffic flow, are also discussed. The aim of the paper is to show the infrastructure developing below our cities and briefly outline some of the complex geotechnical problems faced in the construction of these essential facilities.