top heading and bench method

The top heading and bench method is a tunneling technique used in weaker ground conditions. It involves excavating a smaller upper tunnel (the heading) first, followed by the excavation of the lower section (the bench). This approach helps manage weaker soils by reducing the initial opening size and allowing for progressive support installation.1

This method is an alternative to the full-face excavation, which is more suitable for stronger ground or smaller tunnels. In extremely weak ground, a variation called the multiple-drift method may be employed, where individual drifts are kept very small for safety.1

Modern tunneling also utilizes techniques like hand-mined tunnels for smaller projects, employing methods such as forepoling and breasting to manage unstable ground. Shield tunnels, used in very soft ground, involve a protective shield that workers mine ahead of, with support segments erected within the shield's tail. Regardless of the method, excavation and material transport, ground support, and environmental control are fundamental procedures in all tunneling operations.234