Tunneling and Excavation in Soft Rock and Soil

Abstract

This paper is to provide an overview of the engineering required for the design and construction of excavations in soft rock and soil. Two types of construction are discussed which are commonly termed ‘soil tunnels’ and ‘braced excavations.’ The intent is to give the engineering geologist a framework for identification of what is important in this type of work. The focus is on engineering from design through construction and emphasizes to some degree the perspective of the design engineer. It is intended to illustrate what is technically required in order to develop sufficient information to design for earth loading and to assess the potential impact of construction on adjacent structures. Construction is also discussed from the standpoint of constructability and construction methods. This treatment of what is required for excavation in soft rock and soil should be understood to be extremely broad. It is not intended that this document be used by an individual to directly undertake the process of exploration, design, or inspection during construction for a large, or even a small, project that would involve construction of a soil tunnel or an excavation adjacent to existing buildings. Rather, it is intended that this overview be used as an introduction to the topic for those not initially familiar with this type of construction as well as be used as resource material for future study. Finally, this paper is not intended to be overly technically detailed, recognizing that the members of the intended audience are not specialists in underground construction. An annotated bibliography is provided as a resource for more in-depth study.