Chapter 11 - Rate of Tunneling

Abstract

This chapter examines the rate of tunneling; the excavation of tunnels is affected by many uncertainties. The time of completion of tunneling projects is grossly underestimated in many cases, because proper evaluation of the factors that affect the rate of tunnel excavation is ignored. The factors affecting the blasting and drilling method of tunnel excavation are variation in ground/job conditions and geological problems encountered, quality of management and managerial problems, and various types of breakdowns or holdups. The first factor is important because the rate of tunnel driving is different for different types of ground conditions. Depending upon the ground conditions, different methods of excavation are adopted for optimum advance per round so that the excavated rock can be supported within the bridge action period or the stand-up time. Frequent changes in ground conditions seriously affect the tunneling rate because both the support and excavation method need to be changed. In addition, tunneling management is discussed; tunnel construction is a complex, challenging, and hazardous profession. It demands a high skill of leadership, technology, and communication. On-the-spot decisions are needed in tunneling crises.