Pre-treatment of ground in hard rock TBM tunneling: probe drilling and pre-grouting

There is a global trend in tunneling for more construction in urban areas. This has led to a higher emphasis on the effects on the surrounding environment. Especially important in this regard is to control the water inflow into the tunnel to avoid surface settlements. In some projects where the requirements of water ingress are very strict, it is the authors' understanding that Drill and Blast (D&B) tunneling is the preferred method of excavation due to the common belief that Tunnel Boring Machines (TBMs) are not capable of proper pretreatment of the ground. The Norwegian tunneling practice is internationally recognized for, among other things, the unique focus on probe drilling and pre-grouting in D&B applications. In this paper Robbins and the Norwegian University of Science and Technology (NTNU) work together to look at the benefits of adopting the experiences of probe drilling and pre-grouting from Norwegian D&B tunneling to TBM applications. The following topics will be discussed: The fundamentals of probe drilling and pre-grouting with TBMs; how to efficiently probe drill and pre-grout in TBM tunneling; the latest/coming developments; and the potential of this approach in TBM tunneling.