Integration of Wireless Reflection Seismic Using a Mechanized Impact Source Into Machine Driven Rock Tunneling

Tunneling is a risky job due to unforeseen geological conditions. Geological characterization during the tunnel excavation phase is commonly done using probe drills from the tunnel face. Although useful information provided by this technique is one dimensional and represents only a small fraction of the volume being excavated. Therefore, hazardous areas such as fault and shear zones, cavities, etc., may not be detected on time and the excavation may enter these areas resulting in large collapses, water inrush and other severe events. Hence, the risk of decreasing safety and increasing costs is always latent in this type of projects. In addition, probe drills are cost and time demanding. In mechanized tunneling using Tunnel Boring Machines, the presence of the excavator itself reduces the area available for applying other type of exploration techniques. Moreover, due to cost of this machines, there is a noticeable time pressure for keeping the production cycle, i.e. the entire excavation process, constantly running as much as possible. Not by chance, daily, monthly, and annual advance rate records are reported frequently from projects all around the globe.

Tunnel reflection seismic has been applied for various decades in all type of tunneling tasks in hard rock. Advantages of the seismic method are its penetration depth, spatial coverage (2D or 3D) and spatial resolution. One technology, the Tunnel Seismic Prediction method (TSP) has established as a reliable tool for geological prediction while tunneling. The most recent generation comprises a wireless system which can be set fully independently using a local WiFi network. Seismic sensors and required devices are synchronized together allowing an easy and fast data recording. With this novel system, a unique pneumatic impact hammer, also wireless, can be employed as the seismic source. The impact hammer fulfills all requirements for being used in mechanized tunneling environments. In this paper, the integration of this system is presented and results coming from a tunnel project are discussed.