How to Detect Disorders During Tunnel Digging with a Muons Telescope Mounted on a TBM

Abstract

Summary The fact that the earth is constantly bombarded by an isotropic flux of cosmic rays has permitted to develop a new detection method that can only look over the observation point, but powerful enough to detect anomalies in front of a tunnel boring machine (TBM) digging a gallery. To do that, a cosmic ray detector, a muons telescope is set up on a TBM, looking towards. Cosmic radiations generate very short-lived particles in the upper atmosphere, muons, whose diameter is small enough to penetrate the ground to depths of several hundredths of meters. Muons propagate without changing direction and disintegrates when it hits a proton or a neutron. So it’s a mass detector like gamma ray, and is able to measure density variations. It is used to study volcanoes and galleries. Experiments are occurred in galleries in France and Switzerland, especially in the Croix-Rousse tunnel (Lyon). Since April 2018 a muons telescope is installed on a TBM of the “Grand Paris Express”, moving with the TBM and permanently providing results.