Using mobile muography on board a Tunnel boring machine to detect man-made structures
Abstract
As part of construction work to build a new subway in the suburbs of Paris (line 15), a muon telescope was attached to a Tunnel Boring Machine (TBM) for one year and was able to collect vasts amounts of data related to the density of the ground around the tunnel.
This particular set-up adds a challenge: integrating movement into traditional muongraphy data collection. Indeed, rather than capturing a single 2-D photograph of muon flux, estimated over a lengthy period of time, the data are split into a sequence of short-period 2-D photographs. The latter allowed us to reconstruct an estimate of the 3-D density of the ground. Hopes are high to develop an operational measurement tool able to predict changes in the density of the ground in front of the TBM, detecting the presence of geological heterogeneities or man-made buried objects. Such change, if anticipated, would help optimize the planning of drilling operations. In this study, t he goal is to evaluate if the mobile muography is able to record the existence of man-made structures, and when it is appropriate, to reconstruct their geometry in 3-D, with few prior knowledge. Two different experimental situations are analysed through simulated and real data sets. The first situation concerns the detection of a group of buildings besides the TBM trajectory and the second situation involves the detection of a 1 meter wide sewer above and besides the path of the TBM. Concerning the buildings, simulated and real data sets of apparent density photographs show that buildings drastically affect our estimates of the ground density. While the complexity of their internal structure cannot be precisely accounted for, accounting for their existence (and correcting it) is important for 3-D reconstructions. If their shape is known, a homogeneous density value can be used as an inverted parameter. As for the sewer experiment, our simulation results suggest that it is possible to detect, and reconstruct the sewer. For measurements, the outline of the sewer emerges occasionally from the natural poisson noise. In the subsequent 3-D reconstruction, the sewer is reconstructed as a diffuse density weakening around its precise location. These results can be explained by the joint influence of building and geological heterogeneities.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS43B0839C
- Keywords:
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- 0910 Data processing;
- EXPLORATION GEOPHYSICS;
- 0933 Remote sensing;
- EXPLORATION GEOPHYSICS;
- 0994 Instruments and techniques;
- EXPLORATION GEOPHYSICS;
- 8494 Instruments and techniques;
- VOLCANOLOGY