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Original scientific paper In order to obtain the skewed pressure characteristics, the physical model tests, adopting two kinds of excavation sequences of the bench method and the expanding method, were conducted under the different confining pressures for observation thermal radiation characteristics of the skewed pressure induced by step-by-step excavation for a double-arch tunnel. Firstly, under uniaxial compression test, the cylindrical specimen presented the cooling effect, the correlations between the axial stress of the cylindrical specimen and its surface thermal radiation temperature displayed negative nonlinear correlation in the pre-peak curve and linear correlation in the post-peak curve, respectively. Secondly, for the physical model tests, the stress-temperature-time curves showed obvious two-phase trend as first moderate decline and then rapid decline stages, and the latter was slower than the former for an excavation step after all excavations being completed. The results showed that for two different excavation sequences, the failure positions on the vault of the double-arch tunnel due to being unloaded are diametrically opposed. Then the corresponding relationships between the skewed pressure induced by double-arch tunnel excavation and the temperature field of the infrared thermal radiation were revealed, which can provide a reference for the reasonable excavation and security support of the double-arch tunnel.

Skewed pressure characteristics induced by step-by-step excavation of a double-arch tunnel based on infrared thermography