Abstract:To overcome the subjectivity and ambiguity of the traditional strength reduction method in the evaluation of tunnel stability due to the artificial determination of the instability critical point, the wavelet transform is introduced into UDEC discrete element numerical analysis, and a new instability identification method based on time-frequency analysis is proposed. A tunnel numerical model is established to comparatively analyze the evolution of surrounding rock displacement with the reduction factors under two different working conditions. Results indicate that based on the Morlet wavelet to transform the displacement sequence of key monitoring points, the sudden change points during the displacement development process can be clearly and objectively identified to accurately determining the safety factors. The principal safety factor derived from this method closely aligns with the instability process revealed by numerical simulation, which effectively highlights the differences in local safety factors caused by asymmetric failure. The research result verifies that the combination of wavelet transform with the strength reduction method can achieve the quantification and precise identification of the critical state of surrounding rock instability, offering an objective and reliable analytical approach for stability assessment of tunnel engineering.
