Error mechanisms and applicability boundaries of the vibration input method in tunnel seismic response analysis

This study evaluates the applicability of traditional vibration input methods in tunnel seismic analysis to address limited calculation accuracy and ambiguous applicability. The vibration input method, wave input method, and theoretical solutions are compared to clarify the error mechanism and main influencing factors. Through correlation analyses, the relationships between model dimensions, geological parameters, and accuracy are established. Then an innovative approach is proposed to improve the calculation accuracy and refine the scope of applicability. The results indicate that the assumed bedrock surface position and model boundaries can significantly affect the accuracy of the model, with the height and wave velocity of the surrounding rock being key control parameters. When the model height is fixed, the correlation coefficient between vibration and wave input results shows three stages of change with increasing width: rapid increase, deceleration growth, and asymptotic convergence to 1. In the case of a fixed width, as the height increases, the coefficient follows a trend of “approximately stable slightly decreasing”. The optimal aspect ratio is 1:2. Size optimization formulas under different rock conditions and methods for selecting analysis time periods are proposed to clarify the engineering applicability of the vibration input method.