A new method to determine the surrounding rock pressure in twin tunnels with small clear spacing

This study introduces a new method for calculating the surrounding rock pressure of twin-tunnels with small clear spacing under various working conditions. The proposed method unifies the calculation approaches for surrounding rock pressure under different working conditions into a single framework. A comparison is made between the new method and the standard recommended methods, and the installation procedures for field monitoring instruments of surrounding rock pressure are standardized. Laboratory experiments are conducted to correct the monitored values of surrounding rock pressure in the field. Additionally, the active–passive load separation method is employed to extract the active load component from the measured pressure values. The results show that the surrounding rock pressure calculated using the new method aligns more closely with actual engineering conditions. The variation trends and absolute magnitudes of surrounding rock pressure are smaller than those obtained using the standard methods. The corrected surrounding rock pressure values are closer to the true surrounding rock pressure. By comparing the active load derived from the measured values with the calculated surrounding rock pressure, the comparison results become more accurate. Furthermore, a three-way comparison among the calculated values from the new method, the standard recommended values, and the field-measured values confirms the correctness of the new method and its rationality and applicability in practical engineering projects.