Distribution characteristics and theoretical prediction of ground settlements caused by multiple undercrossing excavations beneath existing underground structures

With the increasing density of underground structures in urban areas, repeated undercrossing excavations have become common, often leading to cumulative disturbance and asymmetric ground settlement. Traditional stochastic medium theory treats sequential excavations as independent events and cannot represent disturbance-superposition effects. In this study, scaled model tests were conducted to investigate settlement evolution caused by multiple undercrossing excavations. Based on experimentally identified disturbance characteristics, a corrected stochastic medium model was developed by introducing a spatially varying disturbance adjustment factor. Numerical simulations and field measurements were used for validation. Results show that disturbance superposition amplifies settlement in overlapping influence zones and shifts the settlement peak toward earlier excavations, producing asymmetric settlement troughs. Compared with conventional superposition methods, the proposed model improves prediction accuracy by more than 20% in representative field cases. The proposed framework provides an experimentally supported, engineering-oriented approach for predicting cumulative settlement under repeated undercrossing.