A Safety-Condition Assessment Framework for Adjacent Deep Excavations Incorporating Nonlinear Indicator Coupling and Neighboring Influence

Adjacent deep excavations may interact through stress redistribution, deformation propagation, structural interaction, and groundwater variation. Existing risk assessment methods mainly focus on individual indicators or single excavations, which may overlook nonlinear indicator interactions and neighboring-excavation influence. This study proposes an extensible framework that combines response-based indicator scoring, expert-derived weights, nonlinear indicator interactions, and a distance-based neighboring-excavation contribution. Its output is a composite safety-condition index on a conventional 0–100 scale, with higher values indicating more adverse conditions under the adopted assessment rules. Indicators are organized into deformation, structural resistance, and hydrological domains. Heterogeneous indicators are converted into dimensionless indicator scores using the adopted scoring criteria. Indicator weights and a nonlinear interaction model are incorporated to aggregate scores and include interaction contributions for selected indicator pairs. A distance-based attenuation operator is further introduced to represent modeled neighboring-excavation contributions to the index. The framework is illustrated using a representative twin-excavation configuration, with weights derived from expert judgment, interaction coefficients estimated from numerical degradation scenarios, and attenuation parameters informed by published excavation cases. The example demonstrates the calculation procedure, scenario comparison, identification of governing support levels and sensitivity effects of selected parameters on the calculated index.