Coupling analysis of schedule risk for underground cavern construction integrating SNA and N-K

In response to the challenges in controlling the construction schedule of underground caverns and addressing the impact of multi-factor coupling on schedule risks, this paper proposes a risk coupling analysis method that integrates Social Network Analysis (SNA) with the N-K model. Firstly, risk factors are systematically identified using the Work Breakdown Structure-Risk Breakdown Structure (WBS-RBS) method, and a comprehensive set of such factors is established. Secondly, a risk association network is constructed using SNA to clarify interaction mechanisms, reveal latent coupling relationships, and evaluate the importance of each node. Building on the risk coupling mechanism, the N-K model is then introduced to develop a schedule risk coupling model for underground cavern construction. This model quantifies coupling strengths under different coupling relationships and derives corresponding coupling values, which are subsequently applied to adjust node importance in the SNA, thereby establishing an integrated SNA and N-K model for coupled risk assessment. Finally, a case study of the Wudongde Spillway Tunnel Project is conducted, identifying four primary risk categories (human, material, environmental, and managerial) and 13 secondary risk factors that significantly contribute to schedule delays. The case study reveals intrinsic coupling patterns among these risk factors and pinpoints the most critical ones. Results demonstrate that a higher number of coupled risk factors leads to greater coupling values and an increased probability of risk events. Key risk factors responsible for schedule delays include adverse geological conditions, severe weather, design changes, and construction interference.