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

To effectively control the construction progress of underground caverns and address the impact of multi-risk factor coupling on the construction schedule, this paper proposes a risk coupling analysis method integrating Social Network Analysis (SNA) and the N-K model. Firstly, risk factors are identified and a risk factor set is constructed using the Work Breakdown Structure-Risk Breakdown Structure (WBS-RBS) analysis method. Secondly, SNA is applied to build a risk association network model, clarifying the interaction mechanism between risk factors, revealing their potential coupling relationships, and analyzing the importance of each node. Thirdly, based on the risk coupling mechanism, the N-K model is introduced to construct a risk coupling model for underground cavern construction progress, which quantifies the coupling strength under different coupling relationships, calculates the coupling values for different coupling types, and uses these values to revise the node importance in the SNA. Finally, a risk factor coupling evaluation model integrating SNA and the N-K model is established. A case analysis is conducted taking the spillway tunnel construction of the Wudongde Hydropower Station as an example. The results show that the more risk factors involved in coupling, the larger the coupling value, and the more likely risk events are to occur. Among the 13 secondary risk factors, adverse geological conditions, severe weather, design modification, and mutual interference in construction are the key risk factors leading to schedule delays in spillway tunnel construction, which is consistent with the actual situation at the construction site.