Three-Dimensional Displacement Analysis and Statistical Modeling of the Pubugou Rockfill Dam Using Multi-Track InSAR

Long-term displacement in ultra-high rockfill dams is spatially heterogeneous, yet point-based monitoring and single-track InSAR provide only a limited account of its three-dimensional evolution. To address this limitation, we develop a workflow combining multi-track three-dimensional InSAR reconstruction, temporal feature clustering and modified HST/HTT modeling. In the modified models, the conventional linear time term is replaced by a predominant displacement component, allowing nonlinear long-term behavior to be represented alongside hydraulic and thermal responses. Three Sentinel-1 tracks acquired between 2014 and 2023 were used to analyze the Pubugou Dam. Maximum vertical and eastward displacement rates reached 17.70 and 19.41 mm/yr, respectively, while cumulative vertical displacement reached approximately 178 mm. Three coherent displacement zones were resolved: the upper dam was dominated by long-term accumulation, the central section displayed the strongest periodic response, and the lower dam and abutments remained comparatively stable. The modified models reproduced the observed series more closely in sample than the conventional formulations, while the fitted coefficients indicated a stronger and more spatially variable response to reservoir level than to air temperature. This integrated analysis provides a spatially resolved account of long-term displacement and environmental response across an ultra-high rockfill dam.