Study on coupling mechanism of high fill settlement-groundwater in southwest red layer

In order to reveal the coupling mechanism between settlement and groundwater activity in high-fill sites in the southwest red bed area, a typical high-fill project in Jintang County, Chengdu City was taken as the object of this study. A comprehensive monitoring system including 116 settlement monitoring points and 4 groundwater monitoring wells was constructed, and multi-source time series data of a hydrological year from July 2024 to June 2025 were obtained. The spatial and temporal evolution of subsidence and groundwater dynamic field and its driving mechanism were studied by using ArcGIS spatial analysis, grey correlation method ( SPSSAU ) and Origin time series analysis. The results show that the time series evolution of site settlement follows the four-stage model of steep drop-slow drop-fluctuation-stationary, and its spatial distribution pattern is mainly controlled by the filling thickness. The groundwater flow field in the study area is controlled by topography and rainfall, and its dynamic change has a high correlation with settlement ( 0.752 ), which is an important driving factor second only to fill load. Finally, it is proposed that the settlement in this area is a multiple driving mechanism dominated by load-groundwater, that is, the filling load lays the basic pattern of settlement, and the groundwater activity modulates the details of its spatial and temporal evolution. The research results can provide a theoretical basis for the optimal design, risk early warning and long-term safety control of high fill projects in the southwest red bed area.