Abstract: Deep excavated expansive soil slopes are influenced by multiple factors, including precipitation, groundwater, geological structure, and support measures, resulting in complex spatiotemporal heterogeneity in deformation. Using the slope of Taocha canal segment in the middle route of the South-to-North Water Diversion Project as a case study, the spatiotemporal deformation characteristics were analyzed. Data mining methods, including variational modal decomposition, weighted multiscale local outlier factor, and clustering analysis, were applied. The temporal variation of deformation was analyzed, and spatial distribution characteristics were identified. The influence mechanisms of factors such as precipitation and groundwater on the trend, periodic, and fluctuating components of deformation were explained. Deformation measuring points were clustered, and potential sliding surfaces and sliding bodies were speculated. The deformation mechanism was discussed, and reinforcement measures were proposed. The results indicate that slope deformation exhibits significant trend changes, as well as seasonal and intermittent fluctuations. Deformation in the lower part is relatively large and gradually decreases upwards. The depth of the significant deformation in the upper part is 3 m, located within the climate-influenced layer. Deformation in the central part is influenced by groundwater fluctuation and dense fissure zones, with a significant deformation depth of up to 11 m. Deformation in the lower part is limited by the retaining system and occurs only in the shallow layer. Perched water in the upper part is replenished by rainwater, causing large fluctuation depths and resulting in deep deformation in the middle and upper parts, and there is a certain degree of deformation within the depth of 16.5 m. The potential sliding surface is a polyline. Due to the influence of groundwater, densely fissure zones, and retaining system, the leading edge is approximately horizontal. Drainage wells should be installed to drain groundwater to reduce the impact of groundwater fluctuations on the swelling-shrinkage deformation of expansive soil. The research results can provide technical support for the operation management and reinforcement disposal of deep excavated expansive soil slopes.

Key words: expansive soil, slope, deformation, sliding surface, groundwater, data mining