Supporting data for "Rainfall-Induced Slope Failure: Understanding the Interplay of Contributing Factors and Soil State Characterization Techniques"

<p dir="ltr">Rainfall-induced slope failure represents a significant and escalating natural disaster, exacerbated by the increasing frequency and intensity of extreme rainfall events due to climate change and intensified land use. Previous studies attempted to investigate the controlling factors and failure mechanisms. However, current understanding does not adequately explain why some slopes with similar configurations remain stable while others fail. Thus, suggesting that the interplay among contributing factors may be overlooked and not well understood. A critical concern is that these failures can develop into flowslides, also known as static liquefaction, which typically occurs in loose sandy soils and is characterized by a sudden collapse and very low residual strength. Such failures can lead to high-velocity movements and extensive runaway distances of the soil mass. Methods to accurately quantify the in-situ state of the soil will be crucial for identifying loose conditions and preventing such failures.</p><p dir="ltr">This research investigates the uncertainties in the interplay of factors contributing to rainfall-induced slope failure. A systematic study was conducted to understand the role of rainfall patterns and the hydraulic properties of soil on slope stability. The critical rainfall patterns resulting from the combination of antecedent and main rainfall are examined through comprehensive numerical analysis based on historical data. The influence of various ways to define the antecedent rainfall and its critical duration is also evaluated. The Soil Water Characteristic Curve (SWCC) is essential in describing the relationship between the water content and matric suction. This research explores the potential contributions of hysteresis and variability associated with the SWCC and its interactions with various rainfall characteristics, permeability, initial suction, and slope profiles. An extensive database of SWCC for four typical Hong Kong soils was collected and characterized.</p><p dir="ltr">Case histories of slope failures provide valuable insights into these complex interactions. The Sau Mau Ping failure in Hong Kong is particularly significant as it involves multiple extreme rainfall events with varying patterns, which lead to catastrophic physical failures. Notably, slopes that remained stable during earlier intense rainfall ultimately failed during a subsequent event with only half the intensity. Through an extensive review of case histories and comprehensive numerical analyses, this study reveals the critical influence of the combined antecedent and main rainfall patterns contributing to the devastating failures.</p><p dir="ltr">Efforts were made to establish an integrated relationship for estimating soil state from in-situ measurements. A comprehensive database of Cone Penetration Test (CPT) and shear-wave velocity measurements is collected, and the influence of fines content on the relationship between these parameters is quantified. An integrated method for predicting the in-situ state is proposed by extending the relationship with the state parameter . The method was successfully applied to well-documented case histories of recent flowslides in tailings dams and provided insights into why certain slopes in New Zealand experienced liquefaction while others remained stable during an extreme rainfall event. This study improved the understanding of the relationship between contributing factors of rainfall-induced slope failures, and the proposed methods potentially contribute to the existing engineering practice and mitigate such failures.</p>