Integrated Risk Assessment of Landfill Flowslides: Sensitivity Analysis of the Initiation Mechanism and Hazard Potential

Abstract

Abstract Numerous landfill flowslide disasters have occurred globally, posing a significant threat to the environment and human lives and property. The progressive evolution of flowslides, encompassing both the slope failure and postfailure motion stages, is influenced by waste properties, rainfall intensity, and leachate level. Traditional analytical methods fail to simulate the large-deformation process after instability and quantify flowslide destructiveness. Therefore, this study employs a smooth particle hydrodynamics (SPH) model to investigate the influences of these critical factors across both stages. Four key indicators, i.e., the rainfall duration preceding flowslide initiation, warning leachate level ratio, the sliding distance, and the mass volume ratio, are adopted to characterize landfill responses under heavy rainfall and high leachate level. Results showed that increasing fiber content from 0.01 to 0.05 extends initiation rainfall duration from 72 to 177 h and triggers a transition from global to local failure modes. However, it simultaneously exacerbates downstream hazards, with sliding distance increasing by 11.3 m and mass volume ratio rising by 16.6%. When rainfall intensity was below the saturated permeability coefficient of waste, the rainfall duration before flowslide initiation decreased with increasing rainfall intensity. When the intensity was sufficiently high ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="greater than 120 m m divided by d a y" display="inline" overflow="scroll"> <mml:mo form="prefix">&gt;</mml:mo> <mml:mn>120</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo stretchy="false">/</mml:mo> <mml:mi>day</mml:mi> </mml:math> ), the duration stabilized at 117.7 h. Higher leachate levels and taller landfills lowered flowslide initiation thresholds, leading to deeper failure surfaces, larger sliding mass volumes, and greater downstream hazard. Additionally, a quantitative risk assessment method is proposed, which quantifies risk as a sum of the products of sliding distance and hazardous rainfall occurrence frequency, validated via a case study. This method provides valuable insights for landfill operation and flowslide risk management.