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Simulation of Rainfall-triggered Landslides with Considering the Rheology Changes in Sandy Soils

Ghorbani, Ramin | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54884 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Taghizadeh Manzari, Mehrdad; Hajilouy-Benisi, Ali
  7. Abstract:
  8. This study presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. The discrete element method (DEM) is used to establish a rheological model that relates the apparent viscosity of a granular sand to shear rate, normal stress, and water saturation. A theoretical model is developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces are embedded in a 3D shear cell as a numerical rheometer and a wet sand is sheared between two walls. A power law rheological model is obtained as a function of inertia number and saturation. It was found that up to a critical saturation, the apparent viscosity increases with saturation and is higher than that of the dry sand. However, when the saturation exceeds a critical value, the viscosity suddenly drops below that of dry condition. To evaluate the rheological model, the collapse of two-dimensional granular material on a horizontal rigid bed is studied using continuum-based numerical simulation which utilizes the proposed rheological model. To describe the entire landslide process, three steps are considered in this study: 1) a coupled hydro-stability analysis which detects the failure plane using the Finite Element Method (FEM) (pre-failure stage), 2) computing the local rheology of the failed mass (wet sandy soil) based on the water saturation at the onset of failure, using the saturation-based rheological model (transition stage), and 3) a continuum-based propagation analysis which solves the flow of the wet material by employing the Smoothed Particle Hydrodynamics (SPH) method (post-failure stage). Finally, to investigate the influence of rheological model on the post-failure behavior, the computed final deposition profile and flow kinetic energy are compared with those of a viscoplastic model.
  9. Keywords:
  10. Discrete Element Method ; Water Saturation ; Rheological Model ; Initiative ; Landslide ; Smoothed Particle Hydrodynamics (SPH) ; Pore Pressure ; Saturation Degree

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  • SCI_Volume 28_Issue 5_Pages 2719-2732
  • SCI226861645389000