A study of rainfall infiltration on slope stability using sand piles to reinforce slopes

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Naseer, S. ORCID: 0000-0003-4914-1077, 2023. A study of rainfall infiltration on slope stability using sand piles to reinforce slopes. PhD, Nottingham Trent University.

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Abstract

Slope instability, predominantly manifested as landslides, stands as one of the most formidable natural hazards, posing significant challenges to sustainability. Prolonged rainfall events are a vital trigger for landslides, with global variations in rainfall patterns primarily attributed to climate change. For instance, on October 3, 2020, the UK experienced its wettest day since 1891, with an average of 31.7 mm of rainfall, illustrating this climatic change.

This research aims to investigate the mechanisms of soil slope failure under varying rainfall conditions by combining finite element modeling with physical modeling. The primary objective is to understand the complexities of soil slope failure under different rainfall intensities and durations and to evaluate the effectiveness of sand piles in mitigating failure and reducing damages.

The study begins with a numerical analysis using finite element methods, examining various soil slopes with different inclination angles subjected to varying rainfall conditions. A coupled flow-deformation analysis is conducted to unravel the behavior of slopes during rainfall infiltration. Sand piles' length, diameter, spacing, and stiffness are optimized for effectiveness.

Next, the optimized parameters from the numerical analysis guide the design and testing of a laboratory-based physical model. This dual approach reveals how slope geometry significantly influences rainfall-induced instability. Gravity forces increase with slope height and inclination, while gentler slopes with longer ponding times, experience more significant rainfall impact. This prolonged infiltration reduces matric suction, diminishing soil shear strength and destabilizing the slope. Conversely, steeper slopes, with shorter ponding times, see more water as surface runoff.

The efficacy of sand piles in stabilizing fine soil slopes is highlighted. Sand piles function as both drainage and reinforcement mechanisms, providing effective drainage paths and facilitating the transfer of infiltrated water to the surface as runoff. This reduces pore water pressure and increases matric suction, thereby enhancing soil shear strength and slope stability. The slope was monitored, and soil displacements were measured using a novel approach called the Automated Sensory and Signal Processing System (ASPS). Images captured during the experimental program were processed in MATLAB, applying mathematical equations to extract useful features and categorize slopes based on displacement levels. Low displacement indicated stable conditions, while high displacement signaled potential instability and the need for further intervention.

To validate the findings, a case study was conducted on the Azad Pattan Road in Kashmir, Pakistan. This site, consisting of fine silty soil similar to the soil type used in the finite element and lab modeling, provided a real-world application of sand piles. The geology of the slope mirrored the conditions studied in the numerical and physical models, allowing for the practical application of optimized sand pile parameters.

In conclusion, this research significantly contributes to understanding slope stability under varying rainfall conditions. By integrating numerical analysis, physical modeling, and the application of sand piles, the study offers a comprehensive view of the factors influencing slope failures and effective stabilization techniques. The case study on Azad Pattan Road in Kashmir further validates these findings, demonstrating practical implications for mitigating landslides in areas prone to slope instability. These insights are invaluable for fortifying resilience against climate change-induced natural hazards.

Item Type:

Thesis

Creators:

Naseer, S.

Contributors: