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This paper investigates soil fluidisation at the microscale using the discrete element method (DEM) in combination with the lattice Boltzmann method (LBM). Numerical simulations were carried out at varying hydraulic gradients across the granular assembly of soil. The development of local hydraulic gradients, the contact distribution, and the associ...
Citations
... Indraratna et al. (2021) suggested boundaries derived from microscale investigations to differentiate between internally stable and unstable soils. Haq et al. (2022) studied internal erosion by coupling the lattice Boltzmann method and DEM. Haq et al. (2023) evaluated the internal instability of granular soils and showed how the transition of soil from an internally stable to an unstable state takes place during shear-induced deformation. ...
Internal instability establishes when fine particles of bimodal soil migrate with seepage flow into voids created by coarse fabric, altering the original gradation. The tendency for soils to undergo internal instability centres on their compaction level and particle size distribution. This study employs the discrete element method to evaluate the potential for internal instability at the particle scale. Numerical simulations enable a thorough analysis of particle contacts in soils, encompassing both internally unstable and stable conditions. The study examines particle connectivity at different relative densities and uses particle connectivity and stress reduction factor to draw clear distinctions between soils that are internally unstable and those that are stable. Grain-scale data allows for a precise measurement of the stress reduction within the finer portion of the materials. The stress distribution is observed to be influenced by the particle-size distribution, percentage of finer fraction, and relative density. The predictions of the current numerical model align with the constriction-based criterion, enhancing practitioners’ confidence in a timely preliminary evaluation of soil internal instability potential.
... The DEM, originally developed by Cundall to address rock mechanics [6], has been extensively applied across various fields. The DEM application spans from analysing road materials in highway engineering [7,8], to investigating soil interaction mechanics [9][10][11], to constructing simplified models for trucks on roads with discrete pebble surfaces [12,13]. This diverse application spectrum not only demonstrates the DEM's versatility but also significantly underscores its efficacy in assessing the load-bearing capacities of pebble aggregates. ...
... The DEM, origina developed by Cundall to address rock mechanics [6], has been extensively applied acr various fields. The DEM application spans from analysing road materials in highway gineering [7,8], to investigating soil interaction mechanics [9][10][11], to constructing simp fied models for trucks on roads with discrete pebble surfaces [12,13]. This diverse app cation spectrum not only demonstrates the DEM's versatility but also significantly und scores its efficacy in assessing the load-bearing capacities of pebble aggregates. ...
The load-bearing capacity of pebble aggregates plays a pivotal role in influencing the operational performance of uncontrolled trucks on arrester beds. The complexity of this phenomenon stems from the nonuniformity in the shapes of the pebbles and their stochastic arrangement within the beds, presenting notable challenges for traditional mathematical modelling techniques in precisely evaluating the contact dynamics of these aggregates. This study leverages the discrete element method (DEM) to extensively analyse the arrester bed aggregate of a standard truck escape ramp. The aforementioned mechanism entails the gathering of morphological parameters of irregularly shaped aggregate particles and introduces a novel method for constructing random shapes that adhere to the observed distribution characteristics. A discrete element model, grounded in the physical properties of these aggregates, is formulated. This study focuses on the aggregate’s load-bearing capabilities, scrutinising the mechanical behaviour of the aggregate particles at the macroscopic and microscopic scales. These insights offer substantial scientific contributions and practical implications for assessing the safety of escape ramps and determining essential parameters for the brake bed design.
... The shallow slope failures described can be classified as slide-debris flows, whose failure process initiates as a planar or slightly circular sliding but can evolve in a single or multiple debris flow. The possible activation of a debris flow is related to the achievement of the critical state corresponding with the fluidisation of the mobilised material (Iverson et al., 1997;Haq et al., 2023). The debris flow is the result of an undrained deformation of the soil that occurs in the presence of a typically contractive behaviour (Sassa and Wang, 2005;Iverson and George, 2014). ...
... Others used cracked model pipes to study the effect due to the defect configuration (Mukunoki et al. 2009;Tang 2017;Zhang et al. 2020;Chen et al. 2022). More recently, powerful visualisation and numerical tools are developed using multiphase flow analyses, which can be modelled using either of three ways namely; Euler-Euler, Euler-Lagrange or Lagrange-Lagrange (Cui et al. 2012;Ibrahim and Meguid 2020;Nguyen and Indraratna 2020;Indraratna et al. 2021;Haq et al. 2022). Table 2 shows the details of adopted numerical model and software used by various researchers. ...
Damage or deterioration of water distribution or storm water drain pipeline systems create a problem of leakage, which has the potential to erode its surrounding soil. This erosion, if not detected in time, can form a large cavity in the ground and consequently results in catastrophic failure. This paper presents a detailed review of soil erosion due to damaged buried pipe using experimental and numerical evidence available in the literature. Herein, erosion is explained using two different flow possibilities, namely, infiltration and exfiltration. A comprehensive discussion on the method of investigation and the erosion mechanism, along with the governing parameters used in the investigation and their challenges, are presented. This review paper also discusses two other issues, that is, the rate of erosion and the volume of cavity formed due to erosion. Both the issues seem to be governed by the hydraulic gradient in the soil, the size of the defect in the pipe and the size of soil particles surrounding the defect. Important empirical and analytical methods which are used to predict the size of the cavity as well as the leakage rate and pressure drop, are also discussed. The location and size of the cavity seems to be highly dependent on the groundwater level.
To gain a deeper understanding of the fundamental characteristics of internal forces and deformations in the directional distribution of granular materials, it is necessary to investigate the directional distribution of particles on the mechanical properties and microstructural evolution process of the soil. The discrete element particle flow program PFC3D is used to construct the particle with the same aspect ratio, convexity, and sphericity as the binary images, and the specimens with directional particle distributions of 0°, 30°, 45°, 60°, and 90° are generated. Furthermore, the quantitative correlations between the constitutive parameters and the deposition angle are examined. The results show that the shear strength and shear expansion of the soil increase with increasing deposition angle. With an increase in axial strain, the dominant direction of contact points and the direction of force chain and normal contact force rotate counterclockwise. In the critical state, the microstructural direction of the specimens with different deposition angles is approximately the same, which is primarily along the direction of 45° + ϕcs. The critical friction angle decays as a power function with the increase of deposition angle in undrained tests. The critical void ratios of the specimens with different deposition angles under drained tests decay linearly as the deposition angle increases. The critical mechanical coordination number decays exponentially with an increase in deposition angle under undrained tests. The conclusions mentioned above serve as a guide for revising the constitutive equations for specimens considering the microscopic behavior.
