Numerical simulation of soil–cone penetrometer interaction using discrete element method

One of the most common methods to measure soil strength in-situ is cone penetrometers. In this paper the development of a three dimensional (3D) discrete element model (DEM) for the simulation of the soil–cone penetrometer interaction in a slightly cohesive loamy sand soil is presented. The aim was to investigate the effects of the soil model’s geometrical (e.g., soil model cross section shape and size and model’s height) changes on variations in the soil penetration resistance. The model area ratio and height ratio values were adopted to analyse the effects of the cross section size and the model’s height, respectively. The results of penetration resistance of the DEM simulations were compared with the in-situ measurement with a cone penetrometer of the same geometry. This comparison allowed the derivation of the contact properties between the elements. To simulate the soil material the so-called Parallel Bond and Linear Models were used in the 3D version of the Particle Flow Code (PFC) software. Finally the mechanical properties of the soil, namely the cohesion and internal friction angle were estimated by DEM simulation of direct shear box. Results showed that the penetration process can be simulated very well using the DEM. The model’s calculated penetration resistance and the corresponding in-situ measurement were in good agreement, with mean error of 14.74%. The best performing models were a rectangular model with an area ratio of 72 and a height ratio of 1.33 and a circular model with an area ratio of 32 and a height ratio of 2. The simulation output of soil material properties with direct shear box resulted in representative values of real loamy sand soils, with cohesion values range of 6.61–8.66 kPa and internal friction angle values range of 41.34–41.60°. It can be concluded that the DEM can be successfully used to simulate the interaction between soil and cone penetrometers in agricultural soils

Utilization of fused deposition method 3D printing for evaluation of discrete element method simulations

FDM 3D printing is used for designing prototype assessment in engineering production. It is usually used to verify the functionality of kinematics mechanisms. It can also be used for innovation in agricultural production, eg. the development of new mechanisms for agriculture tools. Such a mechanism as well as the entire components is printed using FDM and they are made of plastics. This whole can be experimentally verified in a laboratory trough. The article deals with the verification of the possibilities of using FDM technology for the design of agricultural tools. The material properties, namely stress-strain, of the plastics after printing are entered into the Ansys mechanical library, and the DEM results are also imported into Ansys mechanical. Material properties of plastics for FDM technology such as PLA, PETG show that its mechanical properties limited their using for validation

Discrete Element Modeling of the Mechanical Response of Cemented Granular Materials

abstract: With the growth of global population, the demand for sustainable infrastructure is significantly increasing. Substructures with appropriate materials are required to be built in or above soil that can support the massive volume of construction demand. However, increased structural requirements often require ground improvement to increase the soil capacity. Moreover, certain soils are prone to liquefaction during an earthquake, which results in significant structural damage and loss of lives. While various soil treatment methods have been developed in the past to improve the soil’s load carrying ability, most of these traditional treatment methods have been found either hazardous and may cause irreversible damage to natural environment, or too disruptive to use beneath or adjacent to existing structures. Thus, alternative techniques are required to provide a more natural and sustainable solution. Biomediated methods of strengthening soil through mineral precipitation, in particular through microbially induced carbonate precipitation (MICP), have recently emerged as a promising means of soil improvement. In MICP, the precipitation of carbonate (usually in the form of calcium carbonate) is mediated by microorganisms and the process is referred to as biomineralization. The precipitated carbonate coats soil particles, precipitates in the voids, and bridges between soil particles, thereby improving the mechanical properties (e.g., strength, stiffness, and dilatancy). Although it has been reported that the soil’s mechanical properties can be extensively enhanced through MICP, the micro-scale mechanisms that influence the macro-scale constitutive response remain to be clearly explained. The utilization of alternative techniques such as MICP requires an in-depth understanding of the particle-scale contact mechanisms and the ability to predict the improvement in soil properties resulting from calcite precipitation. For this purpose, the discrete element method (DEM), which is extensively used to investigate granular materials, is adopted in this dissertation. Three-dimensional discrete element method (DEM) based numerical models are developed to simulate the response of bio-cemented sand under static and dynamic loading conditions and the micro-scale mechanisms of MICP are numerically investigated. Special focus is paid to the understanding of the particle scale mechanisms that are dominant in the common laboratory scale experiments including undrained and drained triaxial compression when calcite bridges are present in the soil, that enhances its load capacity. The mechanisms behind improvement of liquefaction resistance in cemented sands are also elucidated through the use of DEM. The thesis thus aims to provide the fundamental link that is important in ensuring proper material design for granular materials to enhance their mechanical performance.Dissertation/Thesisundrained simulation with flexible membranecyclic direct simple shear simulationDoctoral Dissertation Civil, Environmental and Sustainable Engineering 201