Experimental analysis of 3D cracking in drying soils using Ground Penetrating Radar

This paper describes the capabilities of a novel technique to investigate crack formation and propagation in drying soils. The technique is a relatively simple, non-destructive indirect technique using a ground-penetrating-radar (GPR) system to detect cracks that form and propagate inside a soil specimen during desiccation. Although GPR devices have been used for multiple applications, their use in soils for the detection of small desiccation cracks has not been demonstrated yet. The experiment and the methodology used to test the accuracy of a small compact commercial GPR device for crack identification are described. The main objective was to identify what type of signals and what crack width and separation between them can be detected using the GPR device. The results indicate that cracks of 1 or 2 mm wide can be detected depending on its position and shape, whereas sub-millimetre cracks are undetectable with the currently existing devices in the market. Regardless of this limitation, the GPR method can be useful to find time-related bounds of when the cracks appear, to point at their location and sometimes at the separation between two of them.Detection of cracks with origin at the bottom or within the specimen was accomplished with this system. Distances of 5 cm or more between cracks can be detected and measured, as well, with accuracy

Numerical and experimental study of initiation and propagation of desiccation cracks in clayey soils

This paper presents the fundamentals and the mathematical formulation to study desiccation cracking in soils based on Unsaturated Soil Mechanics as well as a numerical analysis of a previous desiccation test program. The numerical approach implemented in MATLAB is used in 2D simulations on radial sections of the cylindrical specimens and in a theoretical study of the stress field in plane strain conditions. The numerical analysis, based on two stress stare variables (total net stress and suction) is consistent and in good agreement with the experimental results, including the location of cracks and time of crack initiation

GE Jet Engine Bracket Challenge: A Case Study in Sustainable Design

Open crowdsourcing competitions can provide a large repository of data which can be used to achieve more sustainable product designs. This study looks at the recent General Electric challenge, a competition to minimize the mass of a titanium jet engine lifting bracket, to illustrate the benefits that can be accrued. In the light of current literature the benefits and challenges of crowdsourcing have been considered. Samples of the entrants to the challenge have been compared to identify critical characteristics for interpreting sustainable designs for additive manufacture. Focusing initially on topological optimisation and orientation of the additive manufacture build, critical features have been highlighted. The availability of many CAD designs has been most useful and has potential for future developments. Crowdsourcing as an innovation approach can also be beneficial for both companies and individuals particularly if the entries are open source

Desecación y deformación de suelos arcillosos

Los procesos de desecación en arcillas involucran la pérdida gradual de humedad inducida por la evaporación del agua contenida desde la superficie del suelo. Estos fenómenos son muy complejos debido a la interacción que tienen lugar entre las variables mecánicas e hidráulicas. El proceso de desecación gobernado principalmente por propiedades altamente no lineales, influyen sobre el comportamiento mecánico del suelo haciendo que este se contraiga, se deforme formando rizos o eventualmente se agriete dependiendo de las condiciones de contorno, del grado de heterogeneidad en su interior y de la relación de dimensiones de la porción de suelo sometida a dicho proceso. A pesar de que los cambios de temperatura pueden influir fuertemente en el desarrollo de estos fenómenos, planteamos aquí solo el problema hidromecánico y se establece por hipótesis que se estudiará solo el caso isotermo. En este artículo se presenta una formulación matemática hidromecánica que intenta modelar el complejo fenómeno de desecación. El modelo ha sido implementado en el entorno Matlab y se exponen algunos resultados preliminares de dicho código que capturan el típico rizado cóncavo o convexo que experimentan delgadas muestras de suelos al secarse, así como también distintos resultados obtenidos para diferentes condiciones de contorno

Numerical Modelling of desiccation processes in clayey soils

Desiccation processes in clayey soils involve a gradual moisture content loss induced by evaporation from the soil surface. The desiccation process, mainly governed by very nonlinear hydraulic properties, has an influence on the mechanical behaviour of the soil because the material tends to shrink, thus inducing changes in the stress fields. To understand this process one needs to solve the coupled hydraulic-mechanical problem. In this paper, the formulation (including the unsaturated soil equilibrium and the mass balance equations) and some initial results of a numerical finite element code that solve the boundary value problem are presented. The state variables used in the model are the net stress (total stress) and the suction (negative pore water pressure). For the mechanics part, a non-linear elasticity model based on the state surface concept is chosen, while for the hydraulics problem, Darcy’s law, including unsaturated flow, is used. To relate negative pore water pressure to the degree of saturation the van Genuchten equations are used

Influence of cracking in the desiccation process of clay soils

It is well known that clayey soils undergoing desiccation tend to shrink and eventually crack. Analysis of the behaviour It and influence of cracks in these types of soils is very important in several engineering fields such as mine tailing dams, long-term radioactive waste storage, impervious core of earth dams, and in any situation where clay is used as a barrier to fluid flow. Loss of humidity and cracking changes the permeability of such barriers that may no longer work properly and pose potentially high risks to property and lives. This paper presents an analysis of cracking during drying of soils using a computer code developed within the framework of the finite element and finite differences methods. A study of the influence of crack initiation and propagation in the desiccation process is also undertaken, with a comparative analysis of the phenomenon both with and without crack generation that allows some preliminary conclusions about the desiccation problem

Numerical modelling of formation and propagation of drying cracks in soils

In this paper, a general framework is presented using a finite element model (FEM) combining Continuum Mechanics, Fracture Mechanics and Unsaturated Soil Mechanics, together with re-meshing techniques, to simulate and solve problems due to drying is soils in a consistent manner

Ground penetrating radar system for detection of desiccation cracks in soils

In this paper we explore a relatively simple, non-destructive, indirect technique using a ground penetrating radar (GPR) system to detect cracks that form and propagate inside a soil specimen during desiccation. Although GPR devices have been used for multiple applications, their use in the detection of small cracks (few millimetres wide), has not been demonstrated yet. The experiments and the methodology used to test the accuracy of a small commercial GPR device for crack identification are described. The main objective was to identify what type of signals and what crack width can be detected using the GPR device. The results indicate that cracks of one or two millimetres wide can be detected depending on its position and shape. On the other hand, sub-millimetre cracks are undetectable with the currently existing devices in the market. In spite of the limitations the GPR method can be useful to find time-related bounds of when the cracks appear, and to point at their location. Because the GPR systems are in constant evolution this technique could become a very versatile and convenient method to scan soils under different kinds of processes both in the laboratory and in the field

GE Jet Engine Bracket Challenge: A Case Study in Sustainable Design

Open crowdsourcing competitions can provide a large repository of data which can be used to achieve more sustainable product designs. This study looks at the recent General Electric challenge, a competition to minimize the mass of a titanium jet engine lifting bracket, to illustrate the benefits that can be accrued. In the light of current literature the benefits and challenges of crowdsourcing have been considered. Samples of the entrants to the challenge have been compared to identify critical characteristics for interpreting sustainable designs for additive manufacture. Focusing initially on topological optimisation and orientation of the additive manufacture build, critical features have been highlighted. The availability of many CAD designs has been most useful and has potential for future developments. Crowdsourcing as an innovation approach can also be beneficial for both companies and individuals particularly if the entries are open sourc

Numerical Investigation into Dynamic Loading of Rubber Compound

The present paper analyses the heat generation build(up in silicone rubber samples when subjected to dynamic cyclic loading. Material properties of the rubber were determined through thermal and mechanical experimental testing. These properties are necessary to set up the computational model. The model includes a fully coupled transient nonlinear thermo(mechanical finite element analysis. In order to validate this approach, numerical results are compared with those gathered experimentally. The numerical model developed and validated could be used to simulate various industrial applications, involving rubber parts, for efficient and sustainable desig