Dr James Hambleton

Economic growth in Australia and the rest of the world is linked to the scale of construction and mining, and the amount of earth moved each year in these operations is difficult to fathom. When distributed evenly across the world's population, each individual moves several tonnes of earth each year. This paper highlights current and future research initiatives within the ARC Centre of Excellence for Geotechnical Science and Engineering (CGSE) aimed at developing rigorous, mechanics-based models for fundamental ploughing and cutting processes in soils. State-of-the-art physical modelling is integrated with the development of new techniques for analytical and numerical modelling to elucidate and predict the full progression of forces and deformations in both two-dimensional and three-dimensional processes. A new analytical model for cutting in dry sand is presented, and preliminary results from numerical and physical modelling are described. The analyses reveal effects that available models fail to consider and illustrate how the development of rigorous models may facilitate improvements in production and efficiency in earthmoving operations.

Ploughing processes are difficult to simulate using conventional approaches due to the occurrence of extremely large, predominantly plastic deformation. Numerical techniques such as the Material Point Method and the Discrete Element Method are, in principle, capable of reproducing the deformation observed in these evolutionary processes, but they are not without drawbacks, the most significant being the large processing times required. This paper presents a new numerical technique for modeling the ploughing process in sands. The method rests on the assumption that deformation occurs in the formof strong discontinuities, or shear bands, and considers the full process as a sequence of incipient collapse problems.Within an increment of deformation, the collapse mechanism furnishing the least resistance is used to update the deformed configuration and evaluate force. The model incorporates the effect of softening within the shear bands, as well as material avalanching observed as the slope of the free surface reaches the critical angle at which instabilities occur. Theoretical predictions are compared to experiments, and the basic similarities and difference are discussed. © 2015 Taylor & Francis Group, London.

Helical anchors, which are mostly used to resist uplift, are deep foundations installed by rotation into the ground. Despite the central role of the installation process, especially with respect to the effect of soil disturbance, relatively little is known about the forces and deformations occurring during installation. An exception is the field verification technique known as torque-capacity correlation, which attempts to relate installation torque directly to uplift capacity. However, there are open questions regarding this approach, since not all significant parameters, such as installation vertical force and helix pitch, are taken into consideration. This could be one of the main reasons behind the wide range of torque-correlation factors reported in the literature. This study presents a three-dimensional numerical analysis of the installation process for helical anchors in clay. The results are synthesised into convenient yield envelopes that predict the relationship between installation torque and normal force as functions of helix pitch, roughness, and thickness. The application of the findings to torque-capacity correlation is also discussed. © 2015 Taylor & Francis Group, London.

Off-road vehicles such as ATVs, SUVs, dirt bikes, and hauling trucks cause damage to soft soils in unpaved areas within parks, forests, wetlands, and tundra. These vehicles can form deep ruts which result in destruction of vegetation, changes in water absorption/retention, and reduction in aesthetical land values. Large areas of particularly vulnerable soils are becoming increasingly common in northern regions, where permafrost is disappearing as a result of climate change. In this paper, theoretical models that predict the effect of material properties, wheel geometry, and wheel load on wheel penetration and rutting in cohesive soils are presented. The effects of tire flexibility are considered, as well. The models are approximate, yet predict similar response as that obtained from comprehensive numerical simulation. Copyright ASCE 2008.

In this study, the mechanical behavior of perforated, chopped fiber reinforced polymer plates is investigated. These plates serve as a manifold for polymer heat exchangers, where each perforation would be connected to a tube carrying pressurized fluid. Thus, the plates are subjected to a pressure loading. In order to predict the plate deformation due to the pressure loading, the mechanical bending behavior of these plates is quantified by an equivalent plate modulus E* and equivalent Poisson's ratio ¿*, such that the perforated plate can be modeled as a solid plate. Previous research has shown that by normalizing E* with respect to the modulus of a non-perforated plate, the bending behavior of perforated plates fabricated from isotropic elastic materials was a function of the hole size, spacing and plate thickness. Machining holes in a random fiber composite creates local areas of reduced stiffness due to fiber chopping, while the previous methods used to characterize E*/E assumed uniform, isotropic material properties. The objective of this study is to demonstrate that machined chopped fiber reinforced perforated plates, which have local areas of reduced modulus near the holes, can be characterized by E*/E (an approach which assumes global isotropy). Experimental values for E*/E for non-reinforced (isotropic) and chopped fiber reinforced polymer plates are obtained for a range of hole geometries and two different polymers. These experimental results for E*/E are compared to a model developed for isotropic, elastic materials and also to a finite element solution.