NSW Research Award Presentation

Ana Paula Heitor and Chunshun Zhang

Experimental Investigations into Using Non-Destructive Techniques for Characterising Compacted Soil

Ana Paula Heitor, University of Wollongong

Conventional field compaction control methods, including nuclear gauge, sand cone and rubber balloon, perform well for controlling the compacted soil at time of placement; however because of their localised nature these techniques may not be suitable for deeper fills or for assessing larger surface areas. In those conditions, alternative non-destructive methods should be considered. This study explores the performance of a cost effective method for evaluating the characteristics compacted fills by measuring the shear wave velocity and matric suction. The use of this methodology would enable practitioners to efficiently control compaction over large areas during post-construction stages, and locate areas within the existing formations where the soil was not sufficiently compacted.

Comminution in Geotechnical Engineering: a Continuum Approach Based on Breakage Mechanics

Chunshun Zhang, The University of Sydney

This report investigates the influence of grain crushing on two geotechnical engineering applications through a continuum breakage mechanics approach.

The first investigation is to study the pile end-bearing capacity in crushable granular soils. Finite element results are presented and compared with experiments in a good agreement. A parametric analysis is then performed to propose a new equation to predict the pile end- bearing capacity. This equation highlights the effect of grain crushing on pile end-bearing capacity. For crushable granular soils this new equation leads to a much improved fit between theoretical prediction and experiment compared to that for many existing equations based on rigid-plastic model and cavity expansion model.

The second exploration is to study the hydro-mechanical response of expanding cavities in crushable granular soils. Finite element analysis of cylindrical cavities are considered, as are undrained and then drained (i.e., consolidation) conditions. Permeability reduction, changesin total and effective stresses and excess pore pressure are presented. In particular, a solution is proposed for predicting the generation of the maximum excess pore pressure at the cavity interface. This solution highlights the major influence of grain crushing on generation of excess pore pressure.

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