Engineers Australia

The NSW Research Award

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 research explores the performance of a cost effective method for evaluating the characteristics of 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, University of Sydney

The theory of continuum breakage mechanics is an exciting field with applications in geotechnical engineering, specifically in the influence of grain crushing.

The first application presented involves an end-bearing pile in a crushable granular soil. Based on a comparison between numerical analysis and experimental results, a new equation to predict pile end- bearing capacity is developed. Use of this new equation provides an improved fit between theoretical prediction and experimental results compared with the existing equations based on rigid-plastic models and cavity expansion models.

The second application is for the hydro-mechanical response of an expanding cavity in crushable granular soil. Finite element analysis of an instantaneous expanding cylindrical cavity is able to predict a permeability reduction, the changes in total and effective stresses and excess pore pressures. From this analysis, a simple equation is proposed to predict the generation of maximum excess pore pressure at the soil-cavity interface, conceptually similar to a CPTu test.

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