Professor Stephen Fityus

This paper documents a rock fall in the Hawkesbury Sandstone. Two distinct phases, preceding the ultimate rock fall event have been identified and documented; a creep-loading phase and a rock fracture phase. Water is identified as playing a significant role in the creep-loading phase. Over the long term, peak water pressures from intermittent heavy rainfall events have contributed to the slow, creeping movement of the overlying, joint-bounded block resulting in the progressive loading of the underlying rock mass. The rock fracture phase was extremely rapid and overlaps with the rock fall event. The kinematics of the rock fall has been interpreted from broken surfaces, scratches and positions of debris. From the timing of events, it is likely that wetting/saturation of the intact sandstone from sustained rainfall in the weeks preceding the rock fall would have significantly reduced the intact rock strength. Based on the site investigation and reconstruction of the failure mechanism, the rock fall is classified, in the Crunden and Varnes (1996) scheme, as a complex extremely rapid rock fall and rapid dry debris slide.

From a consideration of the concepts of geological weathering and structure, it can be expected that rockfall hazards should be characteristically different in different geological environments. This paper tests this idea by looking at the geometric characteristics of rock fragments formed on natural slopes in four different geological environments in Eastern Australia, where rockfall phenomena are often characterised by rolling of pre-detached debris. By measuring the three principle dimensions and making a systematic assessment of the shape characteristics of samples of rock debris in significant geological environments, it is found that the distributions of size and shape for the surface debris are statistically different. From the results, it is shown that the size and shape of debris is directly controlled by the rock type, its weathering characteristics and the structure of the parent rock mass. The severity of rockfall hazards is shown to be relatively lower in areas of Tertiary basalt, as the size of rolling fragments is limited by closely spaced fracturing inherited from its formation and the tendency to deteriorate further as it weathers deeply and rapidly. It is also lower in areas of Palaeozoic volcanics, since these tend to produce relatively angular fragments with higher proportions of fragments that are inherently more resistant to rolling. By contrast, thickly bedded sandstones form larger blocks with a larger proportion of shapes that are more prone to rolling. The size distribution of fragments is shown to be well approximated by a log-normal statistical distribution, and using the data provided in this study, it is possible to generate the size and shape data needed to undertake a stochastic assessment of rockfall trajectories in different geological environments. © 2013.

The grading entropy of a soil [S] is derived in terms of the more general concept of statistical entropy. It consists of two terms: the base entropy [So], arising from the difference in the width of the statistical cells in the conventional grading curve, and the entropy increment [¿S]. The goal of the research is to study which grading entropy plays the role of the "true" entropy in a thermodynamic sense (i.e. undergoes an increase during the crushing process being considered as an irreversible thermodynamic process): the entropy increment [¿S] or the sum of the base entropy and the entropy increment [S]. The soil samples are subjected to some crushing tests and direct shear test. The grading curve and the grading entropy are determined before and after each test. It is found that only the entropy increment [¿S] increases in the tests.

© The authors and ICE Publishing: All rights reserved, 2015.Two parameters are introduced being in unique, nearly linear relationship with each-other (density parameter (s0) and base entropy (S0o) which is an abstract mean diameter parameter). Data show that s0 is the asymmetric part of the minimum dry density smin in terms of S0. It is shown that the results of some direct shear and compression tests of sands with very loose initial state are significantly dependent on s0 with a sand data set where the dominant component of smin is s0.

The Hunter Expressway is a $1.7 billion road project in the Hunter Valley, NSW, Australia to provide a new east-west connection between Newcastle and the Lower Hunter. A large part of the materials encountered on site are expansive tuffaceous soils that would normally be discarded. However, because of increasing financial, environmental and space constraints, it is required to make use of these swelling materials in embankments. These materials include highly weathered claystone containing about 20% in mass of smectite. The highly plastic claystone is present in layers alternating with layers of nonplastic coal. Hence, when excavating the material, the claystone is mixed with the coal and it becomes relevant to consider the swelling potential of the mixture instead of that of the claystone alone. Some typical coal and claystone materials used in embankments were characterized by compaction curves and Atterburg limits. Then, a series of swelling tests were conducted on compacted specimens, of mixtures of coal and claystone, prepared in the laboratory with comparable initial conditions (suction and void ratio) so that any change in swelling potential could be solely attributed to the coal content. The results show that the addition of the coal has an effect in reducing the swelling potential of the claystone beyond a simple dilution effect. Some type of swell inhibition is implied. The addition of coal also significantly reduces the time taken for final swell strain to be reached. © 2014 Taylor & Francis Group, London.

In Australia there has been a significant increase in areas affected by dryland salinity over the 200 years since European settlement. As a result of land use and climatic changes this trend is expected to continue, with areas at high risk of dryland salinity predicted to more than double over the next 40 years. This presents a significant risk to road asset managers as concentration of salts within road pavements has been shown to cause damage to pavements and surfacings. The present study explores the impact of dryland salinity on road pavements by assessing the effect of naturally occurring salts on the tensile and shear strength of a sealed granular pavement. Tensile and shear strength testing was conducted on a granular pavement material at a range of salt concentrations. This testing confirmed that the presence of natural salts can have a positive effect on bitumen-sealed granular pavements in contrast to the negative impact salt crystallisation can have on bitumen surfacings. While in solution, salts were found to have a very small positive effect on tensile and shear strength, which is likely related to clay chemistry interactions. Upon crystallisation, salts were observed to form cubic bonds within the pores of the granular material which led to a significant increase in tensile strength. However, at interface between the surfacing and the granular material whisker-shaped crystals were observed to grow from the bitumen. The results suggest that increases in dryland salinity, while presenting a risk to the performance of road surfacings, may actually increase the tensile and shear strength of road pavement materials.