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Lane Cove, Australia

Waddell P.,Coffey Geotechnics Pty Ltd
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2013

Creep settlement is an important aspect to consider where development is planned over deep compacted fill. This paper presents a case study of an earthworks design for infilling a quarry pit with sandstone and shale derived material and a comparison of predicted and monitored creep settlements. Laboratory testing was carried out during filling to assess the creep characteristics of available infilling materials. Based on the laboratory testing the influence of saturation on creep rates is discussed. Settlement monitoring points across the infilled quarry were monitored for up to 455 days. Predicted creep rates based on the results of the testing are compared with predictions based on monitoring. Monitored settlements within a few years of fill placement were variable and substantially greater than predictions based on the laboratory testing. Longer term monitoring data indicates that settlements are likely to be less than predictions based on laboratory testing. The results suggest that predictions over 30 years based on laboratory testing are conservative and lie within the normal range of accuracy of geotechnical predictions.

Flux S.,Coffey Geotechnics Pty Ltd
Australian Geomechanics Journal | Year: 2013

This paper presents a comparison of inferred California Bearing Ratio (CBR) results obtained from a 4.5 kg Clegg Hammer, 20 kg Clegg Hammer, Perth Sand Penetrometer (PSP) and Dynamic Cone Penetrometer (DCP). Fieldwork was undertaken on four occasions at three locations within the Perth metropolitan area, namely at Preston Beach (Safety Bay Sand), Muchea (Colluvial Sand), and twice at Cockburn (engineered fill and Tamala Sand, the name of the sand derived from the Tamala Limestone). CBR values were inferred and the results from the different pieces of field equipment compared. Overall, at the locations tested, the 4.5 kg Clegg Hammer gave results that produced higher inferred CBR values, whilst the PSP inferred lower CBR values, with the CBR values inferred from the DCP and 20 kg Clegg Hammer in between.

Mather P.,Coffey Geotechnics Pty Ltd
Australian Geomechanics Journal | Year: 2013

On the 27th September 2005 a small landslide was noticed across Lewana Road, located approximately 20 km northeast of Nannup, Western Australia. When first observed the landslide was approximately 20 m long. Within a few days the landslide had removed a section of Lewana Road and increased to 150 m in length to be potentially threatening the Nannup-Balingup Road and Blackwood River located another 70 m down slope. Routine monitoring of the landslide was initiated and continued with works to improve local drainage and divert surface water away from the immediate landslide area. A geotechnical consultant was engaged to carry out a site visit as part of an assessment of the landslide occurrence and to provide advice on potential risks for the major road and Blackwood River located down slope. The potential causes of the Lewana Road landslide included a wide range of naturally occurring features including relatively steep topography, above average rainfall and shallow soil overlying rock with unfavourably orientated geological structures concentrating subsurface water flows. In conjunction with these naturally occurring features were a range of man made influences arising from recent removal of vegetation through clear felling of tree plantations, localised over steepening of slopes associated with cut to fill earthworks to construct skyline pads for tree harvesting and the concentration of surface water runoff associated with road drainage. Although the Lewana Road Landslide was a relatively minor feature and did not progress to become a significant occurrence, it provides a useful insight into the range of naturally occurring features and man made influences that are commonly associated with landslides. In addition it provides a useful example of the types of management and remediation responses that can be adopted to limit and contain potential damage to existing infrastructure and environmentally sensitive areas that may be threatened by landslides.

Poulos H.,Coffey Geotechnics Pty Ltd
Proceedings of the Institution of Civil Engineers: Civil Engineering | Year: 2010

High-rise buildings are usually founded on some form of piled foundation subject to a combination of vertical, lateral and overturning forces. However, conventional methods for assessing stability may not be adequate when designing such foundations because they tend to focus on resistance under vertical loading. This paper sets out an ultimate-limit-state approach for computer-based design of pile foundation systems for high-rise buildings and provides an example application on a 151-storey tower in South Korea.

Fatahi B.,University of Technology, Sydney | Fatahi B.,Coffey Geotechnics Pty Ltd | Khabbaz H.,University of Technology, Sydney | Indraratna B.,University of Wollongong
Ecological Engineering | Year: 2010

Bioengineering features of native vegetation are currently being evolved to enhance soil stiffness, slope stabilisation and erosion control. The effects of tree roots on soil moisture content and ground settlement are discussed in this paper. Matric suction induced by tree roots is a key factor, governing the properties of unsaturated soils, directly imparting stability to slopes and resistance for yielding behaviour. A mathematical model for the rate of root water uptake that considers ground conditions, type of vegetation and climatic parameters has been developed. This study highlights the inter-related parameters contributing to the development of a conceptual evapo-transpiration and root moisture uptake equilibrium model that is then incorporated in a comprehensive numerical finite element model. The developed model considers fully coupled-flow-deformation behaviour of soil. Field measurements obtained by the Authors from a site in Victoria, South of Australia, are used to validate the model. In this study, the active tree root distribution has been predicted by measuring soil organic content distribution. The predicted results show acceptable agreement with the field data in spite of the assumptions made for simplifying the effects of soil heterogeneity and anisotropy. The results prove that the proposed root water uptake model can reliably predict the region of the maximum matric suction away from the tree axis. © 2009 Elsevier B.V. All rights reserved.

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