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Geotechnical design and construction aspects of the M80 bridges across Moonee Ponds Creek in Melbourne
This paper describes the design of embankments and piled foundations for new bridges across Moonee Ponds Creek as part of the Melbourne M80 Upgrade Project. The bridges are part of the eastbound duplication and consist of 7 spans (main carriageway) and 8 spans (auxiliary exit). The maximum approach embankment height relative to the existing ground surface levels is 17 m, which is up to 6.5 m higher than the adjacent embankment. Moonee Ponds Creek transects the Newer Volcanics and Melbourne Mudstone forming an incised valley (Moonee Ponds Creek Valley) filled with Quaternary alluvial deposits. Significant settlement was experienced during the construction of the original embankments in the early 1990s. The specification for the new bridges imposed tight settlement requirements. This challenge was compounded by restricted space between assets and a tight construction time frame.
Details of the construction methodology together with the results of settlement monitoring and the monitoring of vibration due to impact rolling and pile driving are presented.
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Forensic investigation of subsidence to dwelling, December 2007
Investigation of house subsidence is always fraught with difficulty, because one doesn’t ever know the full information of the foundation soils, the method of construction or the quality of construction. This report illustrates the importance of undertaking a desktop study and obtaining the origins of the soils to confirm the bore hole logging in order to obtain a correct diagnosis of the likely cause of subsidence.
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Predicting instability of embankments on soft ground from monitoring data
Predicting impending failure of embankments on soft ground remains a challenge to geotechnical engineers conducting routine monitoring as a way of controlling the rate of embankment construction to avoid failures. A literature study has been carried out on available methods of predicting embankment performance. The Authors then propose a method of plotting the inverse of incremental lateral displacement rate at the embankment toe against embankment height. The idea is that the plotted data can be extrapolated to find the maximum embankment height to cause failure. That is, when the inverse rate ratio reaches zero, the embankment is collapsing at infinite rate. In practice, however, embankment distress is likely to have occurred before this ratio reaches zero. Based on several case studies, the Authors propose that an iterative prediction procedure be adopted as the embankment height increases and more data points become available. A projected limit of 0.05 days/mm or 50 days/metre (i.e. incremental lateral displacement rate of 20 mm/day following an embankment lift) be used as a guide to forecast the impending failure height, together with limiting the height of construction to between 80% to 90% of the predicted failure height at any time to control the rate of embankment construction to reduce the risk of embankment failure. This method has been tested only on limited examples, and needs to be further tested on more cases. This method should not be regarded as suitable in all circumstances. In rate sensitive soils for example, failure may occur sometime after embankment construction even though it may appear stable at its final lift. It is important that a number of different methods be used to assess the performance of embankments on soft ground. An essential element in adequately controlling the rate of construction to avoid embankment failure is making sure that there are sufficient levels of instrumentation and monitoring. During embankment construction, it is essential that daily readings be taken and reviewed carefully, and the contractor is prepared to unload the embankment by removing fill if there are tell-tales of impending failure.
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Geotechnical Challenges for Development in the Hunter Region (Part 1)
The Newcastle Chapter of the Australian Geomechanics Society has taken over most of the next two issues of the Journal which are dedicated to the papers that are to be presented at a mini-symposium with the above title.
The topics covered are a development and expansion of the 1995 Publication “Engineering Geology of the Newcastle Gosford Region” and the 1998 Publication “Geotechnical Engineering and Engineering Geology in the Hunter Valley”.
Since those publications the Hunter Region has seen significant changes and development of infrastructure and residential facilities. The closure of the Newcastle Steelworks now appears a minor blip in the life of Newcastle, opening up new opportunities for growth and development of the Hunter Region. The ever expanding extraction of coal has led to Newcastle becoming the largest coal port in the world.
It would appear that the northern side of the Hunter Valley has been largely ignored due to the emphasis on the extractive industries in the Sydney basin. The first paper addresses this imbalance by including an insight into the Engineering Geology of the Southern New England Fold Belt. A paper on the Karuah Bypass project that is located in SNEFB complements this overview paper.
The University of Newcastle’s collection of local data supplemented by data gathered by the NEWSYD testing facility allowed a better understanding of the Quaternary Sediments in the Newcastle Region.
Perhaps the biggest change in recent years has been associated with the continued movement of people to the coast and discovery that Newcastle is a very desirable place to live. This has placed added pressure for more intense development of marginal land particularly that affected by coal mining. Much of the City of Newcastle and surrounding regions are underlain by abandoned underground coal mine workings some dating back over 200 years to convict times. The continued stability of these workings imposes considerable constraints on surface development particularly for high rise development in Charlestown and Newcastle.
Several papers explore the various facets associated with constraints on development and many projects have overcome such constraints including such projects as the West Charlestown Bypass.
Coastal erosion has attracted public attention with boulders and rock falls affecting several prominent areas. The research associated with reactive soils has continued in association with the University of Newcastle.
The organising committee acknowledges the contributions made by the authors and the significant efforts that have been made to cover the topics of most interest to the profession.
Thanks are extended to the peer reviewers and to all the members of the organising committee particularly Chris Bozinovski and Steven Fityus who carried the lion’s share of the work.
On behalf of the AGS we would also like to thank the Principal Sponsor – Keller Ground Engineering Pty Ltd for their support of the symposium.
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Geotechnical Challenges Facing The Roads And Maritime Services
Heavy rainfall in early 2012 caused several highways to be temporarily closed due to flooding or slopes that had collapsed leaving the roadway impassable. Rainfall is still one of the most challenging elements for geotechnical practitioners to provide 24/7 community access to the road network. In the future limited funding for maintenance will require more accurate slope assessments, real time monitoring, innovative durable slope treatments and the development of methodology to assist in cost effective risk management of slope assets.
In the past the RTA (now RMS) has utilised subject matter experts within the organisation and the consulting industry to assess slopes and other geotechnical structures. The use of external practitioners to support the RMS to maintain the road corridor is unlikely to change in the future as the demands to finish sections of the Pacific and Princess Highways continues.
- The top five issues facing RMS geotechnical practitioners are:
- Slope risk assessment and management, and cost effective design solutions
- Deep wall excavation and the elimination of potential damage to the road corridor
- Effective site investigations, interpretation and quality reporting
- Mine subsidence and its impact on the infrastructure
- Ongoing training of young staff before the ageing practitioners retire
This paper will detail these challenges and how RMS geotechnical staff are managing the implementation of technical directions, specifications and training to manage new projects and the effective maintenance of the road corridors in NSW.
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Factors affecting assessment and back-analysis by piezometer monitoring
Prefabricated vertical drains with preloading option are the most widely-used ground improvement method for the improvement of marine clays in land reclamation projects. The assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of preload in such ground improvement projects. This analysis can be carried out by means of piezometer monitoring. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be estimated. Factors that affect the analysis of piezometers include period of assessment, hydrogeologic boundary condition, settlement of piezometer tip and reduction of initial imposed load due to submergence effect. The aim of this paper is to highlight the significance and impact of the various factors that affect assessment by the piezometer monitoring method.
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Review Of Highwall Mining Experience In Australia And A Case Study
The highwall mining method was introduced in Australia in early 1991. Since then, at least 13 mines have used this method to mine coal. Abundant experience has been accumulated during the past 8 years, through some failures as well as successes. This paper presents a brief review of highwall mining experience at four Australian mines, with focus on geotechnical issues affecting mining performance. The paper also summarizes one case study, which involved major pillar/roof instabilities. The aim of the review and the case study is to assist the highwall mining industry to learn from past experience and to avoid similar instabilities in the future.
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Slope Failure In A Complex Volcanic Terrain, Opito Bay, Kuaotunu, Coromandel Peninsula
The Ohinau Drive slope failure has occurred at the northern base of the volcanic Tahanga Hill, Opito Bay. The failure has affected a recent subdivision on Ohinau Drive situated immediately adjacent to the hill. The slide is a complex, variable depth failure encompassing several differing geological units. It extends a distance of 170 m from headscarp to toe with an estimated maximum width of 130 m. It comprises both shallow-seated and deep-seated failure mechanisms to a maximum depth of approximately 20 m. In the winter of 1996 slope instability was recognised following development of a headscarp and ongoing disturbance to kerbing and manholes.
Investigations undertaken revealed complex geological conditions generally comprising hydrothermally altered andesite partially overlain by basaltic debris and weathered basalt lava. Artesian water pressures were encountered within the andesite. The investigation results indicate that both a deep-seated failure through the underlying andesite and a shallow-seated movement involving the basalt debris were recently active. A geotechnical model was constructed along two cross sections with computer aided stability analyses undertaken. Target groundwater levels were determined to achieve a satisfactory Factor of Safety to allow future subdivision development. Drainage installation and monitoring is yet to be established following liaison with Council.