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Unsaturated Soil-retaining Wall Interaction: Experiments And Theoretical Modelling
In this paper experimental observations and theoretical modelling outcomes are presented which show the significant effect suction has on the interaction between unsaturated soils and retaining walls. Firstly, a new testing facility and set of procedures for performing retaining wall model tests in unsaturated soils are described. The facility enables a rigid model wall to be rotated into or away from a soil sample about its toe. Results for samples of unsaturated decomposed granite are presented. Suction changes were measured using vibrating wire piezometers. Pressures on the wall were measured by earth pressure cells embedded in the wall face. Integrating the earth pressure profile enabled an equivalent load acting on the wall to be calculated, and was in reasonable agreement with the measured applied load. Soil deformations were recorded using particle image velocimetry. The pattern of soil deformation observed, particularly strain localisations, was similar to those in tests on dry sands. The suction increases measured during the test were consistent the volumetric dilation that occurred in the sample. Secondly, an extension of slip line theory to unsaturated soils is presented and applied to the rigid retaining wall problem. Suction is introduced using the effective stress concept. The predicted effective normal stresses were found to be in reasonable agreement with experimentally measured values.
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AS3798 – 2007 Guidelines On Earthworks For Commercial And Residential Developments – Recent Revision
The paper presents an outline of the recent revisions to AS 3798 – Guidelines on earthworks for commercial and residential developments.
AS 3798 – Guidelines on earthworks for commercial and residential developments – was first released in 1990. This was followed by a “roadshow” wherein Standards Australia sponsored an afternoon of presentations in most capital cities; these were well attended and, partly, led to the early adoption of the standard by many practising civil engineers. The Standard was revised in 1996 to account for many changes in AS 1289 – Method of testing soils for engineering purposes. More recently the third edition was released in February 2007. It is the authors’ opinion that the Standard has been a useful document and aged well, both revisions introduced only minor changes. This paper provides a commentary on the changes introduced in the latest revision of AS 3798.
Unfortunately, most professional’s contact with the Standard appears limited to Table 5.1 – Minimum relative compaction – with the advanced professional referring to Table 8.1 – Frequency of testing – in their black periods. This is a shame as these two tables, while important, are only a minor part of the Standard. It is hoped that this paper will make a wider group of professionals conversant with more of the Standard.
The authors are respectively a member and the chairman of the Standards Australia committee responsible for drafting the Standard and have been so since the committee was form in the 1980s.
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Thin Sealed Flexible Pavement Design For Gold Coast Sands
Pavement design to the method set out in the Austroads Pavement Design Manual (APDM) is performed as a function of the elastic properties of the subgrade material. Due to the relative uniformity in composition of the aeolian and alluvial sands in the Gold Coast region, the elastic properties of these materials need to be investigated. In this paper, the physical properties of representative samples of these soils from differing regions within this area are established to allow identification of materials. A modification of the Australian Standard Test Method AS1289.6.1.1 “Determination of the Californian Bearing Ratio of a Soil” is used to correlate density index to CBR and the Resilient Modulus of these samples are established from Repeated Load Triaxial Test (RLTT) results. Pavement designs are then compared by the empirical and mechanistic procedures for unbound flexible pavements with thin asphaltic seals. The results of the analyses are presented in graphical form as well as recommendations for correction values to align the two design methods.
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Experimental investigations into subballast filtration behaviour under cyclic conditions
In rail track environments the loading system is cyclic unlike the monotonic seepage force that usually occurs in embankment dams. The mechanisms of filtration, interface behaviour and time-dependent changes of the drainage and filtration properties occurring within the filter medium require further research to improve the design guidelines. A novel cyclic process simulation filtration apparatus was designed and commissioned at the University of Wollongong, and a standard testing procedure was established. The test apparatus was designed to simulate heavy haul train operations. Key parameters that influence the change in porosity and pore water pressure within the subballast layer under cyclic conditions in rail track environments were identified.
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Excavation Induced Response Of Pile Foundations
In urban areas excavations for construction of basements, tunnels and other underground facilities inevitably influence the existing pile foundations. Due to the release of stresses during excavations, confining pressures around existing piles decrease significantly inducing additional deflections and bending moments. It is important to quantify these effects at the design stage, in order to protect the existing structures during nearby deep excavations. In this paper, the impact of excavation induced ground movements on adjacent pile groups is investigated. Numerical simulations based on the finite element method are performed on free-head and capped-head piles in different pile configurations. The problem was modelled considering the three-dimensional geometry, which facilitates to simulate the arching and shielding effect of piles within a group. The response of both interior and peripheral piles is investigated. Results show that the presence of front piles reduces the detrimental effects on the rear piles within the group. In addition the provision of a pile cap significantly reduces the deflection of pile group due to load transfer to the rear piles, which are located away from the wall supporting the excavation. Outcomes of this research will contribute towards the design and construction of resilient pile foundations.
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Tunnelling Boom In Australia: Prospect Of Educating Tunnel Engineers
Australia is in the middle of an infrastructure boom. Nine out of twelve of Australia’s current largest infrastructure projects are tunnelling projects. The value of the planned underground projects in Sydney and Melbourne is over $40 billion. The avoidable social costs of congestion are estimated to increase in all eight Australian capital cities by 2030. To address this problem, the focus is on the development of underground space. Extensive state and federal government infrastructure programs have increased public investment in civil infrastructure programs and are expected to drive growth in the sector over the next 20 years. Despite the number of international companies joining the local market, the issue of recruiting skilled workforce is significant. The professional skills shortage within the local tunnel consulting industry is a major threat to Australia’s underground projects. This paper investigates the benefits of offering tertiary degrees in Australia on tunnelling and development of underground space-related topics. Requirements to establish a tunnel engineering degree with the main focus on current industry skills and knowledge requirements are presented.