Cairns is all set to welcome the geotechnical engineering community as it prepares to host the prestigious Australia and New Zealand Conference on Geomechanics (ANZGEO) 2023.
The four-day conference, scheduled from July 2nd to 5th, will take place at the Cairns Convention Centre, providing a platform for knowledge exchange and networking among experts, researchers, and industry professionals in geomechanics.
ANZGEO 2023 boasts a lineup of notable presenters, including esteemed members from our own team: Dr. Richard Merifield, Sean Goodall & Scott McFarlane, Peter Chan, Jared Schweitzer and Stephen Fityus. We have provided a brief overview of their presentations, below.
Finite element modelling to predict the settlement of pile groups founded above compressible layers Dr. Richard Merifield, Sean Goodall & Scott McFarlane
It is widely accepted that the presence of compressible clay layers beneath pile groups can substantially increase the settlement of a pile group. Furthermore, as the size of the pile group increases this effect is magnified and further complicated by the load distribution across the pile group. A number of simplified methods, such as the equivalent raft or equivalent pier method, are often employed to estimate the settlement of pile groups founded over a compressible layer, however, such methods can lead to both overly conservative and un-conservative results and large variations in results between methods. More recent methods have explored the use of power law functions or energy principles to analyse piles and pile groups in non-homogeneous soil conditions, however, these methods can be difficult to apply in practice. With the availability of modern computers and the advancement of commercially available numerical analyses packages, it is now possible to use the finite element method to analyse pile groups overlying compressible soil layers in order to better understand this problem. This paper presents an extension of previous work by the authors based on the finite element method for use in estimating settlements of pile groups overlying compressible layers. Some dimensionless design charts are provided for a range of commonly encountered geotechnical conditions and pile groups.
Designing a Safe Temporary Working Platform for the Biggest Crawler Crane in the Country
Douglas Partners Pty Ltd was involved with the geotechnical design of a number of temporary working platforms to facilitate the construction of various above-ground superstructures and viaducts as part of the Westgate Tunnel Project. One of the highlights was the design of a working platform for CC-8800, a 1600-tonne crawler crane (understood to be the biggest Crawler Crane in Australia at the time, 3rd largest in the world) to be operated on the west side of Maribyrnong River where the ground conditions comprise the notorious soft and compressible Coode Island Silt. This presentation will cover the journey of the design process from the back of the envelope type closed form analysis to numerical modelling 3D analysis, field settlement trials and back calculation, and platform optimisation using geogrid systems. Construction verification and post-construction platform performance during the period of operation will also be presented.
Surface settlement resulting from mine workings collapse: finite element analysis of soil profile
A project was underlain by historical mine workings, posing risks of subsidence or sinkhole formation. Age and poor records limited interpretation of working geometry. Investigation revealed numerous collapsed, and some open workings with no simple method to detect and predict the presence of either. The proposed development was sensitive to differential settlements and required an alternate design strategy (in lieu of mine grouting) to mitigate surface subsidence. Finite element analysis (FEA) was used to model goaf behaviour, predict surface deformation and design mitigation to maintain tolerable differential settlements. The FEA model was developed from boreholes and cone penetration tests (CPTs) across the site. Bores and CPTs encountered clay soil overlying shallow mined coal, an uncommon profile for Ipswich. Strength inversions encountered in the clay above the seam, indicated goaf behaviour typically associated with collapse of mine rooves and fracturing or loosening of overlying strata. The FEA assessed workings collapse to demonstrate goaf behaviour and investigated development options. The FEA demonstrated settlement tolerance using a pile stiffened fill platform to maintain tolerable slab response following collapse of underground workings.
Comparison of results from 300mm direct shear testing, with and without cap rotation
Whilst most direct shear devices apply the vertical load through a ball mounted between the cap and the loading arm, ISO 17982-10 suggests that the loading cap should be constrained to remain parallel to the shear plane throughout the shearing process. Using a modification to a standard 300 mm square direct shear machine, a comparison between results obtained on specimens with and without cap rotation is presented. Three materials, Stockton beach sand, 20mm volcanic rock aggregate and cohesive mine spoil, were selected as the basis for the comparison. It was found that although significant cap rotation is usually observed in standard equipment where cap rotation is permitted, the use of a direct shear testing arrangement which prevented cap rotation resulted in little difference to the calculated friction angle. The small differences that were observed were for materials with coarser grains were less than 1.5 degrees. Where differences were observed, the free head arrangement measured slightly higher strengths.
ANZGEO 2023 promises to provide a collaborative and engaging platform for attendees to expand their knowledge, share experiences, and foster professional connections. With an exciting lineup of presentations from distinguished experts.