http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:12118 The accuracy of finite element solutions for the consolidation of porous media is influenced by the number and size of the time increments used in the analysis. A solution algorithm for adaptively selecting time increments for the solution of elastic and elastoplastic coupled consolidation problems in finite element analysis has been developed by Sloan and Abbo (1999). By treating the governing consolidation relations as a system of 1st-order differential equations their algorithm utilized subincrementation to automatically adjust the size of time increments used in the analysis. Unlike other time stepping schemes, the procedure adjusts the time increments in order to control the error due to time stepping to lie near a specified tolerance. The algorithm was shown to be robust and to provide an efficient method for the solution of consolidation problems. In this paper the efficiency of the algorithm is further demonstrated through the analysis of the construction of an embankment on a deep layer of soft soil. The time increments required for the efficient and accurate analysis of the consolidation of porous media are shown to differ by orders of magnitude. 2012-11-26T04:10:04.646Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8821 This paper investigates the stability of a plain strain circular tunnel in an undrained clay. Using finite element limit analysis, upper and lower bounds on the stability of the tunnel are determined for a range of tunnel geometries and soil conditions. These results are verified using semi-analytical rigid block upper bound methods. The numerical formulation of the finite element limit analysis techniques are based upon the upper and lower bounds theorems of classical plasticity. Solutions, that provide upper and lower bounds on the true collapse loads, are obtained using advanced conic programming schemes to solve the resulting optimisation problems. Results from this study, in which the two bounds differ by at most 5%, are summarised in the form of stability charts. Finally, an expression that approximates the undrained stability of a circular tunnel has been formulated for use by practicing engineers. 2011-09-05T01:50:07.104Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8175 Performance-based design has slowly been adopted for the use in geotechnical design. In the future, various types of foundations suitable for a variety of soils and applications should be accepted as an alternative to conventional flat foundations for the increase of bearing capacity and the savings of materials. The concept of shells is not new in foundation design, considering the construction with inverted brick arch foundation. Shell foundations are economic alternatives to conventional flat foundations where heavy superstructural or lateral loads are to be transmitted to weaker soils. Various types of foundations with different geometrical shapes have been extensively investigated in the structural design. However, the corresponding studies on the geotechnical design in terms of bearing capacity and deformation are scare. As such the advantages of various types of foundations have not yet been clarified in terms of the geotechnical design. The objective of this paper is to examine the overall geotechnical performance of various types of foundations on sand using model loading tests and the numerical limit analysis. The general superiority of various types of foundations has been revealed by comparing the loading tests with the analytical results. 2011-07-10T23:20:07.564Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:4732 Yield surfaces for unsaturated soils are usually non-convex if the size of the yield surface has to increase with increasing suction. An expanding yield surface with increasing suction is crucial for modelling the volume collapse due to wetting. The non-convexity always exists at the transition between saturated and unsaturated states, irrespective of the stress variables used in the model. Some recent models for unsaturated soils also possess a stress path dependent hardening law. The non-convexity and stress-path dependency of the constitutive model make the implementation into finite element codes very challenging. This paper discusses aspects of stress integration schemes for non-convex and stress-path dependent models for unsaturated soils. 2010-04-27T05:31:01.320Z ]]>