Indraratna, B & Haque, A 1999, 'Triaxial equipment for measuring the permeability and strength of intact and fractured rocks', Géotechnique, vol. 49, no. 4, pp. 515-521.
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Indraratna, B & Locke, MR 1999, 'Design methods for granular filters—critical review', Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, vol. 137, no. 3, pp. 137-147.
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Filters are used to control seepage, and to act as a barrier for preventing base soil erosion. This study is a review of past research into filtration which includes empirical, theoretical and geometric–probabilistic methods. Empirical methods are those involving laboratory testing of many base-soil–filter combinations to determine guidelines for safe filters. Theoretical packing methods determine the maximum size of particles which can fit through idealized models of the filter material. Geometric–probabilistic methods mathematically simulate the filtration process using models of pore voids and statistical techniques to determine the penetration of base particles into the filter. These methods attempt to explain base–filter interaction during filtration. In this paper, filtration of cohesive materials is discussed including problems associated with concentrated leaks and dispersive soils. Broadly graded and gap-graded materials also require individual attention, and methods to identify and deal with their problems are presented. More significantly, a recommended design procedure for filters is described, based on empirical criteria and the newly emerging geometric–probabilistic methods.
Indraratna, B & Redana, IW 1999, 'Closure to “Plane‐Strain Modeling of Smear Effects Associated with Vertical Drains” by B. Indraratna and I. W. Redana', Journal of Geotechnical and Geoenvironmental Engineering, vol. 125, no. 1, pp. 98-99.
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Indraratna, B, Haque, A & Aziz, N 1999, 'Shear behaviour of idealized infilled joints under constant normal stiffness', Géotechnique, vol. 49, no. 3, pp. 331-355.
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The shear behaviour of soft joints containing infill materials was investigated in the laboratory under constant normal stiffness (CNS) conditions. Tests were conducted on joints with asperities having inclinations of 9·5° (type 1) and 18·5° (type II), under a given range of initial normal stresses (σno) 0·30 to 1·10 MPa, and at a constant normal stiffness of 8·5, Kn/mm. It was found that the shear strength of joints decreases considerably even with the addition of a thin layer of infill. Results also show that the effect of asperities on shear strength is significant up to an asperity height to infill thickness (t/a) ratio of 1·4—1·8, whereas the shear behaviour is controlled by the infill alone beyond this critical ratio. The shear displacement corresponding to the peak shear stress is considerably reduced once the infill starts to govern the shear behaviour of the joint. In this study, the drop in peak shear stress under CNS conditions has been modelled by a hyperbolic relationship. In relation to ‘clean’ joints, it is verified that the proposed equation can predict the drop in shear stress as a function of the infill thickness, with good agreement with the measured data. In order to predict the dilatancy behaviour of ‘clean’ joints, a Fourier transform method is introduced, which can be used to predict the shear strength of joints under CNS conditions. Nous avons examiné en laboratoire le comportement de cisaillement de joints tendres contenant des mat´riaux de remplissage dans des conditions de rigidit´ normale constante. Nous avons mené des tests sur des joints qui pr&acuute;sentaient des aspérit´s ayant des inclinaisons de 9·5° (type I) et 18·5° (type Il) sous une gamme donnée de contraintes normales initiales (σno.) variant entre et 1,10 MPa et ´ une rigidit&cute normale constante de 8·5 kN/mm. Nous avons constaté que la r´sistance de...
Ji, JC & Chen, YS 1999, 'Bifurcation in a parametrically excited two-degree-of-freedom nonlinear oscillating system with 1 : 2 internal resonance', APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION, vol. 20, no. 4, pp. 350-359.
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The nonlinear response of a two-degree-of-freedom nonlinear oscillating system to parametric excitation is examined for the care of 1 : 2 internal resonance and, principal parametric resonance with respect to the lower mode. The method of multiple scales is used to derive four first-order autonomous ordinary differential equations for the modulation of the amplitudes and phases. The steady-state solutions of the modulated equations and their stability are investigated. The trivial solutions lose their stability through pitchfork bifurcation giving rise to coupled made solutions. The Melnikov method is used to study the global bifurcation behavior, the critical parameter is determined at which the dynamical system possesses a Smale horseshoe type of chaos.
Ji, JC, Yu, L & Chen, YS 1999, 'Amplitude modulated motions in a two degree-of-freedom system with quadratic nonlinearities under parametric excitation: Experimental investigation', MECHANICS RESEARCH COMMUNICATIONS, vol. 26, no. 4, pp. 499-505.
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Ji, JC, Yu, L & Chen, YS 1999, 'Bifurcation and amplitude modulated motions in a parametrically excited two-degree-of-freedom non-linear system', JOURNAL OF SOUND AND VIBRATION, vol. 228, no. 5, pp. 1125-1144.
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The non-linear response of a T-shaped beam-mass structure is investigated theoretically and experimentally for the case of one-to-two internal resonance and principal parametric resonance of the lower mode. The method of multiple scales is used to determine four first order amplitude- and phase-modulation equations. The non-trivial steady state solutions are obtained from trivial solutions through pitchfork bifurcation. The Melnikov's method is used to predict the critical parameter at which the dynamical system possesses a Smale horseshoe type of chaos. To verify the analytical results, experiments were performed on the T-shaped beam-mass structure. The periodically amplitude-modulated motions and chaotically amplitude-modulated motions were observed during experiments. The results of the experiment showed good qualitative agreement with the theoretical predictions.
Landau, RE, Russell, D, Hird, CC, Pyrah, IC, Indraratna, B & Redana, IW 1999, 'Plane-Strain Modeling of Smear Effects Associated with Vertical Drains', Journal of Geotechnical and Geoenvironmental Engineering, vol. 125, no. 1, pp. 96-99.
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Li, J, Bakoss, SL, Samali, B & Ye, L 1999, 'Reinforcement of concrete beam–column connections with hybrid FRP sheet', Composite Structures, vol. 47, no. 1-4, pp. 805-812.
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Sheng, D & Smith, DW 1999, 'Analytic solutions to the advective contaminant transport equation with non-linear sorption', International Journal for Numerical and Analytical Methods in Geomechanics, vol. 23, no. 9, pp. 853-879.
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Verma, B, Blumenstein, M & Kulkarni, S 1999, 'A New Compression Technique Using an Artificial Neural Network', Journal of Intelligent Systems, vol. 9, no. 1, pp. 39-53.
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In this paper, we present a direct solution method based neural network for image compression. The proposed technique includes steps to break down large images into smaller windows and eliminate redundant information. Furthermore, the technique employs a neural network that is trained by a non-iterative, direct solution method. An error backpropagation algorithm is also used to train the neural network, and both training algorithms are compared. The proposed technique has been implemented in C on the SP2 Supercomputer. A number of experiments have been conducted. The results obtained, such as compression ratio and transfer time of the compressed images are presented in this paper.
Blumenstein, M & Verma, B 1970, 'A new segmentation algorithm for handwritten word recognition', IJCNN'99. International Joint Conference on Neural Networks. Proceedings (Cat. No.99CH36339), International Conference on Neural Networks, IEEE, pp. 2893-2898.
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An algorithm for segmenting unconstrained printed and cursive words is proposed. The algorithm initially over-segments handwritten word images (for training and testing) using heuristics and feature detection. An Artificial Neural Network (ANN) is then trained with global features extracted from segmentation points found in words designated for training. Segmentation points located in `test' word images are subsequently extracted and verified using the trained ANN. Two major sets of experiments were conducted, resulting in segmentation accuracies of 75.06% and 76.52%. The handwritten words used for experimentation were taken from the CEDAR CD-ROM. The results obtained for segmentation can easily be used for comparison with other researchers using the same benchmark database.
Blumenstein, M & Verma, B 1970, 'Neural-based solutions for the segmentation and recognition of difficult handwritten words from a benchmark database', Proceedings of the Fifth International Conference on Document Analysis and Recognition. ICDAR '99 (Cat. No.PR00318), Proceedings of the Fifth International Conference on Document Analysis and Recognition. ICDAR '99 (Cat. No.PR00318), IEEE, pp. 281-284.
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© 1999 IEEE. A new intelligent segmentation technique is proposed that may be used in conjunction with a neural classifier and a simple lexicon for the recognition of difficult handwritten words. A heuristic segmentation algorithm is initially used to over-segment each word. An artificial neural network (ANN) trained with 32,034 segmentation points is then used to verify the validity of the segmentation points found. Following segmentation, character matrices from each word are extracted, normalised and then passed through a global feature extractor, after which a second ANN trained with segmented characters is used for classification. These recognised characters are grouped into words and presented to a variable-length lexicon that utilises a string processing algorithm to compare and retrieve those words with the highest confidences. This research provides promising results for segmentation, character and word recognition.
Blunden, B & Indraratna, B 1970, 'The nature and management of acid sulfate soils in drained coastal lowlands', Proceedings, Annual Conference - Canadian Society for Civil Engineering, pp. 317-326.
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Acid sulfate soils pose severe constraints to the protection of contrete and steel infrastructure, sustainable agriculture and environmental quality in coastal estuarine systems in many parts of Australia. The nature and properties of acid sulfate soils are described with reference to data collected from coastal lowlands with a drainage density of 1.2 km km-2 located on the South Coast of New South Wales, Australia. Deep flood mitigation drains are shown to profoundly influence the drawdown of the groundwater level, which in turn determines the rate of acid generation from the oxidation of pyrite in the acid sulfate soil layer. Numerical modeling is also used to demonstrate the nature of acid generation in acid sulfate soils. Application of SMASS showed that approximately 1.3 tonnes H2SO4 ha-1 was generated by the oxidisation of pyrite during the summer of 1997-98. Extremely acidic groundwater (pH 2-3) was measured after the groundwater rose through the oxidised zone during drought breaking rainfall. Management of the groundwater elevation is shown to be the key for minimising acid generation and Iransport in drained sub-calchments. Strategies including the construction of weirs in flood mitigation drains, increased irrigation and re-designing floodplain drainage schemes are suggested as offering potential solutions for managing acid sulfate soil under various circumstances.
Blunden, B & Indraratna, B 1970, 'The nature and management of acid sulfate soils in drained coastal lowlands', Annual conference of the Canadian Society for Civil Engineering, Regina, June 1999. Vol. 2. 14th Hydrotechnical Speciality Conference., pp. 317-326.
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Acid sulfate soils pose severe constraints to the protection of contrete and steel infrastructure, sustainable agriculture and environmental quality in coastal estuarine systems in many parts of Australia. The nature and properties of acid sulfate soils are described with reference to data collected from coastal lowlands with a drainage density of 1.2 km km-2 located on the South Coast of New South Wales, Australia. Deep flood mitigation drains are shown to profoundly influence the drawdown of the groundwater level, which in turn determines the rate of acid generation from the oxidation of pyrite in the acid sulfate soil layer. Numerical modeling is also used to demonstrate the nature of acid generation in acid sulfate soils. Application of SMASS showed that approximately 1.3 tonnes H2SO4 ha-1 was generated by the oxidisation of pyrite during the summer of 1997-98. Extremely acidic groundwater (pH 2-3) was measured after the groundwater rose through the oxidised zone during drought breaking rainfall. Management of the groundwater elevation is shown to be the key for minimising acid generation and transport in drained sub-catchments. Strategies including the construction of weirs in flood mitigation drains, increased irrigation and re-designing floodplain drainage schemes are suggested as offering potential solutions for managing acid sulfate soil under various circumstances.
Indraratna, B, Ranjith, PG & Gale, W 1970, 'Single phase water flow through rock fractures', Geotechnical and Geological Engineering, Springer Science and Business Media LLC, pp. 211-240.
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Flow analysis plays a major role in various geotechnical applications, and the understanding of flow mechanisms is essential for the development of a hydro-mechanical flow model suitable for underground excavations in rock. Discrete flow analysis through discontinuities is reviewed including empirical and analytical flow models. The influence of external loading on joint deformation and single-phase flow show that the surface roughness and aperture size are the prime factors influencing flow rate. Nevertheless, the idealization of natural fractures as smooth parallel plate joints is still followed in many numerical models, because of the simplicity of the cubic law when applied to fracture networks. A numerical study of water flow through a network of joints employing Universal Distinct Element Code (UDEC) is used to quantify the effects of joint orientation and external stress acting on idealized joints. It is found that, for the same joint spacing, the flow rate into an excavation depends on the boundary block size (A(b)) relative to the excavation size (A(e)). The inflow becomes excessive if A(b)/A(e) is less than 4, but becomes very small if A(b)/A(e) exceeds 8.
Khalili, N & Khabbaz, MH 1970, 'Application of effective stress concept to unsaturated soils', Consolidating knowledge. Proceedings of the 8th Australia New Zealand conference on geomechanics, Hobart, February 1999., pp. 849-854.
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The application of the effective stress concept to unsaturated soils is critically reviewed. The validity and the appropriateness of the relationship proposed by Khalili and Khabbaz (1996, 1998) for the determination of the effective stress parameter χ are examined using both shear strength and volumetric change data. Extremely good agreement is obtained between the measured and predicted values in all cases. It is shown that quantitative predictions of shear strength and deformation in unsaturated soils can be made using the effective stress concept. The model parameters will be exactly the same as those used in saturated soils, except for a single parameter which can be determined in any soil physics laboratory. This is in contrast to the current models of unsaturated soils, which require extensive laboratory testing.
Sheng, D, Sloan, SW & Yu, HS 1970, 'Practical implementation of critical state models in FEM', Consolidating knowledge. Proceedings of the 8th Australia New Zealand conference on geomechanics, Hobart, February 1999., pp. 975-981.
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Practical implementation of critical state models into finite element codes is discussed. Improved algorithms for stress integration and load and time stepping are presented, in order to handle the nonlinearities both in elasticity and plasticity. A new generalised critical state model as well as the model proposed by Yu (1998) is implemented. Both uncoupled and coupled analyses of practical problems are carried out.
