Alireza Mohyeddin

Delineation of riparian vegetation from Landsat multi‐temporal imagery using PCA

A deficiency in crucial digital data, such as vegetation cover, in remote regions is a challenging issue for water management and planning, especially for areas undergoing rapid development, such as mining in the Pilbara, Western Australia. This is particularly relevant to riparian vegetation, which provides important ecological services and, as such, requires regional protection. The objective of this research was to develop an approach to riparian vegetation mapping at a regional scale using remotely sensed data. The proposed method was based on Principal Component Analysis (PCA) applied to multi-temporal Normalised Difference Vegetation Index (NDVI) datasets derived from Landsat TM 5 imagery. To delimit the spatial extent of riparian vegetation, a thresholding method was required and various thresholding algorithms were tested. The accuracy of results was estimated for various NDVI multi-temporal datasets using available ground-truth data. The combination of a 14-dry-date dataset and Kittlers thresholding method provided the most accurate delineation of riparian vegetation. This article is protected by copyright. All rights reserved.

Utilisation of iron ore tailings as aggregates in concrete

Abstract Sustainable handling of iron ore tailings is of prime concern to all stakeholders who are into iron ore mining. This study seeks to add value to the tailings by utilising them as a replacement for aggregates in concrete. A concrete mix of grade 40 MPa was prepared in the laboratory with water–cement ratio of 0.5. The concrete were cured for 1, 2, 3, 7, 14 and 28 days. The properties of the concrete such as workability, durability, density, compressive strength and indirect tensile strength were tested. A controlled mix of concrete was also prepared in similar way using conventional materials and the results were compared with the tailings concrete. It was found that the iron ore tailings may be utilised for complete replacement for conventional aggregates in concrete. The iron ore tailings aggregates concrete exhibited a good mechanical strength and even in the case of compressive strength, there was an improvement of 11.56% over conventional aggregates concrete. The indirect tensile strength did not improve against the control mix due high content of fines in the tailings aggregates but showed 4.8% improvement compared with the previous study where the conventional fine aggregates was partially replaced by 20% with iron ore tailings.

Sensitivity Analysis of Nonlinear Behaviour of Infill-Frames under In-Plane and Out-Of-Plane Loading

This paper addresses the sensitivity of the in-plane and out-of-plane behaviour of reinforced-concrete (RC) frames with masonry infill panels to a select number of material related parameters. Instead of general conclusions, the intention is to facilitate a deeper insight into the behaviour of infill-frames at a micro level over a wide range of drift values. A script, which has recently been developed, is used to generate the finite element (FE) models of an infill-frame with desired geometric and mechanical properties. Also, the same three-dimensional FE model is used for both in-plane and out-of-plane analyses of infill-frames. The sensitivity analyses are conducted in three sequential parts: the analyses of a masonry bare wall under one-way bending, the analyses of an infill-frame under out-of-plane loading and the sensitivity analyses of an infill-frame under in-plane loading. A simple method is delineated to overcome convergence issues which are related to the highly nonlinear finite element models to be solved using the Newton-Raphson algorithm.

Multivariate detection and attribution of land-cover changes in the Central Pilbara, Western Australia

The Multivariate Alteration Detection (MAD) method was applied to locate areas where land-cover changes occurred between 2003 and 2009 in the Central Pilbara, Western Australia. It was demonstrated that each of the six MAD variates contained information of land-cover changes at various spatial scales. This allowed attribution of the identified changes to particular stressors such as climate variability, fire events, and mining activity in the area. The results were analysed and interpreted using time series of multispectral normalized difference vegetation index, normalized difference wetness index, and normalized burn ratio grids derived from Landsat data observed over the study period. In addition, various ground truth data such as fire maps, historical climate data, and the available information about mine operations and water management, which could lead to alteration of natural water regime, were utilized.

Effects of addition of waste tyre fibres and cement on the engineering behaviour of Perth sand

ABSTRACT The use of waste tyres can make the ground improvement project cost-effective, and moreover, this can be a solution to the tyre disposal problem. A series of standard compaction and unconfined compression tests was conducted to investigate the effects of adding tyre fibres (TFs) and cement on the engineering behaviour of Perth sandy soil. The contents were varied from 0% to 3% of dry soil by weight for both cement and TF. The cemented specimens were cured for 7 days. The compaction tests results indicate that the maximum dry unit weight generally increases with addition of cement but decreases by TF inclusion, while adding cement and TF results in a lower optimum water content. The results of unconfined compression tests show that the cement addition increases the unconfined compressive strength () of the sand and sand–TF mixtures. Furthermore, the inclusion of TF in the sand increases its UCS, whereas of the sand–cement mixtures mostly decreases with an increase in TF content, except for a slight improvement at low cement contents.

Slope Stability of Tailing Dam Under Seismic Excitation

The slope stability analysis of the tailing dams or mine dumps becomes a more challenging task for engineers when they are subjected to a combination of static and dynamic loadings. Several tailing dam failures have been observed in the past worldwide. The failure of tailing dam not only releases the waste deposit to the surrounding but also yields the property damage and cause environmental threat to the locality. The waste deposit may liquefy under the earthquake with an increase of the horizontal load on the saturated dam tailing. Hence failure of the dam under liquefaction may lead to catastrophe. In 2015, Samarco tailing dam has failed under the earthquake condition. When the dynamic loading associates with horizontal seismic load along with vertical load, it may reduce the stability of slope leading to failure. A two-dimensional numerical attempt has been made by utilising the commercial software Geostudio, and the same is presented in this paper. Initially stability of the slope is evaluated by considering the finite element stress analysis. A staged pseudo-static analysis has been presented to the study the effect of factor of safety of tailing dam under the action of both horizontal and vertical seismic loads.

Effect of Width of Geosynthetic Reinforcement within the Granular Cover on the Load Distribution over the Tunnel Lining

A realistic estimation of load distribution over the buried structures is necessary for proper analysis of tunnels, culverts and pipes/conduits. Tunnels with linings are often constructed in transportation and hydraulic engineering. For the design of tunnel lining, it is essential to know the load over the lining. Load distribution over the buried structures has been investigated scientifically during the past several decades. The method of investigation includes experimental, numerical and analytical methods. The finite-element models based on some commercial software have been developed for load analyses for design of the tunnel linings and buried structures. The geosynthetic is an effective reinforcement layer to reduce the load over the buried structure. Although some studies have indicated that the geosynthetic layer can reduce the load over the buried structure, but no attempt has been made to determine the optimal width of the geosynthetic reinforcement within the granular cover. Therefore, in this paper, an attempt is made to present effect of width of geosynthetic layer on the load distribution over the tunnel lining. The study has been carried out by developing a numerical model of the problem. The commercial software PLAXIS 2D has been used for numerical modelling. The results have been presented in the form of design charts, mentioning the optimum width of geosynthetic layer, so that they can be used by practising engineers.

Optimum burial depth of geosynthetic reinforcement within sand bed based on numerical investigation

Abstract In model studies as well as in field projects, the burial depth of a geosynthetic reinforcement layer within a sand bed is often assumed to be approximately 0.3 times the width of the footing. However, most studies generally overlook that the ratio will vary according to the angle of internal friction of soil. This paper presents a numerical investigation of the effect of the angle of internal friction of sand on the optimum burial depth of geosynthetic reinforcement. The results reveal that the optimum burial depth depends significantly on the angle of internal friction of sand, especially when the angle is greater than 30°. The findings show a linear relationship between the optimum burial depth of reinforcement and the height of the active zone beneath the footing following the Terzaghi’s failure mechanism for unreinforced foundations. The study also investigates the effect of reinforcement width, with the results showing that the reinforcement width does not affect the optimum burial depth of the geosynthetic layer, although it affects the bearing capacity ratio.