Ali Karrech

• Bsc,Ms,PhD,HDR
• Professor at The University of Western Australia

Rock-shotcrete interfaces are commonly encountered in mining and civil engineering infrastructures, which can trigger localised failure due to stress concentration. These interfaces are usually reinforced with support systems such as rock bolts and the behaviour of rock-shotcrete-bolt systems is often difficult to predict mechanically. In this stud...

The reactivation of faults is governed by the variation of effective stresses in the fault’s plane. These effective stresses are dependent on the total stresses (solely related to the regional geological stresses and lithology) and pore pressure (strongly affected by rock properties, fluid content, and saturation conditions). Injecting fluids into...

Ultra-high-performance concrete (UHPC) is a recent class of concrete with improved durability, rheological and mechanical and durability properties compared to traditional concrete. The production cost of UHPC is considerably high due to a large amount of cement used, and also the high price of other required constituents such as quartz powder, sil...

Cementitious mix with very-low-tricalcium aluminate (C3A) cement or VLAC (C3A ≤ 3%) as the primary binder requires lower water to binder ratio to attain a target flowability than that with moderate-C3A cement or MAC (6% < C3A ≤ 10%). Hence, better mechanical performance, as well as good flowability, can be achieved for the mix with VLAC. Utilizing...

Last few years have seen a substantial growth in the development and application of lightweight concrete (LWC) due to its enhanced mechanical properties and economic benefits in comparison to conventional normal weight concrete (NWC). The use of LWC in infrastructure has been popularised, especially in long-span bridges and high-rise bridges due to...

Recently, various waste materials and industrial by-products such as supplementary cementitious materials (SCMs) have been proposed to improve the properties of self-compacting concrete (SCC). This profitable waste management strategy results in lowering the costs and carbon emission, and a more sustainable, cleaner and eco-friendly production of S...

The usage of structural Lightweight concrete (LWC) has increased over the years and received significant attention owing to its lower density, better economical design, and mechanical properties as compared to conventional normal weight concrete (NWC). However, limited research efforts and codes provisions deal with retrofitting and strengthening o...

Rammed earth (RE) constructions are gaining relevance worldwide for their reduced embodied energy when local materials are employed, and the material is stabilised with sustainable stabilisers or with a low quantity of cement. Besides, RE construction offers good thermal performance under specific climatic and technical conditions. However, the mat...

The growing demand for renewable energy has increased the need to develop large-scale energy storage systems that can be deployed remotely in decentralised and deregulated networks. Vanadium flow batteries employ all-vanadium electrolytes that are stored in external tanks feeding stack cells through dedicated pumps. These batteries can possess near...

There is an increasing demand for lithium, which is perceived as the key element of the green revolution. This green image remains incomplete without the circular economic uptake of delithiated β−spodumene (DβS). In a recent contribution, the authors proved that DβS has remarkable pozzolanic properties (Karrech et al., 2019). This paper sheds more...

This paper optimizes roof shape and associated Building Integrated Photovoltaic (BIPV) mounting strategies based on the newly announced feed-in tariff pricing range in Western Australia to confirm hypothesised benefits and potential influence on grid consumption reduction. Through analysis of a residential building in Perth, the study looks at: the...

Ultra-high performance concrete (UHPC), owing to containing very high cement content, usually exhibits high shrinkage compared to normal strength concrete (NSC). Shrinkage may lead to the formation of cracks. Excessive shrinkage cracks may impair the mechanical performance of concrete and its durability. In this study, the influence of high-volume...

The parameters that influence slope stability and their criteria of failure are fairly understood but over-conservative design approaches are often preferred, which can result in excessive overburden removal that may jeopardize profitability in the context of open pit mining. Numerical methods such as finite element and discrete element modelling a...

The use of structural lightweight concrete (LWC) in the construction industry has increased rapidly in the past few decades, due to its lower density and superior mechanical properties compared to conventional normal weight concrete (NWC). The use of Carbon Fibre Reinforced Polymer (CFRP) sheets to confine concrete, is quite an effective way to enh...

All lightweight concrete (ALWC) is an emerging new type of concrete that has a density lower than 1760 kg/m3 as compared to conventional normal weight concrete (NWC). The use of structural ALWC has increased rapidly in last few years primarily due to its superior mechanical properties and lower cost of construction as compared to NWC. Carbon Fibre...

The aim of this study is to develop an all-lightweight self-compacting concrete (ALWSCC) mixture that possesses a high compressive strength incorporating hybrid steel fibres. Lightweight aggregates (LWAs) such as stalite, leca, scoria and scoria sand were used to achieve an oven-dry density less than 1760 kg/m3. Fly ash (FA) was used to achieve suf...

Theoretical approaches to earthquake instabilities propose shear-dominated source mechanisms. Here we take a fresh look at the role of possible volumetric instabilities preceding a shear instability. We investigate the phenomena that may prepare earthquake instabilities using the coupling of thermo-hydro-mechano-chemical reaction–diffusion equation...

In many regions including Australia and South America (Lithium Triangle), lithium mining needs to thrive without compromising natural ecosystems. In particular, extracting lithium from pegmatites produces significant amounts of Delithiated β-Spodumene (DβS) or equivalent materials. In this paper, an approach is proposed to solidify and stabilise bo...

To ensure ultra-high performance, in terms strength and durability, coarse aggregate is typically avoided in UHPC (ultra-high performance concrete). Instead, very fine quartz sand is usually used as the only aggregate. However, excessive extraction of sand from natural resources and its grinding and refining processes to prepare very fine quartz-ri...

Research on soil biocementation has gained momentum given its advantages over ordinary Portland cement-based techniques that entail a negative environmental impact. Soil biocementation occurs when bacteria-induced urea hydrolysis precipitates calcite crystals that bind sand grains together, hence increasing both the strength and stiffness of the ot...

Substituting cement by supplementary cementitious material (SCM) is the most-practiced approach of reducing CO2 footprint of concrete. However, in case of UHPC, for which ultra-high performance in terms of both strength and durability is of utmost importance, high-volume reduction of cement is often difficult or highly challenging. In this study, t...

Ultra-high-performance concrete (UHPC), despite its superior mechanical and durability properties, has a high CO2 footprint owing to its high portland cement content. This drawback can be offset to a notable extent if a high volume of supplementary cementitious materials can be utilized to produce UHPC while maintaining mechanical and durability pr...

We propose a multiscale approach for coupling multi-physics processes across the scales. The physics is based on discrete phenomena, triggered by local thermo-hydro-mechano-chemical (THMC) instabilities, that cause cross-diffusion (quasi-soliton) acceleration waves. These waves nucleate when the overall stress field is incompatible with acceleratio...

Lightweight concrete (LWC) can reduce the self-weight of structures and can save material and labour costs in industry. Despite these merits, the application of lightweight concrete is mostly limited because of low compressive strength, often <60 MPa; and low workability, due to high absorption capacity and possibility of aggregates floating in the...

Many aspects of gold ores leaching by glycine (C2H5NO2) and glycine-cyanide solutions are still not well understood. The base-metal components have been shown to have a strong impact on gold leaching kinetics. In this research, with the aim of reducing cyanide consumption, leaching of a polymetal (Pb-Cu-Zn) gold ore using a synergistic lixiviant mi...

Waste tyre disposal is increasingly challenging around the world. Innovative solutions include incorporating rubber in concrete to significantly improve the ductility and impact resistance. Rubberised geopolymer concrete (RuG) has several potential advantages over the conventional rubberised cement concrete. For example, the alkaline treatment solu...

Cement-stabilised rammed earth has gained a revived momentum with the increasing awareness of sustainability. In this study, we use a multiscale homogenisation method to predict the impact of embedding low thermal conductivity inclusions that improve the overall insulation. In addition, we propose an experimental campaign where specimens containing...

The aim of this paper is to propose a closed-form solution to the poromechanics problem of stress and pore pressure distribution around noncircular openings at great depth subjected to hydrostatic water pressure and far-field geostresses. The problem is solved by superposing the effects of fluid and solid skeleton obtained over simple circular geom...

Theoretical approaches to earthquake instabilities propose shear-dominated instabilities as a source mechanism. Here we take a fresh look at the role of possible volumetric instabilities preceding a shear instability. We investigate the phenomena that may prepare earthquake instabilities using the coupling of Thermo-Hydro-Mechano-Chemical reaction-...

Australia's national energy system is heavily reliant on coal-fired power plants and requires quick action to decrease CO2 emissions in order to meet the Paris climate change agreement by 2030. As a good alternative to coal power, renewable resources can produce the required energy for Australia while keeping the environment clean. The annual amoun...

In this paper, we develop a novel 3D computational method that describes the behaviour of rock bolts and rough rock-shotcrete interfaces as support systems. Specifically, a Finite Element model has been formulated and implemented using the user-defined element (UEL) subroutine with ABAQUS. The input parameters of the bolted cohesive model are deter...

In recent years, fly-ash based geopolymers have been an alternate binder to ordinary Portland cement commonly used for soil stabilization, as they were found to enhance soil strength and stiffness with the benefits of entailing lower toxic pollution and energy usage. However, most available studies on geopolymer-stabilised soils have focussed on th...

We propose a non-local, meso-scale approach for coupling multiphysics processes across scale. The physics is based on discrete phenomena, triggered by local Thermo-Hydro-Mechano-Chemical (THMC) instabilities, that cause cross-diffusion (quasi-soliton) acceleration waves. These waves nucleate when the overall stress field is incompatible with accele...

Lining is gaining acceptance in underground excavations because of its reinforcing and protecting capacities. The purpose of this paper was to derive an analytic expression based on the complex variable method to describe the behaviour of a tunnel with a liner of finite thickness. The stress functions have been expressed as Laurent series where the...

In order to achieve a successful cemented paste backfill (CPB) mixture design, multiple project requirements such as strength, flowability and cost should be met. For this achievement, the key design parameters, solid content (SD) and cement percentage (C), should be well adjusted. With increasing the amount of cement in the mixture, CPB strength a...

Rammed earth (RE) is a generic term for a number of construction materials that contain stabilised or non-stabilised earthen materials. RE materials are heterogeneous and their bulk performance depends on their mineralogical composition, physical texture, water content and mode of preparation. This category of building materials has recently been t...

Glass fiber-reinforced polymer (GFRP) reinforcement has been considered as a replacement for the traditional steel reinforcement, mainly due to its corrosion resistance. In this paper, a total of 13 concrete columns and beams (length/diameter = 5.3) fully reinforced with GFRP longitudinal bars and spirals were experimentally studied. An additional...

This study compared the effect of seven common curing conditions on the compressive strength, pore alkalinity, efflorescence, and shrinkage of five alkali-activated fly ash and slag (AAFS) mortars and one cement mix. The fly ash to slag ratio and the activator content were altered in the AAFS mortars, which were then placed in the fog room, the car...

The long-term effect of extreme conditions, such as high concentrations of CO2, a combination of chloride and air, and sulfuric acid, on the performance of steel fibre reinforced alkali-activated fly ash and slag (AAFS) mortars was investigated. The selected conditions simulated the long-term exposure to the marine environment and had an influence...

Tube hydroforming (THF) is a frequently used manufacturing method in the industry, especially on automotive and aircraft industries. Compared with other manufacturing processes, THF provides parts with better quality and lower production costs. This paper proposes a design approach to estimate the T-shaped THF parameters, such as counter force, axi...

In this study, the solid activator – the synthetic sodium metasilicate pentahydrate – was compared against water and a hybrid sodium silicate and sodium hydroxide activator solution. It was found that the solid activator outperformed the liquid activator as a part of water remained chemically bound to the undissolved particles, thus reducing the ap...

The current slenderness limits are significantly different in international design codes for cold-formed Circular Hollow Sections (CHS) under pure bending. This paper aims to use the Finite Element (FE) method to understand the behaviour of cold-formed CHS under pure bending and to propose new design rules. The model is calibrated by comparing its...

During the past decades, the application of acoustic emission techniques (AET) through the diagnosis and monitoring of the fracture process in materials has been attracting considerable attention. AET proved to be operative among the other non-destructive testing methods for various reasons including their practicality and cost-effectiveness. Concr...

Cemented hydraulic backfill (CHB) is widely used in underground mine backfilling, especially when regional stability is required. One of the critical backfill properties is uniaxial compressive strength (UCS), the maximum axial compressive stress that the sample can withstand before failing. CHB is expected to have a certain UCS in a specific time...

The increasing demand for smart devices and clean energy vehicles that use lithium-ion batteries has sparked a considerable interest in lithium, which is becoming a strategic element. Lithium deposits can be found in saline lacustrine environments or pegmatite hard-rocks that are located mainly in America (Argentina, Bolivia, Chile, USA, and Canada...

This study experimentally investigates the impact behaviour of rubberized concrete beams strengthened with basalt fiber reinforced polymer (BFRP). Twelve reinforced concrete beams, which consisted of different rubber contents (0%, 15%, and 30%), were tested under impact loads. Various wrapping schemes were considered to determine the most effective...

Solid Expandable Tubular Technology (SETT) finds its extensive applications in the oil and gas industries where it is used for well completion and remediation. The purpose of his work is to investigate the material behavior upon expansion and to optimize the parameters that are relevant to the expansion process. Tube expansion tests have been perfo...

Traditional soil stabilization by chemical additives such as cement and lime is a well-established technique for ground improvement of problematic soils. However, with the advantage of lower carbon emission and energy consumption, fly-ash-based geopolymer has recently become an attractive alternative to traditional stabilizers. Nevertheless, the li...

Glass fibre reinforced polymer (GFRP) reinforced alkali-activated fly ash/slag concrete (AAFS) could potentially be used as a durable construction material, especially in aggressive environments. This study aims to examine the structural behaviour of circular GFRP-reinforced AAFS members under combined loading, and introduces a geometrical factor f...

Existing models on the stress distribution around deep buried tunnels pay little attention to the impact of rock-liner interaction and seepage variation. The conventional solution for deep lined tunnels has an inherent mathematical restriction since it is limited to thin liners. In this paper, we solve the poro-mechanical problem of stress and pore...

Cement-based grouting has been widely used in underground coal mining to improve the overall quality of highly fractured rock masses. Due to the difficulties in obtaining characteristic specimens from highly fractured coal rocks, there are very limited laboratory studies investigating the effect of grout on the strength of coal. The purpose of this...

Many concrete structures have been damaged during recent earthquakes due to the low ductility of their columns. Hence, several recent research contributions have been dedicated to producing high-performance concrete materials. Among these contributions, carbon nanotubes (CNTs) are of superior mechanical properties and can be used as additive in con...

Australia is a key player in the global supply of lithium products given its large resources of spodumene. This mineral occurs in pegmatite rocks and can be processed to extract lithium salts used to make valu- able products such as lithium ion batteries, ceramics, lubricants along with specific by-products such as lithium aluminosilicate residue (...

In this paper, the overall effective thermo-mechanical properties of limestone samples are estimated using a micro–macro mechanical approach. A mathematical framework is proposed to estimate the overall properties based on local geometrical considerations using Mori–Tanaka’s scheme. In addition, a homogenization-based mathematical formulation is pr...

Circular concrete-filled double-skin tubular (CFDST) columns increase considerably the displacement ductility and peak strength of the sandwiched concrete due to the confinement provided by the steel tubes. This study describes the characteristics of short CFDST columns under compression and investigates the influences of the sandwiched concrete th...

Glass fibre-reinforced polymer (GFRP) bar and stirrup reinforced geopolymer concrete (GPC) is increasingly recognised as a potential replacement to the conventional steel-reinforced ordinary Portland cement (OPC) concrete due to its superior durability. This paper proposed an analytical model to predict the load-displacement relationship of the con...

The decreasing grades of some gold deposits combined with the increasing depths, difficult surface topography, socioeconomic and geopolitical pressures often make the processing of such deposits infeasible by conventional mining, comminution and leaching technologies. To overcome these problems, the application of in-place, in-situ, and heap leachi...

Glass fiber-reinforced polymer (GFRP) bars in construction are increasing in popularity due to their excellent corrosion resistance, high tensile strength to weight ratio, and low maintenance. Geopolymer is a modern cementitious material that is known for its corrosion resistance and low carbon footprint. Combining the two could produce a green yet...

The research on rubberised concrete (RuC) could promote the recycling of end-of-life tyres and reduce natural resource extraction. To mitigate the greatly reduced compressive strength and fully utilise the desirable charac- teristics such as improved ductility and energy absorption ofRuC, confinement through a steel outer tube could be adopted. Thi...

The poor durability of ordinary Portland cement concrete and the corrosion of conventional steel reinforcement have a major impact on the viability, safety and serviceability of reinforced concrete structures, particularly in marine environments. Geopolymer concrete (GPC) reinforced with corrosion-free glass-fibre-reinforced polymer bars is ideal f...

Rubberised concrete has the benefit of utilising waste material, preventing resource extraction and improving concrete ductility, however at the cost of reduced strength and stiffness. This paper explored the option to effec- tively confine the rubberised concrete with steel tubes to obtain enhanced strength and ductility. The behaviour and perform...

Concrete filled steel tube (CFST) is increasingly used in engineering construction as columns and beams. CFST is known to absorb large amounts of energy as a result of the composite effect. Internationally, there are increasing amounts of waste rubber. In this study recycled rubber is used as aggregate supplement in concrete. Rubberised concrete is...

Geopolymers are recognised for their environmental benefits and excellent chloride and sulfate resistance. However, information on the material characteristics and bond behaviour of geopolymers based on fly ash (FA) and slag is still relatively scarce. This paper presents a comprehensive study on the integration of two modern construction materials...

In this study, different modelling techniques such as multiple regression and adaptive neuro-fuzzy inference system (ANFIS) are used for predicting the ultimate pure bending of concrete-filled steel tubes (CFTs). The behaviour of CFT under pure bending is complex and highly nonlinear; therefore, forward modelling techniques can have considerable li...

The purpose of this paper is to investigate the in-situ leaching of gold using a microfluidic system with controlled flow, temperature and fluid composition. The microfluidic system is a microchannel embedding a nano-scale layer of gold over which the fluid can flow and etch (erode) gold at various temperatures and concentrations of lixiviant. The...

This edited volume contains the best papers in the geo-engineering field accepted for presentation at the 1st Springer Conference of the Arabian Journal of Geosciences, Tunisia 2018. In addition, it includes 3 keynotes by international experts on the following topics: 1. A new three-dimensional rock mass strength criterion 2. New tools and techni...

In this paper, we focus on the energy alteration during longwall mining in an attempt to mimic the conditions of a coal mine in Western Turkey. We verify the proposed model using existing analytical and numerical solutions in terms of stress components. Based on the verified numerical model, the energy balance during longwall retreat is studied rig...

During the excavation of deep rock, a sudden change in boundary conditions will cause the in-situ stress on the excavation surface to release instantaneously. This disturbance propagates in the form of an unloading stress wave, which will enlarge the damage field of surrounding rock. In this paper, the dynamic unloading problem of the in-situ stres...

Rammed earth (RE) designates natural building materials that can contain stabilized or non-stabilized soils or crushed stone blends. RE materials are non-homogenous and their performance depends on their compositions, grain size distributions, porosity, and mode of preparation. This category of building materials has recently been subject of extens...

Early recognition of concrete deterioration is an important engineering task with many associated monitoring challenges. Ground penetrating radar (GPR) is an important non-destructive testing tool commonly used by engineers to locate internal reinforcement and voids within concrete. However, the general standard of interpreting subsurface condition...

Geopolymer is a cementitious material known for its environmental benefits and characteristics comparable to those of conventional ordinary portland cement. Geopolymer concrete (GPC) is a relatively new construction material that is yet to be regulated by standards due to the high variability in the mix design. This paper thoroughly investigates th...

Over the past three decades, self-compacting concrete (SCC), which is characterized by its superior rheological properties, has been gradually used in construction industry. It is now recognized that the application SCC using supplementary cementitious materials (SCM) is highly attractive and promising technology reducing the environmental impact o...

The purpose of this paper is to describe the nonlinear behaviour of geomaterials within the principles of thermodynamics. The main components of this contribution are (1) a new method to estimate the properties of minerals subjected to the non-hydrostatic compression in diamond anvil cell using the finite strain theory is introduced and (2) a prope...

Fibres in fibre reinforced concrete (FRC) and fibre reinforced shotcrete (FRS) are known to increase the toughness of the composite material thanks to their ability to transfer tensile stresses even after cracks have opened. However, fibres are deemed responsible for uncertainty in mechanical performance of FRC and FRS. This uncertainty is ascribed...

Recently, an aqueous glycine solution has been proposed as a non-toxic environmentally friendly lixiviant to leach precious metals such as gold. In confined spaces, gold can be leached effectively using cyanide as a lixiviant. However, in unconfined applications, cyanide poses detrimental environmental effects due to its high level of toxicity. In...

Waste tyres are among the largest and most problematic sources of waste in modern society due to their durability and high rate of dumping in landfills. One possible recycling alternative is to incorporate waste tyre rubber as an aggregate replacement in concrete to promote sustainability and utilise the elastic properties of rubber. Rubberised con...

Continuous monitoring of mechanical parameters determining the state of natural and man-made systems is essential in a wide range of engineering disciplines from mechanical to civil and geotechnical engineering. To be effective, the monitoring response time needs to be commensurate with the characteristic time of variation of the processes being mo...

Composite steel-concrete construction utilising the benefits of both materials has extensively been used in structural engineering with the ability to be used in onshore and offshore applications. One of these elements is the concrete-filled double-skin tubes (CFDST) which is a concept that has been developed in recent years. In this column, the st...

This study investigates the axial impact resistance and energy absorption of rubberized concrete with/without fiber reinforced polymer (FRP) confinement. The impact tests were carried out by using an instrumented drop-weight testing apparatus. The experimental results have shown that rubberized concrete significantly reduced the maximum impact forc...

Conventional steel-reinforced ordinary Portland cement concrete is prone to corrosion. Geopolymer concrete is a new durable cementitious material, and the glass fibre-reinforced polymer (GFRP) is an attractive alternative to steel because of GFRP's compelling physical and mechanical properties, corrosion resistance and electromagnetic transparency....

Understanding the behaviour of natural calcium sulphates is important to ensure the sustainable integrity of civil structures. The phase transitions of these minerals are associated with considerable volume variations, creation of porosity with local defects, and water exchanges. Such changes can jeopardise the integrity of structures when the cond...

Mechanically lined pipe consists of a load bearing carbon steel outer pipe with a thin corrosion resistant alloy (CRA) liner and is a proven and economical solution for oil and gas pipelines. The bond between the two pipes is purely mechanical and under large bending loads plastic deformation of the liner results in non-reversible liner wrinkling....

The adequacy of rubberised concrete (RuC) for use in structural columns is, currently, investigated experimentally through the use of cold-formed double-skin circular steel tube confinement. The RuC is of particular interest because the aggregate can be sourced from recycled tyres, so it is a form of sustainable concrete, and it possesses superior...

This paper investigates the effect of rock mass alteration on the initiation and propagation of fractures. Mining-induced fractures influence the stability of overburden and may provide pathways for mass transfer in underground environments. However, the usefulness of existing fracture modeling techniques with discrete element methods and tradition...

Abstract

Existing semi-analytical solutions to the problem of reactive transport in porous media are either restricted to single aqueous species, to decoupled processes or to infinite/semi-infinite domains. Our approach addresses the problem of multicomponent reactive transport in finite columns, where coupling feedbacks emanating from the non-equilibrium t...

Despite a number of recent studies illustrating the effective use of Glass Fibre Reinforced Polymer (GFRP) rebars as longitudinal reinforcement for concrete compression members. There is a lack of sufficient experimental and numerical studies on their combined action response. This paper demonstrates the use of finite element analysis to predict th...

Concrete-filled double-skin tubular (CFDST) columns are formed by sandwiching concrete between two concentric hollow steel tubes. The result is a composite column with the benefits of both steel and concrete properties. When compared to a traditional concrete-filled steel tube (consisting of a single hollow steel tube instead of two), CFDST column...

Rock drilling efficiency is nowadays a challenge for resource engineers. The present paper focuses on the nu-merical investigation of rock mass behavior under indentation characterized by various physical and microstruc-tural properties. The numerical model is implemented to study the effects of normal percussion in rock drilling conditions. The re...