Sustainable utilisation of calcium-rich industrial wastes in soil stabilisation: Potential use of calcium carbide residue.

Calcium carbide residue (CCR), a by-product of the acetylene industry, is generated at a rate of 136 million tonnes per year, posing significant environmental risks. This review examines the potential utilisation of CCR in soil stabilisation, focusing on its stabilisation mechanism, performance in improving mechanical properties, environmental safety, and sustainability. The aim is to identify future research directions for CCR-based stabilisation to promote its broader application, and to provide references for managing similar Ca-rich wastes. CCR-based materials demonstrate promising benefits in enhancing various soil properties, such as uniaxial strength, swelling properties, triaxial shear behaviour, compressibility, and dynamic responses, while also reducing the mobility of contaminants. Compared to conventional stabilisers, CCR-based materials exhibit comparable performance in soil improvement, environmental impact and safety, and economic feasibility. However, further research is required to delve deeper into stabilisation mechanisms, mechanical properties, and stability of contaminants for the soil treated with CCR-based materials under diverse conditions.

Effects of Fly Ash Inclusion and Alkali Activation on Physical, Mechanical, and Chemical Properties of Clay.

This study investigated the improvement in the behaviour of a clay soil due to the addition of alkali-activated fly ash as a stabilising agent, and the effects of different activation factors such as alkali dosages and silica moduli. The alkali activator solution used was a mixture of sodium silicate and sodium hydroxide. Class F fly ash was used as the precursor material for the geopolymerisation process. Soil samples stabilised with non-activated class F fly ash were prepared and tested to compare the results with samples stabilised with alkali-activated fly ash. Compaction tests, unconfined compressive strength tests, X-ray diffraction analysis, and scanning electron microscopy analysis were carried out on samples cured 1, 7, and 28 days at room conditions. The results showed that the compressive strength of stabilised soil significantly increased when the fly ash was activated. The optimal activation parameters to stabilise the soil were found to be alkali dosages in the range of 12% to 16% and a silica modulus of 1.25. The highest compressive strength recorded was at 1293 kPa with an alkali dosage of 16% and a silica modulus of 1.25, while for the non-stabilised soil, it was at 204 kPa at 28 days of curing. Mineralogical analysis showed a decrease in the peak intensities of kaolinite and illite, while microstructural analysis indicated an alteration in soil texture with the addition of the alkali-activated fly ash.

Experimental investigation on a combination of soil electrokinetic consolidation and remediation of drained water using composite nanofiber-based electrodes.

A novel electrokinetic geosynthetic (EKG) can be efficient in achieving multiple objectives. In this study, a new EKG as an electrode and a drainage channel in the electro-osmotic consolidation was fabricated by electrospun nanofibers containing graphene nanoparticles (GNs) attached to a carbon fiber substrate. To investigate the effectiveness of the fabricated electrodes in electro-osmotic consolidation and remediation of water drained from the system, an experimental apparatus was constructed while considering loading capability in expanded ranges and applying the electric field, and was filled with copper (Cu)-contaminated kaolinite. Experiments were divided into control (CT) and EKG groups, and three categories, C-EK, ES1-EK, and ES2-EK (using carbon fiber, electrospun nanofibers containing 1 wt% GNs, and electrospun nanofibers consisting of 2 wt% GNs, respectively). All the experiments were conducted with the same conditions, loading, drainage condition, and duration. However, EKG experiments were performed by employing the electric field under the vertical pressure in the range of 7-113 kPa, while the CT was conducted without the electric field. According to experimental results, 18 wt% polymethyl methacrylate in the dimethylformamide solvent containing 1 and 2 wt% GNs was selected for making a nanofibrous layer on the carbon fiber. The average diameters of the fibers were 404 ± 36 and 690 ± 62 nm and yielded at 1 and 2 wt% GNs, respectively. The results revealed that using the EKG accelerated kaolinite consolidation. The average degree of consolidation was 68 and 85% in the CT and EKG experiments, respectively. Furthermore, the fabricated electrodes were highly effective as a drainage channel for remediating water drained from the system. Moreover, the highest Cu removal efficiency was obtained in ES2-EK (97%) and ES1-EK (92%), respectively. Conversely, the lowest Cu removal efficiency was observed in the C-EK group (85%).

Effects of Class C and Class F Fly Ash on Mechanical and Microstructural Behavior of Clay Soil-A Comparative Study.

A large amount of coal fly ash produced in thermal power plants is disposed of in landfills which causes many environmental problems. The utilization of fly ash can be encouraged in geotechnical engineering projects. In this paper, the effects of class C and class F fly ash on the mechanical and microstructural behavior and stabilization of clay soil were evaluated through a program of laboratory experiments. The experiments included compaction, unconfined compressive strength, consolidated-undrained triaxial, one-dimensional consolidation tests, and scanning electron microscopy analysis on samples of fly ash-stabilized clay soil after 1, 7, and 28 days of curing. The tests were conducted on mixtures of clay with class C or class F fly ash, ranging from 0% to 30% of the soil. Experimental results showed that the strength parameters and permeability of the stabilized soil improved while the compression and swelling indices decreased by the addition of fly ash and by the increase of curing days. The results obtained from the mechanical tests agreed with the results from the SEM analysis. Based on the results, the soil could be successfully stabilized by using class C fly ash. The improvements in strength, swelling, and permeability parameters of the stabilized soil were higher with the class C fly ash compared with class F fly ash.

Understanding the NEEDS for ACTING: An integrated framework for applying nature-based solutions in Brazil.

Nature-based solutions (NBS) support the provision of multiple benefits for the environment and society. First idealised in 2008, NBS are recommended by worldwide reports and guidelines as strategies to protect, sustainably manage and restore ecosystems. However, their operationalisation is still in the early stages, especially in developing countries, and only a few studies consider their full potential. This article contributes to this context by developing an integrated framework, with spatial and participatory tools, for analysing flood risk mitigation in Brazil. The approach enables a deep understanding of the societal challenges and vulnerabilities of the area (i.e., NEEDS) for subsequently planning the appropriate NBS (i.e., ACTIONS), with the participation of 255 stakeholders of Campina Grande municipality. Results show mappings of flood-prone areas, in which approximately 52% of the flooded areas will see an increase in the future. Hotspots (i.e., hazard, vulnerability, and exposure) are shown and discussed with four application cases. Finally, multiple benefits of seven NBS alternatives are analysed in 53 scenarios of application, in which the higher rates of reductions are found to combined alternatives. The discussion emphasizes the importance of spatially assessing the 'needs' and 'multiple benefits' of NBS, including reducing vulnerabilities and increment of resilience.

Insights into enhanced electrokinetic remediation of copper-contaminated soil using a novel conductive membrane based on nanoparticles.

Electrokinetic remediation is a process in which a direct electric current is applied across a section of contaminated soil to remove metals. To improve the electrokinetic remediation in this study, a conductive membrane was fabricated via in situ chemical polymerization employing pyrrole and copper oxide nanoparticles. The fabricated membrane was placed in an electric field as part of the electrode structure. A physical model was constructed and filled with copper-contaminated kaolinite in the concentration of 200 mg/kg. To control the pH, 0.1 M citric acid and 0.01 M potassium chloride were used as the electrolyte solutions. Experimental parameters such as voltage, current, pH, EC, drained flow, and copper concentration were measured. The results showed that the minimum surface resistivity of the fabricated membrane under a maximum pressure of 8.2 kPa was 2.55 kΩ/m2. The experimental results demonstrated that the use of citric acid as an electrolyte was more useful to desorb the copper due to the formation of the copper-citrate complex. When employing the fabricated membrane, the copper removal increased from 13% (in CT-2) to 63% (in GM-2), while the removal of copper using potassium chloride electrolyte increased from 42% (in CT-1) to 52% (in GM-1). The highest power consumption was obtained in experiments using citric acid. Due to the higher removal efficiency of copper in GM-2, the energy utilization efficiency (ß) increased and reached 29.9 near ß value of GM-1 with the lowest power consumption.

Developing a fuzzy logic-based risk assessment for groundwater contamination from well integrity failure during hydraulic fracturing.

Recent natural gas development by means of hydraulic fracturing requires a detailed risk analysis to eliminate or mitigate damage to the natural environment. Such geo-energy related subsurface activities involve complex engineering processes and uncertain data, making comprehensive, quantitative risk assessments a challenge to develop. This research seeks to develop a risk framework utilising data for quantitative numerical analysis and expert knowledge for qualitative analysis in the form of fuzzy logic, focusing on hydraulically fractured wells during the well stimulation stage applied to scenarios in the UK and Canada. New fault trees are developed for assessing cement failure in the vertical and horizontal directions, resulting in probabilities of failure of 3.42% and 0.84%, respectively. An overall probability of migration to groundwater during the well injection stage was determined as 0.0006%, compared with a Canadian case study which considered 0.13% of wells failed during any stage of the wells life cycle. It incorporates various data types to represent the complexity of hydraulic fracturing, encouraging a more complete and accurate analysis of risk failures which engineers can directly apply to old and new hydraulic fracturing sites without the necessity for extensive historic and probabilistic data. This framework can be extended to assess risk across all stages of well development, which would lead to a gap in the modelled and actual probabilities narrowing. The framework developed has relevance to other geo-energy related subsurface activities such as CO2 sequestration, geothermal, and waste fluid injection disposal.

A three-dimensional finite element analysis of the human hip.

A three-dimensional hip model was created from the MRI scans of one human subject based on constructing the entire pelvis and femur. The ball and socket joint was modelled between the hip's acetabulum and the femoral head to analyse the multiaxial loads applied in the hip joint. The three key ligaments that reinforce the external surface of the hip to help to stabilise the joint were also modelled which are the iliofemoral, the pubofemoral and ischiofemoral ligaments. Each of these ligaments wraps around the joint connection to form a seal over the synovial membrane, a line of attachment around the head of the femur. This model was tested for different loading and boundary conditions to analyse their sensitivities on the cortical and cancellous tissues of the human hip bones. The outcomes of a one-legged stance finite element analysis revealed that the maximum of 0.056 mm displacement occurred. The stress distribution varied across the model which the majority occurring in the cortical femur and dissipating through the cartilage. The maximum stress value occurring in the joint was 110.1 MPa, which appeared at the free end of the proximal femur. This developed finite element model was validated against the literature data to be used as an asset for further research in investigating new methods of total hip arthroplasty, to minimise the recurrence of dislocations and discomfort in the hip joint, as well as increasing the range of movement available to a patient after surgery.