Conventional Engineering Practice Research Articles

Passive Mooring-based Turbine Repositioning Technique for Wake Steering in Floating Offshore Wind Farms

Power loss due to wake effects from upstream wind turbines is an important factor in the design of floating wind farms. These wake disturbances also increase fatigue loads on downstream units. Economic-driven wind farm layout optimization may culminate in non-standard, irregular configurations of offshore wind farms that deviate from conventional engineering practices. Consequently, wind farm developers are inclined towards a more geometrically coherent layout that are sub-optimal. Floating wind turbines horizontal offsets can be used to overcome wake losses. In this study, a novel method suggesting various mooring orientation methods to passively reposition the wind turbines in the farm to maximize annual energy yield. Preliminary parametric optimization demonstrates the effectiveness of the proposed method for standard floating wind farm designs to reduce wake effects by as much as 30% at rated wind speed compared to a baseline case, while preserving the farm’s overall uniformity.

Enhancing Nutrition, Crop Resilience, and Food Security through Biofortification

Biofortification is a process of enhancing the nutritional quality of food crops through conventional plant breeding, genetic engineering, or agronomic practices. It has emerged as an important agricultural strategy to improve public health by increasing the micronutrient density in staple crops and vegetables. Biofortification provides a cost-effective and sustainable approach to combat micronutrient deficiencies, also known as hidden hunger, which affects over 2 billion people worldwide. This review provides an overview of biofortification efforts targeting major micronutrients such as iron, zinc, vitamin A, and folate. The genetic and molecular mechanisms underlying elevated micronutrient accumulation are discussed. The review also summarizes the impacts of biofortification in enhancing micronutrient intake, nutritional status, and health outcomes based on results from efficacy and effectiveness studies. The role of biofortification in building climate resilience and food security is also examined. Overall, biofortification has shown considerable promise in tackling malnutrition sustainably in developing countries. However, continued research and policy support are needed to maximize its impact on nutrition security worldwide.

Numerical Investigation into the effects of rainfall and long stem plants spacing on Root Water Uptake (RWU)

Woody plants on earthen slopes are a bioengineering solution for the prevention of shallow landslides that occur mostly during a wet season. From a soil-hydrological point of view, slope stability is influenced by plant roots reducing soil water content through transpiration. Despite this, conventional engineering practice tends to ignore the effects of Root Water Uptake (RWU), in part due to the complexity of soil-vegetation-atmosphere interactions. This paper investigates the hydrological effects of plants, which involved seepage simulations performed on two different soil types. Each soil was exposed to different rainfall intensities, and the influence of plants over time was seen from the RWU over time for different configurations of plant spacing and canopy densities. This information with in-situ rainfall data, is useful to assess the effectiveness of plants for slope stability. Further, the relative importance of different mechanisms acting in soil-plant-atmosphere interactions was seen in the RWU data. Although the conducted simulations refer to a horizontal soil profile, the results are useful in more complex geometries such as earthen slopes and may help the design of bioengineering solutions (woody plants) and slope stability assessment. Future research is aimed to investigate additional soil-vegetation-atmosphere mechanisms and additional model geometries and plant species.

Stability analysis of unsaturated soil slope considering softening and non-softening approach

In conventional geotechnical engineering practice, peak shear strength parameters are widely used in the design of geo-structures constructed with or within unsaturated soils. However, a reduction inshear strength from the peak to the residual value is typically observed during the shear deformation in typical fine-grained unsaturated soils. Several geo-structures in unsaturated soils undergo a large shear deformation prior to reaching the failure condition. Thus, the factor of safety of such geo-structures will gradually but significantly decrease with the development of the shear deformation. For this reason, the strain-softening behaviour of unsaturated soils should be considered for reliable design of the geo-structuresin unsaturated soils. In this study, an unsaturated clay slope under 10 years rainfall infiltration were modelled using softening and non-softening approach using commercial finite element software SIGMA/W. The responses of the studied slope to the long-term rainfall infiltration were analysed. The results of the softening and non-softening analysis were compared. This study provides valuable information with respect to the significance of the strain-softening that are useful in the rational design of slopes in unsaturated soils.

Study on Water Sinking Sand Method for Sand Backfilling

Based on the partial culvert backfilling project of the JI-HEI Expressway construction in Heilongjiang Province, China, this study investigates the impact of the physical and mechanical characteristics of backfill sand on the compaction degree of sand backfilled using the water sinking sand method. The research includes on-site sampling of the backfill sand, indoor geotechnical testing, water sinking sand method backfilling, and compaction degree testing of the backfilled material. The study explores the particle size distribution, moisture content, density, compaction characteristics, California Bearing Ratio (CBR), rebound modulus, and other physical and mechanical attributes of the sand. It also delves into the water sinking sand method backfilling process and the compaction degree of the soil layer after backfilling. The findings indicate that the backfill sand in this project is a loose, medium to coarse sand with a low moisture content. Its maximum dry density is approximately 1.92 g/cm³, and the optimal moisture content is around 8%. When the sand reaches maximum dry density, both CBR value and rebound modulus reach their highest levels. The reduction in rebound modulus of the sand is not significant, suggesting good water stability. The actual compaction degree of the soil layer achieved through water sinking sand method backfilling ranges from 96% to 99%, meeting the compaction requirements of conventional engineering practices. The application of the water sinking sand method for sand backfilling is characterized by its simplicity, high construction efficiency, and quality assurance, making it suitable for widespread adoption in future engineering projects.

Controlling Gas Generation of Li-Ion Battery through Divinyl Sulfone Electrolyte Additive.

The focus of mainstream lithium-ion battery (LIB) research is on increasing the battery’s capacity and performance; however, more effort should be invested in LIB safety for widespread use. One aspect of major concern for LIB cells is the gas generation phenomenon. Following conventional battery engineering practices with electrolyte additives, we examined the potential usage of electrolyte additives to address this specific issue and found a feasible candidate in divinyl sulfone (DVSF). We manufactured four identical battery cells and employed an electrolyte mixture with four different DVSF concentrations (0%, 0.5%, 1.0%, and 2.0%). By measuring the generated gas volume from each battery cell, we demonstrated the potential of DVSF additives as an effective approach for reducing the gas generation in LIB cells. We found that a DVSF concentration of only 1% was necessary to reduce the gas generation by approximately 50% while simultaneously experiencing a negligible impact on the cycle life. To better understand this effect on a molecular level, we examined possible electrochemical reactions through ab initio molecular dynamics (AIMD) based on the density functional theory (DFT). From the electrolyte mixture’s exposure to either an electrochemically reductive or an oxidative environment, we determined the reaction pathways for the generation of CO2 gas and the mechanism by which DVSF additives effectively blocked the gas’s generation. The key reaction was merging DVSF with cyclic carbonates, such as FEC. Therefore, we concluded that DVSF additives could offer a relatively simplistic and effective approach for controlling the gas generation in lithium-ion batteries.

Effect of wave-current interaction on a long fjord-crossing floating pontoon bridge

Fjord-crossing floating bridges are sophisticated structures subjected to complex environmental loadings including combined action of wave and current. However, the effect of wave-current action is often neglected in a conventional engineering practice. This paper presents a numerical study of the dynamic response of a floating bridge under the combined action of waves and current. The effect of wave-current interaction on the hydrodynamics associated with the bridge pontoons are first evaluated by using a three-dimensional potential flow solver. A model of the entire floating bridge is then established and analysed in the time domain. The accuracy of the model is verified by comparison with available experimental data for a 1 km long curved floating bridge. Parametric studies are subsequently carried out to investigate the effect of wave-current interaction on a 4.6 km long floating bridge model for crossing the Bjørnafjord. Results show that the wave-current interaction has a significant effect on a fjord-crossing floating bridge studied in this paper. Neglection of such an interaction could lead to substantial overestimation or underestimation of the structural responses depending on the environmental headings.

Guest Editorial: Want To Learn Something New About DFITs? Start With an Old Book

Early in the development of unconventional reservoirs, the industry had little choice but to rely on the toolsets handed down from decades of conventional engineering practices. Later, new tools would be crafted in the hopes of better fitting the unconventional paradigm. This presents a choice to the technical community—rely on a traditional and proven method, or one designed for the unconventional system but less tested? Recently, many hydraulic fracturing engineers have been asking themselves this question when it comes to the diagnostic fracture injection test (DFIT). That includes myself, and the journey I took to find an answer culminated in a technical paper (SPE 206239) that was presented at the 2021 SPE Annual Technical Conference and Exhibition. What follows are some of that paper’s key findings which are being shared with the intent to further the discussion on best practices for those challenged with interpreting unconventional diagnostics. The paper utilizes the concept of permeability to validate traditional minimum stress interpretations across multiple reservoir conditions by comparing DFIT fracture closure time permeability estimates with core, pressure buildup, after-closure pressure, and rate transient analysis. This author was able to further support the results by the integration of a wide range of diagnostic technologies such as fiber optics, microseismic, and, among others, DFIT numerical inversions shared through eight case histories. Diagnostic Injections, a Long History Made Short One of the few ways to begin a conversation with a reservoir is by pumping treated fluid at fracturing rates and analyzing how the pressure falls off with time after the injection is stopped. The language for such dialogue and information exchange is formed by the dimensionless time function called “G-function” and was introduced by Ken Nolte in 1979. Nolte’s innovative postulations allowed our industry to determine the expected frac geometry, its conductivity, the formation flow capacity, and the optimum hydraulic fracture design as well as the means necessary to place the treatment. Recently introduced into industry literature is the proposed fracture closure pressure interpretation based on the fracture compliance method, interpreting an earlier, higher-stress estimation than estimates from well‑established methodologies. The practitioner is now faced with the dilemma of finding out which fracture closure interpretation technique is correct since this has a profound impact on how fracture geometry is modeled and optimized. To answer this question, a multibasin analysis of pre-frac tests from the Russia, North Sea, Europe, North Africa, and South America regions was undertaken.

Nature-based solutions for improving navigation reliability on the Madeira River, Brazil.

The Madeira River Navigation and Improvement Project provides a unique opportunity to incorporate nature-based solutions (NbS) into the built environment to promote sustainable communities and water resources infrastructure. The Madeira River has no major physical interventions (river training structures, navigation locks and dams, etc.) to improve navigation, and so is one of the world's last remaining undeveloped megarivers that exhibits natural morphological processes. The objective of this study is to create a safe, reliable, and sustainable navigation channel in the Madeira River. This is being accomplished by designing navigation improvement measures that leverage natural geomorphic processes of the river while minimizing conventional engineering practices that alter the river's morphology. To meet this objective, fluvial geomorphology analysis and hydrodynamic modeling studies have been performed to improve understanding of the morphological behavior of the system. Measures that incorporate beneficial reuse of dredged sediment within the system are being prioritized and incorporated into the study's design. Natural processes are being leveraged through the implementation of an adaptive management process to shape the navigation channel by incorporating the use of dynamic structures using natural local materials (e.g., large woody debris already in the system), a direct application of NbS in practice. This process includes extensive stakeholder collaboration and utilizing nature's energy to balance navigation, ecological, and social benefits along the Madeira River. This project demonstrates that nature-based approaches not only provide navigation benefits but can also provide ecological and social benefits in ways that are sustainable in the long term, consistent with United Nations Sustainable Development Goals (SDGs) and the International Union for the Conservation of Nature's global standard for NbS. Integr Environ Assess Manag 2022;18:115-122. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Simple Approaches for the Design of Shallow and Deep Foundations for Unsaturated Soils I: Theoretical and Experimental Studies

Bearing capacity is one of the key properties required in the design of shallow and deep foundations. In conventional engineering practice, simple approaches are widely used for determining the bearing carrying capacity of foundations based on the shear strength parameters of saturated soils. However, foundations are typically placed in part or fully in the soil zone above the natural ground water table, which is in a state of unsaturated condition. The shear strength of unsaturated soils is significantly influenced by the matric suction. The bearing capacity of foundations cannot be reliably determined by extending conventional soil mechanics principles for soils that are in a state of unsaturated condition. This Companion Paper I, introduces how the shear strength can be used as a tool in the interpretation and prediction of the bearing capacity of foundations in unsaturated soils. In addition, both theoretical and experimental studies related to the bearing capacity of unsaturated soils are succinctly summarized. Numerical techniques that can be used for predicting the stress versus settlement behavior used for the design of shallow and deep foundations are summarized in Companion Paper II. The succinctly summarized information in the companion papers are valuable for geotechnical engineers for understanding and implementing the mechanics of unsaturated soils in the design of shallow and deep foundations.

Simple Approaches for the Design of Shallow and Deep Foundations for Unsaturated Soils II: Numerical Techniques

Numerical techniques are widely used in conventional engineering practice for obtaining the stress versus settlement or load versus displacement (P–δ) behavior, respectively, and use the information in the design of shallow and deep foundations, extending the principles of saturated soil mechanics. This Companion Paper II summarizes the details of numerical techniques that can be used in the design of shallow and deep foundations in unsaturated soils. The two key properties required for performing the numerical techniques are the shear strength and the modulus of elasticity of unsaturated soils. A user-friendly subroutine (USDFLD) has been developed for use in the commercial software, ABAQUS to predict the variation of these soil properties with respect to matric suction. The only additional information required for performing the numerical modeling in addition to the conventional soil properties is the soil–water characteristic curve. Good agreements were observed between the proposed numerical techniques and from theoretical approaches and experimental studies. The numerical techniques discussed in this paper are simple and can be used by the geotechnical engineers in the design of shallow and pile foundations in unsaturated soils.

A numerical technique for modeling the behavior of single piles in unsaturated soils

Pile foundations are widely used in both saturated and unsaturated soils. In certain scenarios, these foundations are subjected to combined vertical and lateral loads. Conventionally, saturated soil mechanics principles are routinely used for the design of pile foundations in unsaturated soils. Such approaches contribute to unreliable estimates of the behavior of piles due to ignoring the influence of matric suction. In this paper, a comprehensive numerical technique is proposed for simulating the behavior of single piles subjected to combined vertical and lateral loads in unsaturated soils by taking account of the nonlinear behavior of shear strength and the elastic modulus of unsaturated soils. This is achieved through a subroutine that was developed for use in the ABAQUS software. The proposed numerical method provided reliable prediction of the vertical load-displacement behavior of a published model pile tested in saturated and unsaturated sands. In addition, 3D finite element analysis was extended to simulate the influence of variations in ground water table (GWT) on the vertical bearing capacity and the influence of vertical loads on lateral response of piles. The proposed numerical technique is a promising tool for implementing the state-of-the-art understanding of the mechanics of unsaturated soils into conventional engineering practice.

Hysteretic behavior of link beams with different cross-sections and stiffener arrangements

In conventional engineering practice, the use of stiffeners and flanges on both faces of stiffened web panels for I-shaped link beams provides fully restrained boundary conditions. In tubular link beams, however, the stiffened web panels possess simply supported boundary conditions due to the use of single-sided stiffeners and flanges.This study investigates the boundary condition effects of stiffened web panels in tubular and I-shaped link beams on their rotation capacity assuming similar area, moment of inertia, length and stiffener spacing. Based on the numerical results, I-shaped link beams demonstrated an approximately 78% higher rotation capacity compared to tubular link beams under the same conditions which could be due to the better behavior of the stiffened web panels of I-shaped link beams.In order to improve the boundary conditions in tubular link beams, a new stiffener arrangement is proposed. This novel arrangement led to 30% increase in stiffener spacing and 15% decrease in stiffener sizing. Furthermore, another stiffener arrangement is suggested to boost the rotation capacity of long tubular link beams by utilizing additional stiffeners on flanges. Using this arrangement, the rotation capacity was enhanced up to four times the conventional tubular link beams through the Tension-Field Action taking place in the flanges due to additional flange stiffeners.

Seismic damage evaluation of an entire underground subway system in dense urban areas by 3D FE simulation

Underground structures often pass beneath high-rise buildings or are located close to them in megacities. Given complex site-city interactions, conventional earthquake engineering practices may leave megacities in seismically prone areas in potential danger. Rather than focusing purely on the interaction between soil and either surface structures or underground structures, this study aims to explore the earthquake-induced hazard of a dense urban area with an entire subway station, two long subway tunnels and 36 fully modeled high-rise piled frame buildings. The study is conducted through the 3D fully coupled dynamic analysis in both the time and frequency domains, emphasizing the influence of aboveground buildings on underground structures. The results reveal that the existence of aboveground buildings generally decreases the station’s response and can either increase or decrease the subway tunnel’s responses. The presence of either aboveground structures or underground structures affects the wavefield and in turn the responses of adjacent structures, highlighting the importance of considering soil-city interactions. The station is most dangerous at the columns’ bottoms. The existence of subway stations and tunnels increases the nearby peak ground accelerations.

Assessing the sustainability literacy of the Nigerian engineering community

Being the lifeblood of socioeconomic progress, engineering is implicated in the unprecedented challenge of sustainability. The global engineering community devised sustainable engineering as a conceptual departure from conventional engineering practices. However, the extent to which the sustainability worldview has permeated the Nigerian engineering community remains unanswered. This paper is an attempt to answer the question of how sustainability literate are the members of the Nigerian engineering community. The paper undertakes an assessment of the sustainability literacy of the community with the aid of a stakeholder survey and a devised sustainability literacy test. Three criteria that are used to gauge the stakeholders’ sustainability literacy are awareness of the UN Decade of Education for Sustainable Development, score on the sustainability literacy test, and self-assessment of sustainability knowledge. Survey participants were recruited mainly from two federally-run Nigerian higher education institutions, and engineering professional associations. The assessment reveals an unsatisfactory performance of the Nigerian engineering stakeholders on all three sustainability literacy criteria. The results show that the majority of the students (81%), educators (67%), and practitioners (64%) were unaware of the UNDESD. The paper therefore highlights the need to improve the sustainability literacy of the Nigerian engineering community, possibly through a sustainability education intervention.

Prediction of lateral swelling pressure behind retaining structure with expansive soil as backfill

Lateral swelling pressure (LSP) develops in expansive soil when the volume expansion associated with water infiltration is restrained in the horizontal direction due to a rigid infrastructure. Various types of testing techniques, used to determine the LSP from both laboratory and field studies, are critically reviewed by focusing on two key factors, namely, the boundary conditions and the saturation path. Most testing techniques are capable of reasonably simulating the stress state of a soil element behind a retaining structure by applying a fixed boundary condition in the horizontal direction and a stress boundary condition in the vertical direction. However, they are only used to determine the LSP following a simple path, which is from an initially unsaturated state to a fully saturated state. In other words, these tests fail to provide information on the variation in LSP with respect to changes in the degree of saturation, the water content or the matric suction during the infiltration process. Furthermore, the literature review suggests that a reliable model for the prediction of the LSP during the infiltration process is not available. For this reason, a model is proposed in this paper to estimate the lateral earth pressure (LEP) considering the variation in LSP behind fixed rigid retaining structures with respect to the matric suction during the infiltration process. The proposed model is simple and only requires information, which includes the soil water characteristic curve (SWCC) and a limited number of soil properties. Data from one large-scale model test and two field case studies from published literature are used to illustrate and verify the proposed model. Reasonable comparisons are made between the predictions and the measured data. The proposed model will be a valuable tool for use in conventional engineering practice for the quick prediction of the increasing LEP behind retaining structures with expansive soils as backfill due to the development of LSP associated with water infiltration.

Optimization and design of a low-cost, village-scale, photovoltaic-powered, electrodialysis reversal desalination system for rural India

This paper presents the cost optimization of a photovoltaic-powered electrodialysis reversal (PV-EDR) system for village-scale applications in rural India based on current component costs and performance. A PV-EDR alternative was explored because it requires half the specific energy (and thus half the power system cost), and reduces water wastage from 60% to less than 10%, compared to small-scale reverse osmosis (RO) systems for groundwater salinity levels commonly found in India. Through co-optimization of the PV and EDR subsystems, the optimal system was predicted to cost $23,420 (42% less than a system designed using conventional engineering practice). A key to the cost reduction was flexible water production that accommodates daily changes in solar irradiance with overproduction on sunny days and water buffer storage tanks. A sensitivity analysis revealed that the capital cost of the total system is most sensitive to membrane area; reducing membrane cost by 87% would half the system capital cost. The optimization method presented here, as well as the cost saving strategies of time-variant operation and load matching with solar irradiance availability, provide design strategies that are relevant to other PV-EDR architectures and general off-grid desalination applications.

REVIEW OF NANO MATERIALS FOR PREDICTING STRENGTH AND VOLUME CHANGE BEHAVIOUR OF EXPANSIVE SOILS

Expansive soils are problematic to Civil Engineering by increase and decrease its volume due to movement of water in and out. This kind of soils is portrayed by its outrageous hardness while drying and with high swelling process on the wetting. Several researches during the past 20 years have proposed different nano materials for the soil stabilization approaches to counter the hazards present in the soils. This paper elaborates various studies on different nano materials are nano silica, nano clay, nano composites were used to control the behavior of expansive soils on the current soil stabilization. In this paper, a state-of-art of the nano materials soil stabilization succinctly summarized. The nano materials are critically reviewed in terms of their soil stabilization with their strength and limitations. The review highlights the need for prediction of materials that are conceptually simple yet efficient for use in conventional engineering practices for different types of expansive soils for sustainable development purpose.

A Resilience-Based Methodology for Improved Water Resources Adaptation Planning under Deep Uncertainty with Real World Application

Resilience of a water resource system in terms of water supply meeting future demand under climate change and other uncertainties is a prominent issue worldwide. This paper presents an alternative methodology to the conventional engineering practice in the UK for identifying long-term adaptation planning strategies in the context of resilience. More specifically, a resilience-based multi-objective optimization method is proposed that identifies Pareto optimal future adaptation strategies by maximizing a water supply system’s resilience (calculated as the maximum recorded duration of a water deficit period over a given planning horizon) and minimizing total associated costs, subject to meeting target system robustness to uncertain projections (scenarios) of future supply and demand. The method is applied to a real-world case study for Bristol Water’s water resource zone and the results are compared with those derived using a more conventional engineering practice in the UK, utilizing a least-cost optimization analysis constrained to a target reliability level. The results obtained reveal that the strategy solution derived using the current practice methodology produce a less resilient system than the similar costing solutions identified using the proposed resilience driven methodology. At the same time, resilience driven strategies are only slightly less reliable suggesting that trade-off exists between the two. Further examination of intervention strategies selected shows that the conventional methodology encourages implementation of more lower cost intervention options early in the planning horizon (to achieve higher system reliability) whereas the resilience-based methodology encourages more uniform intervention options sequenced over the planning horizon (to achieve higher system resilience).

Prediction of the variation of swelling pressure and one-dimensional heave of expansive soils with respect to suction using the soil-water retention curve as a tool

The one-dimensional (1-D) potential heave (or swell strain) of expansive soil is conventionally estimated using the swelling pressure and swelling index values that are determined from different types of oedometer test results. The swelling pressure of expansive soils is typically measured at saturated condition from oedometer tests. The experimental procedures of oedometer tests are cumbersome as well as time-consuming for use in conventional geotechnical engineering practice and are not capable of estimating heave under different stages of unsaturated conditions. To alleviate these limitations, semi-empirical models are proposed to predict the variation of swelling pressure of both compacted and natural expansive soils with respect to soil suction using the soil-water retention curve (SWRC) as a tool. An empirical relationship is also suggested for estimating the swelling index from plasticity index values, alleviating the need for conducting oedometer tests. The predicted swelling pressure and estimated swelling index are then used to estimate the variation of 1-D heave with respect to suction for expansive soils by modifying Fredlund’s 1983 equation. The proposed approach is validated for eight field sites from six countries — namely, Saudi Arabia, Australia, Canada, China, USA, and UK — and on six different compacted expansive soils from USA.