Research Articles (Civil Engineering)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1701

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Internal stability of coal discard in coal co-disposal facilities
Abimaje, Faith O.; Jacobsz, Schalk Willem (Southern African Institute of Mining and Metallurgy, 2026-06)
Internal stability is a key consideration in the design and long-term performance of granular filters, as it precludes particle migration and internal erosion. This study evaluates the internal stability of coal discard material in coal co-disposal facilities. Reusing coal discards could reduce mine waste volumes and mitigate associated environmental impacts. However, coal discard material differs from most soils in terms of particle strength and density, with possible implications for hydraulic stability. Laboratory seepage tests were conducted on coal discard material under varying void ratios, subjected to a range of hydraulic gradients, and the results were used to confirm the applicability of the widely used empirical Kenney and Lau filter criterion to coal discard. Findings revealed that particle loss increased with higher void ratios. Nonetheless, particle migration remained minimal, with a maximum particle loss of only 0.2%, suggesting that coal discard exhibits sound internal stability under the tested conditions.
Development of Master Curve to characterise resilient modulus of unbound granular materials
Rugabandana, Gabriel; Anochie-Boateng, Joseph K.; Maina, J.W. (James); Rimoy, Siya (Springer, 2026-07-04)
This study presents a simplified sigmoidal model integrated with the Master Curve approach to estimate the resilient modulus (MR) of unbound granular materials (UGMs). MR measurements under varying moisture conditions were used to construct the Master Curve, with the optimum moisture content (OMC) adopted as the reference condition. Laboratory testing evaluated the influence of moisture on UGM resilient behaviour at three moisture levels: 0.75 OMC (dry of optimum), OMC, and 1.15 OMC (wet of optimum). The measured MR values were normalised and horizontally shifted along the bulk-stress axis to develop a unified, moisture-independent Master Curve that represents material behaviour across different stress and moisture states. Six UGM types were analysed to assess the model’s robustness and predictive capability, with a unique sigmoidal function developed for each material. The resulting Master Curves demonstrated strong predictive performance, achieving an average coefficient of determination (R2) of 0.86. Comparative analysis showed that the proposed sigmoidal model outperformed conventional MR prediction models in both accuracy and reliability across diverse materials and moisture conditions, demonstrating its suitability for pavement engineering applications.
Willingness to pay for travel time savings on public transport : past practice, new evidence and implications for policy
Hayes, Gary Patrick; Venter, C.J. (Christoffel Jacobus) (Wiley, 2025-12)
Several significant urban transportation projects implemented in South Africa over the last decade have had disappointing results at odds with ex-ante and ex-post economic appraisals of their feasibility. The economic and financial implications are significant and enduring and, in the case of the bus rapid transit (BRT) systems, have resulted in criticism of their value for money proposition. A key input into the economic appraisal of transport schemes is the value of travel time (VTT), which is based on micro-economic theory of time allocation and derived from users' willingness to pay for travel time savings. This paper contends that the correct valuation of VTT benefits has been under-researched in South Africa. We review historical values of non-work–related travel time and compare these with values derived from two types of discrete choice models estimated from a consolidated stated preference dataset from Tshwane, Johannesburg and Ekurhuleni in Gauteng Province, South Africa. An elasticity analysis highlights that the key BRT demand sensitivities are the number of transfers, fare levels and travel time. A mean value of non-work–related travel time of R13.89/h (currently US$0.80/h) confirms that public transport commuters in South Africa have lower VTTs than previously assumed. These findings are contrary to the characteristics of the BRT systems that have been implemented, which emphasise faster travel times and higher fare levels. The analysis also highlights the significant heterogeneity in VTT across the population because of a combination of taste, mode and income effects. These findings have important implications for public transport system designs and operations, which should emphasise reliable services, minimising transfers and lower fares.
Large-scale testing of free-ended piles in unsaturated expansive clays under cyclic and monotonic lateral loading
Murison, Ruan Andrew; Gaspar, Tiago A.V.; Heymann, Gerhard; Jacobsz, Schalk Willem; Osman, Ashraf S. (Brazilian Association of Soils Mechanics and Geotechnical Engineering, 2025-10)
This article presents an investigation into the influence of swell on the behaviour of large-scale free-ended piles installed in an unsaturated expansive clay deposit when subjected to lateral loading. A ‘dry’ pile was founded in a profile kept at natural water content conditions, and a ‘wet’ pile was founded in a profile which was flooded for six months to allow swelling of the clay prior to testing. Load cycles under two different load magnitudes were applied to the piles, followed by monotonic loading to failure. The applied load, pile head displacement and bending strain distributions with depth (determined using fibre Bragg gratings) were recorded during these tests. The behaviour under 113 kN load cycles was similar for the two piles, with the ‘wet’ pile exhibiting marginally stiffer response. This was attributed to a swell-induced increase in lateral stress acting against the pile shaft. Under load cycles of 145 kN and during the monotonic test, the ‘wet’ pile exhibited a substantially softer response and significantly lower ultimate capacity than that of the ‘dry’ pile. This was attributed to the effects of swell-induced softening and the reduced yield stresses in the swelled clay. These phenomena were interpreted with reference to a site investigation programme including seismic continuous surface wave tests and standard penetration tests, as well as some laboratory testing. Effects of local yielding of the bonded material at fissure interfaces upon pile ratcheting during cyclic loading have also been discussed.
We are not all the same : preference-based market segmentation among public transport users in Soweto, South Africa
Cheure, Namatirai; Venter, Christoffel Jacobus (Elsevier, 2026-10)
Identifying travel needs and preferences of different market segments is important in planning public transport systems. Preference-based market segmentation has been researched globally but rarely in the Sub-Saharan African context. This paper seeks to investigate variations in mode preference behaviour amongst public transport users in Soweto, Johannesburg. Revealed and stated preference surveys were conducted to capture travel choices in hypothetical scenarios involving bus rapid transit (BRT), bus, minibus taxis, Gautrain, car, and walk modes. The survey data was used to determine if preference heterogeneity exists amongst the respondents through a priori segmentation based on income and estimating multinomial and nested logit models, and by applying a latent class model. The latent class model identified two segments, labelled as, a “transfer sensitive” group and a “walk sensitive” group. The transfer sensitive group does not like using an access mode, transferring, and waiting, while the walk sensitive group tolerates access trips, transferring and waiting but does not like walking. The paper discusses the implications for public transport design. These include strategies that minimize transfers and reduce stop distances to attract both potential user groups as the network connectivity and access characteristics of a mode determine its attractiveness to different user groups.
Numerical modeling of plate sinkage and in-situ bevameter shear tests using FEM and the density-dependent NorSand critical state constitutive soil model
Kruger, R.; Crous, Petrus Arnoldus; Trinidad, Y.; Tekeste, M.Z. (Elsevier, 2026-10)
Please read abstract in the article. HIGHLIGHTS • Open-access multi-scale dataset comprising bender-element, triaxial, and Bevameter tests. • Novel application of critical state NorSand FEM model to simulate in-situ Bevameter tests. • Achieved forward-only lab-to-field prediction of plate sinkage and shear with 6%–16% error. • Developed automated Bayesian optimization scheme for NorSand hardening rate calibration. • Formulated density-dependent meta-models for soil shear stiffness and hardening parameters.
Characterisation of the reworked residual norite in the Rustenburg region of South Africa
Zannoni, E.; Grobler, T.; Heymann, Gerhard (Southern African Institute of Mining and Metallurgy, 2026-04)
Many tailings storage facilities in the Rustenburg region of South Africa's North-West Province are founded on reworked residual norite derived from the weathering of the Bushveld Igneous Complex. The weathering of these rocks results in the formation of residual soils, typically characterised by high-reactivity clays near the surface, grading into coarser materials with depth. The upper horizon, commonly referred to as reworked residual norite or black turf, typically comprises of clay contents of up to 80% with high plasticity. Cyclic swelling and shrinkage result in remoulding and the development of non-continuous slickensides characteristic of residual soils. With the implementation of the Global Industry Standard on Tailings Management, increased emphasis is placed on robust material characterisation, as this layer frequently controls tailings storage facility stability under both drained and undrained conditions. Laboratory testing is challenging due to very low permeability, high overconsolidation, and a nonlinear shear strength envelope characterisation, with yield stresses of approximately 800 kPa. Oedometer results show decreasing coefficients of volume compressibility and consolidation with increasing stress, likely due to closure of microfissures. Undrained triaxial shear testing on undisturbed and compacted specimens indicates contractive behaviour, with peak strength mobilised at shear strains of approximately 7% -10%, followed by mild strain softening. The results support a nonlinear failure envelope for effective stresses below the yield stress, transitioning to linear behaviour at higher stresses.
Calibrated finite element modelling of the progressive structural response of the Yusufeli concrete arch dam during impoundment
Cassells, Ryan; Jacobsz, Schalk Willem; Roth, Chris P. (South African Institute of Civil Engineers, 2026-03)
Concrete arch dams are complex three-dimensional structures subject to multifaceted loading conditions. Design of concrete arch dams follows an iterative structural analysis approach in which advanced numerical modelling has become the current state-of-the-art tool for analysis. Advancement in the processing power of the personal computer and commercial availability of user friendly and efficient numerical modelling software packages has enabled the development of high-resolution numerical models of arch dams with complex foundation conditions. The finite element method can be used to create elaborate three-dimensional models of concrete arch dams with complex foundation conditions. The models are however only as reliable as the modelling assumption inputs, particularly the constitutive material modelling parameters. Material testing procedures of the dam concrete and foundation conditions provide a good estimate of the material modelling constitutive parameters, but the inherent variance in these test results and the difference in conditions between site and laboratory, mean these parameters may not necessarily accurately reflect those present under dam operating conditions. As a result, it is important to validate the material model parameters assumed for the finite element model by calibrating the deformation response of the dam under actual loading conditions. This study examines the validation of a finite element model of the Yusufeli arch dam in Turkey, during reservoir impoundment, by calibrating the computed static deformation response predicted by the model to that of the dam observed from deformation measurement instrumentation. The model of the dam was shown to be well calibrated by the close comparison between predicted and measured displacement. Results from the model calibration process are discussed and presented, providing insight into the deformation behaviour of a large concrete arch dam during impoundment and the accuracy with which this can be modelled using linear elastic material modelling assumptions. The calibrated model was used to study the progressive structural behaviour of a large concrete arch dam during impoundment of the reservoir. Due to the inherently favourable structural mode of an arch in compression, it is shown that the stress state of a loaded concrete arch dam is preferable to that of an empty one. These are important considerations to be made during first filling of the dam reservoir. A comprehensive validation of the modelled stress and strain behaviour of the dam in relation to that measured by stress meters and strain gauges was not achieved due to numerous inconsistencies in measurement data obtained from these instruments.
Benchmarking contiguous aggregate ratios with asphalt compactability and rut resistance
Komba, Julius Joseph; Sebaaly, Haissam; Horak, Emile; Maina, J.W. (James) (ASTM International, 2026-01)
Aggregate packing is the primary determinant of the shear strength, stiffness, and durability of asphalt mixes. The current asphalt mix design practices emphasize using aggregate gradation envelopes as control mechanisms to achieve an enhanced aggregate packing structure with optimum shear strength, durability, and stiffness, and to guarantee rutting resistance. However, experience in South Africa has shown that the bias toward rut-resistant mix designs often leads to compactability problems. The significant knowledge embedded in the basic aggregate gradation curve has the potential to improve the understanding of the compactability and rut resistance of asphalt mixes. Based on the well-known Bailey method, the basic aggregate grading curve is used in this paper to determine various revised rational Bailey ratios (RBRs) that adhere to the contiguous aggregate fractions (i.e., aggregate with consecutive sizes). The determined ratios demonstrated a better description of the aggregate packing. The subsequent correlations analysis performed in this paper indicated that the revised RBRs exhibit strong relationships with compactability (i.e., R2 up to 0.99) and rutting resistance (i.e., R2 up to 0.81) of asphalt mixes. The research work presented in this paper indicates that the revised RBRs can be used to optimize asphalt mix designs via benchmarking methodology. Ranges of the revised rational Bailey parameters for such a benchmarking methodology are proposed to enhance the asphalt grading selection and mix design process.
Structural health monitoring of an onshore wind turbine piled-raft foundation
Louw, Hendrik; Kearsley, Elsabe P. (Sage, 2026)
Over the years, wind turbine design has substantially changed to reduce cost and maximise performance, resulting in increased wind turbine height, blade size and power rating, seeking steadier wind at higher elevations while capturing more wind with longer blade lengths. This resulted in not only the vertical load but also the already dominating horizontal load and overturning moment caused by the wind acting on these turbine foundations, increasing significantly. Onshore turbine structures are often built on piled-raft foundations, which were historically not designed for dominant horizontal loads. Thus, with the increased popularity of these larger wind turbine models, the need arose to physically determine the response of these foundation types to large horizontal loads and overturning moments. In this article, a full-scale operational piled-raft foundation supporting a 117 m high onshore wind turbine in South Africa was instrumented and monitored for an extended period of time, focusing on the foundation’s response during turbine installation and the first year of operation. A good correlation between the wind data and foundation strains existed and is presented, with load sharing between the different foundation components also highlighted. The cyclic loading of the foundation from the wind resulted in the piles carrying increased loads over time compared to the loads carried after turbine installation (increasing from 35% to roughly 60% after 1 year of operation). The permanent bending moments in the piles also increased with time. Additionally, seasonal temperature variations caused significant strain changes in the raft, which cannot be ignored.
Electric minibus taxis in Cape Town : energy demand, emissions, and costs
Sello, Joshua Tokollo; Knipe, Mienke; Marais, Maria Elizabeth; Abdelgadir, Salma; Venter, Christoffel Jacobus; Booysen, Marthinus Johannes (MDPI, 2026-02)
Minibus taxis are Cape Town’s ubiquitous public transport mode, carrying about 69% of public transport users. As electric mobility accelerates, the implications of electrifying this paratransit fleet must be quantified. We present a multi-perspective assessment of energy, environmental and operator impacts of electric minibus taxis (eMBTs). Using a high-resolution tracking dataset representative of MBT operations in Cape Town, South Africa, we estimate daily charging energy demand, compare greenhouse gas and particulate matter emissions for electric and internal combustion operation under South Africa’s coal-dominated grid, and evaluate the operator’s total cost of ownership. Key results show that eMBTs require approximately 50.8 kWh of energy per day, based on the fleet’s median daily distance. Under current grid conditions, diesel minibus taxis emit 14.37% less CO2e than eMBTs, but eMBTs drastically reduce noise pollution and particulate matter emissions when compared to diesel vehicles. Despite higher purchase prices, eMBTs can reduce operating costs and become financially attractive under favourable electricity prices and financing conditions. The study provides evidence to guide charging infrastructure planning, grid policy and incentive design for paratransit electrification in developing regions.
Bus rapid transit in Africa - is it still relevant?
Venter, Christoffel Jacobus (Routledge, 2026)
No abstract available.
Exploring mode choice behaviour and preferences of transport users in small cities in South Africa : the case study of Bloemfontein
Burger, Everardt André; Chetty, Alison (Palacký University Olomouc, 2026-03-23)
This study investigates mode choice behaviour and transport preferences in Bloemfontein, South Africa, a medium-sized metropolitan area facing distinct transportation challenges related to accessibility, affordability, and limited modal integration. While urban mobility research in South Africa has largely focused on major metropolitan regions, smaller cities such as Bloemfontein require tailored, context-sensitive strategies to address their specific economic, spatial, and social dynamics. Adopting a pragmatic research paradigm and guided by the Theory of Planned Behaviour (TPB), this study employs a structured quantitative research design and an Ordinal Logistic Regression Model to examine the factors shaping user preferences across private vehicle (PV), public transport (PT), and non-motorized transport (NMT) modes. Key predictors evaluated include accessibility, reliability, affordability, flexibility, and perceived health benefits. Data were collected through a structured survey targeting regular commuters across different demographic groups. Initial descriptive analysis revealed that demographic variables, particularly gender, age, and employment status, significantly influence transport choices. Women tended to prioritize safety and personal security, while men placed greater emphasis on reliability and on-road performance. Full-time employees showed stronger preferences for PV and PT, whereas part-time workers and unemployed respondents relied more heavily on NMT, reflecting differences in income levels, travel constraints, and daily activity patterns. Subsequent regression analysis confirmed that accessibility (ease of accessing a service) is the most significant predictor of mode choice, followed by service reliability and affordability. While safety concerns remain relevant, their influence was comparatively weaker than service quality and convenience factors. The findings further indicate a substantial willingness among PV users to shift to PT if improvements in reliability, flexible operating hours, and transparency of service information are implemented. The integration of NMT infrastructure, including pedestrian-friendly environments, bike-sharing programmes, and park-and-ride facilities, is identified as essential for strengthening first- and last-mile connectivity. Overall, the study provides empirically grounded, user-focused insights to inform transport policy and planning in smaller cities. By linking behavioural theory with quantitative evidence, the findings support targeted interventions aimed at enhancing PT accessibility, affordability, and reliability, thereby contributing to more inclusive, sustainable, and equitable urban transport systems.
A critical review of resilient modulus characterisation in unbound granular materials
Rugabandana, Gabriel; Boateng, Joseph Anochie; Maina, J.W. (James); Rimoy, Siya (Springer, 2026)
The resilient modulus (MR) is a fundamental parameter used to characterise the resilient response of unbound granular materials (UGMs), which are widely employed in the construction of flexible pavement systems. MR plays a pivotal role in estimating the stress-strain behavior of pavement layers under traffic loading and serves as a key control metric during construction and quality assurance processes. Moreover, it is critical in understanding the mechanisms behind common pavement distresses, including fatigue cracking and rutting. The primary objective of this study is to conduct a comprehensive literature review on the resilient behavior of UGMs, emphasizing the conceptual framework of MR, the key influencing factors, and the evolution of mathematical models developed to estimate and predict this mechanical property. The review concludes with insights into current research gaps and recommendations for future investigation. Despite significant research over the past decades, the resilient behavior of UGMs remains incompletely understood, largely due to the inherent heterogeneity of these materials and their nonlinear, anisotropic responses under varied cyclic loading paths and moisture conditions. The mechanical behavior of UGMs is influenced by both macroscopic and microscopic material characteristics, such as gradation, density, porosity, surface texture, mineralogical composition, particle shape, and orientation. Environmental conditions, particularly temperature fluctuations, also play a critical role. One major limitation of existing MR models is that their parameters are typically difficult to determine through experimentation and are not true intrinsic material constants. Instead, they act as state-dependent variables, influenced by stress level, moisture content, boundary conditions, and loading history. Furthermore, most models are calibrated using data from repeated load triaxial (RLT) tests, which fail to replicate the complex, multiaxial stress states experienced by UGMs in actual pavement structures especially the simultaneous action of vertical, horizontal, and shear cyclic stresses. While these studies have provided valuable insights, further research is needed to establish definitive conclusions and to enhance the predictive reliability of existing MR models.
Experimental comparison of rainfall simulation methods for urban stormwater management research
Van Zyl, Rachel Neleah; Loots, Ione (IWA Publishing, 2026-04-01)
Rainfall simulators are typically categorised as either pressurised or drop-forming systems, each offering distinct advantages depending on the research application. This study presents a comparative experimental analysis of a pressurised nozzle-based rainfall simulator and a drop-forming needle-based rainfall simulator, assessing their suitability for urban stormwater management research. Both setups were constructed indoors with a 1.5 × 1.5 m rainfall area and a 2.3 m raindrop fall height. The simulators were evaluated based on rainfall intensity, spatial uniformity, drop size distribution and drop velocity. The pressurised system produced intensities from 23.9 to 109.7 mm/h, while the drop-forming system achieved 4.5–21.0 mm/h. Uniformity coefficients ranged from 81.2 to 93.3% (cups) and 86.6 to 96.4% (trays) for the pressurised system, and 85.7% (cups) and 94.8% (trays) for the drop-forming system. D50 raindrop sizes ranged from 0.8 to 1.2 mm for the pressurised system and 1.7 mm for the drop-forming system. Estimated median drop velocities ranged from 82.5 to 98.5% of terminal velocity. While both systems replicated key rainfall characteristics, the pressurised simulator was limited to high-intensity events. The drop-forming simulator offered finer control and broader applicability, supporting its use in urban hydrology and stormwater management research. HIGHLIGHTS Experimental comparison of pressurised and drop-forming rainfall simulators under identical scale conditions. Drop-forming needle-based simulators offer finer control over rainfall intensity. A mesh in drop-forming rainfall simulators improves uniformity and drop size distribution. Results promote drop-forming rainfall simulator use in sustainable urban stormwater management research.
Estimating urban impervious surface connectivity to drainage systems in a developing country : field evidence from Tshwane, South Africa
Loots, Ione; Smithers, Jeffrey; Kjeldsen, Thomas Rodding (Taylor and Francis, 2026)
The connectivity of impervious areas to drainage systems, or directly connected impervious area (DCIA), is a key factor in urban runoff and water quality modelling, but is rarely measured in developing countries due to cost and complexity. This study provides new, visually observed field data on connectivity for 272 urban sites in Tshwane, South Africa, to support low-cost DCIA estimation across land use classes. Linear regression, logistic regression, and visual interpretation were used to estimate drainage connectivity. Results show that, contrary to findings from developed countries, most formal and informal residential areas exhibit 0% DCIA. In contrast, industrial and commercial sites show consistently high DCIA, aligning with international trends. These findings offer practical guidance for DCIA estimation in data-scarce urban environments: zero connectivity can be assumed for residential areas with total impervious area below 50%, with 100% DCIA for commercial/industrial sites.
The measured and modelled thermal response of reinforced concrete T-beams subjected to environmental loading
Kleynhans, Amé; Kearsley, Elsabe P.; Skorpen, Sarah Anne (South African Institute of Civil Engineers, 2025-12)
In this study, the thermal response of two reinforced concrete T-beams with identical outer dimensions but differing internal geometry, and therefore different thermal inertia, is investigated. Both T-beams were instrumented with thermocouples and vibrating wire strain gauges and subjected to purely thermal environmental loading. The weighted average (effective cross-sectional) temperature, along with the vertical and transverse temperature distributions, were analysed. In addition, theoretical thermal strains and self-equilibrating stresses were calculated. Uniquely, the mathematical model and assumptions were compared to and validated by experimentally measured strains as opposed to validation through comparisons of predicted temperatures. Effective temperature ranges were related to crosssectional area per unit width and compared to results from literature. Furthermore, the greatest difference in thermal response between the two sections was found to be effective temperature and subsequent longitudinal movement. Calculated bending moments, caused by thermal loading effects and self-equilibrating stresses, approached 30% of the concrete’s ultimate tensile capacity, emphasising their structural relevance.
Capacity-based feasibility boundaries for shared priority infrastructure for minibus taxis at signalised intersections
Mwenda, John Paul; Venter, Christoffel Jacobus (South African Institute of Civil Engineers, 2025-12)
The minibus taxi (MBT) is the most widely used mode of public transport in South Africa, accounting for over 66% of peak hour public transport trips. Unlike buses, which benefit from dedicated infrastructure such as bus rapid transit (BRT) lanes with priority transit signals at intersections, MBTs currently lack such priority infrastructure to enhance their efficiency. Efforts by South African road authorities to provide priority infrastructure for MBTs are hindered by the absence of technical guidance on planning, design, and feasibility. This study addresses this gap by developing an analytical method to determine feasible traffic volumes for shared queue bypass priority lanes at pre-timed signalised intersections. The basic problem is that any priority given to MBT vehicles likely reduces the capacity available to other vehicles, which could lead to performance losses. Taking account of this interaction between MBT and general traffic volumes and the reallocation of vehicles to different lanes, we define feasibility as the combination of volumes where capacity is not exceeded for either vehicle type while still offering potential delay savings for MBTs. We produce a set of graphs that can serve as an initial assessment of whether intersections with medium to high MBT volumes may qualify for priority treatment, considering only existing geometric and traffic characteristics. Additionally, the study provides guidance on expected storage lengths for these priority lanes. Overall, the findings indicate that shared queue bypass lanes are effective when medium taxi volumes (approximately 20 PCU/hr to 85 PCU/hr) are present, provided that turning traffic in the shared left-turn lane is not excessively high (between 50 PCU/hr and 640 PCU/hr, depending on green time). Noting that drivers may adapt to priority intersections in unknown ways, we recommend further studies on the traffic safety implications of priority treatments under real operating conditions.
Cross-laminated timber : a state-of-the-art review towards a proposed structural analysis strategy
Boulle, Benedict E.; Van der Merwe, Johann E.; Roth, Chris P. (South African Institute of Civil Engineers, 2025-12)
Cross-laminated timber (CLT) has experienced growing global popularity in recent years, extending to South Africa with the adoption of SANS 8892 (2020), which allows for local manufacturing of performance-rated CLT. However, this standard requires all locally produced CLT layups to undergo extensive mechanical verification to determine strength and stiffness properties. Analytical methods have proven relatively accurate in predicting the out-of-plane mechanical properties of CLT. Incorporating these methods into design equations can aid in the structural design and sizing of CLT elements. The currently proposed prEN 1995-1-1 (2023) contains design factors specific to CLT, largely common with sawn timber. Adopting such an approach would simplify CLT design in South Africa, using established partial factors, as is the case for plywood. Resistance equations are therefore proposed using existing partial factors for sawn timber design in SANS 10163-1 (2003), incorporating Timoshenko beam theory calculations for bending and shear stresses in CLT. However, the material resistance factor value of 0.68 proposed for sawn timber may be overly conservative due to CLT’s inherent load-sharing behaviour. Using the methods outlined by Pagel (2019) and variability results of South African pine-only CLT obtained by Jacobs (2023), an average resistance factor of 0.79 was determined.
Application of cement-cassava peel ash mix for the stabilisation of marine clay soil : a review
Oruabena, Bernard; Steyn, Wynand Jacobus Van der Merwe (Springer, 2026)
This review investigated the application of cement and Cassava Peel Ash (CPA) for stabilising Marine Clay Soil (MCS). This material exhibits unusually high plasticity and compressibility and low shear strength, creating challenging conditions for stabilisation. In recent decades, lime and cement have been utilised to enhance the resilience of MCSs. However, the environmental and economic sustainability of this practice has come into question due to the substantial carbon dioxide emissions produced during cement manufacturing. Cement-free stabilisation using the scientifically innovative agricultural by-product CPA has been developed as an eco-friendly and cost-effective alternative, leveraging its improved pozzolanic activity to enhance the structural characteristics of MCS, such as strength, stiffness, and permeability. Although the combination of cement and CPA could significantly benefit the structural engineering of MCS, understanding the detailed mechanisms of cement-free stabilisation remains complex, limiting its widespread application. This review indicates that the CPA-cement mix can enhance key aspects of MCS, including permeability, California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS).

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