Dune Research Articles

From lab to landscape-scale experiments for the morphodynamics of sand dunes

From lab to landscape-scale experiments for the morphodynamics of sand dunes

Durability enhancement in self-compacting sand concrete using mineral additives

Purpose The study aimed to explore the effects of mineral admixtures – especially limestone filler (LF), brick powder (BP) and ceramic powder (CP) – on the performance of self-compacting sand concrete (SCSC). It studies their effect on mechanical properties and mass loss when exposed to acidic solutions (H2SO4 5% and HCl 5%) over periods of 28, 90 and 180 days. The study seeks to develop SCSC technology by taking advantage of locally available sand resources. Design/methodology/approach Using an experimental design, the study explores different formulation parameters, including the use of silty sand (AS) and dune sand (DS) in fixed proportions, where AS constitutes 70% and DS 30% of the total sand content. The superplasticizer ratio (SP) and water-to-binder ratio (W/B) are constant with varying amounts of mineral additives. The study immerses SCSC samples in acidic solutions (5% H2SO4 and 5% HCl) for 28, 90, and 180 days to evaluate mass loss and mechanical properties. This endeavor to advance such concrete technology is motivated by the desire to incorporate sand concrete into the realm of self-compacting concrete technology while also harnessing the advantages of locally available sand resources, particularly dune sand, which is abundant in the southern regions of Algeria. Findings SCSC results with mineral additives showed enhanced resistance in both tensile and compression tests, indicating improved durability compared to the reference sample without additives. However, excessive proportions of BP (>60%) or CP led to exceptions in this trend An exception to this trend was observed when BP was added in proportions exceeding 60% or when CP, indicating potential limitations in some additive formulations. Overall, the research provides valuable insights into improving the performance and durability of SCSC through the strategic incorporation of mineral admixtures, contributing to advances in self-compacting concrete technology. Originality/value 1 – Valorization of local materials and recycling of waste: DS, LF, BP and CP, which are available in great quantities in the south of Algeria; 2 – Combination, at the same time, of alluvial sand and dune sand as aggregate and LF, BP and CP as filler. 3 – Application of the design of experiments method methodology for the optimization of these elements of the new sand concrete studied. The new building material elaborated present indeed a technical, economic and environmental interest.

Effects of grazing on the relationship between dominant shrubs and understory vegetation along sand dune stability gradient.

During the process of dune vegetation restoration, understanding how grazing disturbance affects the relationship between plant species is a critical issue in ecological studies. However, there is insufficient evidence on the changes in the interaction between dominant shrubs and understory vegetation under grazing behavior. We aimed to study how grazing and dune stabilization affects the relationship between Caragana microphylla and understory vegetation. We established fencing at various stages of dune stabilization and proceeded to compared the performance indicators (e.g., richness and biomass) and the relative interaction index of understory vegetation and different functional groups along the dune stability under grazing and fencing conditions. Results showed that C. microphylla had facilitation on understory plants, and increased with dune stability, while the facilitation of Caragana microphylla on understory vegetation was stronger under grazing conditions. As sand dune stabilization increases, the facilitation of C. microphylla on understory vegetation diversity decreases significantly. However, there was no significant difference in the facilitation of C. microphylla on understory vegetation biomass at different stages of sand dune stabilization. This is related to the survival strategy of perennials being less tolerant to environmental stress than annuals, because grazing increased the richness of both annuals and perennials while reducing the overall biomass, and in the later stages of sand dune stabilization, and the facilitation of C. microphylla on perennials was higher than on annuals. Our study highlights the importance of the responses of different life-form groups to environmental factors and grazing disturbance during the process of sand dune vegetation restoration, as they play a crucial role in shaping the development of the relationship between understory vegetation and dominant shrubs.

Perched Hydrologic Systems of the Monahans and the Kermit Dune Fields, Northern Chihuahuan Desert, West Texas, USA

Perched Hydrologic Systems of the Monahans and the Kermit Dune Fields, Northern Chihuahuan Desert, West Texas, USA

Thermal analysis of mortar based on crushed dune sand

This study investigates the thermal decomposition behavior of mortars formulated using crushed dune sand and thixotropic polyester resin. Thermal analysis techniques, including Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA), and Gravimetric Thermal Analysis (GTA), were employed to characterize the thermal transitions, decomposition stages, and stability of these mortars. Results indicate that crushed dune sand maintains consistent glass transition (Tg) and crystallization temperatures (Tc) when integrated into the mortar matrix, highlighting its thermal stability. However, the melting point (Tm) varies due to the presence of the resin, which significantly influences the composite’s thermal behavior. Decomposition analysis reveals two major weight loss stages: water evaporation between 200°C to 400°C and organic decomposition of the resin between 700°C to 800°C, with minimal weight change beyond 800°C, indicating thermal stability. The DTA results exhibit distinct endothermic reactions related to dehydration and dehydroxylation, along with a pronounced exothermic peak around 400°C, signifying resin decomposition. Elemental analysis confirms that the crushed dune sand is predominantly silica with minimal impurities, making it suitable for construction applications. This research contributes to a deeper understanding of the thermal behavior of polymer-modified mortars, with implications for enhancing thermal and mechanical properties in construction materials.

Topographic–Vegetation Interactions on an Incipient Foredune Field Post-Tropical Storm

Sand dunes protect the most important economic and ecologically critical landscapes from coastal hazards (storms and high-tide flooding). The characteristics of the dune affect their protective ability. This paper qualitatively and quantitatively assesses the relationships between pre- and post-storm conditions for vegetation and the morphology of an incipient dune system along the South Carolina coast. Field-based dune vegetation and morphology measurements were obtained before and after tropical storm Dorian (2019). Vegetation is assessed with respect to distribution and functional type, and subgroups are introduced to categorize land cover transitions. At the quadrat scale (0.2 m2) following the storm, there was a shift from stabilizer to builder, a decrease of sand (2%), and the vegetation remained consistent at around 61% of the land cover. Transect-level analysis (0.2 m × 1.0 m) revealed distinct variability concerning post-storm morphology change in the extreme study site extents. Dorian resulted in approximately 10% volumetric loss over the entire study site (101 m2). This study demonstrated changes to a dune system following a tropical storm with wind as the dominant forcing factor. This study revealed that vegetation presence is not broadly correlated with reduced levels of post-storm erosion.

A hybrid, genetic programming and physically-based predictor of dune geometry

Subaqueous sand dunes are found in many natural environments and pose significant operational challenges. However, classic dune predictors found in the literature fail at predicting equilibrium dune dimensions. In this study, we first investigated the potential of using genetic programming to derive predictive equations of dune wavelength and height. The predictors outperformed existing relationships, yet the equations remain complex due to the intricate physics governing dune evolution. We carried out a global sensitivity analysis to evaluate the most influential parameters of the GP predictors. Finally, we proposed a set of robust predictors, for equilibrium dune heights and wavelengths, relying on basic environmental parameters.

Optimization of Alkali-Activated Ladle Slag-Fly Ash Composites Using a Taguchi-TOPSIS Hybrid Algorithm

The effect of multiple mix design factors on the properties of ladle slag-fly ash alkali-activated composites was investigated. Taguchi-TOPSIS hybrid algorithm was adopted to optimize mix design parameters, including ladle slag replacement by fly ash (LSR), sodium hydroxide molarity (SHM), the ratio of sodium silicate to sodium hydroxide (NS/NH), the ratio of alkaline activator solution to binder (AAS/B), and crushed stone replacement by desert dune sand (CSR). The results revealed that the mix proportions of the optimum strength response comprised LSR, AAS/B, SHM, NS/NH, and CSR of 10%, 0.5, 8 M, 2, and 75%, respectively, with a compressive strength of 21 MPa. Conversely, the mixture proportions for superior fresh properties had a flow of 240 mm and entailed LSR, AAS/B, SHM, NS/NH, and CSR of 40%, 0.5, 8 M, 2.5, and 75%, respectively. Additionally, the hybrid method prediction model proved to be robust, with the ability to predict strength and workability at 93 and 100% accuracy. The optimum mixes comprised an intermix of calcium aluminosilicate hydrate and sodium aluminosilicate hydrate gels, with traces of calcium silicate hydrate gel, as identified by microstructure analysis and using ternary diagram system of Ca/Si-Na/Si-Al/Si ratios.

Fixing active sand dune by native grasses in the desert of Northwest China

BackgroundDesertification is the most severe environmental problem in arid and semi-arid regions and has caused great economic loss every year. However, artificial sand fixation barriers function on sand fixation for only 10–20 years. Searching for a native species with long-term sand fixation effect and strong environmental adaptive capacity, and low water consumption is needed. In this study, we investigated the environmental adaption and sand fixation effect of a grass from Poaceae family (Psammochloa villosa) that is indigenous to the desert of Northwest China.ResultsThe results showed that P. villosa has a streamlined leaf form, strong mechanical strength, and flexibility to adapt to wind. Leaf curling of P. villosa under drought decreased water loss rate through decreased evaporation area to adapt to drought. Significant negative relationship between adventitious root length and horizontal root burial depth indicates that adventitious roots help P. villosa absorb water and nutrients from soil under shallow sand burial condition, which enables P. villosa to adapt to different sand burial conditions. P. villosa fixed sand dunes through the distribution of the population at the top of the dune and the vertical relationship between the direction of windblown sand and the direction of growth of P. villosa, which stopped the expansion of the dune.ConclusionsGrowth characteristics of wind and drought tolerant leaf traits and adventitious roots under sand burial indicate that P. villosa is well adapted to dry sandy desert conditions and burial by sand. The distribution of the P. villosa population on the sand dune is a “brake” on its expansion. These findings provide new insight for active sand dune fixation and desertification control using native grass in the desertified regions.

Manufactured soil: A new use for bauxite residue

Bauxite processing residue produced at an Alumina refinery was used to produce manufactured soil. The residue was first acidified and then leached to remove excess salts. Green waste compost was added at rates of 5 and 10 % w/w, with or without the addition of 20 % w/w dune sand. The products were dried, crushed and sieved and the chemical, physical and microbial properties of the materials characterized. Products had an electrical conductivity and pH of 1.0–1.1 dS m−1 and 8.0–8.1 respectively in 1:5 soil:water extracts and corresponding values in saturation paste extracts were 5.4–5.7 dS m−1 and 7.4–7.5. The effective cation exchange capacity was 202–351 mmolc kg−1, exchangeable Na percentage was 41–46 %, Colwell-extractable P was 108–119 mg kg−1 and the Toxicity Characteristic Leaching Procedure showed that extractable metal concentrations were an order of magnitude below regulatory limits so the material can be considered as non-hazardous. Diethylenetriaminepentaacetic acid-extractable Cu, Zn and Mn were below reported critical levels. Addition of compost lowered concentrations of extractable Cr, As and V and drying the material further reduced extractable levels. When the material was dried it shrunk and solidified and the aggregates produced had a low macroporosity and high microporosity and water holding capacity compared with dune sand. Aggregates were very stable as measured by wet sieving. Compost addition increased organic C content, and the size (microbial biomass C) and activity (basal respiration and the activity of enzymes involved in C, N, S and P mineralization) of the soil microbial community. It was concluded that the materials produced had soil-like chemical, physical and microbial properties and could potentially be used as a soil substitute.

Latest Triassic Active Aeolian Dune Field Preserved by CAMP‐Related Lava Flows

ABSTRACTFieldwork investigations and stratigraphic analyses in the Parnaíba Basin, northern Brazil, reveal the interaction of the uppermost part of the Triassic Sambaíba aeolian dune field (erg) system with the latest Triassic–earliest Jurassic Mosquito lava flows. The lava flows originated as part of the Central Atlantic Magmatic Province (CAMP, ~201 Ma) and covered the aeolian system, allowing almost complete preservation of large‐scale in situ aeolian bedforms, even preserving lee‐ and stoss‐side. During the emplacement, the lava flows interacted with unconsolidated aeolian sediment, generating sediment–lava deformation features that are preserved at the interface between these units. This occurrence attests to arid conditions in the low latitudes of Gondwana at the Triassic–Jurassic transition.

A new species of Bromus sect. Ceratochloa (Poaceae: Bromeae) from Argentina

A new species of Bromus section Ceratochloa (Poaceae) is described. Bromus alonsae is characterized by its perennial, creeping or semi-creeping habit, blades glaucous green with short and dense pubescence, folded to rolled vernation, and loose and semi-contracted panicles. It begins flowering in October and inhabits the maritime coastal sand dunes of the southeast of Buenos Aires province, Argentina. It differs from B. catharticus var. catharticus in both morphology and phenology.

LBM-DEM modeling of particle-fluid interactions on active small solar bodies

Aeolian-like surface features observed on small Solar System bodies have piqued interest in their underlying formation mechanisms. Understanding the evolution of fluid-solid interactions is crucial for elucidating the nature of cometary activity. We established a resolved fluid-particle simulation approach and implemented it into our self-developed DEMBody and LBMCoupler codes to simulate the wind erosion process on comet 67P. We developed this novel framework by applying the lattice Boltzmann method-discrete element method (LBM-DEM) in a low-gravity and rarefied atmosphere environment. The inter-particle forces were modeled using the Hertz contact model, friction, and cohesion. The fluid field was calculated by solving the lattice Boltzmann equations, which use the distribution function as the variable. The fluid-particle forces were modeled using the partially saturated cells method, in which the force is calculated based on the populations of the fluid cells occupied by the solid phase. We conducted 2D and 3D validation simulations and a series of simulations of a regolith layer as a preliminary application to validate the framework. The validation results of the drag coefficient under 2D and 3D conditions are in good agreement with previous theoretical and numerical estimates. Additionally, the wind erosion process on the surface of comet 67P is reproduced using the presented approach. This preliminary application show that the threshold velocity to initiate grain motion on comet 67P is about $25$ $ m/s$, which is consistent with the observations that sediment transport driven by winds frequently occurs near the perihelion of comet 67P. The proposed LBM-DEM framework can be successively applied to simulate the fluid-solid interaction on small solar bodies that have extremely low-gravity and rarefied atmosphere environments. Future works based on this tool and focused on aeolian geologic landforms, such as sand dunes, can help us understand the dynamics of cometary activity.

Thermo-mechanical behavior of compressed earth blocks (CEB) stabilized and reinforced with fibers

This study is part of the development of eco-materials (dune sand, clay soil and natural fibers) for masonry and the rehabilitation of heritage in arid and semi-arid environments which are found in abundance in North Africa. The manufacture of compressed earth bricks stabilized (BTCS) has gained some momentum over the last decade. First, we present the results of characterization tests of sand-clay mixtures based on the compressive strength criterion. Secondly, an optimization of the stabilizer of the sand-clay mixtures using different percentages of lime was carried out. The choice of lime as a stabilizer remains an environmental reason. In the last step, the optimal mixture obtained (sand-clay-lime) based on the compressive strength criterion will be reinforced with different percentages of natural fibers of different lengths. The formulation of the mixture (sand-clay-lime-fibers) optimally meets the regulatory requirements (mechanical and thermal) of arid and semi-arid zones known as very hot in summer and cold in winter. Finally, the results obtained open up a field of contribution to the manufacture of a local ecological eco-material at low cost.

Effect of adding dune sand to tuff in Saharan road construction

The south region of Algeria is characterized by a wide surface, a scattered population and a very small ratio of road length per habitant. To allow the development of agricultural, industrial and touristic activities between different cities in the south of Algeria, it is necessary to maintain and to develop the road infrastructure. However the development of these infrastructures necessitates the use of huge amount of certified aggregates from quarries which is not available in the vicinity of the need. For these raisons, in the framework of sustainable development, a strategy which consists in using local materials like fine sediments (dune sand) and other types of material is engaged. The materials constituting the road layers, until today, have been limited to certain so-called noble materials (gravel, aggregates, etc.), but these are being depleted as a result of the intensive exploitation and the scarcity of quality careers. Gypso-limestone encrustation tuffs, the most used materials in pavements (base course and base course) in the Saharan areas such as southern Algeria, have shown acceptable behavior for many years until these last days, when this type of material begins to present certain limits under the effect of the intensity of the traffic. In order to promote the abundant wind sands in these regions, we are interested in developing the dune sands in the pavement as a mixture with the tuffs. The present work presents a contribution to the study of the behavior of the tuff of the Adrar region (South of Algeria) alone and mixed with the sand dunes in different formulations. The aim is to evaluate the evolution of mechanical properties including resistance to simple compression, the ability to compaction and punching (RBC). The work also discusses the influence of the addition of cement in low levels on the performance of the mixture.

Erosion and Deposition Patterns Over a Wind‐Blown Sand Dune Behind a High Vertical‐Type Sand Fence

ABSTRACTSand dunes are the primary factor influencing wind‐sand disasters. To explore the evolution law of wind‐blown sand dunes surrounding high vertical‐type sand fences along desert railways, numerical simulation analyses based on computational fluid dynamics coupled with a discreet element method of the wind‐sand flow field and sand particles trajectories around sand fences were conducted. The focus of this study was the Yandun section of the Lanzhou‐Xinjiang Railway in Xinjiang, China (42.38°N, 93.95°E). By combining ERA5 wind data with field measurements and monitoring, a three‐dimensional coupling model was established. According to the results of L9 (33) orthogonal tests, the sensitivity of the three factors to the evolution of sand dunes can be ordered as wind speed > porosity > height, indicating that wind speed is closely related to sand dune evolution (p < 0.05). The results of single‐factor tests indicate that the structure of wind‐sand flow fields, sand accumulation patterns, and sand particle movement trajectories vary significantly under different wind speeds. The sand accumulation rates on the windward slope of the sand dune are 29.67%, 25.91%, and 20.04%, while on the leeward slope, these rates are 40.33%, 34.09%, and 29.96%, respectively. The obtained information on the evolution law of sand dunes surrounding high vertical‐type sand fences provides a scientific basis for wind‐sand prevention measures along railways in desert regions.

Vegetation Growth and Physiological Adaptation of Pioneer Plants on Mobile Sand Dunes

The Hunshandake Sandy Land is one of the largest sandy areas in China and the closest source of sand dust to the Beijing and Tianjing areas. Sand fixation by vegetation is considered the most efficient strategy for sand control and sustainable development, so clarifying the vegetation coverage and plant adaptation characteristics in the Hunshandake Sandy Land is helpful in guiding restoration and improving local sustainability. Here, we investigated the vegetation growth on the mobile sand dunes in the Hunshandake Sandy Land and specified the photosynthesis and stomatal characteristics of the pioneer plants for sand fixation. The vegetation survey showed that the windward slopes of the mobile sand dunes had far lower plant coverage (6.3%) and plant biodiversity (two species m−2) than the leeward ones (41.0% and eight species m−2, respectively). Elymus sibiricus L. and Agriophyllum squarrosum (L.) Moq. were the only two sand-fixing pioneer plants that grew on both the windward and leeward slopes of the mobile sand dunes and had higher plant heights, greater abundance, and more biomass than other plants. Physiological measurements revealed that Elymus sibiricus L. and Agriophyllum squarrosum (L.) Moq. also had higher photosynthetic rates, transpiration rates, and water use efficiency. In addition, the stomata density (151–197 number mm−2), length (18–29 μm), and area index (13–19%) of these two pioneer species were smaller than those of the common grassland species in Inner Mongolia, suggesting that they were better adapted to the dry habitat of the mobile sand dunes. These findings not only help in understanding the adaptive strategies of pioneer plants on mobile sand dunes, but also provide practical guidance for sand dune restoration and the sustainable development of local areas. Pioneer sand-fixing plant species that are well adapted to sand dunes can be used for sowing or aerial seeding in sand fixation during ecosystem restoration.

Speculation on an early Pleistocene origin of the Parker dunes of southwest Arizona, USA

The Parker Dunes in western Arizona, USA represent the largest dune system in the Sonoran Desert. This study presents a simple 10Be-26Al cosmogenic burial age of 1.90 ± 0.20 Ma, obtained from well cuttings 240–270 m deep in Butler Valley, just east of the dune field. Given the large errors associated with burial dating, we can only speculate that this oldest known aeolian sediment within the Parker Dunes is roughly concurrent with the Bat Cave flood event ca. 2.1 Ma of the nearby Colorado River, as well as regional climatic aridity during the early Pleistocene. Since older dune deposits may be present at other locations in the Parker Dunes, its origin dates back to at least the early Pleistocene. The more important, broader implication rests in highlighting the underutilized potential of well cuttings as a sediment source for cosmogenic burial dating in aeolian research.

Navigating complex riskscapes: the Koudiet Eddraouch GIS substation project in Sub-Saharan Africa

Learning outcomes Risk identification and qualitative assessment are the learning outcomes. Case overview/synopsis The Bharat Bijlee Construction Limited (BBCL) was one of the largest construction companies operating in the power sector in India. After successfully completing a few projects in the Middle East, BBCL decided to expand its presence into African region. The BBCL was awarded a $85m contract for three sub-station projects to modernise Algeria’s power grid system by the “Shariket Karhaba Koudiet Eddraouch Spa”, a state-owned company in charge of power generation, transmission and distribution in Algeria. The project, which is the first of BBCL in Saharan region in Algeria’s, presents many unique situations that company had never encountered before, including sand dunes, severe weather, remote locations, supply chain & logistics, strict contractual deadlines and a high level of construction risk. The project manager for BBCL was sceptic about how well his company would perform under the present project circumstances. How could he better align himself with the client, the various on-site local contractors and the numerous suppliers spread around the world? The case emphasises the identification of various project risks that the project manager might encounter in the project. What do the PESTLE and ASCE frameworks for risk identification each represent, and how are they helpful for the project team in understanding various risks? How should the project’s qualitative risk assessment be conducted? And how can a heat map be a better tool for comprehending the criticality of each risk in the project? Complexity academic level Undergraduate and post graduate courses in project management, civil engineering and architecture domain. Supplementary material Teaching notes are available for educators only. Subject code CSS 2: Built Environment.

A cluster of Pleistocene hominin ichnosites on South Africa’s Cape South Coast

Seven Pleistocene tracksites and two lithic sites, identified with varying degrees of confidence and attributed to Homo sapiens, have been identified in aeolianite deposits along a 1200 m coastal stretch at Brenton-on-Sea on South Africa’s Cape south coast. Some sites contain more than one track- or trace-bearing layer, and each site is from a geological different unit. The aeolianites adjacent to the ichnosites that have been dated span an age range from 113 ± 8 ka to 76 ± 5 ka. Globally, hominin tracks preserved in aeolianites are rare, as are tracks preserved in hyporelief, which are observed at several of the Brenton-on-Sea sites. Clusters of hominin tracksites older than 40 ka are also rare. The sites represent groups of hominins of different sizes traversing dune fields, sometimes jogging or using sticks, and provide details of their tool-making and diet. The ichnological record thus complements the extensive and globally significant archaeological record from the region. The likely presence of nearby accessible caves, and a shoreline that was not too distant, provide an explanation for the profusion of ichnosites and their registration over millennia.