Search Results (79)

The eruption of the Cumbre Vieja volcano on 19 September 2021 resulted in the deposition of over 20 million cubic meters of tephra, posing significant environmental and logistical challenges in the affected areas. This study aimed to explore the valorization of volcanic ash (VA) by evaluating its potential use in producing sustainable mortar by incorporating it as a replacement for cement or sand. Various experimental mixtures were prepared with different proportions of VA which substituted either cement or sand, and these mixes were characterized through a mechanical and microstructural campaign. Additionally, shrinkage was evaluated for the mixtures which showed good mechanical results. The results suggest that partially replacing cement with up to 15% ground VA as well as substituting sand with up to 25% VA are promising strategies for the production of sustainable mortar mixes. This research contributes to the understanding of the influence of VA in cementitious matrices and offers a novel approach for integrating locally available geomaterials into infrastructure design in volcanic active regions. Full article

Posidonia oceanica is an endemic seagrass of the Mediterranean Sea, forming extensive meadows and providing valuable ecosystem services underwater as well as on the shore. P. oceanica constantly generates new leaves while shedding the older ones. The latter may be deposited on the shoreline, forming “banquettes” that exhibit variable thickness, ranging from a few centimeters to several meters. These deposits act as natural barriers against coastal erosion, preventing sand loss and dissipating wave energy. Moreover, the degradation of the washed-up leaves releases large amounts of nutrients, relevant for the coastal food web. However, the presence of banquettes in touristic areas is often perceived as a nuisance, thus leading to their removal by local administrations. This study proposes a multidisciplinary approach for the assessment of P. oceanica banquettes along the coastline of the Campania region (Southern Italy), estimating their biomass and the associated concentrations of nutrients and other chemical elements, with the final aim to assess the potential loss of natural capital and ecosystem services due to their removal. Regional estimates show that approximately 40 tons of C are stored annually in the beached biomass, representing a potential carbon loss associated with their removal. The results highlight the crucial role that P. oceanica banquettes play in the blue carbon cycle and provide valuable insights to support their sustainable management. Full article

In order to study the influence of multi-cycle stress sensitivity on the injection–production effect, it is necessary to conduct multi-cycle stress sensitivity experiments on reservoir permeability and fracture conductivity first and then calculate the impact on the injection–production effect after the occurrence of the stress sensitivity effect by using the CMG software. After stress sensitivity occurs and the production rate decreases, the constraints of the well should be adjusted. The results showed that the conductivity of the 30–50 mesh ceramsite decreased by 15.94% after 100 cycles, while the conductivity of the 20–40 mesh quartz sand decreased by 51.17%. Under alternating stress, the reservoir permeability decreased significantly during the first 50 cycles, with an average decrease of 20.8%, but remained relatively stable in the later stages. When stress sensitivity was disregarded, the gas production rate of the ceramic and quartz sand stabilized at approximately 3700 m³/h and 2600 m³/h, respectively. When stress sensitivity was considered, the secondary gas cushion for ceramsite had to reach at least 500,000 m³ to maintain a gas production rate of over 3700 m³/h within 40 cycles after the gas cushion. When stress sensitivity was considered, the secondary gas cushion for quartz sand had to exceed 800,000 cubic meters to maintain the gas production rate of over 2600 m³/h within the first 30 cycles after the gas cushion. To sustain the gas production rate over the long term, it was necessary to increase the injection pressure per cycle. The gas injection pressure for ceramsite should be adjusted to more than 17 MPa, and the gas injection pressure for quartz sand should be adjusted to more than 19.3 MPa. Full article

This work investigates the impact of sea level rise (SLR) of up to 3 m on flood protection and freshwater availability in the Netherlands. We applied an exploratory modeling approach to consider the large degree of uncertainty associated with SLR. The results show the current degree of flood protection can be technically and financially maintained for up to three meters of SLR. A primary finding of this work is that a similar degree of safety against floods can be maintained. There are, however, several challenges: First, maintaining this degree of safety against floods requires considerable spatial allocations to maintain and upgrade flood defenses, often in populated areas with limited space. Second, the supply of sand for coastal nourishments will be challenging due to other functions in the North Sea (wind energy, shipping) and explosive remnants of war. Third, an acceleration in the rate of SLR may impact the overall feasibility of maintaining flood defenses. Maintaining the freshwater strategy will be challenging due to SLR-induced salt intrusion, which aggravates climate impacts including droughts. Continued flushing of salinized areas of regional water systems and polders with fresh river water will increasingly compete with other demands. Our analysis highlights the vulnerabilities of the flood protection and freshwater strategies and gives input to follow-up analyses on societal impact and perspectives of actions for adaptation. Full article

Coastal erosion affects all coastal areas with different intensities, and its effects may be severe. This is the case of the Black Sea sandy beaches on the Romanian coast, where the beaches have been used for tourism since the mid-19th century. In 2012, a project was launched to reduce erosion and protect the Romanian Black Sea coast from its destructive effects. By the 2021 tourist season, the completed works in Mamaia resort resulted in beaches exceeding, in some cases, 300 m in width. However, while these efforts successfully curtailed erosion, they also brought unintended consequences. The imported coarse sand and increased seawater depth canceled the resort’s traditional advantages, raising concerns among both tourists and local stakeholders. The purpose of our article was twofold—to present the case of the Mamaia resort and the expansion works conducted and to present the results of an exploratory study highlighting the tourists’ perceptions regarding the beach extensions, as well as their motivations, preferences, and expectations for the development of a modern beach. Our results suggest that while the beach extension works were necessary and long-awaited, they inadvertently caused dissatisfaction among tourists, leading to shifts in tourist flows and financial losses for local tourism operators. Data visualization techniques were employed to explore the complex relationships between tourist satisfaction with the extension works (in both 2021 and 2022) and factors influencing their comfort and overall experience. Additionally, the extraction of millions of cubic meters of sediment for the extensions disrupted marine habitats, raising ecological concerns. Future coastal protection efforts should balance erosion mitigation, ecological sustainability, and tourism needs by adopting environmentally sensitive methods, preserving marine ecosystems, and engaging stakeholders to align projects with tourists’ expectations, thus ensuring the long-term viability of popular tourist destinations like Mamaia. Full article

Narrow Fluvial Sand Bodies are primarily developed along the river center, with horizontal wells for injection and production in some Bohai waterflooded oilfields. This results in a rapid increase in water cut due to a single injection–production direction. Over time, dominant water breakthrough channels form between wells, and the remaining oil moves to deeper regions, which makes conventional profile control measures less effective. We developed a quantitative method based on integrated dynamic and static big data to identify these breakthrough channels and measure the flow intensity between injection and production wells. To address deep remaining oil mobilization, we performed micro-analysis and physical simulations with heterogeneous core models, which led to the development of a deep profile control system using emulsion polymer gel and self-assembling particle flooding. Experiments show that the combined technology can reduce oil saturation in low-permeability layers to 45.3% and improve recovery by 30.2% compared to water flooding. Field trials proved to be completely effective, with a cumulative oil increase of over 23,200 cubic meters and a 12% reduction in water cut per well. This deep profile control technology offers significant water cut reduction and enhanced oil recovery. It can provide technical support for efficient water control and profile management in similar reservoirs. Full article

Ground source heat pump systems rely on soil conductivity for optimal performance, and soil conductivity is primarily influenced by soil moisture content. In this study, we investigate how biochar, a porous material derived from biomass gasification and pyrolysis, influences capillary water rise and moisture retention in soil. Mixtures of biochar with soil and sand in varying ratios, along with control mixtures, were prepared and tested on lab-scale equipment. The results showed that biochar-amended samples exhibited a significantly higher capillary water rise. At a height of 0.25 m above the water level, the minimum moisture content in the biochar-treated samples was 43.5%, much higher than the 6.5% recorded in the control group, which consisted of soil or soil and sand only. Even in the long term, mixtures with biochar maintained high moisture content, ranging from 36% to 57%, compared to the control’s 8%, at heights near 0.5 m over the free surface of the water. Moreover, the utilization of biochar as a soil improver in geothermal application is an innovative way for carbon sequestration which, in the analyzed conditions, leads to the storage of up to 0.7 tons of CO_2eq per square meter of geothermal field. Full article

C50 manufactured sand concrete requires good workability and strength, and economic efficiency and carbon emissions also need to be considered. This study incorporates sensitivity and significance analyses to recommend the optimal economic mix composition for C50 manufactured sand concrete. The relationship between cost, workability, and mechanical properties was analyzed by considering the water/binder ratio, sand ratio, fly ash content, and superplasticizer dosage. An optimal composition of C50 manufactured sand concrete was recommended. The cost and carbon emissions were quantified at the optimal composition. The results showed that the water/binder ratio had the most significant impact on the cost and carbon emission, while the sand ratio and superplasticizer dosage had the least. All factors significantly affected its cost and carbon emission. Compared to natural sand concrete, manufactured sand concrete achieved a lower cost but higher carbon emissions. Considering the workability, strength, and cost per cubic meter of concrete, the most economical mix proportion for C50 concrete was recommended with a water/binder ratio of 0.36, a fly ash content of 25%, a sand ratio of 0.42, and a superplasticizer dosage of 1.2%. This composition cost 356 yuan, and carbon emission was 352.6 kg CO₂ per cubic meter of concrete. Compared to a composition with a water/binder ratio of 0.34 and fly ash content of 15%, the unit cost can be reduced by 18.4 yuan, and carbon emission can be minimized by 56.6 kg CO₂ e/m³. The appropriate water/binder ratio and fly ash content can reduce cost and carbon emissions without compromising the workability, compressive strength, or elastic modulus of C50 concrete. This achieves triple benefits in terms of performance, economy, and the environment when applying C50 manufactured sand concrete. Full article

River ecosystems are integral to sustainable environmental development, playing a crucial role in understanding suspended solid matter (SSM) transport dynamics and soil conservation. Accurate monitoring of SSM concentrations in watersheds is foundational for these studies. This research introduces and evaluates a novel HHSW·NUG-1 photoelectric sand meter, specifically designed for SSM measurement. Its reliability was validated at three hydrological stations, including Xiaolangdi. The instrument, based on light scattering principles, is optimized for environments with high SSM loads and rapid flow rates. Laboratory tests indicate a measuring range of 0 to 730 kg/m³, and field trials show effective operation within 0 to 375 kg/m³, meeting the monitoring needs of hydrological stations. Through comparative analysis of measurement data, we established conversion relationships for various SSM concentration ranges, confirming that the instrument’s system error is less than 1%. The photoelectric sand meter adheres to standards outlined in the “Guidelines for SSM Test in Rivers”, demonstrating stability in reliability, calibration methods, observation accuracy, real-time monitoring, data storage, and continuous operation. For optimal use, adherence to relevant hydrological instrument standards is recommended, particularly in stations requiring SSM analysis. Standard sampling and calibration of conversion coefficients should be conducted, and proper sensor installation is crucial to avoid interference from flow conditions. In conclusion, the HHSW·NUG-1 optoelectronic sand meter exhibits stable and reliable performance in practical applications, with broad potential for rapid deployment in other river hydrological stations. Full article

The aim of the presented research was to evaluate the impacts of modifications to the technical properties of fly ash-based geopolymer composites, particularly focusing on enhancing the thermal insulation. Through the utilization of a generalized utility function, optimal dosages of additives such as perlite sand, waste perlite powder, and cenospheres were determined. The study aimed to increase the thermal insulation of the composites while maintaining satisfactory compressive and flexural strength. The results indicated that dosages of perlite dust and cenospheres significantly influenced the technical characteristics of the composites; an exception was the flexural strength, for which these modifications did not show a statistically significant effect. The average compressive strength values, except for the mixes with poor workability, were at least 3.5 MPa (RILEM class II). Notably, a balanced dosage of additives, around 75 kg per cubic meter of the mixture in the total mixture, yielded the most favorable outcomes in terms of thermal isolation (0.18–0.24 W/(m·K) and workability (cone immersion 40–70 mm). Additionally, perlite dust emerged as a potentially superior modifier due to its waste origin. However, further analysis considering life cycle parameters including the carbon footprint and water footprint would be necessary to validate this claim. Overall, the study highlights the potential of utilizing perlite-based modifiers to enhance the thermal insulation of geopolymers while addressing environmental concerns. Full article

We studied the Jafnayn Formation’s lithostratigraphy, microfacies, depositional environment, and uncertain presence of the Paleocene/Eocene boundary and present the first detailed analysis of a 127-m-thick section using the standard microfacies (SMF)/facies zone (FZ) system. The formation is dominated by foraminiferal grainstones and packstones of SMF 18-FOR, followed by peloidal grainstones and packstones of SMF 16. Coral-red algae floatstones of SMF 8 occur sporadically. SMF 18-DASY appears only once. SMF 16 and 18-FOR suggest a restricted lagoon, whereas SMF 8 and 18-DASY reflect episodic open marine lagoonal conditions. The section consists of four lithostratigraphic units. Considerable detrital quartz near the base (Unit 1: 22%; sand, sandstone, conglomerate) and top (Unit 4: 40%; sand) coincides with a restricted lagoon affected by near-shore processes (base) and near-shore conditions (top). Open marine conditions show an elevated bioclast diversity in units 3 and 4. Unit 2 displays very thickly-bedded limestones of the restricted lagoon. The lagoon barriers likely consist of foraminifera and other allochems that were reworked from the lagoon to form shoals. Coral remains in units 3 and 4 suggest that coral build-ups in the upper part of the formation protected the lagoon as well. The early Eocene age of several basal Alveolina species in the lowermost 9 m of the studied section indicates that the section is incomplete, with the late Paleocene part and meters-thick basal yellow marl missing. The Paleocene/Eocene boundary is unexposed. Full article

The effects of the interaction between sandy, mobile, low-relief (sorted) bedforms and two sewage outfalls were investigated along the south shore of Long Island, NY. Sand bedforms at scales from ripples to ridges are common on continental shelves. In dynamic environments, these features can migrate 10s to 100s of meters per year, especially during storms. Beyond engineering considerations, little is known of the interaction between these mobile features and anthropogenic structures. Modification of bedform topography and sediment grain-size distribution can be expected to alter the species composition, abundance, and diversity of the benthic community. At the study site, the interaction increased the scour of modern fine- to medium-grained sediments extending out to a kilometer and uncovered coarser-grained late Pleistocene sediments. This alteration of the seafloor in turn resulted in changes in composition, higher abundance, and lower diversity in the species assemblage found in the impacted area. The most advantaged species was Pseudunciola obliquua, a sightless, tube-building, surface deposit-feeding amphipod that is known to prefer a dynamic coarse sand habitat. Overall, the ecological effects of artificial structures on a wave-dominated seabed with sorted bedforms have not been adequately assessed. In particular, and of great importance, is the pending large-scale development of wind farms off the East Coast of the U.S. Full article

Argillaceous fine silt hydrate reservoirs have a clay content of 20–25% and a median sand particle size of 10–15 um. Sand control is extremely difficult, restricting the continuous and stable testing of gas hydrate. This paper focuses on the sand production mechanisms, plugging characteristics, and clogging mechanisms of these hydrate reservoirs. Based on the actual characteristics of hydrate reservoirs, it presents an understanding of the sand production mechanism of argillaceous fine silt. The characteristics and properties of three different sand control methods and six kinds of sand control screens are analyzed. Clear design concepts for sand control screens in argillaceous fine silt hydrate reservoirs are proposed. Two types of new sand control screen with metal filter screens and pre-filled screens have been innovatively designed, and the sand control ability and overflow performance of the screens are evaluated using the meter production index conversion method. Sand production simulation and comprehensive experimental evaluation and analysis of the flow performance of seven kinds of screens (themselves from two categories of screens) were carried out using a self-made special experimental testing device. The experimental results show that the newly designed screens have good flow performance and can meet the requirements of a certain gas production rate. Specifically, Class A metal screens (60/70 mesh) and Class B pre-filled screens (40/70 mesh) have excellent sand control capacity and flow performance, with 10 g sand output and 300 L total water output, thus fulfilling the sand control requirements and achieving the purpose of “effective sand control, prevention without plugging, and continuous stable production” of argillaceous fine silt gas hydrate reservoirs. They therefore provide a reference for future research on sand control and new screen designs for argillaceous fine silt hydrate reservoirs. Full article

Studies were carried out in order to verify the research hypothesis that “the introduction of organic matter in the form of high peat, brown coal, and wheat straw to the mineral soil contaminated with nickel will reduce the content of this metal in the lettuce”, the main purpose of which was to determine the impact of various organic materials with varying degrees of decomposition on the content of nickel in lettuce leaves. The factors of the experiment were different types of organic material that were added to the mineral soil (loamy sand), such as high peat, brown coal, and wheat straw. The substrates in which lettuce was grown were contaminated with increasing doses of nickel: 0, 50, 75, and 100 mg Ni·dm⁻³ of the substrate. This research shows that the type of organic material introduced into the mineral soil as a source of soil organic meter has a significant impact on the content of nickel in lettuce leaves. Full article

To study the bearing characteristics of rock-socketed single piles on the southeast coast of Fujian Province, we conducted similar material ratio tests and single pile model tests. Initially, based on the mechanical parameters of strongly weathered granite, 10 groups of similar material samples were prepared using iron concentrate powder, barite powder, and quartz sand as aggregates, with rosin and alcohol as the cementing agents and gypsum as the modulating agent. Through triaxial testing and range and variance analysis, it was determined that the binder concentration has the most significant impact on the material properties. Consequently, Specimen 1 was selected as the simulation material. In the model test, the strongly weathered granite stratum was simulated using the ratio of Specimen 1. A horizontal load was applied using a pulley weight system, and the displacement at the top of the pile was measured with a laser displacement meter, resulting in a horizontal load–displacement curve. The results indicated that the pile foundation remained in an elastic state until a displacement of 2.5 mm. Measurements of the horizontal displacement and bending moment of the pile revealed that the model pile behaves as a flexible pile; the bending moment initially increases along the pile length and then decreases, approaching zero at the pile’s bottom. The vertical load test analyzed the relationship between vertical load and settlement of the single pile, as well as its variation patterns. This study provides an experimental basis for the design of single pile foundations in weathered granite formations on the southeast coast of Fujian Province and aids in optimizing offshore wind power engineering practices. Full article