Arabian Journal of Geosciences最新文献

A crucial issue in dam design is seepage from the dam. If water flow from dams is not adequately controlled, it can lead to problems that result in dam failure. The present study focuses on numerical modeling seepage and investigates the effects of water sealing systems on the foundation and body of an earth dam under various sustained flows. Various conditions ranging from optimal to critical have been considered in this research. The sealing elements under investigation include clay blankets, drains, and curtain grouting in the foundation. In general, the combined effects of the sealing elements, without considering their geometrical dimensions, have been studied. According to the results, a diversity in the types of flow reduction systems significantly impacts reducing flow within the dam body and foundation. Seepage discharge increases with height from the foundation floor, reaching its maximum between 38 and 46 m, and further downstream exhibits a descending trend. The combination of drains, clay blankets, and curtain grouting can, on average, reduce velocity by 83.2%, decrease seepage discharge by 15.5%, and alleviate 9.5% of the hydraulic load downstream of the dam. This combination improves hydraulics and promotes the stability of the dam.

The summer rains (July to September) in 2007 caused massive flooding in Sudan. It is important to understand the factors that lead to heavy rainfall to improve future forecast accuracy of similar events. This will help to minimize the associated loss of lives and destruction of property. We investigate the anomalous atmospheric circulation associated with the heavy rainfall event in Sudan during the 2007 summer. The study used precipitation data from the Climatic Research Unit (CRU) TS version 4.06 for precipitation data, and atmospheric variables from the National Center for Environmental Prediction (NCEP)—Department of Energy (DOE) reanalysis II. The study area was divided into three zones, and the time series for each zone was calculated by averaging the data from all grids within that zone. The results show that the August 2007 rainfall significantly exceeded the long-term average in all zones, with zones 1 and 2 experiencing the most substantial increase of approximately 100 mm/month, while zone 3 saw an increase of about 40 mm/month. The 2007 summer rain is significantly influenced by the West African monsoon (WAM) and the tropical easterly jet (TEJ). The WAM strengthened south-to-southwesterly winds, bringing excess moisture from the Equatorial Atlantic Ocean (EAO) into Sudan. The absence of Harmattan winds allowed the moist air to penetrate further north. The convergence of moisture fluxes from the East Atlantic Ocean, the Congo Forest, and the Red Sea significantly facilitated favorable conditions for strong convection, contributing to the high rainfall in Sudan. Additionally, this study looks at how the TEJ contributes to the moist air associated with the 2007 summer rainfall. Results show that strong La Niña conditions of 2007 intensified and shifted the TEJ westward, enhancing the northward penetration of moist air and increasing rainfall over Sudan. The findings further indicate that La Niña conditions influenced the WAM flow, shifting the Intertropical Convergence Zone (ITCZ) by approximately 2° northward. This knowledge of how La Niña influences the characteristics of the WAM and TEJ can help local weather forecasters improve the accuracy of their predictions for heavy rainfall events in Sudan on a seasonal timescale.

The determination of the friction factors in an underground excavation are crucial to reach an adequate model of the ventilation system and, consequently, to select the ventilation system and improve the comfort and safety of the mine. The diversity of calculation methods and experimental data sources makes it necessary to carry out a state of the art on this matter. An assessment of the friction factors is provided for different types of underground mining, soft and hard rock mining. Some data using TBM (tunnel boring machine) is also gathered and analyzed. Considering the excavation system, support applied, and mining method. A particular focus on the different techniques to obtain the friction factor values has also been described, including the new approaches available.

In this work, the reinforcing mechanics of ceramic products of three porous clays from Tunisia were investigated by adding non-plastic minerals such as the industrial ceramic waste. Three different mixtures (X1, X2, and X3) were prepared and assessed for their possible ceramic applications. X-ray diffraction, thermal analyses, dilatometry, scanning electron microscopy, and physical–mechanical tests such as stress to strength, Young modulus, shear modulus, and water absorption were used to evaluate the phase evolution and microstructure of the mixtures fired between 900 and 1150 °C for X1 and X2 and between 900 and 1100 °C for X3. The required performance of the ceramic product has been improved due to the formation of the vitreous and anorthite phases. The European Norm EN 14411 was used to classify ceramic products for each firing temperature and to determine their field of application. In accordance with this Norm, X1 and X2 sintering at 1150 °C for 12 min with water absorption ≤ 0.5% can be used for the porcelainized and fully vitrified stoneware production. X3 sintering at 1100 °C for 12 min with water absorption of ˃14% is suggested for the earthenware and unglazed stoneware production.

Drought is a climatic phenomenon that has increased in severity over time. This study analyzed drought spread in the Alto Patía basin (13,047 km²) in South America, applying the Standardized Precipitation Index (SPI), Vegetation Health Index (VHI), and Streamflow Drought Index (SDI) to assess meteorological, agricultural, and hydrological drought, respectively. Synchronous and asynchronous correlations were estimated, and Wavelet analysis was conducted to verify relationships among drought types. Results show that the lag between drought types varies based on the intensity, temporal continuity, and spatial extent of meteorological drought. A lag of zero months (1–2 months) was observed between meteorological and hydrological drought when moderate (severe) meteorological drought partially (fully) covers the basin. Agricultural drought, however, does not always correspond to meteorological drought during isolated rainfall events. As the first study in Colombia to systematically connect these drought types, this research addresses a gap in understanding how drought impacts progress across systems in regions with complex rainfall patterns. These findings offer critical insights into the interdependencies among drought types, supporting enhanced drought monitoring and early warning systems in similar climatic regions. By identifying specific lags between meteorological and hydrological droughts, this study provides practical guidance for land management, water conservation, and crop planning, offering a foundation for future research on drought resilience strategies.

Assessment of urban carbon balance is imperative to address anthropogenic climate change. Biotic sequestration by urban vegetation and soil boosts terrestrial carbon storage and helps in maintaining the balance. However, unplanned urbanization in developing nations has caused an alarming loss of stored carbon. This study aims to quantify the spatio-temporal change in carbon storage for past, present, and future scenarios in Kolkata and its surroundings using the InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model. Four plausible future scenarios were simulated using a two-axis scenario analysis, based on two major drivers of urban sustainability: economic growth and restoration of UGS (urban green space). Each simulated scenario corresponds to the presumptive narrative of a 10% change in the LULC (land-use land-cover). The findings indicate a substantial loss of stored carbon (2.03 Tg) with a valuation of $ 410 million from 1992 to 2022. Notable reduction of carbon storage can be detected in the eastern and southern periphery, in a 10–15 km radius from the center of the city. This loss is mostly attributed to the emergence of key urban growth centers, characterized by large-scale infrastructural development. Compared to 2022, total carbon storage decreased by 10–15% in scenarios directed by economic development (least focus on UGS restoration), whereas it increased by 21% when UGS were restored. The methodology combines scenario analysis with carbon storage modelling, providing researchers and urban planners with valuable insights for proactive policy planning that support healthy urban livelihoods and ecosystems. It also helps in assessing the importance of urban vegetation and soil as natural carbon sinks.

Clastic injection dikes were identified within the prehistoric liquefaction fields of Kashmir Karewas, India. Clastic injection dikes are the geological evidence of the past earthquakes formed by seismic liquefaction of susceptible Karewa sediments. The study of clastic injection dikes proves vital paleoseismic tools for understanding prehistoric seismicity. Moderate to strong earthquakes often trigger soil liquefaction that can cause more destruction than the earthquake itself. This study will be helpful in answering: where was the possible seismic source? What were the magnitude, intensity, and PGA of the prehistoric earthquakes? What were the energy values of past earthquakes that were expended to generate observed clastic injection dikes? Empirical relationships were used to estimate paleoseismicity and site-specific seismic liquefaction hazard. The seismic parameters of past earthquakes were obtained using width, height, and regional pattern of observed clastic injection dikes. Paleomagnitudes obtained in this study were computed as a function of paleoepicentral distance,({W}_{cd}) and ({h}_{cd}) values of the clastic injection dikes. ({M}_{S}) values were ranging from 5.0 to 7.7, and their equivalent ({M}_{W}) values were ranging from 5.4 to 7.7. The ({I}_{L}) values computed as a function of ({W}_{cd}) and ({h}_{cd}) values of clastic injection dikes were ranging from 6.06 to 13.97. PGA values computed as a function of ({I}_{L}) values were ranging from 0.07 to 3.75 g. Tremendous amount of ({E}_{o}) values in joules were expended to generate the observed clastic injection dikes corresponding to ({M}_{s}) and their equivalent ({M}_{w}) values. The incorporation of obtained ({E}_{o}) values in mass-energy equivalence relationship suggests that there is a small amount of Earth’s mass loss during an earthquake. The findings of this study suggest that Kashmir Valley is seismically active region and is giving credible answers to paleoseismic problems. The results of this study provide data set to engineers, urban planners, and policy makers to design earthquake-resistant infrastructure to withstand against great earthquakes in the future.

Cyclic triaxial tests are one of the common methods to study the liquefaction behaviour of granular material. Here, the liquefaction behaviour of densely packed granular material is studied using numerical experiments with the discrete element method, for 2D particle assemblies. Cyclic biaxial loading is imposed via two boundary conditions, viz. using prescribed velocity for rigid platens and a penalty method that imposes corrective forces on the boundary particles that deviate from an affine velocity field. Simulations are performed for different void fractions of the assembly and for both boundary conditions. The initial void ratio and the boundary conditions are found to influence the liquefaction resistance of the assembly. The number of cycles for liquefaction increases with a greater constraint on the boundary. Further, the initiation to liquefaction occurs due to a gradual weakening of the force chain structure over the entire assembly. Also, particle rolling may play an important role in the rearrangement of particles and needs further exploration.

Hydrocarbon prospection and scholarly research have centered around three basins: the Barotse, Luangwa, and Mid-Zambezi Rift. Research work has so far been reliant on exposed sedimentary outcrops. However, basin correlation is challenging as relatively little work has been conducted to constrain the depositional ages of the Karoo Basin that outcrops in Zambia, despite their rich paleontological records. One such basin, the mid-Zambezi Basin, contains Karoo-aged sediments that have been studied since the 1970s, and it has been observed that the Madumabisa Mudstone fluvial sequence within the lacustrine origin overlies the coal-bearing sequence, the Permian Gwembe Coal. Studies have been done to fully characterize the petroleum system elements and processes in this part of the basin. A few thermal alteration index (TAI) values range from − 2 to + 2, total organic content (TOC) from 0.71 to 50.65 wt.%, hydrogen index from 90.68 to 168.85 mg HC/g TOC, and oxygen index from 1.35 to 22.6 mg CO2/g. Rock has been presented. There was little attention to non-coal-bearing sequences during the 1960s subsurface investigations and a small sampled area for palynological studies. Therefore, studies suggested that pollens and spores were not sufficiently abundant for quantitative analyses. Samples from previous work were thus far only subjected to standard palynological processing techniques. The occurrence of macrofossils and microfossils gives interest to further micropaleontological and geochemical studies; for significant microfossil distribution and frequency, TOC contributes to the conclusion of hydrocarbon potential.

Remote sensing technique, which is not limited by accessibility, financial status, unusually large areal extent and climate when used at the initial stage, together with other geological data sets, will make an exploration process faster, easier and most importantly very efficient and cost-effective. There is limited information on this belt due to the size of the belt, complexity of the belt and the fact that it falls within the Kumasi Basin where mineralisation is not highly expected. Although the major structures on this belt are similar to that on the Ashanti belt, mineralisation on this belt has not been high as that on the Ashanti belt. This study seeks to use GIS to integrate geological methods with remote sensing methods to delineate mineralised zones on the Asankragwa gold belt (AGB) to produce information on anomalies which will entice exploration companies to explore further on this belt and to provide guidelines for grassroot explorers in areas where there is limited geochemical and geophysical information. Band combinations (bands 5, 4, 3 and 5, 6, 7), as well as band ratios (5/6, 5/7, 7/2 and 2/4), were implemented to the visible, near-infrared and shortwave infrared bands of Landsat 8, which were used to determine alterations in the study area. Lineaments were mapped from the Digital Elevation Model (DEM) of the area. About 80% of these lineaments were observed to be trending NE-SW. The structures contributed to about 70% of the anomalies observed in the area. The results of this investigation demonstrate the capability of the applied imagery enhancement methods in distinguishing different features, identifying hydrothermally altered rocks and structures as well as delineation of probable anomalies. It was observed that the effectiveness in the identification of mineralised zones was enhanced by integrating remote sensing data sets. Structures and alteration information obtained from remote sensing provided enough information for the delineation of gold potential areas on the entire belt.