Hydrochemical characteristics and evaluation of the granite aquifer in the Alwadeen area,southwest Saudi Arabia     

Sattam Almadani  Hussain Alfaifi  Abdullah Al-Amri  Mohamed Fnais  Elkhedr Ibrahim  Kamal Abdelrahman  Mohammed Shehata  Faisal Zaidi 《Arabian Journal of Geosciences》2017,10(6):139

This study was carried out in the Alwadeen area of Khamis Mushayt district of southwestern Saudi Arabia to evaluate the hydrochemical characteristics of the shallow hard rock aquifers. These hard rock aquifers mostly comprise granites and contain significant quantities of groundwater that complement the available groundwater from the unconsolidated alluvial sediments in the nearby wadis. The field investigation indicates two main fracture sets which intersect each other and are oriented in the west-northwest and east-west directions. The granitic rocks in the area are intruded by coarse-grained and quartz-rich monzogranite and pegmatite veins. Hydrogeologically, the fracture systems are important since they facilitate the groundwater storage and assume the transmissive function during times of groundwater abstraction. Given the fact that groundwater in the fractured rock aquifers generally occurs at shallow depths, it may be exposed to contamination from surface and/or near-surface sources, and it is therefore important to evaluate its quality. To this end, a hydrochemical analysis was carried out on six groundwater samples collected from the area. The hydrochemistry revealed that the groundwater is fairly fresh, and facies analysis reveals mixed Na-Cl and Ca-Mg-Cl-SO₄ types. Overall, the results reveal that the groundwater is saturated with calcite and dolomite, but unsaturated with gypsum and halite. The degree of salinity increases in the direction of the groundwater flow due to increased rock-water interaction.  相似文献   

Seawater Intrusion in Semi-Closed Convergent Estuaries (Case Study of Moroccan Atlantic Estuaries): Application of Salinity Analytical Models   总被引：1，自引：0，他引：1  

Soufiane Haddout  Mohammed Igouzal  Abdellatif Maslouhi 《Marine Geodesy》2017,40(5):275-296

Salinity is an important parameter influencing the water quality of estuaries, and can constitute a serious problem to society due to the need for freshwater for industry and agriculture. Therefore, the determination of salt intrusion length in estuaries is a challenge for managers as well as scientists in this field. The managers tend to use simple and reliable tools for salinity variation. Although 2-D and 3-D numerical models are common tools for the prediction of salinity intrusion now, analytical models of salinity variation are much more efficient, and also require minimal sets of river data. In this paper, two analytical solutions, Brockway and Savenije used worldwide to assess longitudinal salinity variation in alluvial estuaries, are applied to the Moroccan Atlantic semi-closed estuaries, i.e., Sebou and Loukkos. The solutions are derived from salt convection-dispersion equations, with different assumptions for the dispersion coefficient. The estuaries' bathymetry is described by an exponential function. The performance of these two solutions was evaluated by comparing their results with field-measured salinity data. The Brockway model's salinity predictions performs well to observations especially in downstream reaches of the two estuaries (Sebou: R² = 0.95, root mean square error [RMSE] = 1.50‰, normalized root mean square error [NRMSE] = 3.45‰; Loukkos: R² = 0.95, RMSE = 1.13‰, NRMSE = 3.01‰), while the Savenije model outperformed the Brockway's model and is better to predict salt intrusion length and salinity variation along the two estuaries (Sebou: R² = 0.97, RMSE = 1.15‰, NRMSE = 2.85‰; Loukkos: R² = 0.98, RMSE = 0.95‰, NRMSE = 1.94‰). This revealed that both analytical solutions apply well to the estimation of salinity variation and the prediction of salt intrusion in these two estuaries.  相似文献   

Vertical vibration capacity of a single pile in dry sand     

Mohammed Y. Fattah  Bushra S. Zbar  Faris S. Mustafa 《Marine Georesources & Geotechnology》2017,35(8):1111-1120

In this study, the dynamic response of pile foundation in dry sandy soil excited by two opposite rotary machines was considered experimentally. A small scale physical model was manufactured to accomplish the experimental work in the laboratory. The physical model consists of two small motors supplied with eccentric mass (0.012?kg) and eccentric distance (20?mm) representing the two opposite rotary machines, an aluminum shaft as the pile, and a steel plate a pile cap. The experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (L/d, where L is the pile length and d is its diameter) and operating frequency of the rotary machines. All tests were conducted in medium dense fine sandy soil with 60% relative density. Twelve tests were performed to measure the change in load transferred through the pile’s tip to the underlying soil. To predict precisely the dynamic load that will be induced from the rotary machines, a mini load cell with a capacity of 100?kg was mounted between the aluminum plate (the machine base) and the steel plate (pile cap). The results revealed that, before machine operation, the pile tip load was approximately equal to the static load (machine and pile cap), whereas during machines’ operation, the pile tip load decreased for all embedment depth ratios and operating frequencies. This reduction was due to the action of skin friction that was mobilized along the pile during operation, and as a result the factor of safety against pile bearing failure increases. For all operating frequencies and pile lengths, the factor of safety against bearing failure increased during machines’ operation, where the pile tip load became less than its value before starting operation. During operation, the skin friction resistance mobilized along pile length led to decrease the bearing load.  相似文献   

影响三大洲的北非强沙尘暴动力机制WRF-chem模拟与分析北大核心          下载免费PDF全文

Altayeb Raga  王坚红  Abdoul Aziz Saidou Chaibou  Muhammad Arsha  Mohammed AbdAllah  Birhanu Asmerom Habtemicheal 《气象科学》2022,42(6):769-780

基于WRF-chem模式对北非2018年3月下旬的典型强沙尘暴过程进行模拟,分析了此次强沙尘发生季节、持续时间、局地特征以及传输路径的关键动力系统与动力机制。鉴于起沙是沙尘暴发生的关键点之一,并且起沙主要取决于风力和下垫面沙源性质,本文测试了三种起沙参数化方案的影响,并将模拟结果与卫星MODIS监测及其再分析资料MERRA-2进行了对比,又经系列统计方法检验。结果显示,宏观思路的起沙方案GOCART比AFWA和UoC两种起沙方案更适合此次大尺度强沙尘暴数值模拟(锋面跨度接近60个经度)。综合沙尘暴关键系统的动力机制分析和数值模拟结果显示,强沙尘暴关键系统为深厚的西风槽、沙尘冷锋锋面和锋后的地面高压反气旋。北非中部深厚的西风槽为后倾槽,该系统稳定,造成沙尘暴持续时间长。沙尘暴锋后反气旋中的下沉气流抑制了扬沙向高层扩散,造成低层能见度恶劣。沙尘锋区结合了动力、热动力以及湿热动力不稳定,因此锋区风力大,地面沙尘驱动力强。而西风槽和强大反气旋依托环流形势,提供了沙尘传输到三大洲的长途输送力。  相似文献