Arabian Journal of Geosciences

The detection of stress redistribution in a mining area is essential for forecasting and preventing coal burst disasters in underground mining practices. Active seismic velocity tomography (SVT) is an effective way of investigating large-scale regional stress distribution. Active SVT technology was applied to a complex isolated coal pillar twice to assess coal burst hazard level and to guide the design of de-stress measures as well as to verify their de-stress effect. Test results show that high stress concentration existed in scattered zones along the boundary of the coal pillar rather than in the whole coal pillar. Qualitative comparison of the two SVT tests conducted before and after implementing de-stress measures indicates (1) if high-density wave sources and receivers are appropriately arranged, the spatio-temporal detection precision of active SVT technology could be sufficiently high to identify the de-stress effect of a single deep-hole roof blasting or a group of coal seam blasting upon their completion; (2) The implementation of de-stress measures in the isolated coal pillar area helped drive the stress concentration away from the de-stressed area to the adjacent area instead of fully eliminating the stress concentration. This stress-driving effect indicates that a possibly advisable strategy of coal burst control in the isolated coal pillar area could be driving stress concentration to the area further away from the area of high production activities rather than attempting to eliminate stress concentration.

The eastern coast of the Algiers, which stretches over 15 km, is currently experiencing very intense socioeconomic and urban development that is causing severe disturbances to the coastal environment. The main issue of this study concerns itself with understanding the evolutionary trends of this system and assessing its state of vulnerability towards erosion phenomena. This work focuses on the historical study of the variation in the shoreline position by combining photogrammetry data and in situ DGPS measurements (Differential Global Positioning System). Data treatment was carried out using a geographic information system (GIS) and the Digital Shoreline Analysis System (DSAS) geostatistical computing tool. These techniques have enabled identification of the erosion/accretion rates and description of the evolutionary trends over a period of 58 years by calculating the net rates of coastline changes over three time periods (1959–1980, 1980–2003 and 2003–2017). The results show that the net rate fluctuates between sites, with an overall tendency towards erosion (49% of the coastline), associated with a significant variation in the average annual rates. The computed statistics show that the study area was in a state of accretion between 1959 and 1980, with an average end point rate (EPR) equal to 0.72 m/year. This net rate of change turned negative and became alarming during the period between 1980 and 2017 when the EPR decreased to − 0.54 m/year. These trends are due to a combination of the cumulative effects of storms and anthropogenic actions. Hence, sustainable management policies must be developed rapidly by coastal managers to rehabilitate the area.

Identification with accuracy of prospective and dry zone from well log data is of prime importance in reservoir or hydrocarbon studies. This issue has greater stake, where in return many conventional methods have been established. The purpose of this study is to recognize the hydrocarbon and non-hydrocarbon bearing portion within a reservoir by using a non-conventional technique. Application of rescaled range (R/S) analysis and wavelet-based fractal analysis (WBFA) on the wire-line log data to obtain the pre-defined hydrocarbon (HC) and non-hydrocarbon (NHC) zones by their fractal nature is demonstrated in this paper. Among these two techniques, the WBFA tool has provided more prolific results. Applicability of the proposed approach is tested with the help of the most commonly used well log data like self-potential, gamma ray, and porosity log responses. These are used in the industry to distinguish several HC and NHC zones of all wells in the study region belonging to the Upper Assam Basin, India. The results are found to be of lower fractal dimension in this study for a particular log response having HC-bearing zones, which are mainly situated in a variety of sandstone lithology. On the other hand, NHC-bearing zones correspond to lithology with higher shale content categorized with higher fractal dimension. Hence, the WBFA technique can overcome the chance of misinterpretation, which is quite possible in the case of conventional reservoir characterization.

In order to study the improvement of the mechanical properties of basalt fiber geogrids on semi-rigid base asphalt pavement and the prevention and control effect of reflection cracks, this paper laid the basalt fiber geogrid and test sensor in the different positions of the semi-rigid base of Yanchong Expressway experimental Sect. (625 m long) are divided into three working conditions: I, II, and III according to different reinforcement levels. Through the test, the temperature and strain at the corresponding positions of the top and bottom of the semi-rigid base course change with time, and the crack performance of the basalt fiber geogrid-reinforced semi-rigid base course is analyzed under the action of temperature and the linear regression equations between the temperature and the strain of the base course. Atmospheric temperature between substrate strain and substrate temperature is obtained. The field test results show that adding basalt fiber geogrid to the semi-rigid base can prevent reflection cracks and improve the anti-crack performance of the semi-rigid asphalt pavement, the best anti-crack effect in the middle position of the semi-rigid base.

Fault-slip bursts in underground mines could cause devastating damage to mine openings. In the present study, three types of underlying mechanisms that could trigger fault-slip are examined, namely asperity shear, stope extraction, and a combination thereof, with numerical analysis. First, a numerical model is constructed, in which a fault running parallel to a steeply dipping, tabular orebody is modeled. Static analysis is then performed, whereby stopes in the orebody are extracted. Based on the stress state obtained from the analysis, dynamic analyses are carried out to simulate fault-slip, using different simulation techniques representing the mechanisms of fault-slip. The results show that when fault-slip is induced by asperity shear, slips could spread over an extensive area of the fault. In contrast, the fault-slip area is limited to the vicinity of an extracted stope when fault-slip is caused by stope extraction. The results further indicate that asperity shear could induce strike-slip faulting. It is revealed that when fault-slip is caused by the combination, the magnitude of fault-slip significantly increases. Investigation of the slip rate shows that fault-slip induced by stope extraction induces slightly higher slip rates than that caused by asperity shear. It is also found that fault-slip induced by stope extraction ruptures faster along the fault than that induced by asperity shear. Lastly, the effect of the mining rate on the magnitude of fault-slip is examined. The result indicates that stope extraction with a low mining rate can considerably decrease the cumulative seismic moment of fault-slip that takes place during the mining sequence.

Các carbonate được nghiên cứu có mặt trong phần trên cùng của Jabal Farasan, cách thành phố Jeddah 150 km về phía Đông Bắc, thuộc vùng Tây Trung Ả Rập. Những carbonate này nằm trên các lớp đá lửa cơ bản tối màu hơi biến chất dày và các trầm tích liên quan thuộc nhóm Samran. Các cuộc điều tra địa tầng và khoáng vật học hiện tại đã tiết lộ sự hiện diện của chín đơn vị xen kẽ chính (đơn vị I đến IX). Các đơn vị carbonate (cẩm thạch) hiện tại được xen kẽ với các trầm tích volcaniclastic cơ bản đến trung bình màu xanh lá, hơi biến chất. Năm đơn vị carbonate (đơn vị I, III, V, VII, IX) được xen kẽ với bốn đơn vị volcaniclastic màu xanh. Có sự biến đổi lithologic rất đặc trưng theo chiều dọc và chiều ngang trong các trầm tích carbonate, nơi mà các facies carbonate nằm ngay trên các sự xen kẽ volcaniclastic màu xanh thì mỏng và có màu xám và xanh. Dưới kính hiển vi, các facies carbonate này được cấu tạo từ tuff cứng đã thoái hóa, chứa nhiều khoáng vật mafic, như chlorite và wollastonite với các lớp và mảng calcite ít gặp hơn. Khi đi vào phần trên của các chân trời chứa cẩm thạch, các carbonate bao gồm các vùng dày màu trắng và trắng đỏ chủ yếu bao gồm calcite tinh thể mịn và thô mà không có khoáng vật silicate màu xanh. Kết luận rằng nhiều vấn đề khai thác ở các trữ lượng cẩm thạch Farasan có liên quan đến thành phần lithologic rất phức tạp của các trầm tích cẩm thạch. Điều này có liên quan đến sự biến đổi ngang và dọc trong môi trường lắng đọng cổ và vị trí của các địa điểm lắng đọng (gần hoặc xa) trong khung tổng thể của tình huống đảo cung. Đầu vào volcaniclastic kiểm soát phần lớn độ tinh khiết của các carbonate đã được lắng đọng và cũng như loại trầm tích cẩm thạch.

Natural gas hydrates represent a valid opportunity in terms of energy supplying, carbon dioxide permanent storage and climate change contrast. Research is more and more involved in performing CO2 replacement competitive strategies. In this context, the inhibitor effect of sodium chloride on hydrate formation and stability needs to be investigated in depth. The present work analyses how NaCl intervenes on CO2 hydrate formation, comparing results with the same typology of tests carried out with methane, in order to highlight the influence that salt produced on hydrate equilibrium conditions and possibilities which arise from here for improving the replacement process efficiency. Sodium chloride influence was then tested on five CO2/CH4 replacement tests, carried out via depressurization. In relation with the same typology of tests, realised in pure demineralised water and available elsewhere in literature, three main differences were found. Before the replacement phase, CH4 hydrate formation was particularly contained; moles of methane involved were in the range 0.059–0.103 mol. On the contrary, carbon dioxide moles entrapped into water cages were 0.085–0.206 mol or a significantly higher quantity. That may be justified by the greater presence of space and free water due to the lower CH4 hydrate formation, which led to a more massive new hydrate structure formation. Moreover, only a small part of methane moles remained entrapped into hydrates after the replacement phase (in the range of 0.023–0.042 mol), proving that, in presence of sodium chloride, CO2/CH4 exchange interested the greater part of hydrates. Thus, the possibility to conclude that sodium chloride presence during the CO2 replacement process provided positive and encouraging results in terms of methane recovery, carbon dioxide permanent storage and, consequently, replacement process efficiency.

In the arid irrigated lands, understanding the impact of shallow groundwater fluctuation on soil salinization has become crucial. Thus, investigation of the possible options for maintaining the groundwater depth for improving land productivity is of great importance. In this study, under saline irrigation condition, the effects of shallow groundwater depth on water and salt dynamics in the root-zone of date palms were analyzed through a particular field and modeling (SWAP) investigation in a Tunisian Saharan oasis (Dergine Oasis). The model was calibrated and validated against the measured soil water content through the date palm root-zone. The good agreement between measured and estimated soil water content demonstrated that the SWAP model is an effective tool to accurately simulate the water and salt dynamics in the root-zone of date palm. Multiple groundwater depth scenarios were performed, using the calibrated SWAP model, to achieve the optimal groundwater depth. The simulation results revealed that the shallow groundwater with a depth of ~80 cm coupled with frequent irrigation (20 days interval) during the summer season is the best practice to maintain the adequate soil water content (>0.035 (cm3 cm−3) and safe salinity level (<4 dS m−1) in the root-zone layer. The results of field investigation and numerical simulation in the present study can lead to a better management of lands with shallow water table in the Saharan irrigated areas.

The Wadi Faliq El Sahl–Faliq El Waar area comprises four various types of rocks including metavolcanics, older granites, Hammamat sediments, and younger granites of monzogranite and syenogranite composition. From the various structural analyses in the investigated area, the main trends controlling the structural and tectonic framework are ENE-WSW and NE-SW, while the trends NNE-SSW, WNW-ESE, and N-S are less abundant. Three major phases of deformation are detected in the study area, each of which gives its specific trends according to the applied stress axis during the time of deformation. The first phase shows compressive stress whose σ1 maximum compressional axis was E-W trend (N81°W). The second phase is a compression phase in which the σ1 maximum compression axis was directed N13°W. The third phase represents a trans-tensional (extensional) stress system, in which the maximum tension force (σ1) is in the N-S trend. The study area passed through four stages of evolution, which are (1) the arc-metavolcanic formation with island arc assemblage and the intrusion of older granitoids during the inter-collision of the island arcs; (2) the tectonic processes forming the inter-mountainous basins; (3) the folding of the Hammamat basin under Najd-related shear zones; and (4) the intrusion of syenogranite and uplifting of the Hammamat sediments during the Late Precambrian rifting. The potash-rich outer zone of pegmatite bosses in the younger granites recorded high values of gamma radioactivity with U content.