Arabian Journal of Geosciences最新文献

Lime treatment has long been used in construction for its cost-effectiveness and simplicity. In clay soils, lime induces chemical reactions that enhance workability and reduce plasticity, followed by gradual strength development. Despite extensive research on clay–lime interactions, the mechanisms behind these transformations remain partly unclear. This study focuses on the fundamental process driving strength gain. Bentonite samples were treated with lime and with other reagents, calcium chloride, barium chloride, and sodium hydroxide, chosen for their potentially similar behavior (electrolyte concentration and pH increase). Changes in plasticity, grain size distribution (GSD), and strength were assessed and compared to gain insight into the lime–clay mechanisms of reaction. A dispersing agent was also used to test the durability of lime-induced effects. Results revealed all additives reduced liquid limit, indicating increased floc size with additive content. However, only lime significantly raised the plastic limit, confirming persistence of the flocs that formed. GSD analyses showed lime caused fine clay particles to cluster, with cluster size growing with curing time. These lime-induced clusters remained intact, unlike those formed by other reagents, which broke down under manipulation or dispersant exposure. Crucially, only lime led to measurable strength development. Findings suggest clay–lime reactions begin with a resilient flocculation, followed by a slow chemical process that produces cementitious bonds within clusters. Other reagents appear to act through reversible electrostatic effects. The study also shows that low lime content fails to trigger the reaction, as the conditions of the pore water chemistry favor dispersion over flocculation. The short-term stability of lime–clay formed flocs observed in this study is attributed to an early clay–lime chemical reaction whose nature is inconclusively explained until today.

This study investigates shear deformation of the casing during shale gas well fracturing through mechanical analysis and deformation calculations. We evaluated casing deformation induced by natural fracture shear slip, critical slip activation conditions, and key factors governing casing shear stress and deformation. The results demonstrate that elevated fluid pressure within natural fractures increases both the shear stress on the casing and the range of fracture approach angles favorable for shear activation. Consequently, this elevates the likelihood of shear-activated fractures and the associated risk of casing shear deformation. And maximum shear stress occurs within fracture approach angles of 30–45° and their supplementary range. For wellbores intersecting well-developed natural fractures, maintaining fluid pressure below the critical shear strength threshold during hydraulic fracturing operations mitigates casing deformation risks by preventing induced shear slip. Shear stress of the casing is positively correlated with horizontal in situ stress difference, natural fracture length, and the Young’s modulus and Poisson’s ratio of the cement sheath and casing. Conversely, it is negatively correlated with the Young's modulus and Poisson's ratio of the formation rock, the friction coefficient, and casing wall thickness. Variations in the Young's modulus and Poisson's ratio of the casing material itself exhibit minimal impact on casing shear stress. Using cement possessing a low Young’s modulus and a low Poisson’s ratio for well cementation effectively mitigates casing shear failure. Higher Young’s modulus and Poisson’s ratio values in the formation rock result in reduced casing deformation displacement. Conversely, greater horizontal in situ stress differences and longer natural fracture lengths increase deformation displacement. Within the fracture approach angle range of 0–180°, casing shear deformation exhibits a bimodal distribution, with maxima occurring within the 30–60° range and its supplementary angular interval. Geo-mechanical instability induced by in situ stresses within naturally fractured shale reservoirs constitutes the primary cause of casing deformation. At direct intersections between well trajectories and natural fractures, maintaining a distance from the fracture central zone is advised to minimize induced shear displacement. These findings provide a theoretical foundation for understanding casing shear failure stress-deformation characteristics, elucidating governing mechanisms, and guiding deformation prevention and control strategies.

The Sunai River, a right-bank tributary of the Budhabalanga River in Odisha, originates near Siriapal village in Mayurbhanj district and confluences with the Budhabalanga near Dolagohira village in Baleshwar district, Odisha. The basin, categorized as a 7th order system, covers an area of 1,432.26 km² and a basin length of 63.63 km. The mean stream length ratio (14.06) reflects an advanced stage of erosion and high runoff conditions, indicating active fluvial processes. A bifurcation ratio of 3.85 suggests a stable tectonic setting, while a drainage density of 2.27 km/km² indicates moderate to long overland flow. The drainage texture (6.47) and stream frequency (2.85) point to low infiltration and high surface runoff, increasing susceptibility to erosion. Moreover, the low drainage intensity value (1.25) shows a higher vulnerability to soil erosion, likely exacerbated by sparse vegetation or unconsolidated surface material. Morphometric shape indices form factor (0.35), elongation ratio (0.67), and circulatory ratio (0.35) reveal the basin’s elongated form, which can influence flow concentration and flood risk. The low RHO coefficient (0.15) suggests limited water storage during heavy discharge periods, contributing to flash flood vulnerability. The region exhibits steep slopes and significant elevation variation on the basis of basin relief (1,151 m) and a high relief ratio (18.09). Despite this, the ruggedness number (2.61) reflects a relatively smooth and moderately dissected terrain. The analysis highlights the basin’s dynamic runoff and stream flow behavior, emphasizing the urgent need for integrated and sustainable watershed management strategies to counteract environmental degradation and hydro-geomorphological challenges.

The Buah Formation, a key carbonate unit within the Huqf Supergroup of Oman, was deposited during the latest Ediacaran to early Cambrian (~ 541–530 Ma) and is well-exposed in the Jabal Akhdar (JA) and Huqf regions. These carbonates offer critical insights into early Cambrian diagenetic processes and serve as valuable records for geochemical and isotopic investigations. Samples from both regions were analyzed for carbon, oxygen, and strontium isotopes, along with elemental ratios using multiple mass spectrometry techniques. JA samples exhibit a broader and more variable range of δ¹³C and δ¹⁸O values compared to the more constrained values in Huqf, reflecting more extensive diagenetic overprinting. Positive δ¹³C–δ¹⁸O correlations in both regions indicate diagenetic alteration by meteoric and/or burial fluids. In the JA section, δ¹³C values as low as − 8‰ at lower stratigraphic levels likely result from the oxidation of Neoproterozoic organic carbon, releasing ¹²C-enriched DIC, a signature consistent with the Ediacaran Shuram excursion in the underlying Shuram Formation. Mn/Sr ratios distinguish diagenetic systems, with burial diagenesis and/or organic carbon oxidation dominating in JA, and meteoric diagenesis prevailing in Huqf. Strontium concentrations in Huqf samples range from 20 to 2600 ppm, with most exhibiting uniform ⁸⁷Sr/⁸⁶Sr ratios (~ 0.7088), outside typical marine dolomite values. A subset aligns with marine signatures, suggesting mixed Sr sources including terrigenous, hydrothermal, and weathering-derived inputs. Two δ¹³C-based sample populations (< 0.5‰ and ≥ 0.5‰) in Huqf highlight diagenetic variability with implications for reservoir quality, fluid migration, and source preservation in early Cambrian petroleum systems in Oman.

Engineering practices have shown that the accurate assessment of stratum hydraulic conductivity (SHC) is crucial for ensuring engineering safety. A method proposed by Elsworth and Lee (2005) based on on-the-fly piezocone sounding provides an effective approach to SHC evaluation, but previous studies overlooked SHC anisotropy. The literature review reveals that the anisotropy ratio (horizontal-to-vertical SHC) typically ranges between 1.1 and 2.7 for most sedimentary formations, reflecting moderate but consistent directional dependence in SHC. This study addresses this limitation by incorporating SHC anisotropy into the original assumptions and further explicitly considers the effect of OCR. To validate the efficacy of this modified method, two case histories are examined. The results indicate that the predicted SHCs obtained using the modified method are in closer agreement with measured values compared to previous methods. The influence of SHC anisotropy and OCR on predicted SHCs cannot be disregarded, and the modified assumptions demonstrate a stronger correlation with engineering outcomes.

Cut blasting is a critical technique in roadway excavation, where the layout of cut holes directly affects the quality of excavation blasting. Based on the engineering context of phosphate mining in Hubei Province, this study first analyzed the effects of blasting gases and stress waves according to rock blasting mechanics, derived the calculation formula for the fracture zone radius, and determined the optimal distance between cut holes and empty holes. Subsequently, based on the calculated optimal distance, two empty hole layouts were designed: a six-empty-hole pattern and an eight-empty-hole pattern. Using ANSYS/LS-DYNA software, the effectiveness of cut blasting under these different layouts was analyzed from the perspectives of surrounding rock damage, dynamic evolution of the stress field, and extent of the cut cavity, followed by validation through field experiments. The results indicate that the optimal hole spacing between cut holes and empty holes is 170 mm, and that at the same distance, empty holes arranged at 45° generate greater circumferential (hoop) stress compared to those arranged horizontally. Furthermore, when sufficient compensation space cannot be provided, it is advisable to appropriately reduce the hole spacing, thereby reducing the rock volume between cut holes and empty holes to allow adequate expansion space for the rock.

Documentation of historic structures is widely recognized as an initial and crucial step in safeguarding tangible cultural heritage. Capturing and preserving detailed information (geometry and any architectural ornamental features) of these structures can ensure long-term conservation and provide valuable resources for research, education, and future conservation efforts. Selecting appropriate methods and techniques for documentation to create a comprehensive 3D representation of the historic structure is always a subject of research, and it is a challenging issue, specifically if the site is in an area with security concerns. This research aims to evaluate the Digital Surface Model of the Minaret of Amedy, a heritage site that is nationally registered. The data collection process was planned and executed, involving an e-survey GNSS receiver for measuring ground control points and a total station (TS, Leica TS06) for measuring control points on the four sides of the Minaret. Two hundred three images were taken by UAV, DJI Phantom 4 pro manually flown, and 196 images using Nikon D5300. The data was processed using the Agisoft Metashape photogrammetry software to create the final 3D Surface model and orthophotos. The RMS errors gained from UAV orthophotos are presented relative to the TS. Sub-centimeter accuracy for horizontal and vertical positions was obtained at low flight altitudes. The 3D digital models’ accuracy of the Minaret was assessed using conventional survey measurements, resulting in a maximum standard deviation in the coordinates of ±2.4 cm. The relative accuracy in distance measurement ranged from 0.00% to 0.20% and 0.00% to 0.30% in the horizontal and vertical directions, respectively. In addition, the maximum inclination of the Minaret in the East and West direction is about 18 cm and 13 cm, respectively, which were observed. These results reveal that the finding is valuable for future intervention and further research.

Based on preliminary seismic and drilling studies suggesting substantial thickness of the Dengying Formation in the Taiyang-Changning area along the southern margin of the Sichuan Basin's Northern Yunnan and Guizhou Depression as a platform margin, the risk exploration well TT1 was implemented to investigate sedimentary reservoir characteristics and exploration potential of the Dengying platform margin. Integrated analysis of astrochronological cycles, core tests, and log interpretations from the TT1 well enabled comprehensive 3D seismic interpretation of the Dengying Formation in the Taiyang area. Results demonstrate that Milankovitch cycles are extractable from calcium-element logging data of the TT1 well's Dengying Formation, with sedimentation controlled by a 35-kyr obliquity cycle at rates ranging from 6.24 to 13.17 cm/ka (mean: 9.81 cm/ka). Comparative analysis with the Yang-1 well at the same platform margin reveals well-developed reservoirs in the Yang-1 well's Dengying Formation, whereas the TT1 well exhibits overall poor reservoir development—only thin reservoirs occurring at the tops of the Deng-4 and Deng-2 Members—showing no correlation between reservoir presence and sedimentation rates, indicating dominant control by dissolution during the late Tongwan Movement. Integrated regional geological and seismic interpretation indicates that although the Changning-Taiyang platform margin features considerable stratigraphic thickness, the strong reservoir heterogeneity necessitates re-evaluation of reservoir formation and hydrocarbon accumulation mechanisms in the Dengying Formation..

Considering the interaction between the lining and soil, the analytic solutions to the stress function for the soil and lining deformation caused by the excavation are put forward for the shallow and deep tunnels. The applicability of the algorithm for the shallow and deep tunnels is verified by field monitoring data. Furthermore, through the parameter analysis, a comparison study on the variation of the soil and lining response caused by the excavation for the shallow and deep tunnels is conducted. It is observed that for the soil settlement trough with the value of zero, it is a “groove type” for the shallow tunnel, while “horizontal line” for the deep tunnel. The soil horizontal displacement is “butterfly type” for both shallow and deep tunnels. The lining tangential displacement for the shallow tunnel is an “oblique 8-type” with a smaller bottom, while that for the deep tunnel is a normal “oblique 8-type”.