Search Results (33)

Integrated Electrical Resistivity Imaging (ERI) and Induced Polarization (IP) studies were performed to identify potential tin (Sn) mineralization prospects in the Eastern Tin Belt of Peninsular Malaysia. A total of 23 profiles were obtained utilizing a Schlumberger configuration, generating resistivity and chargeability sections employed to delineate weathering structures, lithological connections, and structurally regulated anomalies. ERI models consistently delineate a three-tier subsurface structure consisting of conductive soil/alluvial deposits (5–300 Ωm), weathered bedrock (300–1500 Ωm), and resistive fresh bedrock (>1500 Ωm), featuring undulating basement relief beneath floodplain layers. IP data indicate localized, often pronounced chargeability anomalies (~5–40 ms; locally reaching ~50 ms), interpreted as corridors influenced by fractures and veins, especially when they align with significant resistivity contrasts at metamorphic–granitic boundaries and intrusive contacts. The integration of fence diagrams in the alluvial-over-granite zone reveals laterally consistent chargeability peaks at the alluvial–bedrock interface, suggesting enduring subsurface conduits. XRF examination of quartz-vein samples verifies Sn enrichment (599–717 ppm), corroborating a granite-related vein/alteration hypothesis and indicating possible isolated greisenized zones within the weathered granite. The integrated ERI–IP analysis identifies priority targets for subsequent trenching and borehole drilling to verify an anomaly’s origins and evaluate Sn grade and continuity. Full article

Soil erosion in the hilly and gully region of the middle reaches of the Yellow River is severe, threatening regional ecological security and the water–sediment balance of the Yellow River. The area features fragmented topography and significant spatial heterogeneity in soil thickness, forming a unique binary “soil–rock” structural system. The soil in the study area is characterized by silt-based loess, and the underlying bedrock is an interbedded Jurassic-Cretaceous sandstone and sandy shale. It has strong weathering, well-developed fissures, and good permeability, rather than dense impermeable rock layers. However, the spatiotemporal differentiation mechanism of soil moisture in this system remains unclear. This study focuses on the typical hilly and gully region—the Geqiugou watershed. Through field investigations, soil thickness sampling, multi-scale soil moisture monitoring, and analysis of meteorological data, it systematically examines the cascade relationships among microtopography, soil–rock combinations, soil moisture, and meteorological drivers. The results show that: (1) Based on the field survey of 323 sampling points in the study area, it was found that soil samples with a thickness of less than 50 cm accounted for 85%, which constituted the main structure of soil thickness in the region. Macrotopographic units control the spatial differentiation of soil thickness, forming a complete thickness gradient from erosional units (e.g., Gully and Furrow) to depositional units (e.g., Gently sloped terrace). Based on this, five typical soil–rock combination types with soil thicknesses of 10 cm, 30 cm, 50 cm, 70 cm, and 90 cm were identified. (2) Soil–rock combination structures regulate the vertical distribution and seasonal dynamics of soil moisture. In thin-layer combinations, soil moisture is primarily retained within the shallow soil profile with higher dynamics, whereas in thick-layer combinations, under conditions of substantial rainfall, moisture can percolate deeply and become notably stored within the fractured bedrock, sometimes exceeding the moisture content in the overlying soil. (3) The response of soil moisture to precipitation is hierarchical: light rain events only affect the surface layer, whereas heavy rainfall can infiltrate to depths below 70 cm. Under intense rainfall, the soil–rock interface acts as a rapid infiltration pathway. (4) The influence of meteorological drivers on soil moisture exhibits vertical differentiation and is significantly modulated by soil–rock combination types. This study reveals the critical role of microtopography-controlled soil–rock combination structures in the spatiotemporal differentiation of soil moisture, providing a scientific basis for the precise implementation of soil and water conservation measures and ecological restoration in the region. Full article

Mesa de Los Santos is an elevated plateau of the Eastern Cordillera of Colombia bordered by escarpments, where groundwater resources are limited to the local recharge. The geological unit with the greatest hydrogeological potential is Los Santos Formation (Lower Cretaceous), which presents three members (Lower, Medium and Upper). Based on stratigraphic information and hydrogeological information, three aquifer systems were characterized in the Upper Member: The Shallow Aquifer System (SAS), the Upper Aquifer 1 (UA1), and Upper Aquifer 2 (UA2). The SAS comprises discontinuous aquifers with groundwater flowing very close to the surface, circulating through weathered and fractured levels. UA1 and UA2 contain groundwater flowing through fractures. Groundwater in UA1 circulates through the top of the Upper Member, is underlain by a predominantly muddy base and exhibits an E-W and NE-SW flow consistent with the dip of the layers and the main directions of fractures. UA2 groundwater flows through the base of the Upper Member and is limited by the impermeable Middle Member. Stable water isotopes (δ¹⁸O, δ²H) data show three behaviors: (i) large temporal variability indicating a rapid flow through fractures in the three aquifers, and through primary porosity mainly due to weathering in the SAS; (ii) slower flows, with low temporal variability, showing well-mixed water of meteoric origin in the SAS, UA1, and UA2; (iii) groundwater with signs of evaporation indicating the connection between wetlands and the SAS in some cases. Full article

EMFIT, also referred to as EMFi, is a ferroelectret film related to polyvinylidene fluoride (PVDF) sensors. It is an electroactive polymer (EAP) based on a polyolefin structure and consists of three layers of polyester film. Its application in geophysical monitoring has not been reported in the literature. At present, EMFIT is mainly employed in ballistocardiography and medical sleep monitoring, as developed by the manufacturer Emfit Ltd. (Vaajakoski, Finland). Within the multidisciplinary monitoring network of the National Institute for Earth Physics (NIEP), EMFIT is used as a pressure sensor in combination with infrasound transducers and microphones deployed in seismic areas. The primary aim of this study is to evaluate its suitability for detecting seismic noise that precedes earthquakes, generated by rock fracturing associated with crustal deformation. Although similar studies have been reported, they have not involved the use of EMFIT sensors. The novelty of this approach lies in the large surface area and mechanical flexibility of the material. Beyond seismic forecasting, the research also examines whether this type of sensor can contribute to seismic monitoring as a complement to conventional instruments such as accelerometers, seismometers, and microbarometers. Data analysis relies primarily on spectral time-series methods and incorporates measurements from other acoustic sensors (microphones and microbarometers) as well as a weather station. The working hypothesis is the potential correlation between the recorded data and the presence of enhanced noise prior to the detection of seismic waves by standard seismic sensors. The target area for this investigation is Vrancea, specifically the Vrâncioaia seismic station, where multidisciplinary monitoring includes infrasound, radon, thoron, soil temperature, and atmospheric electrical discharges. Preliminary tests suggest that the EMFIT sensor may function as a highly sensitive device, effectively serving as an “ear” for detecting ground noise. Full article

This study investigates slope stability in an open-pit mining area by integrating engineering geological surveys, field investigations, and laboratory rock mechanics tests. A coordinated multimethod analysis was carried out using finite element-based numerical simulations from both two-dimensional and three-dimensional perspectives. The integrated approach revealed deformation patterns across the slopes and established a multiscale analytical framework. The results indicate that the slope failure modes primarily include circular and compound types, with existing step slopes showing a potential risk of wedge failure. While the designed slope meets safety requirements under three working conditions overall, the strongly weathered layer in profile XL3 requires a slope angle reduction from 38° to 37° to comply with standards. Three-dimensional simulations identify the main deformations in the middle-lower sections of the western area and zones B and C, with faults located at the core of the deformation zone. Rainfall and blasting vibrations significantly increase surface tensile stress, accelerating deformation. Although wedges in profiles XL1 and XL4 remain generally stable, coupled blasting–rainfall effects may still induce potential collapse in fractured areas, necessitating preventive measures such as concrete support and bolt support, along with real-time monitoring to dynamically optimize reinforcement strategies for precise risk control. Full article

Lithology identification is a critical technology for geological resource exploration and engineering safety assessment. However, traditional methods suffer from insufficient feature representation and low classification accuracy due to challenges such as weathering, vegetation cover, and spectral overlap in complex sedimentary rock regions. This study proposes a hierarchical multi-feature random forest algorithm based on Feature-Preserved Compressive Sampling (FPCS). Using 3D laser point cloud data from the Manas River outcrop in the southern margin of the Junggar Basin as the test area, we integrate graph signal processing and multi-scale feature fusion to construct a high-precision lithology identification model. The FPCS method establishes a geologically adaptive graph model constrained by geodesic distance and gradient-sensitive weighting, employing a three-tier graph filter bank (low-pass, band-pass, and high-pass) to extract macroscopic morphology, interface gradients, and microscopic fracture features of rock layers. A dynamic gated fusion mechanism optimizes multi-level feature weights, significantly improving identification accuracy in lithological transition zones. Experimental results on five million test samples demonstrate an overall accuracy (OA) of 95.6% and a mean accuracy (mAcc) of 94.3%, representing improvements of 36.1% and 20.5%, respectively, over the PointNet model. These findings confirm the robust engineering applicability of the FPCS-based hierarchical multi-feature approach for point cloud lithology identification. Full article

In high-altitude corrosive environments, weathering steel is widely applied due to its excellent corrosion resistance. However, the welded joint regions, where the chemical composition and microstructure undergo changes, are susceptible to the corrosion-induced degradation of mechanical properties. This study investigates the corrosion–mechanical synergistic degradation behavior of a 16 mm thick Q500 qENH base metal and its V-type and Y-type welded joint specimens. Periodic immersion corrosion tests were conducted to simulate plateau atmospheric conditions, followed by mechanical performance evaluations. Corrosion metrics—including corrosion rate, cross-sectional loss, penetration depth, and corrosion progression speed—were analyzed in relation to mechanical indicators such as the fracture location, yield load, ultimate load, yield strength, and tensile strength at varying exposure durations. The results indicate that the corrosion process exhibits distinct layering, with a two-stage characteristic of rapid initial corrosion followed by slower progression. Welded joints consistently exhibit higher corrosion rates than the base metal, with the rate difference evolving nonlinearly in an “increase–decrease–stabilization” trend. After corrosion, the mechanical performance degradation of welded joint specimens is more severe than that of base metal specimens. Full article

After the 2011 earthquake, lake water depletion has become a widespread issue in Sikkim, especially in regions classified as high to very high seismic zones, where many lakes have turned into seasonal water bodies. This study investigates Chochen Lake in the Barapathing area of Sikkim’s Pakyong district, which is facing severe water seepage and instability. The problem, intensified by the 2011 seismic event and ongoing local construction, is examined through subsurface fracture mapping using Vertical Electrical Sounding (VES) and profiling techniques. A statistical factor method, applied to interpret VES data, helped identify fracture patterns beneath the lake. Results from two sites (VES-1 and VES-2) reveal significant variations in weathered and semi-weathered soil layers, indicating fractures at depths of 17–50 m (VES-1) and 20–55 m (VES-2). Higher fracture density near VES-1 suggests increased settlement risk and ground displacement compared to VES-2. Contrasting resistivity values emphasize the greater instability in this zone and the need for cautious construction practices. The findings highlight the role of seismic-induced fractures in ongoing water depletion and underscore the importance of continuous dewatering to stabilize the swampy terrain. Full article

The migration of radioactive waste in geological environments often exhibits anomalies, such as tailing and early arrival. Fractional derivative models (FADE) can provide a good description of these phenomena. However, developing models for solute transport in unsaturated media using fractional derivatives remains an unexplored area. This study developed a variably saturated fractional derivative model combined with different release scenarios, to capture the abnormal increase observed in monitoring wells at a field site. The model can comprehensively simulate the migration of nuclides in the unsaturated zone (impermeable layer)—saturated zone system. This study fully analyzed the penetration of pollutants through the unsaturated zone (retardation stage), and finally the rapid lateral and rapid diffusion of pollutants along the preferential flow channels in the saturated zone. Comparative simulations indicate that the spatial nonlocalities effect of fractured weathered rock affects solute transport much more than the temporal memory effect. Therefore, a spatial fractional derivative model was selected to simulate the super-diffusive behavior in the preferential flow pathways. The overall fitness of the proposed model is good (R² ≈ 1), but the modeling accuracy will be lower with the increased distance from the waste source. The spatial differences between simulated and observed concentrations reflect the model’s limitations in long-distance simulations. Although the model reproduced the overall temporal variation of solute migration, it does not explain all the variability and uncertainty of the specific sites. Based on the sensitivity analysis, the fractional derivative parameters of the unsaturated zone show higher sensitivity than those of the saturated zone. Finally, the advantages and limitations of the fractional derivative model in radionuclide contamination prediction and remediation are discussed. In conclusion, the proposed FADE model coupled with unsaturated and saturated flow conditions, has significant application prospects in simulating nuclide migration in complex geological and hydrological environments. Full article

Recent exploration efforts in the Qiongdongnan Basin have revealed hydrocarbon resources within granitic basement rocks in buried hill traps. However, the formation mechanisms and primary controlling factors of these reservoirs remain poorly understood. In this study, we utilized data from six wells in the Qiongdongnan Basin, including sidewall cores, thin sections, imaging logging, and seismic reflection profiles, to analyze the petrological characteristics, pore systems, and fracture networks of the deep basement reservoir. The aim of our study was to elucidate the reservoir formation mechanisms and identify the key controlling factors. The results indicate that the basement lithology is predominantly granitoid, intruded during the late Permian to Triassic. These rocks are characterized by high felsic mineral content (exceeding 90% on average), with them possessing favorable brittleness and solubility properties. Fractures identified from sidewall cores and interpreted from image logging can be categorized into two main groups: (1) NE-SW trending conjugate shear fractures with sharp dip angles and (2) NW-SE trending conjugate shear fractures with sharp angles. An integrated analysis of regional tectonic stress fields suggests that the NE-trending fractures and associated faults were formed by compressional stresses related to the Indosinian closure of the ancient Tethys Ocean. In contrast, the NW-trending fractures and related faults resulted from southeast-directed compressional stresses during the Yanshanian subduction event. During the subsequent Cenozoic extensional phase, these fractures were reactivated, creating effective storage spaces for hydrocarbons. The presence of calcite and siliceous veins within the reservoir indicates the influence of meteoric water and magmatic–hydrothermal fluid activities. Meteoric water weathering exerted a depth-dependent dissolution effect on feldspathoid minerals, leading to the formation of fracture-related pores near the top of the buried hill trap during the Mesozoic exposure period. Consequently, the combination of high-density fractures and dissolution pores forms a vertically layered reservoir within the buried hill trap. The distribution of potential hydrocarbon targets in the granitic basement is closely linked to the surrounding tectonic framework. Full article

Unsustainable groundwater extraction for domestic and agricultural purposes, particularly crop irrigation, is leading to dramatic reductions in the quantity and quality of groundwater in many developing countries, including Ethiopia. Assessing and predicting groundwater responses to hydraulic stress caused by overexploitation related to anthropogenic activities and climate change are crucial for informing water management decisions. The aim of this study is to develop a three-dimensional steady-state groundwater flow model for the Golina River Sub-Basin to understand the relationship between groundwater recharge and groundwater pumping and their impacts under steady-state conditions from the perspective of groundwater management. The model was created using MODFLOW 6 and discretized into 345 rows and 444 columns with a grid resolution of 100 m by 100 m. The subsurface was modeled as two layers: a clastic alluvial layer overlying a weathered and fractured bedrock. The surface-water divide of the Golina River Sub-Basin was treated as a no-flow boundary. The initial values of horizontal hydraulic conductivity ranged from 0.001 m/day for rhyolite to 27.26 m/day for alluvial deposits. The aquifer recharge rates from the WetSpass model ranged from 1.08 × 10⁻³ to 2.25 × 10⁻⁴ m/day, and the discharge rates from the springs, hand-dug wells, and boreholes were 2.79 × 10⁴ m³/day, known flux boundaries. Sensitivity analysis revealed that the model is very sensitive to hydraulic conductivity, moderately sensitive to aquifer recharge, and less sensitive to groundwater pumping. Calibration was performed to match observed and simulated hydraulic heads of selected wells and achieved a correlation coefficient of 0.998. The calibrated hydraulic conductivity ranged from 1.2 × 10⁻⁴ m/day for rhyolite to 20 m/day for gravel-dominated alluvial deposits. The groundwater flow direction is toward the southeast, and the water balance indicates a negligible difference between the total recharge (207,775.8297 m³/day, which is the water entering the aquifer system) and the total pumped volume (207,775.9373 m³/day, which is the water leaving the aquifer system). The scenario analysis showed that an increase in the pumping rate of 25%, 50%, and 75% would result in a decrease in the hydraulic head by 4.64 m, 10.18 m, and 17.38 m, respectively. A decrease in recharge of 25%, 50%, and 75% would instead result in hydraulic-head declines of 6 m, 15.29 m, and 46.97 m, respectively. Consequently, the findings of this study suggest that decision-makers should prioritize enhancing integrated groundwater management strategies to improve recharge rates within the aquifer system of the study area. Full article

This study aims to estimate the shear wave velocity and identify the depth of the bedrock and the engineering site characterization utilizing the multichannel analysis of surface waves (MASW) method for sustainable urban development in the Al-Madinah Al-Munawarah area. Twenty-seven MASW profiles were carried out using Geode digital seismographs with a 24-geophone array of 4.5 Hz in the urban expansion area of Al-Madinah Al-Munawarah. The methodology entailed rigorous calibration during data collection, processing, and inversion to ensure precise shear velocity measurements. Results reflect subsurface conditions accurately where shear wave velocity (Vs) varies between 180 m/s and 1200 m/s across three main layers: alluvium deposits, which transfer laterally in some areas into vesicular basalt with Vs ranges from 180 to 360 m/s; fractured basalt where Vs varies between 360 and 760 m/s; and weathered basaltic rock with Vs that spans from 760 to 1200 m/s. Moreover, the average shear wave velocity of up to 30 m depth (Vs30) and ranging from 180–480 m/s indicate Site Class D (stiff soil) and Class C (soft rock and dense soil) according to National Earthquake Hazards Reduction Program (NEHRP). Furthermore, the depth of bedrock varies between 18 and 29 mm indicating the great thickness of soil deposits throughout the study area. These results provide civil engineers and urban planners with vital data about soil deposits characterization and geotechnical conditions in the area where alluvium deposits and vesicular basalt represent weak zones that require more attention during urban construction. Results will contribute as well, to a great extent, in achieving the sustainable development plans of Saudi Vision 2030. Full article

The land section of the Huangdao end of the Jiaozhou Bay Second Submarine Tunnel is extensively underlain by the Quaternary Loose Accumulation Layer. The tunnel passes through a weathered granite fracture zone with well-developed rock joints beneath the buildings. The tunnel excavation process significantly disturbs the buildings above, making them prone to settlement, cracking, and tilting. This research conducts numerical simulations of three tunnel excavation methods, and based on the results, compares the deformation behaviors of the ground surface and buildings under various conditions. The findings show that the double side-wall guide pit method has better adaptability in controlling surface settlement and building deformation than the vertical or curved CD method. Moreover, the removal of temporary supports significantly affects building settlement and tilt; this risk can be effectively reduced by controlling the stress relief ratio during the removal phase of the temporary supports in the tunnel. The significance of the study lies in the fact that by choosing an appropriate tunnel excavation support scheme, the disturbance impact on the overlying buildings can be minimized, and the construction safety and stability of the surrounding buildings can be guaranteed. The results of this study can provide initial guidance for constructing shallow-buried tunnels beneath existing buildings. Full article

The development of fracture zones (broken zones) and underground karst rivers in underlying granite can significantly reduce the recovery rate of ion-adsorption-type rare earth ores. Additionally, leaching solutions flowing along unfavorable geological formations can lead to environmental pollution. Therefore, investigating the development of fracture zones (leakage channels) in granite basements is of great significance. In Changting, Fujian, China, several methods have been used in exploration areas (C1 and C2) to study the characteristics of rare ores. This study has focused on the stratigraphic and structural characteristics of the C2 exploration area. Twelve exploration profiles were designed to collect data using electrical resistivity tomography, and a deep electrical structure model of the study area was obtained through inverse calculations. The results indicated that the exploration profiles effectively delineated the thickness of the weathered granite layer and the spatial distribution characteristics of the deep-seated fault structures, which were consistent with the drilling results within the study area. These findings provide important reference materials for the assessment of ion-adsorption-type rare earth ore reserves, blocking leakage channels, and the layout of recovery tunnels. Full article

Traditional seismic wave-based tunnel advanced geological forecasting techniques are primarily designed for drill and blast method construction tunnels. However, given the fast excavation speed and limited prediction space in tunnel boring machine (TBM) construction tunnels, traditional methods have significant technical limitations. This study analyzes the characteristics of different types of TBM construction tunnels and, considering the practical construction conditions, identifies an effective observation system and data acquisition method. To address the challenges in advanced forecasting for TBM construction tunnels, a method of ellipsoid positioning velocity analysis, which takes into account the constraints of three-component data directions, is proposed. Based on the characteristics of the advanced forecasting observation system, this method compares the maximum values on the spatial isochronous ellipsoidal surface to determine the average velocity of the geological layer rays, thereby enabling accurate inversion of the spatial distribution ahead. Utilizing numerical simulation, a model for the advanced detection of typical unfavorable geological formations is established by obtaining the wave field response characteristics of seismic waves in three-dimensional space, and the velocity structure of the model is retrieved through this velocity analysis method. In the engineering example, the fracture property, water content, and weathering degree of the surrounding rock are predicted accurately. Full article