Hasil untuk "Geology"

A. .. Ringwood, S. Kesson, N. Ware et al.

N. L. Falcon, W. B. Harland

R. Passega

GENG Jiabo, ZHANG Hong, ZHENG Siying et al.

Water inrush disaster is one of the most threatening disasters in the process of deep coal mining, coal under the action of mining stress to produce damage fractures to form seepage paths, groundwater through these seepage paths into the working face to cause water inrush disasters, different mining methods caused by different damage degrees and fracture distribution, resulting in different distribution of seepage paths, directly affecting the risk of water inrush. Therefore, the damage characteristics and seepage path distribution of deep coal under three mining modes: protective layer mining (PCM), top coal mining (TCM) and pillarless mining (NM) were systematically studied through the triaxial seepage test with axial and confining pressure cycles, and the three-dimensional fracture scanning with a high-precision scanner. The results show that the high stress loading amplitude (NM>TCM>PCM) significantly aggravates the deformation of coal samples and drives the hysteresis loop to change from sparse to divergent, and the strain mutation of TCM and NM in the late cycle indicates the risk of instability. The damage accumulation rate of TCM and NM was significantly higher than that of PCM, and the damage degree of the rupture surface became more serious. The permeability increased in stages with the increase of stress level, and the high stress loading amplitude promoted the fracture propagation and penetration, which significantly optimized the connectivity of the seepage channel. The seepage paths of PCM, TCM and NM showed bifurcation tree, network and surface shape, respectively, and the seepage effect increased sequentially. This study provides a reference for the damage control and prevention of water inrush in deep coal.

Mu’ayyad Al Hseinat, Malek AlZidaneen, Ghassan Sweidan

The Karak Wadi Al Fayha Fault (KWF) is a major NW-trending intraplate wrench fault system extending over 325 km from Western Karak in Jordan to Wadi Al Fayha in Saudi Arabia. Structurally linked to the Precambrian Najd Fault System, the KWF has been previously mapped using field observations, gravity, magnetic, and reflection seismic methods. However, these approaches lacked the vertical resolution necessary to characterize its shallow structure, leaving its influence on recent deposits and surface topography poorly understood. This study employs reflection seismic sections integrated with a Digital Elevation Model to refine terrain analysis and enhance fault mechanism solutions for determining the regional stress field pattern. Our results provide compelling evidence of the KWF’s upward propagation into the surface, as demonstrated by deformation of the uppermost Cretaceous and Cenozoic successions, distinct geomorphic features in the Digital Elevation Model, alignment of earthquake epicenters along the fault, and active landslides associated with its movement. We suggest that the reactivation of the KWF has been influenced by changing stress fields from the Late Cretaceous (Turonian) to the present. The Northwestern Arabian plate has undergone multiple tectonic stress transitions, including WNW–ESE compression associated with the Syrian Arc Fold-Belt system (Turonian–Plio-Pleistocene) and subsequent NNE–SSW extension linked to Red Sea rifting (Neogene–present). The analysis of fault mechanism solutions suggests that the latest fault movements result from the continued activity of the Irbid Rift event (Eocene) and the Dead Sea Transform Fault since the Miocene.

M. Vrac, D. Allard, G. Mariéthoz et al.

<p>For investigating, assessing, and anticipating climate change, tens of global climate models (GCMs) have been designed, each modelling the Earth system slightly differently. To extract a robust signal from the diverse simulations and outputs, models are typically gathered into multi-model ensembles (MMEs). Those are then summarized in various ways, including (possibly weighted) multi-model means, medians, or quantiles. In this work, we introduce a new probability aggregation method termed “alpha pooling” which builds an aggregated cumulative distribution function (CDF) designed to be closer to a reference CDF over the calibration (historical) period. The aggregated CDFs can then be used to perform bias adjustment of the raw climate simulations, hence performing a “multi-model bias correction”. In practice, each CDF is first transformed according to a non-linear transformation that depends on a parameter <span class="inline-formula"><i>α</i></span>. Then, a weight is assigned to each transformed CDF. This weight is an increasing function of the CDF closeness to the reference transformed CDF. Key to the <span class="inline-formula"><i>α</i></span> pooling is a parameter <span class="inline-formula"><i>α</i></span> that describes the type of transformation and hence the type of aggregation, generalizing both linear and log-linear pooling methods. We first establish that <span class="inline-formula"><i>α</i></span> pooling is a proper aggregation method by verifying some optimal properties. Then, focusing on climate model simulations of temperature and precipitation over western Europe, several experiments are run in order to assess the performance of <span class="inline-formula"><i>α</i></span> pooling against methods currently available, including multi-model means and weighted variants. A reanalysis-based evaluation as well as a perfect model experiment and a sensitivity analysis to the set of climate models are run. Our findings demonstrate the superiority of the proposed pooling method, indicating that <span class="inline-formula"><i>α</i></span> pooling presents a potent way to combine GCM CDFs. The results of this study also show that our unique concept of CDF pooling strategy for multi-model bias correction is a credible alternative to usual GCM-by-GCM bias correction methods by allowing handling and considering several climate models at once.</p>

Thanh Thach Luong, An Dinh Nguyen, Dinh Hai Nguyen et al.

The mean sea surface in different regions is non-equipotential, rendering Vietnam's traditional approach, which relies on the Hon-Dau tide gauge station as a reference, not yet scientifically invalid. To overcome this, our study utilized the Vietnam national mean dynamic topography model (MDTVN22) for depth observations, particularly in the Gulf of Tonkin. Covering 3430 monitoring sites in Hai Phong and 813 sites in Quang Ninh, our experiments highlighted a 5 to 6 mm difference between the mean sea surface and MDTVN22 references. • Our research establishes a resilient methodology, integrating shore tide gauge station data and the MDTVN22 model, aimed at enhancing precision in depth observations. • Validation experiments in Hai Phong demonstrate a minimal discrepancy of ±0.006 m between measurements obtained from the traditional mean sea surface and the MDTVN22 model. • These findings underscore the significance of adopting the MDTVN22 model for improved accuracy in assessing Vietnam's seabed topography.

A. Heim, A. Gansser

QIU Dapeng 1, 2, CHEN Jianyun 3, WANG Wenming 1, 2, CAO Xiangyu 4

The increase dynamic analysis (IDA) curves of seismic responses of the underground large-scale frame structure (ULSFS) are investigated during the single horizontal earthquakes and horizontal-vertical earthquakes, respectively. The influence mechanism of vertical earthquakes on the seismic responses of different vulnerable positions is revealed. Aiming at the interlayer drift deformation and flexural deformation in the ULSFS, the interlayer drift ratio (IDR) and interlayer rotation angle (IRA) are employed as the seismic performance evaluation indexes. Therefore, the influence mechanism of vertical earthquakes on structural seismic performance is further revealed. The seismic fragility curves of the ULSFS are achieved during horizontal earthquakes and horizontal-vertical earthquakes, respectively. The results show that the vertical earthquakes have small seismic influences on the seismic fragility of the ULSFS based on the IDR. However, the vertical earthquakes enlarge the local flexural deformation of the ULSFS and decrease the seismic performance of the ULSFS based on the IRA. The seismic fragility considerably increases after considering the vertical seismic effects. The IDR aiming at the horizontal drift deformation and the IRA aiming at the interlayer flexural deformation are advised to be employed to assess the seismic fragility of large underground structures during both horizontal and vertical earthquakes comprehensively.

I. A. Izbrodin, A. G. Doroshkevich, V. B. Khubanov et al.

The Borgoy and Botsy massifs are a part of the Dzhida alkaline province of the Western Transbaikalia. It has been stated that the rocks of the Borgoy massif were formed during the period from 246 to 243 Ma, which coincides with the formation period of the Permian-Triassic alkaline magmatic rocks common in the Vitim province. The age obtained from the zircons in the Botsy massif (121±1.0 Ma) is typical of the final stage of the transformation of the rocks related to rifting and alkali basalt lava flow. The presence of negative Nb-Ta anomaly and a relative enrichment in Rb, Ba, Sr and U imply interaction between the material of the plume and the earlier accretionary complexes of the subduction zones.

Jennifer Günther, Dejan Prelević, Dieter F. Mertz et al.

Abstract The origin of Italian kamafugites and lamproites is a matter of debate, not least due to their “crustal signature” displayed by trace element compositions and isotopic ratios, but also due to puzzling geodynamic significance. We combine in situ EMPA and LA‐ICP‐MS analyses with in situ analyses of oxygen isotopes (SIMS) on olivine from the Pleistocene San Venanzo kamafugites and Torre Alfina lamproites. Lamproitic olivine shows extremely high Mg# and Ni concentrations whereas Ca and Mn concentrations are low. Their δ18OV‐SMOW values are very high up to +11.5 ‰. In kamafugites we recognize three genetically different olivine groups: (a) phenocrystic one with high Mg#, very low Ni, high Ca and Mn. Values of δ18OV‐SMOW are up to +10.9 ‰; (b) melt‐related xenocrystic grains that compositionally resemble lamproitic olivine; (c) skarn‐related almost pure forsterite of extreme δ18OV‐SMOW ∼27 ‰, with negligible amounts of minor and trace elements. The melting and crystallization conditions of Italian kamafugites and lamproites indicate compositionally heterogeneous mantle sources on very small scales. Distinct geochemical features of the olivine macrocryst populations observed in kamafugite point to a range of processes occurring both within the magma storage and transport system. We suggest that the diversity of metasomatic agents was involved in mantle processes on local scales, coupled with magma mixing and/or the uptake of xenocrysts during magma ascend.

SADEGHI Hamed, KOLAHDOOZ Ali, AHMADI Mohammad-Mehdi

Natural soils contain a certain amount of salt in the form of dissolved ions or electrically charged atoms, originated from the long-term erosion by acidic rainwater. The dissolved salt poses an extra osmotic water potential being normally neglected in laboratory measurements and numerical analyses. However, ignorance of salinity may result in overestimation of stability, and the design may not be as conservative as thought. Therefore, this research aims to first experimentally examine the influence of pore water salinity on water retention curve and saturated permeability of natural dispersive loess under saline and desalinated conditions. Second, the measured parameters are used for stability analyses of a railway embankment in an area subjected to regional rainfall incident. Eventually, a numerical parametric study is carried out to explore the significance of different rainfall schemes, construction patterns, and anisotropic permeability on the factor of safety. Results reveal that desalinization suppresses the water retention capability, which in turn results in a tremendous declination of unsaturated hydraulic conductivity. Despite the natural saline embankment, rainfall can hardly infiltrate into the desalinated embankment due to the lower conductivity. Therefore, the factor of safety for natural saline conditions drops notably, while only marginal changes occur in the case of the desalinated embankment.

Tao Wen, Zheng Hu, Yankun Wang et al.

AbstractHigh geotemperature seriously impacts personnel and equipment during railway and expressway tunnel construction. In this study, the Nige tunnel in the expressway from Gejiu to Yuanyang in Honghe Prefecture was used as an example. Firstly, automatic temperature recording devices were used to monitor the variation characteristics of the tunnel temperature. Afterward, the variation characteristics of the temperature at 5-10 days and 150 days after tunnel’s completion were revealed. The results showed that the evolution laws of air temperature in each stage could be revealed by logarithmic functions of increasing type and decreasing type. Based on the monitoring over 5-10 days after tunnel’s completion, the temperature range was 26-44°C, and the highest temperature in the tunnel is located near the middle of the tunnel. The temperature fluctuation near the tunnel entrance is relatively small, while it fluctuates greatly near the tunnel exit. Based on the monitoring over 150 days, the air temperature was maintained between 16 and 31°C. The temperature near the tunnel entrance was high, while the temperature near the tunnel exit was low. The performance had a guiding significance for the design and construction of the high-geotemperature tunnel.

Guoping Hu, Yingzhi Xia, Mingxin Zheng et al.

Arch-chord-coupled antisliding structure is a new type of structure composed of multiple small-diameter piles for strengthening small- and medium-sized landslides, especially suitable for the reinforcement of slopes that are sensitive to deformation. In order to further explore the mechanical properties of the antisliding structure, physical model tests under four cases were carried out to study the deformation and stress characteristics of the structure under different types, and the optimal structural type was determined. The displacement test results show that even if there is no crown beam at the top of the piles, all the piles can deform in coordination, and when the number of rear piles is large, all the piles can basically deform synchronously. The test results of the bending moment of the pile body show that the crown beam has a great influence on the extreme value of the bending moment of each pile. For the structural type with more piles arranged in the rear row, the standard deviation of the extreme value of the bending moment of the pile body before and after adding the crown beam decreases from 2.0 to 1.03; the presence of crown beams effectively adjusts the internal force of each pile. The comprehensive analysis results show that the arch-chord-coupled antisliding structure with more piles in the rear row is the best.

María José Domínguez-Cuesta, Laura Rodríguez-Rodríguez, Carlos López-Fernández et al.

Gravitational processes on inaccessible cliffs, especially in coastal areas, are difficult to study in detail with only in situ techniques. This difficulty can be overcome by the complementary application of remote sensing methods. This work focuses on an active complex landslide affecting the slope of the Tazones Lighthouse (Cantabrian coast, North Iberian Peninsula), which has been monitored since June 2018. The aim of this research is to establish a conceptual model of the internal structure of the slope. A remote multitechnique approach was applied, including landscape deformation analysis from photogrammetric surveys, ground motion detection applying A-DInSAR techniques and Sentinel-1 satellite data, and electrical resistivity tomography. The obtained results showed the great potential of some of the remote techniques, such as UAV photogrammetry and electrical tomography, and the ineffectiveness of others, such as A-DInSAR, which failed to provide adequate results due to the profuse vegetation. This work made it possible to establish a geological model of the functioning of the slope of the Tazones Lighthouse and to deduce the surface extent of the destabilized mass (70,750 m²), the rupture surface shape (stepped), its in-depth extent (10–50 m), the volume of materials involved (~3,550,000 m³) and the type of landslide (complex including a predominant translational slide). The combination of field and remote sensing data significantly increased the possibility of reaching a comprehensive geological interpretation of landslides on rocky coasts.

H. Sioli

Nagina Naveed Riaz , Fazzal Ur Rehman , Shabbir Hussain et al.

The current study is performed to assess the physio-chemical characteristics and drinking water quality in three Tehsils (Mailsi, Burewala and Vehari) of District Vehari, Punjab (Pakistan). The water samples of investigated regions were subjected to physicochemical characterization (pH, EC, TDS, HCO3-, CO3 -2, Cl-, NO3+, PO4-3, SO4-3, Na+, K+, Ca+2, Mg+2, Fe+2, Cu+2, Zn+2 and Mn+2). It was demonstrated that certain parameters were exceeding WHO standard limits. The water of Lalazar colony, college town, Y-Block and Sharqi colony was found unfit for drinking purposes so it may cause serious health concerns in the citizens of the investigated areas

Prabhin Sukumaran, Dhananjay A. Sant, K. Krishnan et al.

Analyses of a fluvial sedimentary sequence from the lower reaches of the Narmada River establish a record of rhythmic cycles of sediment facies that represent floods during the late Holocene. The south-west Indian monsoon strongly influences the study area, and heavy rainfall or cyclones which originate from either the Bay of Bengal or the Arabian Sea, also affect the region. Optically stimulated luminescence dating places the 8 m thick sediment sequence in the climate transition phase which ranges from the Medieval Warm Period to the Little Ice Age. Multi-proxy analyses including high-resolution granulometry, magnetic susceptibility, ferromagnetic mineral concentration, facies major oxide geochemistry, and micro-fossil records (from two sedimentary units) are used to study these late Holocene flood events. The latter are characterised by multiple sediment facies, depositional events, changes in channel morphology, and distinctive flood signatures. Integration of these records enables to identify two distinct aggradations viz. phase I and phase II, as well as a relative change in channel morphology. The study describes 11 flooding events and their imprints over multi-proxy records. Historic documents and instrumental records from the town of Bharuch referring to floods, movement of channel sand, channel shallowing, and the dysfunction of the ancient port of Bharuch further validate the inferences drawn from the sedimentary sequence. The study exemplifies the need to use high resolution and multi-proxy studies to interpret paleoflood records and climate signatures in order to build archives of monsoonal rivers.

Rui BI, Shu GAN, Raobo LI et al.

Taking the debris flow gully of the tributary of the Dabaini River on the left bank of the middle reaches of the Xiaojiang River Basin in Dongchuan District, Yunnan Province as the research object, the surface landform data of the debris flow gully was collected by Unmanned Aerial Vehicle (UAV) remote sensing technology. This paper proposes a method of extracting the control points of the same-named objects in combination with the ground three-dimensional laser scanning modeling data to realize the absolute orientation of UAV image data. Through Smart3D image data processing, a three-dimensional terrain model of the study area is constructed to obtain digital orthophoto map (DOM), digital surface model (DSM) and high-density matching point cloud. The point cloud data is processed using the Irregular Triangle Network progressive encryption technology in PhotoScan software to obtain a digital elevation model (DEM) with a resolution of 0.5 m. Combined with the relevant terrain analysis modules in ArcGIS and Cloud Compare, the terrain characteristics of this section of debris flow valley area can be analyzed. The technical route and method used in the modeling and analysis of debris flow gully terrain based on UAV remote sensing are of important empirical case reference value and practical guiding significance for qualitative and quantitative detection of geological disasters in the plateau complex mountain area and their monitoring and prevention.

C. S. Ho