Geological Journal最新文献

The deformation and failure of the surrounding rock mass is a key issue during the construction of large-scale underground powerhouse, and large discontinuities are likely to cause this problem in the presence of complex geological structures. This article takes the right bank underground powerhouse of the Baihetan Hydropower Station as a case study. In this case, deformation mutation of the surrounding rock mass occurred in the south section of the main powerhouse, with the maximum deformation reaching 178 mm, and the deformation and failure of different parts showed differences. A comprehensive study integrating field survey, site monitoring, laboratory test and numerical simulation was carried out. By field survey and monitoring, characteristics of deformation and failure are described, and the spatiotemporal difference in deformation is analysed. The stress evolution during excavation is studied based on numerical simulations, the mechanical response of rock is derived through laboratory tests, and the mechanism of spatiotemporal difference is revealed. The results indicate that the main reason for the spatiotemporal difference is the presence of slightly inclining interlayer shear zone C₄. In the south section, the excavation-induced stress concentration at the arch was enhanced due to C₄, with the maximum principal stress exceeding 70 MPa, and the high compressive stress here triggered the deformation mutation of surrounding rock mass. After undergoing a stress path from concentration to unloading, the surrounding rock mass at the downstream sidewall was seriously damaged, and its deformation also mutated under approximately vertical stress. The mutation resulted in the uneven spatial distribution, large increment and time-dependent feature of deformation.

The Dunhuang Basin, situated in western China along the Altyn Tagh Fault (ATF) zone, intersects the Tethys and Paleo-Asian Ocean tectonic domains. Influenced by both the ATF system and the far-field effects of the Qiangtang-Lhasa-Eurasia collision during the Mesozoic, the mechanism of the Jurassic sedimentary migration of the basin in response to tectonic movements is unclear so far. The paper uses a comprehensive approach, including field geological surveys, lithologic and lithofacies discern, stratigraphic relationships analysis and 2D seismic profile interpretation, to examine the distribution of Jurassic residual strata in the basin. The comprehensive results of our study suggest that the Dunhuang Basin exists as an isolated block with unique tectonic and sedimentary evolution characteristics. In the Early Jurassic, the Dunhuang Basin underwent initial rifting, leading to the formation of small segmented intermontane sags. This phase was marked by the coarse particle sedimentary system of alluvial fans and braided rivers, represented the near source rapid deposition in the initial formation period of the basin. Stratigraphic distribution was primarily influenced by pre-Jurassic basement topography and was not significantly constrained by faulting during this period. The formation of these isolated discontinuous small intermontane sags indicates the segmented activities of the ATF in the Early Jurassic period. In the Middle Jurassic period, influenced by the ATF dextral strike-slip faulting, sedimentation extended eastward and the depocenter migrated clockwise compared with the distribution of the Middle Jurassic strata within the Dunhuang Basin. This period witnessed the development of coal measure strata at the basin's margins and lacustrine fine-grained clastic deposition in the centre. The segmented fracture of the ATF gradually initiated a unified dextral strike-slip tectonic movement. In the Late Jurassic period, sedimentary strata were locally present in the Wanyao Sag but absent in other sags. The depocenter migrated counterclockwise compared with the distribution of Middle Jurassic strata within the Dunhuang Basin, due to regional uplift accompanied by the ATF sinistral strike-slip faulting caused by the collision between the Lhasa Block and the Eurasia Plate. The depocenter migration of the Dunhuang Basin constrained within the ATF system from the Early to Middle and Late Jurassic can be attributed to the transition of the ATF strike-slip faulting in context of the stress relaxation and compression between the collision of the Qiangtang and Lhasa blocks to the Eurasia Plate, respectively.

The Ramagiri greenstone terrane (RGT) of Central Dharwar craton, India, is recognized as remnants of Archean oceanic crust squeezed between ancient proto-continental terranes. The granites and gneisses formed as a result of partial melting, resisted subduction and collided, sinking the intervening ocean basin. The geochemical characteristics of the bimodal metavolcanics of RGT were carefully assessed using suitable proxy. An insight into them suggests that the mafic rocks bear characteristics of island arc tholeiites belonging to suprasubduction zone setting, as corroborated by their low TiO₂/Yb (avg 443) and high Th/Nb (avg 0.8). Their high V/Ti (avg 0.3) ratio points towards a mantle source that has been influenced by subduction, whereas low Ti/Yb echoes high degrees of shallow melting with little residual garnet. The felsic rocks on the other hand are metaluminous–peraluminous, mostly calc-alkaline and geochemically akin to I- and S-type syncollisional and volcanic arc granite emplaced during intercontinent collision. Their immobile element plot with low Nb + Y (avg 25) concentration also points towards a volcanic arc environment.

Tunnelling in complex geological strata is a challenging task that can affect the performance of shield machines and result in unexpected hazards. Therefore, extensive knowledge of unfavourable environments and shield operational parameters is essential for ensuring successful and safe tunnelling. This study aims to analyse the geological and hydrological conditions of the Chunfeng Tunnel and present the key construction technologies of a large slurry shield machine when crossing complex strata. To this end, attempts were made to (i) discuss the geological and environmental challenges encountered during the tunnelling process and present some early interpretations based on the database information, (ii) analyse the factors affecting tunnel performance and simulate the ground surface settlement along the tunnel alignment and (iii) discuss the countermeasures under adverse ground conditions and propose future directions. The results revealed that tunnelling in fault zones with soft upper and hard lower strata led to severe wear of disc cutters and controlling the tunnelling parameters could provide a suitable method for adjusting the construction process. This study leveraged extensive experience gained during tunnelling using a large slurry shield machine, with special emphasis on mixed ground strata, by providing valuable insights and suggested responses for effective tunnelling strategies.

Malan loess possesses unfavourable engineering mechanical properties that may vary depending on the geological context in which it exists. In the context of roadbed loading, the structural characteristics of the loess roadbed often result in uneven settlement, which significantly impacts transportation safety. To investigate the dynamic behaviour of loess under the influence of vehicle loading, groups of dynamic rebound modulus tests were conducted using a dynamic triaxial apparatus. Three key aspects are highlighted: compaction degree, moisture content and stress state. The results reveal that the dynamic rebound modulus of loess tends to increase with higher compaction degrees, decrease with increased moisture content and rise under greater confining pressure. For Maran loess, the water content has the greatest influence on its physical and mechanical properties. Under conditions of a confining pressure of 60 kPa and a deviatoric stress of 30 kPa, as the moisture content increased from w = 9% to w = 18%, the minimum dynamic rebound modulus decreased by 63%.

Following the latest Permian mass extinction (LPME), abundant unusual sedimentary features and fabrics were widely distributed in Early Triassic carbonate platforms. As a unique type of carbonate grain, spheroids from the Lower Triassic are infrequently reported, yet differ significantly from giant ooids and oncoids. Griesbachian micritic spheroids are well preserved in the Lower Triassic Feixianguan Formation at the Baimiaozi (BMZ) outcrop in Beibei, Chongqing, southwestern China. These spheroids (diameter: 3.9–10.8 mm) were in a marl layer interbedded with massive oolites. They were deposited in the wave troughs of ripple marks comprising micritic clots, sparry calcite, clay minerals, organic matter and pyrite. A microbial spheroid origin is implied based on the coccoidal microbes (coccoid-like microspherules and bacterial clump-like microspherules), numerous pyrite framboids (indications suggest the presence of many sulphate-reducing bacteria and the high iron content in seawater can promote nitrogen-fixing cyanobacteria proliferation) and microbial-derived microspherules. The dark-coloured matrix between the spheroids primarily included microcrystalline calcite, clay minerals, organic matter and metazoan fossils. The spherical and ellipsoidal shapes of the spheroids suggested rapid accretion and lithification. As a unique carbonate depositional mode, Greisbachian spheroids may have been recorded for a palaeo-ocean with dysoxic and calcium carbonate supersaturation shortly after the LPME.

In the process of landslide susceptibility prediction (LSP) modelling, there are some problems in the model dataset relating to landslide and non-landslide samples, such as landslide sample errors, subjective randomness and low accuracy of non-landslide sample selection. In order to solve the above problems, a semi-supervised machine learning model for LSP is innovatively proposed. Firstly, Yanchang County of Shanxi Province, China, is taken as the study area. Secondly, the frequency ratio values of 12 environmental factors (elevation, slope, aspect, etc.) and the randomly selected twice non-landslides are used to form the initial model datasets. Thirdly, an extreme gradient boosting (XGBoost) model is adopted for training and testing the initial datasets, so as to produce initial landslide susceptibility maps (LSMs) which are divided into very low, low, moderate, high and very high susceptibility levels. Next, the landslide samples in initial LSMs with very low and low susceptibility levels are excluded to improve the accuracy of landslide samples, and the unlabelled twice non-landslide samples in initial LSMs with low and very low susceptibility levels are randomly selected to ensure the accuracy of non-landslide samples. These new obtained landslide and non-landslide samples are reimported into XGBoost model to construct the semi-supervised XGBoost (SSXGBoost) model. Finally, accuracy, kappa coefficient and statistical indexes of susceptibility indexes are adopted to assess the LSP performance of XGBoost and SSXGBoost models. Results show that SSXGBoost model has remarkably better LSP performance than that of XGBoost model. Conclusively, the proposed SSXGBoost model effectively overcomes the problems that the accuracy of landslide samples needs to be further improved and that non-landslide samples are difficult to select accurately.

The development of earth fissures, which are linear fractures with openings or offsets on the land surface, can severely affect landforms, especially in urban areas, in the form of earthquakes causing major concern on human lives as well as damage to infrastructures. Thus, an early warning map for lands susceptible to earth fissures can better equip planners for formulating mitigation strategies. In this study, we focus on the Damghan Plain in Iran for preparation of earth fissure susceptible maps using several topographical, hydrological, geological and environmental conditioning factors. In order to train these conditioning factors and preparation of earth fissure susceptibility maps, 124-earth fissure field-based samples, for training and validation purposes, were used by random subspace (RS) model based on four other machine learning ensemble methods such as RS-Naïve-Bayes Tree (NBTree), RS-alternating decision tree (ADTree), RS-Fisher's Linear Discriminant Function (FLDA) and RS-Logistic model tree (LMT). From the validation technique, the receiver operating characteristic (ROC) curve performance test demonstrates that the RS-NBTree model was the best suited with area under curve (AUC) = 0.974 followed by RS-ADTree (AUC = 0.966), RS-LMT (AUC = 0.954), RS-FLDA (AUC = 0.948) and RS (AUC = 0.923). The results from our study can be useful for environmental management and risk reduction.

Retraction: ‘ Socio-economic impact of natural resource management: How environmental degradation affects the quality of life’ by LiJie An, XiuJing Jiang, Zhen Liu, Qiong Li, Geol J 2023, 58: 3310–3325. The above article, published online on 9 July 2023 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/full/10.1002/gj.4787) has been retracted by agreement between the journal's Editors in Chief, Ian D. Somerville and Yunpeng Dong, and John Wiley & Sons Ltd.

The retraction has been agreed following concerns raised by a third party. Further investigation by the publisher has found manipulation of the peer review process. The retraction is warranted due to the compromised integrity of the article's peer review.

Retraction: ‘ Systematic review on gully erosion measurement, modelling and management: Mitigation alternatives and policy recommendations’ by Rabin Chakrabortty, Subodh Chandra Pal, Geol J 2023, 58: 3544–3576. The above article, published online on 13 March 2023 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/full/10.1002/gj.4709) has been retracted by agreement between the journal's Editors in Chief, Ian D. Somerville and Yunpeng Dong, and John Wiley & Sons Ltd.

The retraction has been agreed following concerns raised by a third party. Further investigation by the publisher has found manipulation of the peer review process. The retraction is warranted due to the compromised integrity of the article's peer review.