Search Results (606)

Phyllostachys edulis (Moso bamboo) is a subtropical bamboo species endemic to China and holds substantial economic and ecological value. Ongoing climate change is reshaping the geographic distribution of its suitable habitats. To reveal these climate-driven dynamics, we calibrated the maximum entropy (MaxEnt) species distribution model using the ENMeval R package version 4.5.2 and evaluated model robustness via spatially independent block cross-validation. We identified nine critical environmental predictors to model spatiotemporal variations in suitable habitats for Moso bamboo, examining both present-day climate and four future periods under four Shared Socioeconomic Pathway (SSP) scenarios. Model performance was optimized at regularization multiplier (RM) of 1.5 with the feature class combination LQHPT, yielding a spatial validation AUC of 0.9104 and robust predictive capacity. Environmental controls were dominated by mean temperature of the coldest quarter (bio11, 63.9% relative contribution) and precipitation of the driest quarter (bio17, 31.2%), while soil clay and organic carbon content modulated suitability at local scales. Under current conditions, the total suitable habitat area encompasses approximately 218.88 × 10⁴ km², with the majority distributed throughout the subtropical zone of southeastern China. Under nearly all future scenarios, high-suitability habitats showed a general contracting trend of 20.94%–95.29% relative to the current baseline, while moderate-suitability habitats exhibited a fluctuating expansion trend, reaching a peak increase of 47.90% in the 2030s under SSP585, but contracted by 18.65% in the 2090s. Meanwhile, habitat centroids underwent small-scale oscillatory shifts in multiple directions and remained entirely within Hunan Province across all periods. MESS analysis confirmed that 90.60%–99.82% of China’s land area fell within climate-analogous ranges, indicating low extrapolation risk for core habitat projections. Core climate refugia with high cross-scenario stability were primarily concentrated in the traditional bamboo-producing regions of southeastern China. This study provides a scientific basis for the sustainable management of Moso bamboo resources, biodiversity conservation, and ecological risk prevention in the context of ongoing climate change. Full article

Recent studies have demonstrated that installation-induced soil disturbance, advancement ratio, and installation rate can substantially affect the subsequent axial response of helical piles. However, systematic experimental comparisons that simultaneously relate installation torque, axial thrust, and post-installation uplift capacity across multiple geometric and operational variables in clay remain limited. This study investigated the coupled effects of helix pitch, advancement ratio, penetration speed, and shaft style on the installation and uplift behavior of helical anchors in prepared clay. Laboratory model tests were conducted using grouped anchor configurations, and installation torque, installation thrust, and uplift load–depth responses were recorded. An area method was introduced to quantify accumulated installation resistance from torque–depth and thrust–depth curves. Within the tested fixed-advancement-ratio pitch series, the tested pitch–speed combinations produced comparatively moderate variations in installation resistance and uplift capacity when the helix plate diameter was fixed. The installation condition represented by the advancement ratio and corresponding penetration speed influenced penetration–rotation compatibility: lower advancement ratios increased repeated shearing and torque, whereas higher advancement ratios reduced torque but increased thrust. Increasing penetration speed markedly increased accumulated torque but reduced ultimate uplift capacity from 478 N to 315 N. The shaft-style tests showed differences in plugging, suction, and local penetration resistance, with limited variation in helical-anchor uplift capacity. These findings indicate that installation parameters and geometric configuration should be considered together when optimizing helical-anchor installation in clay. The findings provide model-scale references for selecting helical-anchor geometry and installation procedures in prepared kaolin clay under conditions comparable to those tested. Full article

In total, 1000+ specimens of coprolites have been collected from the Eocene Sundby bed, which marks the top of the Stolleklint Clay of the Ølst Formation at the locality Sundby Klint East on the island Mors in northern Jylland, Denmark. The coprolites contain seven distinct morphotypes, including three new ichnospecies of coprolites, Uberosteus henrikmadseni igen. et isp. nov., Iotabotulus mettehofstedtae igen et isp. nov. and Microbromus sundbyensis igen et isp. nov. The coprolite assemblage from the Sundby bed is among the five largest Eocene coprolite faunas worldwide. The record of vertebrate coprolites across the Cretaceous/Paleogene boundary records distinct changes in morphotypes which correspond to changes in the body fossil record. Full article

Cement production is associated with substantial carbon dioxide (CO₂) emissions due to the high material and energy intensity of Portland clinker manufacture. Partial clinker replacement with supplementary cementitious materials is one of the most promising strategies for reducing the carbon footprint of cement; however, the thermal activation of aluminosilicate raw materials does not always yield highly reactive products. In this study, a pillaring approach is proposed as a controlled method for modifying the structure of clays and unlocking their latent reactivity. Different clay types—namely, kaolinitic, montmorillonitic, and illite–chlorite clays—were sequentially treated with an aluminum sulfate solution and calcined at 650 °C. Their phase composition and microstructure were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), while specific surface area was determined by BET analysis and pozzolanic activity. The results showed that pillaring doubled the specific surface area of montmorillonitic (2:1) and illite–chlorite (2:1:1) clays. Replacing 30% of clinker with pillared clays and limestone increased the compressive strength to 86.5 MPa and the flexural strength to 34.6 MPa. The developed low-carbon composite cements also exhibited high durability: the density of the hardened cement mortar increased to 2.410 g/cm³, the strength loss after 200 freeze–thaw cycles decreased to ≤5.5%, and the sulfate resistance coefficient (Ks) increased to 0.98 (with minimal expansion of the samples <0.02%). The proposed approach makes it possible to reduce the carbon footprint of cement by 25–30% while enabling the use of locally available raw materials for the production of competitive low-carbon green cements. Reported reductions of this order are broadly consistent with the known effect of lowering clinker content through supplementary cementitious materials in blended cement systems. Full article

The emplacement of mafic dikes into carbonate-bearing sedimentary successions commonly produces localized mineralogical and geochemical variations in adjacent country rocks. However, the spatial distribution of these variations remains poorly documented in the Permian sedimentary successions of Thailand. The study investigates spatial mineralogical and geochemical variations across intrusive rocks and adjacent sedimentary rocks in the Permian Nam Duk Formation, Phetchabun Province, Thailand. Petrographic observations and whole-rock geochemical analyses (XRF and ICP-MS), supported by qualitative XRD phase identification, were integrated to characterize mineral assemblages and whole-rock geochemistry. The intrusive rocks display porphyritic textures dominated by plagioclase and hornblende, whereas the adjacent country rocks are characterized by quartz, calcite, feldspar, clay minerals, and secondary alteration phases. Spatial variations in mineral assemblages are accompanied by changes in contents of some major oxides (SiO₂, Al₂O₃, Fe₂O₃, MgO, and CaO) and selected trace and rare earth elements. The sedimentary country rocks generally contain higher total REE concentrations, particularly La and Ce, whereas the contact-proximal sample shows values closer to the mafic dike. Site A shows the clearest spatial variations across the exposed mafic dike–country rock contact, whereas site B exhibits compositional variability associated with strongly altered porphyritic andesite and heterogeneous sedimentary rocks. The integrated results document localized mineralogical and geochemical variations across the investigated intrusive–sedimentary rock systems, although primary lithological heterogeneity and secondary alteration may also contribute to these patterns. Full article

Ultra-deep circular shafts are increasingly deployed in congested urban environments, yet their structural performance in highly sensitive soft clay remains susceptible to diaphragm wall panel joints, structural imperfections, and complex interactions with adjacent structures. This study presents a high-fidelity three-dimensional (3D) numerical investigation into the excavation behavior of an ultra-deep circular shaft with a diameter of 30 m and an excavation depth of 56.3 m in Shanghai soft clay by synthesizing high-resolution field monitoring with advanced finite element modeling. The numerical framework was established in PLAXIS 3D utilizing the Hardening Soil model with small-strain stiffness (HSS), explicitly incorporating an equivalent structural stiffness reduction scheme (0.8 vertically and 0.5 circumferentially) to capture panel segmentation, joint compliance, and concrete cracking. The reduced-stiffness model successfully reproduces the measured deep-seated bulging profiles and internal force distributions with high fidelity. The findings reveal exceptional deformation control capabilities of the circular geometry, yielding a maximum lateral wall deflection of merely 9.1 mm (0.016%H_e), which is significantly smaller than the normalized deformation ratio of 0.3%H_e observed in five analogous rectangular excavations in Shanghai. The numerical results indicate that circumferential compression governs the overall load transfer behavior, while vertical bending response remains relatively limited. Furthermore, a pronounced circumferential anisotropy in wall deformation is governed by asymmetric boundary conditions, where localized Metro Jet System (MJS) ground improvement significantly restrain movements, whereas the non-grouted area experience peak deflections. Crucially, interaction with the adjacent external diaphragm walls of ancillary structures induces a complex 3D stress redistribution rather than a beneficial shielding effect, amplifying the peak shaft wall displacement by nearly 62.8% (from 4.73 mm to 7.70 mm). These insights underscore the criticality of integrating small-strain soil mechanics, equivalent structural degradation, and adjacent structural boundaries into predictive design protocols for ultra-deep circular retaining systems. Full article

Solar-assisted underground thermal energy storage (UTES) can reduce the seasonal mismatch between summer solar availability and winter heat demand. However, regional planning requires renewable charging resources and subsurface thermal performance to be evaluated jointly. This study developed a lithology-resolved GIS–laboratory framework for preliminary borehole thermal energy storage screening in the Euganean Hills, northeastern Italy. Thermal conductivity and volumetric heat capacity were characterized for 23 local specimens under dry and water-saturated conditions. Conductivity was measured parallel and perpendicular to the dominant rock fabric. Additional basalt measurements and clay/silt reference values were used where local sampling was insufficient. Normalized thermal effusivity was combined multiplicatively with normalized seasonal solar radiation to define a dimensionless Ground Thermal–Solar Suitability (GTSS) index. Property uncertainty was propagated using 10,000 non-parametric bootstrap realizations. Saturated conductivity generally exceeded 3.0 $\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ in compact carbonate formations. From the conservative dry/perpendicular to the favorable saturated/parallel scenario, lithology-level GTSS increased by 2.6–9.4%. Approximately 30.1% of mapped cells increased by one suitability class and 0.5% by two classes. Relative 95% GTSS interval widths ranged from 2.5–16.9% in the conservative scenario and 1.1–13.5% in the favorable scenario. Maiolica and Scaglia Rossa provided the strongest combination of thermal performance and spatial continuity. At Turri, field-equivalent conductivity was 5.10 $\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$, or 2.50–3.45 times the laboratory-weighted estimates. This difference confirms that field-scale fracture, groundwater, and borehole effects lie outside the laboratory calibration domain. GTSS therefore supports uncertainty-aware regional prioritization, not site-specific performance prediction. Full article

Small-scale clay-brick yards require molding equipment that increases output while remaining mobile, locally serviceable, and compatible with intermittent material supply. This article documents the functional architecture and exploratory operational performance of the mobile 12-cavity hydraulic clay-brick molding machine (ML12). Its design contribution is the integration of a dimensioned wheeled steel chassis, seated paired-lever controls, a translating feed hopper/distributor, a 12-cavity mold, two vertical hydraulic actuators, and a water-spray cleaning subsystem in a four-stage operating cycle. A retrospective concept-appraisal matrix compares this architecture with fixed automated and mobile manual concepts; equal weighting and one-at-a-time ±25% weight variations preserve the ML12’s highest internal score, without establishing stakeholder preference or empirical superiority. The evidence base also comprises sequential daily production logs: ten days of traditional manual molding followed by ten days of ML12-assisted molding. Mean gross green-brick output was 720 ± 86 bricks/day in the traditional period and 1495 ± 16 bricks/day in the ML12 period; corresponding descriptive throughputs were 86.5 and 186.9 bricks/h. A rejection-rate sensitivity analysis shows that, if traditional production had no rejects, ML12 conforming output would equal the traditional gross mean at a 51.8% ML12 rejection rate; this quantity boundary is not an estimate of quality or economic break-even. A preliminary linear-static finite-element case for a reconstructed frame returned a maximum von Mises stress of 112.3 MPa, 1.82 mm resultant displacement, and a minimum elastic safety factor of 2.23 on the reported medium mesh; the result is limited to the specified 1.0 kN load case and is not structural certification of the complete machine. Because the operational comparison was non-randomized and did not control staffing, operators, clay batch, moisture, weather, energy use, or rejection rate, the observed difference cannot be attributed exclusively to the machine. The results establish the machine architecture, an operational signal, and a bounded preliminary frame response, but not brick quality, ergonomic benefit, full structural safety, environmental benefit, or commercial return. Full article

We study prediction-to-decision certification for inverse design with vector-valued response surfaces. An unknown response map is estimated from data, a target response is prescribed, and a decision is obtained by minimizing a target-loss function. The main question is how statistical prediction error and approximate global optimization error propagate to the true decision quality. We prove an end-to-end certificate showing that a high-probability uniform response bound and a certified global-search tolerance imply a high-probability bound on the true excess risk of the selected decision. Under a growth condition, the same event also yields an explicit distance-to-argmin bound. We provide finite-sample ordinary least squares response certificates, conditional ridge certificates with explicit bias decomposition, certified Lipschitz branch-and-bound, and polynomial sum-of-squares formulations. The formal certificate is demonstrated on a controlled synthetic benchmark. A clay-coloration example illustrates the workflow, while the pilot measurements are treated only as local forward-color checks. Full article

This study investigates the occurrence characteristics of solid bitumen and its control on pore structure in the overmature marine shales of the Wufeng–Longmaxi Formations in the Jianshi–Badong area, Middle Yangtze region. Total organic carbon analysis, Rock-Eval pyrolysis, organic petrography, organic matter reflectance measurements, petrographic thin-section observations, and scanning electron microscopy were integrated. The shale samples contain 0.10%–6.73% total organic carbon, with an average of 2.20%, and the organic-rich intervals are mainly concentrated in the middle to lower part of the Longmaxi Formation. The average equivalent vitrinite reflectance (EqRo), calculated from solid-bitumen reflectance, is 2.06%, indicating an early overmature stage. The original organic matter is inferred to have been dominated by Type II₁ kerogen, which was extensively transformed into indigenous solid bitumen during thermal evolution. Four principal occurrence types of solid bitumen were identified: laminated, dispersed, massive, and mineral-associated. Organic-pore development differs among these occurrence types. Nanometer-scale pores are locally preserved in laminated and mineral-associated solid bitumen, whereas dispersed solid bitumen in clay-rich matrices generally shows poor pore development. The pore structure is jointly controlled by the occurrence mode of solid bitumen, rigid-mineral support, clay-mineral compaction, thermal maturity, and hydrocarbon generation and expulsion. Quartz- and pyrite-associated solid bitumen is comparatively favorable for pore preservation, whereas clay-associated solid bitumen is more susceptible to pore deformation and closure. These results clarify the petrographic control of solid-bitumen occurrence on pore preservation in overmature marine shales. Full article

Pressurized seepage alters the water-accessible pore system of clay-mineral-rich slate, but its scale-dependent response remains unclear. Argillaceous calcareous slate from the Lower Cambrian Qiongzhusi Formation (Є₁q) was investigated using paired low-field NMR measurements on two specimen batches before and after 72 h treatments at nominal 0 MPa (low-head seepage), 1, 3, and 5 MPa. Total pore volume, pore-size composition, characteristic radii, and pore-size non-uniformity were evaluated. The total pore-volume increment increased from 0.98% to 1.43% in Batch I and from 0.88% to 1.56% in Batch II between 0 and 5 MPa. The dominant peak remained near 1.2 × 10⁻² μm, whereas its amplitude and large-pore spectral tail increased. The combined nanopore and micropore proportion decreased from 90.16–95.28% before treatment to 83.13–89.69% after treatment. The macropore increment increased from 0.15%/0.16% to 0.52%/0.52% in Batches I/II, while r₅₀, r₆₀, and C_u increased and r₁₀ changed only slightly. Sensitivity analysis over ρ₂ = 5–50 μm/s preserved the larger-pore enhancement. These results indicate pressure-enhanced opening, water accessibility, and local redistribution of pre-existing pores rather than extensive pore-system reconstruction, providing a pore-scale reference for seepage-related deterioration assessment. Full article

Water retention availability remains a primary constraint on both vegetation restoration and agricultural productivity across the Chinese Loess Plateau. Attapulgite (ATP) has considerable potential as a soil amendment for improving soil water retention and crop performance, yet its effectiveness is likely to depend on soil texture and climatic water availability. Here, we evaluated the effects of five ATP application rates (0%, 1%, 2%, 3%, and 4%, w/w) on soil hydraulic properties and maize (Zea mays L.) grain yield in three representative soils: clay loam, loam, and sandy loam. Soil water retention curves and field maize experiments were conducted to quantify the hydrological and agronomic responses to ATP addition. The classical van Genuchten (VG) model was further modified by incorporating ATP-dependent parameter relationships to better characterize the water retention behavior of ATP-amended soils. The modified model consistently provided a more accurate representation of the relationship between soil water content and matric suction than the original VG model. The derived soil hydraulic parameters were subsequently incorporated into the DSSAT cropping system model, which was calibrated and evaluated against field observations from Yangling in 2019 and 2020. The calibrated model was then used to simulate maize yield responses to ATP application from 2011 to 2020 at three representative sites: Yangling (clay loam), Changwu (loam), and Yan’an (sandy loam). Simulated yield responses varied markedly with soil texture and interannual climatic conditions. In clay loam, maize yield generally decreased with increasing ATP application, although positive responses occurred in relatively dry years. In sandy loam, ATP application generally increased maize yield across most years, whereas the loam soil exhibited stronger interannual variability in yield response. These contrasting responses indicate that the agronomic effectiveness of ATP is governed by the balance between enhanced soil water retention and local climatic water availability. Overall, the coupled soil hydraulic–crop modeling framework provides a mechanistic basis for developing site-specific ATP management strategies and highlights the importance of matching soil amendments to both soil texture and climatic conditions in water-limited agroecosystems. Full article

Accurate oil saturation evaluation is critical for shale oil sweet-spot prediction and reserve assessment, but conventional resistivity-based interpretation is commonly challenged in clay-rich lacustrine shale oil reservoirs. In some favorable shale intervals, high oil-bearing potential is accompanied by low resistivity, which weakens the applicability of Archie-type saturation models and may lead to underestimation of oil saturation. To clarify the origin of this abnormal electrical response and improve saturation interpretation, this study investigates the upper fourth member of the Shahejie Formation in the Boxing Sag, Jiyang Sub-basin. Core description, thin-section observation, XRD mineral composition, porosity, measured oil saturation, TOC, S1 and conventional logging data were integrated to establish a core-calibrated and SOM-based reservoir classification workflow. Using GR, AC, CNL, DEN, Rt and Rs as input curves, the shale oil reservoirs were divided into Type I, Type II and Type III classes. Type I reservoirs exhibit better pore development and hydrocarbon enrichment, with mean porosity, oil saturation, TOC and S1 values of 4.95%, 59.18%, 2.21 wt% and 2.77 mg/g, respectively. However, their mean Rt is only 22.75 Ω·m, much lower than that of Type III reservoirs. This response defines a typical “three-high and one-low” logging pattern, characterized by high GR, high AC, high CNL and low resistivity. The resistivity-reversal behavior is mainly associated with clay-related conduction and relatively higher absolute water content, whereas organic matter and pyrite do not form continuous conductive pathways in the studied interval. Based on this mechanism, a class-dependent electrical–non-electrical log fusion model was developed by combining clay-corrected electrical saturation with neutron–density saturation constraints. Compared with the single electrical model and single non-electrical model, which yield mean absolute errors of 12.65 and 13.84 percentage points, respectively, the proposed fusion model reduces the error to 8.88 percentage points. Application to more than 40 wells identifies the central–western part of the Boxing Sag as the most favorable shale oil sweet-spot area. The cumulative thickness of Type I reservoirs generally exceeds 100 m in this area and locally reaches more than 150 m. The proposed workflow provides a practical method for identifying favorable low-resistivity lacustrine shale oil reservoirs using conventional logging data. Full article

The morphological evolution of mineral-filled fractures in low-clay shale during water exposure remains poorly understood, particularly regarding how infilling mineralogy, fracture geometry, and fluid accessibility control the response. In this study, fixed-field scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS) was used to track selected fracture regions in Longmaxi Formation shale recovered from a depth of approximately 4072 m in the southern Sichuan Basin, China. The same regions were examined before immersion and after 3 and 6 days of static immersion in deionized water (18.2 MΩ·cm; essentially zero initial ionic strength). Changes in fracture trace length, apparent aperture, area fraction, and box-counting fractal dimension were quantified using a consistent image-analysis procedure and interpreted together with elemental distributions. Three fracture-evolution patterns were identified: sustained enlargement, initial enlargement followed by partial reduction, and moderate aperture increase accompanied by pronounced trace-length extension. Calcium-sulfate-rich fractures exhibited the first two patterns. Their initial enlargement was associated with dissolution of the mineral infilling, whereas the contrasting later-stage responses appeared to be influenced by fracture geometry and fluid accessibility. Relatively open fractures continued to enlarge, while more confined fractures showed partial loss of the initial enlargement and local accumulation of crystalline material. However, the composition and origin of this material (including possible drying-induced crystallization) remain uncertain. Clay-rich fractures showed modest aperture enlargement and continued trace-length extension, consistent with clay–water interaction, although the underlying mechanism could not be resolved conclusively. These results demonstrate that fractures with similar mineral infillings can follow different temporal evolution paths during water exposure. The fixed-field SEM–EDS workflow provides a reproducible method for quantitatively tracking microscale fracture evolution and improves understanding of mineral- and geometry-dependent fracture responses in low-clay shale, though the results are derived from a single specimen and should be interpreted as illustrative observations rather than population-level statistics. Full article

Natural gas hydrate reservoirs in the South China Sea contain pore-filling, fracture-filling, and pore–fracture composite occurrences in fine-grained, clay-rich, and locally sandy sediments. Existing logging studies provide numerous resistivity, acoustic, nuclear magnetic resonance, image-log, and multimineral methods, but model assumptions are not always matched to occurrence type. This review organizes evidence from the Shenhu, Qiongdongnan, and Dongsha areas along an occurrence type–response mechanism–model selection–independent validation–uncertainty chain. Pore-filling reservoirs require mineral and clay constraints before integrated volumetric inversion using resistivity, acoustic, density/neutron, and Nuclear Magnetic Resonance (NMR) logs. Fracture-filling reservoirs should be evaluated primarily from electrical images, azimuthal resistivity, and electrical/acoustic anisotropy, with fracture and matrix porosities treated separately. Composite reservoirs require staged matrix inversion and fracture-component estimation, whereas hydrate–free-gas coexistence intervals require multiphase rock physics. We propose a workflow that classifies occurrence type before inversion, imposes model entry and exit criteria, validates results with independent evidence, and reports ranges rather than unsupported point estimates. This framework clarifies why no universal high-resistivity–high-velocity template or saturation equation is valid for all South China Sea hydrate reservoirs. Full article