Search Results (218)

Thermal pollution in underground spaces is one of the current challenges faced by subway tunnels. Energy tunnel technology based on heat pumps can not only solve the problem of thermal pollution but also realize the resource utilization of waste heat. However, the influence mechanisms of the tunnel air environment on the heat transfer characteristics of energy segments are still insufficiently studied. Taking the shield energy tunnel as the research object, this study proposed an energy segment model based on a capillary heat exchanger and established a fluid-thermal coupled numerical model on the COMSOL 6.4 simulation platform. Then, the effects of tunnel air temperature and speed on the heat transfer performance of the energy segment were systematically investigated. The results indicate that an increase in the temperature differential between the tunnel air and the inlet water of the capillary heat exchanger significantly enhances the heat transfer rate of the energy segments. Specifically, a 5 °C rise in air temperature corresponds to a 60.7% increase in the heat extraction rate of the CHE during the heating season, whereas it results in a 58.8% decrease in the heat release rate of the CHE during the cooling season. An increase in tunnel air speed enhances the overall heat transfer coefficient by strengthening convective heat transfer between the tunnel air and the energy segment. Although the enhancement of convective heat transfer is limited, the system already demonstrates relatively optimal heat transfer performance at a wind speed of 4.61 m/s. The study further reveals that increasing these two parameters not only enhances heat exchange but also exacerbates the non-uniformity of temperature distribution across the segment. This study conducts an in-depth analysis of how tunnel environmental parameters impact the thermal performance of energy segments, thereby offering a theoretical foundation for the optimized design of these energy segments in shield tunnels. Full article

Magnesium phosphate cement (MPC) shows great potential for complex underground environments due to its rapid-hardening and early-strength properties. However, its large-scale application is hindered by several drawbacks, including high hydration heat, rapid setting, and insufficient long-term durability. To address these limitations, this study developed a novel MPC grouting material modified with steel slag (SS) and redispersible latex powder (LP). We systematically investigated the workability, mechanical properties, durability, and microstructural evolution of this modified system. Results indicate that incorporating SS and LP decreases both the fluidity and setting time of the grout. An optimal SS dosage accelerates reaction kinetics and raises the peak hydration temperature. Conversely, the LP-induced polymer film suppresses the overall temperature rise, delaying the first exothermic peak and advancing the second. The incorporation of 5% steel slag increased the 28-day compressive strength of the MPC to 54.86 MPa. Building on this, the combined addition of 0.15% latex powder further elevated the strength to 58.82 MPa. Microstructural and pore analyses confirmed that the steel slag enhanced interfacial bonding through physical filling and the formation of calcium phosphate crystals. Meanwhile, the latex powder formed a continuous polymer film, which tightly wrapped and bridged the hydration products and unreacted particles. This synergistic mechanism effectively sealed the capillary pores and reduced the proportion of harmful pores by 15.99% compared to the control group. Consequently, the densified MPC matrix laid a solid microstructural foundation for the material’s excellent durability. It offers reliable, high-performance material for seepage control and strata reinforcement in complex environments. Full article

Water scarcity is a critical constraint to sustainable agricultural production in arid and semi-arid regions. This study evaluated the effectiveness of subirrigation controlled drainage (SCD) systems in improving water use efficiency, soil conditions, and productivity of Egyptian clover (Trifolium alexandrinum L.) over two consecutive growing seasons (2022–2024). Three drainage treatments were investigated: subirrigation controlled drainage with water table depths of 0.4 m (SCD-0.4) and 0.8 m (SCD-0.8), and conventional free drainage at 1.2 m (SFD-1.2). The results demonstrated that SCD significantly reduced irrigation water requirements, achieving water savings of up to 27% under SCD-0.4 compared with conventional drainage. The shallow water table enhanced groundwater contribution to crop evapotranspiration, reaching over 40%, which improved soil moisture availability and reduced soil water depletion. Consequently, SCD-0.4 increased fresh and dry biomass yields by approximately 18% and significantly improved water productivity and irrigation water productivity. However, controlled drainage led to increased soil salinity due to reduced leaching, particularly in upper soil layers. Economic analysis revealed that SCD-0.4 achieved the highest net returns and water use profitability. Overall, controlled drainage at shallow depths represents an effective strategy to enhance water productivity, crop yield, and economic efficiency, although long-term salinity management must be considered for sustainable implementation. Full article

The Ordos Basin hosts abundant lacustrine shale oil resources. Adequately retained hydrocarbons in source rocks, together with favorable mobility, are prerequisites for large-scale shale oil exploitation. Therefore, the quantitative characterization of retained hydrocarbon content and mobility is a core research focus in shale oil exploration and development. This study investigates Chang 7 shale with varying lithofacies and geochemical characteristics. Stepwise pyrolysis and pyrolysis gas chromatography–mass spectrometry (GC–MS) were applied to analyze retained hydrocarbons in different occurrence states, their compositions, and biomarkers. In addition, nuclear magnetic resonance (NMR) combined with CO₂ flooding experiments was conducted, and the collected products under different displacement pressures were analyzed using GC–MS. The aim was to quantitatively examine the variations in expelled oil volume, compositional differences during migration, and occurrence features of shale oil within reservoir micro-pores. The results show the following: (1) Organic-rich shale is characterized by higher proportions of light and medium hydrocarbons, lower heavy fractions, and elevated aromatic hydrocarbon content. In contrast, low-organic-carbon mudstone or siltstone contains more medium and heavy hydrocarbons, with lower light and aromatic fractions. The C13−/C14+ ratio increases with total organic carbon (TOC). (2) In black shale, oil displacement is mainly contributed by mesopores. At low pressures, oil expulsion is difficult and dominated by heavy hydrocarbons. When pressure reaches a threshold, the capillary-bound oil in micropores is released, increasing production and improving oil quality. Muddy siltstone shows higher displacement efficiency than black shale, with contributions from pores of all sizes. At low pressures, its expelled oil volume is larger and lighter than that of black shale. With increasing pressure, the oil yield rises significantly, and medium–large pores produce heavier fractions compared with micropores, likely because light hydrocarbons preferentially enter micropores and are less prone to dissipation. (3) The main controlling factors for shale oil enrichment include retained hydrocarbon content, mobile hydrocarbon fraction, fluidity, and engineering-related parameters. Thick shale layers with high organic matter abundance, high proportions of light–medium hydrocarbons, and favorable porosity–permeability conditions, as well as interbedded siltstone, are enriched in mobile hydrocarbons. Full article

Recently, a substantial quantity of oil and gas has been discovered in the pre-salt Lower Cretaceous microbialite successions of Brazil’s Santos Basin, thereby prompting a global surge in research related to microbialites. It has been demonstrated that microbial shoal reservoirs yield the highest hydrocarbon production, with optimal reservoir properties, as evidenced by experience in the field of oilfield production. However, as research progresses, it has become increasingly evident that significant heterogeneity exists in both the lithology and physical properties within microbial shoal bodies. In order to address the identified knowledge gap, the present study employs systematic petrological and petrophysical datasets. These include 30-m continuous core samples, thin-section analyses, routine petrophysical tests and mercury injection capillary pressure (MICP) measurements. The aim is to characterize the internal microfacies architecture and reservoir heterogeneity of microbial shoals. It is imperative to ascertain the principal factors that govern the heterogeneity observed in these reservoirs. This critical step is essential for a comprehensive understanding of the subject matter. The results of the study demonstrate that: the Barra Velha Formation microbial shoals in the Santos Basin can be subdivided into three microfacies, which are delineated from base to top. The foundation of the shoal is the shoal base. The rock composition is dominated by the presence of spherulites, with intracrystalline pores functioning as the primary reservoir spaces. The compositional rocks of the shoal flank are poorly sorted microbial debris, with intergranular and intragranular pores formed by penecontemporaneous dissolution. The sedimentary succession of the shoal core is characterized by well-sorted microbial debris rocks displaying multiple shallowing-upward sequences, with reverse-graded textures. The primary storage space is constituted by fabric-selective pores from penecontemporaneous dissolution, though these are subject to local disruption by destructive silicification. Meanwhile, the microbial shoals demonstrate wide porosity (8.8–26.4%, mean 16.8%) and permeability (0.13–839 mD, mean 169 mD) ranges, thus classifying them as medium-porosity, high-permeability reservoirs. The superimposition of microfacies and diagenetic processes gives rise to considerable reservoir heterogeneity. It is evident that the shoal core microfacies exhibits robust energy and substantial grain size, characteristics that facilitate its exposure above lake level during periods of high-frequency lake-level oscillation. This exposure is further compounded by the influence of atmospheric water dissolution, which remodels the microfacies during the quasi-contemporaneous period. The reservoir quality is optimal, exhibiting the highest proportion of large pores. The reservoir properties of the shoal flank are closely followed by medium and large pores, and those of the shoal base are the worst, with micro and medium pores. Full article

The preservation of cultural heritage presents persistent challenges due to the heterogeneity of methodologies, data structures, and information requirements involved in heritage projects. While conventional Building Information Modeling (BIM) workflows commonly rely on the Level of Development (LOD), heritage contexts require flexible and requirement-driven approaches to manage both geometric and semantic information according to stakeholder needs. To address these challenges, this study adopts a design-oriented approach that investigates the integration of the Level of Information Need (LOIN) within an OpenBIM-based Historic Building Information Modeling (HBIM) framework. The proposed methodology combines a systematic literature review with a practical case study to develop and implement an interoperable workflow articulating HBIM, Level of Information Need (LOIN), Industry Foundation Classes (IFC), and Information Delivery Specification (IDS). Within this framework, LOIN governs the relevance and granularity of information, while IFC and IDS ensure interoperability, data exchange, and conformity checking. The methodology is applied to a Moroccan heritage case study focusing on the documentation and management of building pathologies, including cracks, humidity, capillary rise, and material degradation. The results demonstrate that the proposed approach overcomes the limitations of LOD by enabling requirement-driven information management, thereby improving pathology documentation and supporting informed decision-making for cultural heritage conservation. Full article

A large number of low-resistivity and low-permeability reservoirs have been discovered in the deep Paleogene strata of the Wenchang Sag. These reservoirs are characterized by complex porosity–permeability relationships and difficulties in fluid property identification, which restrict the progress of exploration and development operations. However, existing reservoir studies mostly focus on either low-permeability or low-resistivity reservoirs, with relatively few investigations targeting this specific type. Using petrological analysis and physical property testing as the main methods, combined with sedimentary and diagenetic studies, this paper examines the characteristics and genesis of low-resistivity and low-permeability reservoirs in the Paleogene of the Wenchang Sag. The results show that the Paleogene reservoirs are dominated by lithic quartz sandstones, with secondary pores as the main reservoir space, consisting of medium–small pores and fine throats. Samples of the same grain size exhibit a favorable porosity–permeability correlation. Based on capillary pressure curve morphology, the reservoirs can be classified into three types: high mercury intrusion saturation with low displacement pressure, medium mercury intrusion saturation with medium displacement pressure, and medium mercury intrusion saturation with medium–high displacement pressure. The low porosity and permeability are mainly attributed to the fact that the reservoir rocks are primarily deposited in near-source braided fluvial delta underwater distributary channels, resulting in low compositional and textural maturity of sandstones. Strong compaction resistance leads to a significant reduction in primary pores during burial, and intergranular cement filling further deteriorates physical properties. On the other hand, rapid lithological changes and complex pore structures give rise to abundant isolated pores and poor connectivity, leading to high irreducible water saturation. Coupled with high formation water salinity, these factors collectively give rise to low-resistivity reservoirs in the study area. This study clarifies the formation mechanism of low-permeability and low-resistivity reservoirs in the Paleogene of the Wenchang Sag, providing guidance for reservoir evaluation in subsequent oil and gas exploration and serving as a reference for analogous areas. Full article

The urgent global need for sustainable infrastructure drives the demand for high-value buildings and waste removal. This paper studies the feasibility of using recycled foam concrete aggregate (FCA) as a substitute for natural coarse aggregate (NCA) in concrete and studies its impact on rheology, mechanical degradation, shear resistance, and the full-range replacement ratio (0–100). The experimental results show that the monotonic change in the workability of fresh concrete determines the lubrication threshold at 60% replacement, which is driven by the volume proportion effect. Beyond this value, capillary suction dominates, and the viscosity rises rapidly. From a mechanical perspective, the porous structure of FCA is conducive to “internal curing” so that moisture is released from the drying interface, but it also becomes a source of defects that change the fault topology. Specifically, the critical transition of the shear failure mode shifts from the debonding of the interface to the crushing of the cross-particle aggregate. At this time, the shear capacity decreases substantially, experiencing a reduction of 71.8% when completely replaced. There is a strong correlation between ultrasonic pulse velocity (UPV), rebound number, and compressive strength, and a multivariate nonlinear regression model (R² > 0.85) with non-destructive strength prediction is ultimately obtained. Based on the balance between mechanical capacity and resource cyclability, an optimal alternative zone of 20% to 40% is proposed. This work not only provides a mechanism for multi-scale coupling between pore structure and structural properties but also provides a data-driven method for the safety assessment of lightweight recycled aggregate concrete (RAC). Full article

The Qianlong Stone Classics are the largest and best-preserved ensemble of officially commissioned stone inscriptions of Confucian classics extant, yet their stele bases are currently threatened by salt efflorescence. Fluctuations in ambient temperature and humidity contribute significantly to this deterioration. Taking Stele 17 as a representative case, this study assesses the risks of surface condensation and moisture-induced salt phase transitions through integrated temperature–humidity monitoring, infrared thermography, and soluble salt analysis. The risk of condensation remains low under typical conditions, as the stele base surface temperature exceeds the dew point by at least 0.5 °C. However, risks of salt deliquescence and hydration are substantial. The stone surface contains elevated levels of soluble salts, including four highly soluble species (sodium sulfate, calcium nitrate, sodium nitrate, and sodium chloride) and one moderately soluble species (calcium sulfate). Deliquescence phase transition humidities are approximately 50.5% for calcium nitrate, 74.3% for sodium nitrate, and 75.4% for sodium chloride, while sodium sulfate exhibits a hydration phase transition near 81%. Exhibition Hall humidity fluctuates around these critical thresholds, driving repeated dissolution–crystallization and hydration–dehydration cycles that progressively erode the stone microstructure. These hygrothermal cycles exhibit pronounced seasonal patterns, with frequent air-conditioning operation in summer amplifying thermal and humidity impacts. This study elucidates an air-moisture-driven salt deterioration mechanism distinct from classical capillary rise, clarifies the persistent progression of efflorescence in transitional seasons, and provides a scientific basis for optimizing environmental control strategies. Full article

Soil salinity poses a major challenge to agricultural productivity, especially threatening food security in arid and semi-arid areas. Traditional soil reclamation methods, such as leaching, chemical amendments, and drainage engineering, usually need large amounts of water, involve high costs, and can lead to environmental problems. This review compiles existing knowledge on innovative strategies for managing saline soils, focusing on buried interlayer systems that use materials like straw, sand, gravel–sand mixtures, and biochar. These interlayers improve soil hydraulic properties by preventing capillary rise, encouraging salt leaching, and reducing surface salt buildup. Biochar stands out as a particularly useful material because of its stability, large surface area, porosity, and high cation exchange capacity. These features help improve soil structure, increase water retention, and effectively retain sodium. Evidence from lab and field tests shows that buried biochar layers can stop salt from moving upward, aid in desalinating the root zone, and boost crop yields. While straw and sand interlayers show potential in reducing salinity, biochar is noted for its multifunctionality and long-term effectiveness in addressing salinity problems. The success of buried biochar systems depends on several factors, including the properties of the biochar, how much is used, how deep it is buried, and the specific soil and climate conditions. This review highlights how these systems work, compares their performance, and points out research gaps, advocating for their potential as a sustainable, resource-efficient way to manage salinity and improve soil health over the long term. A substantial proportion of the existing evidence is derived from controlled laboratory studies, and the buried biochar layer approach remains an emerging technique that requires further validation under field conditions. Still, significant knowledge gaps persist regarding long-term performance and water-salt dynamics, while site-specific soil variability and scalability challenges may limit the effective implementation of biochar interlayer systems under field conditions. Full article

Diabetic retinopathy (DR) is more than a capillary disorder. Diabetes affects neurons, glial cells, vascular cells, and immune signals within the retinal neurovascular unit (NVU). Retinal neurovascular coupling (NVC) is a useful functional marker of NVU integrity because it reflects the rise in local blood flow that follows neural activity. Many human flicker-light studies report smaller vessel dilation or weaker flow responses in diabetes. This finding can appear even in patients without clear fundus lesions. When NVC is reduced, retinal tissue may receive less oxygen. Lower oxygen delivery can raise oxidative stress and promote inflammation. These changes can then worsen vascular injury. This review describes key NVC pathways and diabetes-related NVU changes in Müller glia, astrocytes, microglia, pericytes, and endothelial cells. The review highlights sympathetic activation as a common stress signal. Pain, anxiety, perioperative stress, and sleep loss can increase sympathetic activity and circulating catecholamines. In the diabetic retina, vascular reserve is often limited. Under these conditions, catecholamines can increase mural cell constriction, reduce nitric oxide (NO)-dependent relaxation, and increase endothelial activation and barrier strain. These effects can shift the baseline state of glial and immune cells and further weaken NVC. The review also summarizes translational tools that can test these links. These tools include heart rate variability, standardized NVC protocols with diameter and flow measures, and retinal organoid and organ-on-a-chip platforms with controlled adrenergic exposure. The review discusses perioperative care packages that reduce stress responses, protect sleep, and manage glucose as practical ways to support retinal microcirculation. More longitudinal human studies are still needed. Retina-specific perioperative endpoints are also needed to clarify causality and to guide intervention trials. Full article

Tight sandstone reservoirs are characterized by highly heterogeneous pore structures, in which multiscale pore–throat systems jointly control the shapes of capillary pressure curves and relative permeability, thereby exerting a fundamental influence on water production behavior and the overall development performance of gas reservoirs. The Ordos Basin is generally characterized by the development of tight sandstone. The tight sandstones exhibit porosities of 2–13% and permeabilities of 0.01–10 × 10⁻³ μm². To quantitatively elucidate the controlling mechanisms of multiscale pore structure on capillary pressure curve morphology and relative permeability, this study systematically investigates the fractal and multifractal characteristics of pore structures in tight sandstones based on high-pressure mercury intrusion (MICP) and nuclear magnetic resonance (NMR) experimental data, and establishes a quantitative relationship between fractal parameters and the capillary pressure curve shape parameter λ. First, capillary pressure curves were fitted using the Brooks–Corey model within the effective saturation interval to extract the shape parameter λ, which characterizes the concentration degree of pore-size distribution and the drainage behavior. Subsequently, based on NMR T₂ spectra, the small-pore fractal dimension D₁, large-pore fractal dimension D₂, and the multifractal singularity spectrum width Δα were extracted to quantitatively describe the geometric complexity of pore structures at different scales. On this basis, the correlations between λ and D₁, D₂, and Δα were systematically analyzed, and the predictive performance of λ under different parameter combinations was compared. The results indicate that: (1) the pore structures of tight sandstones exhibit pronounced fractal and multifractal characteristics at the NMR T₂ scale, with significant differences among samples; (2) λ shows an overall negative correlation with fractal parameters, among which the correlations with the large-pore fractal dimension D₂ and the multifractal spectrum width Δα are the most significant; (3) compared with models using a single fractal dimension, the multiparameter model incorporating Δα provides a more comprehensive characterization of multiscale pore heterogeneity, leading to a substantial improvement in the accuracy and stability of λ prediction; and (4) λ exerts a clear control on the shape of relative permeability curves, where a larger λ corresponds to earlier initiation and forward-shifted rising segments of water-phase flow, while a smaller λ results in overall flatter relative permeability curves. From the perspectives of fractal and multifractal theory, this study establishes an intrinsic linkage among pore structure, capillary pressure curve shape parameters, and relative permeability, providing a novel quantitative framework for constraining relative permeability curve morphology in tight sandstones under conditions where systematic relative permeability experiments are unavailable. Full article

Nature-based solutions (NBSs), such as green roofs, are among the most effective ways to manage urban stormwater, improve building energy efficiency, and adapt to climate change. However, conventional green roofs confront several restrictions related to stormwater drainage, retention capacity, irrigation demand, and pressure on urban water networks during dry periods. This study proposes and experimentally validates a novel system applicable to green roofs and other NBS, including streetside planting systems and vegetated sports grounds. The novelty of the proposed system lies in a double-layer design, the integration of filters within soil substrate to enhance short-term stormwater retention and controlled drainage, and passive subsurface capillary irrigation with cords to improve irrigation efficiency. Infiltration tests showed that filter hydraulic conductivity strongly depends on pore size, with measured infiltration rates ranging from 0.01 mm/min (ceramic, 0.1 μm) to 20 mm/min (polypropylene, 50 μm). The results showed that filter material and pore size significantly influence infiltration behaviour and short-term storage capacity. When integrated with the soil substrate, the combined system exhibited infiltration rates of 0.8–2.0 mm/min, decreasing as hydraulic head declined. Capillary rise experiments demonstrated a maximum vertical rise of 32 cm and horizontal rise of 39 cm for polyester cords (6 mm width), confirming the feasibility of passive subsurface irrigation through stored runoff reuse without external energy. The experiments were conducted at a laboratory scale (25 × 25 cm) as a proof-of-concept validation. Finally, the study results demonstrate the feasibility of the proposed system as a multifunctional NBS solution that enhances stormwater retention while enabling passive irrigation using retained runoff. Full article

To meet the requirements of high-efficiency thermal management without external power in long-distance and distributed multi-heat source scenarios, this paper proposes a dual compensation chamber multi-evaporator loop heat pipe system (DCCME-LHP). The system uses a capillary pump to provide capillary driving force, and through the step-by-step advancement of multiple condenser-evaporator combination, it achieves heat transfer and long-distance transportation among multi-heat sources. The experimental system investigates the effects of working fluid charge ratio, time interval, and heat load on the system’s hydrodynamic stability and heat transfer limit. The results show the optimal comprehensive performance of startup and steady state can be achieved with the charge ratio of 75% and a time interval of 8–10 min. The system operates stably under a total heat load of 270 W (90 W for the capillary pump and 60 W for each of the three evaporators). When the heat load of a single-stage evaporator rises to 70 W, the system enters the operation failure zone, and the steady-state temperature plateau jumps. This study provides a theoretical basis and experimental support for the design and stable operation strategy of long-distance multi-heat source thermal control systems. Full article

The wettability of a carbon fiber surface is an important factor that determines the strength of its bonding with matrices, and hence, an optimized criterion is required to accurately measure the wettability. In this study, the Washburn capillary rise method was used to select the capillary constant with the minimal deviation among various carbon fiber lengths, and it was applied to determine the contact angle and surface free energy of each carbon fiber length according to the wetting liquid. The smallest deviation in the contact angle was observed for a carbon fiber length of 2 inches, and this observation was attributed to the pores in the fibers and the orientation of the carbon fibers packed inside the column. By reducing the number of pores and achieving favorable packing, the surface free energy of carbon fibers can be measured with a high degree of accuracy, contributing to an improved understanding of fiber–matrix interactions. Full article