Search Results (1,610)

More and more urban underpass tunnels are being constructed to alleviate traffic congestion; however, for this type of underground structure, the soil–structure interaction mechanisms under earthquake loading remain unclear, and dedicated advice and guidance for their seismic design are still lacking. This paper endeavors to investigate the dynamic interaction mechanisms of an underpass tunnel and surrounding soft ground using the finite element (FE) method. Firstly, the accuracy of the FE model in reproducing seismic responses of the layered half-space is validated by comparison with results of equivalent linear one-dimensional site response. Then, the dynamic response characteristics of 3D boat-shaped excavation are analyzed to determine the influence of potential local site amplification on the underpass tunnel. Finally, seismic behaviors of open and buried sections of the underpass tunnel are investigated in detail. The results show that under high-intensity rare earthquakes, severe damage occurs at the ceiling slab near the longitudinal beam and at the base of the side wall of the tunnel’s buried section; seismic underpass–site interactions might be influenced the most by the local topography effect of the 3D boat-shaped excavation, as well as a sudden stiffness change between the open and buried sections. Full article

Background: Smart urban logistics has emerged as a key element of sustainable city development, with direct effects on economic performance, environmental quality, and urban livability. Issues with traffic, pollutants, infrastructure strain, and last-mile delivery efficiency have become more pressing due to rapid urbanization and the expansion of e-commerce. In this regard, underground or enclosed corridor-based tube-based freight transit systems have surfaced as a viable smart infrastructure option for automated and low-impact commodities delivery. Methods: This study adopts an analytical literature review complemented by a structured case study analysis to examine the potential role of tube-based freight transport systems in future urban logistics. Key technological concepts, including pneumatic tubes, automated capsule transport, and integration with digital platforms, the Physical Internet, and smart city management systems, are examined through a structured analytical review of the literature. Results: The outcome of the reviewed studies indicates that tube-based systems can contribute to congestion alleviation, emission reduction, and improved delivery reliability by shifting selected freight flows away from surface transport networks. However, governance frameworks, infrastructure integration, and institutional coordination mechanisms continue to have a significant impact on claimed performance outcomes. Conclusions: Tube-based freight systems represent a promising but conditional pathway toward smarter and more sustainable urban logistics. Their large-scale deployment is forced by high capital costs, standardization challenges, regulatory uncertainty, and social acceptance issues. Coordinated investment plans, encouraging legal frameworks, and integrated urban planning techniques in line with smart city goals are needed to overcome these obstacles. Full article

To achieve high-precision and real-time quantitative evaluation of gas production in underground gas storage (UGS), this study focused on 11 typical injection-production wells in the Sudong UGS group. To address the common challenges posed by deviated well structures and complex wellbore temperature field distributions, a gas flow-rate calculation method based on Distributed Temperature-Sensing (DTS) data was developed. By standardizing the processing of multi-well temperature data, deviated wellbore trajectories were straightened to convert measured depth (MD) to true vertical depth (TVD). By incorporating a geothermal correction mechanism, temperature anomalies closely related to fluid flow were extracted, and a spatially unified temperature field model was constructed. On this basis, a “Dual-Point Temperature Difference Method” is proposed as a novel approach for single-well production evaluation. Based on thermodynamic phenomena such as the Joule–Thomson effect and expansion cooling, two critical sensing points, upstream and downstream of the production layer, were selected, with their temperature anomaly difference (∆T) serving as a sensitive indicator of flow rate variations. Combined with downhole pressure parameters and synchronized wellhead metering data, a nonlinear quantitative relationship model between ∆T and gas production rate Q was established, enabling accurate conversion of wellbore thermal response to macroscopic flow parameters. The results indicated that the gas production rates calculated by this method align well with traditional wellhead metering data, with errors maintained within engineering tolerances. Notably, the method demonstrates higher reliability and corrective capabilities in wells with drifting or faulty meters. This achievement breaks the reliance of traditional methods on specific layers or mechanical meters. It enables the effective application of multi-well, full-section, and non-contact temperature data in gas volume assessment. This research provides new technical support for dynamic monitoring, efficient operation, and remaining gas evaluation of UGS, offering significant prospects for engineering applications. Full article

Tunnel linings are critical structural components of underground infrastructure, and their seismic performance plays a decisive role in maintaining the serviceability and safety of tunnels. Under dynamic loading, excessive deformation and damage of the lining may reduce the effective cross-sectional capacity and threaten the minimum safety clearance required for tunnel operation. Therefore, it is essential to investigate the deformation behavior and failure mechanisms of tunnel linings subjected to seismic excitation and to evaluate the effectiveness of reinforcement measures. In this study, a coupled numerical framework combining the finite difference method (FLAC3D) and the discrete element method (PFC3D) is developed to analyze the dynamic response of tunnel lining systems. The surrounding rock mass is modeled in FLAC3D to simulate stress wave propagation and global deformation, while the tunnel lining is represented in PFC3D using bonded particles to capture crack initiation, propagation, and post-peak failure behavior. The proposed FLAC3D–PFC3D coupled approach provides an effective tool for evaluating the seismic performance of reinforced tunnel linings and offers a practical basis for the design and assessment of seismic strengthening measures in underground engineering. Full article

The structural integrity of isolation dams in deep coal mines is critical to preventing underground disasters, particularly those involving water and waste-mixture inrushes. This study presents a forensic root-cause analysis, using reverse-engineering techniques, of a specific isolation-dam rupture to determine the failure mechanism under complex stress conditions and limited data availability. A hybrid investigative methodology was employed, combining sequential post-failure documentation analysis with physical-scale modelling and numerical simulations to reconstruct a deadly disaster for criminal investigation purposes. A 1:5 scale physical model of the excavation and dam was constructed using original construction materials to test the structure’s resistance to hydrostatic pressure. The experimental results demonstrated that the dam maintained integrity under static hydraulic loads representative of real-world conditions, with only minor seepage (“sweating”) and no structural failure over a 7-day monitoring period. To investigate external geomechanical factors, Finite Element Method (FEM) simulations were conducted using ANSYS software. The numerical analysis evaluated the effects of rock mass pressure and convergence on the dam’s stability. The results indicate that while the dam was designed to withstand significant hydraulic head, the failure was precipitated by excessive rock mass pressure at a depth of around 600 m, which induced critical stress concentrations exceeding the masonry’s load-bearing capacity. This study confirms that the dynamic rupture was driven by unforeseen geomechanical forces rather than hydrostatic overload alone, highlighting the necessity of considering rock mass–structure interaction in the safety assessment of underground isolation barriers. This approach enables mutual verification of the results obtained and reduces the ambiguity of interpretation that often accompanies the analysis of accident events in underground mining. It also confirms the application of tested methodology for mining disaster reconstruction as proof at the stage of investigation and in the Court. Full article

To address the durability deficiencies and limited service life of concrete structures exposed to complex service environments such as chloride attack in marine and underground engineering, this study employs fly ash (FA) and ground granulated blast-furnace slag (GGBS), typical eco-friendly materials, as functional mineral admixtures to systematically investigate the effects of their combined incorporation on the mechanical properties, durability, drying shrinkage, and microstructural characteristics of concrete. The objective is to develop a concrete material that achieves high durability while maintaining structural safety and service performance, with the additional benefit of improved resource utilization efficiency. Single-factor tests were first conducted to determine the sensitivity ranges of FA and GGBS within 10–30% for slump, compressive strength, chloride migration coefficient (RCM), and drying shrinkage. Subsequently, response surface methodology (RSM) was employed to establish quadratic regression models using FA and GGBS as independent variables and compressive strength, RCM, and drying shrinkage as response indicators. The models exhibited high fitting accuracy, and their reliability was validated through analysis of variance (ANOVA), residual analysis, and predictive performance indices. Multi-objective optimization based on the desirability function identified the optimal mix proportion as FA = 14.8% and SL = 29.3%, yielding predicted values of 56.2 MPa for 28-day compressive strength, 6.03 × 10⁻¹² m²/s for RCM, and 639 με for 90-day drying shrinkage. Microstructural analysis using SEM and MIP further revealed that the binary-blended system promotes the formation of a dense C–S–H/C–A–S–H gel network, refines pore-size distribution, and reduces pore connectivity, thereby improving long-term mechanical and durability performance. The findings provide quantitative guidance for designing high-durability, environmentally friendly concrete suitable for marine and underground engineering applications. Full article

The borehole-to-surface electromagnetic (BSEM) method is widely employed in oil and gas exploration and downhole monitoring. However, the strength of the ground observation signals of the BSEM method is affected by the metal steel casing in the well. To investigate the response characteristics of the BSEM method under metal casing conditions, this study performed three-dimensional BSEM forward modeling based on a cylindrical grid. The finite volume method was adopted to discretize and solve the governing equations of the electromagnetic field, and the cylindrical grid was partitioned in accordance with the axisymmetric geometric features of the wellbore-casing system, thereby achieving high-precision adaptation to the well structure. To explore the impact of metal casing in an alternating electromagnetic field, four typical models were established: a linear source, a long metal wire, a metal casing, and a casing with a cement sheath. The characteristics of ground signals under low-frequency alternating emission conditions were systematically studied. By comparing the simulation results with the 1D analytical solution, this method was verified to have high numerical accuracy, which can accurately reflect the responses of a metal casing and multiple media interfaces to the alternating electromagnetic field. Based on comparative analysis, the differences in underground electromagnetic field distributions among different source models and their applicable ranges were clarified, and the applicable scenarios and effective detection depths of different models in actual monitoring were explored. This research provides numerical simulation cases to investigate the role of metal casings in BSEM observations, and also lays a theoretical foundation for the interpretation of downhole electromagnetic data, which is of positive significance for improving the effect of applying BSEM technology in oil and gas exploration. Full article

The development of cement composites that simultaneously achieve high compressive strength and low density remains a fundamental scientific challenge, particularly because optimizing weight reduction often compromises mechanical performance under sustained high-pressure conditions. In modern construction—especially high-rise buildings, large-span structures, and underground projects—there is an urgent applied need for lightweight materials that can reduce structural self-weight, enhance seismic resilience, simplify foundation design, and improve construction efficiency without sacrificing load-bearing capacity or long-term durability. To address this dual problem, this study investigates high-pressure-resistant lightweight cement composites incorporating hollow glass microspheres (HGMSs) of three different particle sizes as functional fillers, modified with isobutyl triethoxy silane (IBTES) to strengthen interfacial bonding. Ten formulations with varying HGMS types and dosages (5%, 10%, and 15% by volume) were systematically evaluated through creep tests, uniaxial compression experiments, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The scientific results demonstrate marked qualitative and quantitative improvements: the optimal formulation (25 μm HGMS at 5% dosage) exhibited a 22.01% reduction in creep deformation and a 67.85% increase in compressive strength compared to plain cement, while bulk density was reduced by 8.8–19.0%. Enhanced hydration was confirmed by a 23.6% reduction in residual Ca(OH)₂ content and a 31.2% increase in chemically bound water, indicating more complete formation of calcium silicate hydrate (C–S–H) gel. Energy evolution analysis revealed a prolonged elastic energy accumulation stage (increasing from 56% to 95% of total compression duration), signifying a transition toward quasi-ductile failure behavior. From an applied perspective, these quantitative enhancements translate directly into practical construction benefits: the 8.8–19.0% density reduction enables lighter structural components, easing transportation and installation; the 67.85% higher compressive strength ensures reliable performance in high-pressure environments; and the 22.01% lower creep deformation guarantees long-term dimensional stability. Collectively, these findings confirm that the HGMS-IBTES-modified composite offers a scalable, high-performance solution for advanced construction applications where both weight reduction and superior pressure resistance are critical. Full article

Variations in the groundwater chemical environment are a critical factor affecting the mechanical property degradation and structural alteration of coal measure strata. Addressing the engineering challenges commonly encountered in coal mining areas of Northwest China, where groundwater with varying pH leads to difficulties in controlling surrounding rock in underground spaces, this study established a comprehensive experimental methodology integrating mechanical loading, nuclear magnetic resonance (NMR) quantitative pore analysis, and scanning electron microscopy (SEM) microstructural characterization. The study revealed the mechanical degradation mechanisms and microstructural evolution characteristics of coal measure coarse sandstone under groundwater environments with different pH values (6–10). With prolonged immersion time, the peak strength and elastic modulus of the coarse sandstone exhibited exponential decay across all pH environments. NMR analysis revealed that the porosity evolved through a path of “increase–decrease–re-increase,” while the macroscopic mechanical failure mode shifted from brittle to brittle-ductile and finally to ductile characteristics. Micropores continuously transformed into medium and large pores, and the macroscopic failure mode exhibited a transition from brittle to brittle-ductile. The findings indicate that groundwater with varying acidity/alkalinity systematically alters the integrity and load-bearing capacity of coal measure coarse sandstone through the complex mechanism of “mineral dissolution (acidic H⁺ corrosion, alkaline OH⁻ hydrolysis)—structural damage—pore/fracture evolution—mechanical degradation.” This mechanism not only reveals the essence of progressive rock damage in weak acid to moderately strong alkaline environments but also provides important insights for the integrity, sealing capacity, and permeability modification of various underground engineering applications, such as CO₂ geological storage, unconventional natural gas development, and underground space utilization. Full article

The cemented backfill mining method has progressively become the preferred mining technique for underground metal extraction due to its advantages such as environmental friendliness, high efficiency, and economic viability. The mechanical properties of the backfill are fundamental to ensuring effective strata control and structural stability within backfilled stopes. Hydration reaction serves as the critical factor in the formation of backfill mechanical properties, while temperature influences these properties by governing the progression of the hydration process. This paper systematically reviews five fundamental hydration models (NG, CEMHYD 3D, Krstulovic-Dabic, Heat of Hydration and Thermodynamic Phase Equilibrium), critically analyzing their limitations in predicting performance under extreme geothermal and cryogenic conditions. Distinct from previous reviews, this study reveals the nonlinear mapping between dynamic temperature fields and microstructural evolution. Furthermore, it incorporates recent advancements in multi-field coupling mechanisms and AI-driven strength prediction. Ultimately, this study establishes that with the emergence of advanced modeling software and machine learning algorithms, the investigation of temperature effects on backfill is poised to move toward a more comprehensive, intelligent, and refined direction. Full article

Reliable vision-based sensing of protective equipment wearing compliance is essential for safety monitoring in underground mining environments, where complex lighting conditions, similar background textures, and large variations in the scale of wearable items significantly degrade detection performance. To address these challenges, this study proposes a vision-based protective equipment wearing compliance detection method for underground personnel based on CGALS-YOLO. Traditional object detection models often introduce substantial redundant background information during multi-scale feature fusion, which weakens the perception of key wearing regions, particularly for small-scale targets. To alleviate this issue, a content-guided feature fusion (CGAFusion) module is incorporated into the neck of the YOLOv8 network, enabling adaptive fusion of same-scale multi-path features through the collaborative effects of channel, spatial, and pixel attention mechanisms. This design enhances target-related feature representation while suppressing background interference in complex underground scenes. Furthermore, to reduce parameter redundancy and improve cross-scale discrimination consistency in the detection head, a lightweight shared convolution detection (LSCD) structure is introduced. By employing cross-scale shared convolution parameters, group normalization, and scale-adaptive regression, the proposed model achieves a parameter reduction of approximately 23.9% while lowering computational complexity and maintaining stable multi-scale detection performance. Experimental results on an underground protective equipment wearing compliance dataset demonstrate that CGALS-YOLO improves detection accuracy by approximately 4.6% and recall by 3.1% compared with the baseline YOLOv8n, achieving an mAP@0.5 of 89.4%. These results validate the effectiveness and practical applicability of the proposed method for real-time vision-based safety monitoring in underground environments. Full article

The mechanical durability of gangue-based roadway shotcrete material (GRSM) in aqueous environments was systematically investigated by evaluating the effects of immersion duration, dry–wet cycles, and pH variations on its uniaxial compressive strength (UCS). The results indicate that prolonged immersion significantly degrades the mechanical performance of GRSM. After 28 days of immersion, the UCS decreased by 8.68 MPa (22%) compared with specimens under standard curing conditions. In contrast, limited dry–wet cycling (up to two cycles) enhanced the UCS to 36.05 MPa by promoting continued hydration and pore refinement, whereas additional cycling led to progressive deterioration. GRSM exhibited pronounced pH sensitivity: acidic environments induced the most severe strength loss, followed by alkaline conditions, whereas neutral to weakly alkaline environments (pH 8–12) resulted in relatively stable mechanical performance. Mercury intrusion porosimetry (MIP) confirmed that pore structure evolution governed strength variation, with acidic exposure and dry–wet cycles producing the greatest increases in porosity. Mechanically activated gangue (MA-gangue) was prepared by ball milling and partially substituted for cement. Although MA-GRSM exhibited lower UCS than conventional GRSM under all conditions, both materials demonstrated similar environmental response patterns. These findings elucidate the coupled physicochemical mechanisms governing the durability of gangue-based shotcrete materials in underground water-bearing environments. Full article

Railway transport is increasingly promoted as a sustainable and low-carbon mode of transportation. However, track-induced vibration propagation remains a significant challenge, particularly in metro systems situated near residential areas, where vibrations can transmit through the infrastructure into nearby buildings, disturbing residents and damaging structures. This study aimed to evaluate the cause of the significantly different vibration impact on nearby buildings caused by two nominally identical adjacent slab tracks on a metro line in Austria. Controlled weight drop tests were carried out in both track directions, and accelerations were measured to characterize wave transmission and energy dissipation. The data were processed using frequency response functions and Short-Time Fourier Transform to extract time–frequency signatures, modal parameters, and propagation delays. A three-dimensional finite element model of the railway superstructure was then calibrated against the experimental modal properties and transfer functions and used to simulate cracking or stiffness loss in the sleeper–slab region. The simulations reproduced the observed increase in slab acceleration and underground strain energy, linking the anomalous vibration transmission to hidden stiffness loss rather than to global design differences. Overall, the study demonstrates that combining impact testing, advanced signal processing, and calibrated finite element modelling provides an effective framework for diagnosing track defects and guiding the design and maintenance of more sustainable, low-vibration urban rail infrastructure. Full article

Historical water management infrastructures, often comprising underground environments, represent a significant example of the interplay between built heritage and the natural substrate. This study proposes an interdisciplinary, integrated and multi-scalar investigative methodology for such structures. Through the analysis of the case study of Palombaro Purgatoro Vecchio, a large historical public water cistern located in Matera in Italy, this paper presents a rigorous methodology replicable in different contexts. Bibliographic and archival research establish the knowledge base regarding the structure’s historical evolution; territorial and hydromorphic analyses, supported by GIS, highlight the dynamics of the surrounding watersheds. Meanwhile, a digital survey integrating SLAM and photogrammetry provides geometric-dimensional data, serving as the foundation for analysing construction techniques and materials. The selection of accessible and manageable technologies promotes a practical, replicable investigative methodology aimed at the protection, comprehension, enhancement and dissemination of water UBH. Full article

Ensuring the stability of the surrounding rock is the primary objective in the construction of an underground powerhouse at a hydropower station. Real-time monitoring, stability assessment, and evolutionary trend prediction of surrounding rock deformation and support structure stress are essential for maintaining rock mass stability. Using safety monitoring data and numerical simulation, the evolutionary behaviour of surrounding rock deformation and rock bolt stress during construction of the Kala Hydropower Station underground powerhouse was analysed. Surrounding rock stability and its future state were evaluated. Deformation in the first to third layers was mainly controlled by excavation disturbance and local geological conditions. The crown within the influence zone of the F152 fault exhibited the maximum deformation of 14.60 mm, whereas deformation in other areas was relatively small. Surrounding rock deformation in the cavern remained safe. Rock bolt stress showed spatio-temporal consistency with deformation, with maximum values concentrated in fault-cutting areas. The proportion of anchor bolts with stress below 200 MPa was 96.3%, indicating that the overall stress on the rock bolts in the cavern was in a safe state. Numerical simulation results predict that significant deformation during subsequent excavation and support will be concentrated between faults F152 and F75. The maximum surrounding rock deformation may occur in the fifth-layer sidewall affected by the F75 fault. Relatively high rock bolt stress is expected in the fifth to seventh layer sidewalls influenced by the F152 fault. This study identifies potential locations and development characteristics of stability deterioration during subsequent construction, providing guidance for construction design. The results serve as a reference for surrounding rock stability evaluation and prediction in similar underground powerhouse projects. Full article