Search Results (339)

China has entered a period of urban renewal, with the focus shifting from large-scale incremental construction to both upgrading existing building quality and adjusting incremental structures. There are three main types of urban renewal: demolition and reconstruction, comprehensive improvement, and organic renewal. The latter systematically optimizes and enhances urban functions, spaces, and culture through gradual renovation methods and is, therefore, suitable for use in ancient cities. To promote organic renewal, the problem of limited space resources must first be addressed, which can be resolved to a certain extent by the moderate development of underground spaces; preliminary evaluations of the development potential are also required. In consideration of the demands of organic renewal, we constructed a novel indicator system for evaluating underground space development potential (USDP) in ancient cities that assesses two dimensions: development demand and development suitability. A multi-factor comprehensive evaluation method was adopted to quantify the indicators of USDP, taking Shaoxing Ancient City (SAC) as the case study. According to the USDP evaluation, SAC can be divided into four kinds of areas: high-potential, general-potential, low-potential, and prohibited development areas. High-potential areas accounted for 16.38% of the total evaluation area and were primarily concentrated in or near key locations: train transit stations (Shaoxing Railway Station), public service facilities, evacuated land, and cultural and tourism facilities around historic districts (Shusheng Guli Historical and Cultural Street). The proposed development strategies for these areas included the interconnection of metro stations, redevelopment of relocation-related and vacated land, construction of underground cultural corridors, and supplementation of parking facilities. For developed underground spaces with low utilization efficiency, functional renewal and management improvement measures were put forward. Our method of evaluating the USDP of ancient cities and the strategies proposed to optimize the utilization of underground space can provide reference examples for SAC and other similar ancient cities. Full article

This study investigates underground heat sources and develops effective strategies for mitigating heat hazards in coal mines, with a focus on the design and optimization of cooling systems. Using the 3107 fully mechanized mining face of Menkeqing Coal Mine as a case study, geological survey data and in situ measurements were combined to evaluate the severity of thermal hazards. Thermodynamic and heat transfer models were applied to quantify heat dissipation from multiple sources. Computational fluid dynamics (CFD) simulations, based on data-driven modeling and geometric reconstruction, tested different equipment layouts and spacing configurations to identify optimal cooling schemes. Field implementation of the designed cooling system confirmed its effectiveness, offering practical guidance for improving heat hazard control and cooling system optimization in deep coal mines. Full article

The adverse propagation environment in underground coal mine tunnels caused by enclosed spaces, rough surfaces, and dense scatterers severely degrades reliable wireless signal transmission, which further impedes the deployment of IoT applications such as gas monitors and personnel positioning terminals. However, the conventional power enhancement solutions are infeasible for the underground coal mine scenario due to strict explosion-proof safety regulations and battery-powered IoT devices. To address this challenge, we propose singular value decomposition-based Lagrangian optimization (SVD-LOP) to minimize transmit power at the mining base station (MBS) for IRS-assisted coal mine wireless communication systems. In particular, we first establish a three-dimensional twin cluster geometry-based stochastic model (3D-TCGBSM) to accurately characterize the underground coal mine channel. On this basis, we formulate the MBS transmit power minimization problem constrained by user signal-to-noise ratio (SNR) target and IRS phase shifts. To solve this non-convex problem, we propose the SVD-LOP algorithm that performs SVD on the channel matrix to decouple the complex channel coupling and introduces the Lagrange multipliers. Furthermore, we develop a low-complexity successive convex approximation (LC-SCA) algorithm to reduce computational complexity, which constructs a convex approximation of the objective function based on a first-order Taylor expansion and enables suboptimal solutions. Simulation results demonstrate that the proposed SVD-LOP and LC-SCA algorithms achieve transmit power peaks of $20.8\mathrm{dBm}$ and $21.4\mathrm{dBm}$, respectively, which are slightly lower than the $21.8\mathrm{dBm}$ observed for the SDR algorithm. It is evident that these algorithms remain well below the explosion-proof safety threshold, which achieves significant power reduction. However, computational complexity analysis reveals that the proposed SVD-LOP and LC-SCA algorithms achieve $\mathcal{O}\left(N^3\right)$ and $\mathcal{O}\left(N^2\right)$ respectively, which offers substantial reductions compared to the SDR algorithm’s $\mathcal{O}\left(N^7\right)$. Moreover, both proposed algorithms exhibit robust convergence across varying user SNR targets while maintaining stable performance gains under different tunnel roughness scenarios. Full article

To address the technical challenges in dynamic monitoring of grout diffusion patterns under complex geological conditions, in this study, a distributed parallel grouting monitoring system based on electrical resistivity tomography was developed. The system achieves three-dimensional visualization of grout propagation through hardware architecture innovation and the integration of inversion algorithms. At the hardware level, a cascadable distributed data acquisition terminal was designed, employing a dynamic optimization strategy for electrode combinations. This breakthrough overcomes traditional serial acquisition limitations. Algorithmically, a Bayesian estimation-based geological unit merging inversion model was proposed; it dynamically calculates merging thresholds through the noise posterior probability, achieving an improvement of more than 30% in the inversion boundary resolution compared with traditional least squares methods. Numerical simulations and physical experiments demonstrated that dipole arrays with 0.5 m electrode spacing exhibit optimal sensitivity to variations in grout resistivity, accurately capturing electrical response characteristics during diffusion. In practical roadbed grouting applications, the system yielded a grout diffusion radius showing only a 0.3 m deviation from the core sampling verification results, with three-dimensional imaging clearly depicting the diffusion morphology. This system provides reliable technical support for the precise control and quality assessment of underground engineering grouting processes. Full article

This paper presents a phase-based analysis of the spatial and architectural development of underground stations in the Warsaw Metro, focusing on 28 non-transfer stations constructed between 1983 and 2019. The research examines how design and functional solutions evolved over five construction phases in response to changing engineering methods, organizational frameworks, and urban contexts. A comparative analytical framework was developed, incorporating quantitative and qualitative parameters related to spatial layout, access schemes, and interior design features. The methodology combines archival documentation analysis, in situ field surveys, and typological classification. Findings reveal a clear trajectory from utilitarian, dual-purpose stations emphasizing structural durability and civil defense, toward more user-oriented designs prioritizing accessibility and intuitive navigation. Later phases show an expansion of multifunctional elements, including retail spaces, reflecting contemporary trends in metro station design. It contributes to a broader understanding of how adaptive design strategies enable metro infrastructure to respond to evolving urban needs and challenges, highlighting the importance of contextual integration for future metro developments. Full article

Accurately identifying surrounding rock failure modes and designing matching support systems are critical to the safety of deep-earth and underground space engineering. We develop a graded classification scheme based on the rock strength-to-stress ratio and the Stress Reduction Factor (SRF) to quantify failure types and guide support design. Within the convergence–confinement method (CCM) framework, we establish analytical models for shotcrete, rock bolts, steel arches, and composite support systems, enabling parameterized calculations of stiffness, load-bearing capacity, and equilibrium conditions. We conduct single-factor sensitivity analyses to reveal how the Geological Strength Index (GSI), burial depth (H), and equivalent tunnel radius (R₀) govern the evolution of surrounding rock pressure and deformation. We propose targeted reinforcement strategies that address large-deformation and high-stress instabilities in practice by linking observed or predicted failure modes to specific support schemes. A large-deformation case study verifies that the proposed parameterized design method accurately predicts the equilibrium support pressure and radial deformation, and the designed support scheme markedly reduces convergence. Accordingly, this study provides a practical tool for tunnel support parameter design and an analytical platform for safe, reliable, and efficient decision making for initial support. Full article

The construction of urban underground space develops very fast, and tunnel intersection construction has become a common practice, attracting significant attention due to the associated deformation responses and risk control challenges. To systematically review the research landscape and cutting-edge developments in this field, this study conducts a comprehensive analysis based on 744 publications (1994–2025) from the Web of Science Core Collection using bibliometric methods. Firstly, through visual analyses of annual publication trends, journal distributions, and keyword co-occurrences, the study reveals the evolution and research hotspots of the past three decades. Subsequently, three core dimensions are explored in depth: deformation mechanisms and patterns, deformation analysis methods for ground and existing structures, and ground control and reinforcement techniques. The review highlights the following: (1) Research focus has shifted from single construction scenarios to the complex interactions among multiple tunnels, yet the cumulative deformation effects caused by repeated soil disturbances during sequential excavation remain inadequately understood. (2) The bidirectional coupling between existing tunnels and surrounding soil has become a major research focus and challenge. Particularly in the presence of high-stiffness structures, the “free-field” assumption in the commonly used two-stage method is being questioned, necessitating the development of more refined computational theories. (3) Optimization of construction schemes under complex conditions is key to disturbance control, but current research still lacks systematic multi-objective optimization approaches. In addition, this paper analyzes the current research status and future directions to enhance the deformation perception capability and control technologies in tunnel construction influence zones, thereby further improving the safety and intelligence level of tunnel construction. Full article

Pressure on fresh water resources has been aggravated in recent decades, basically due to population growth, rapid urbanization, and global warming. Integrated engineering solutions and the circular economy, considering the urban water cycle as a whole, are becoming fundamental, particularly in arid and semi-arid regions under permanent or recurrent hydric deficit. This study aims to develop and present an integrated engineering solution for water supply, wastewater collection, and treated wastewater reuse for landscape irrigation in a large, topographically complex, and arid to semi-arid coastal urban region at the south of Santiago Island, Cape Verde. The region is one of the driest and most arid of the Island, with a current average annual precipitation between about 100 and 200 mm, and has very limited underground water resources. The main study area, with about 600 ha, has altitudes ranging from values close to sea level up to about 115 m and has several topographic difficulties, including several relatively rugged zones. The devised water supply system considers four altimetric distribution levels, three main reservoirs connected to each other by a serial system of pipelines with successive pumping, a fourth downstream reservoir for pressure balance in one of the levels, and desalinated water as the source. The sanitary sewer pipes of the urbanizations drain to an interceptor system that operates predominantly in open channel flow in a closed pipe. The long interceptor crosses laterally along the coast several very dug valleys in the path to the Praia Wastewater Treatment Plant in the east, and requires several conduits working under pressure for the crossings, either lifting or governed by gravity. The under-pressure pipeline system of recycled water is partially forced and partially ruled by gravity and transports the treated wastewater from the plant in the opposite direction of the interceptor to a natural reservoir or lake located in the region of urbanizations and the main green spaces to be irrigated. The conceived design of the interceptor and recycled water pipeline minimizes the construction and operation costs, maximizing their hydraulic performance. Full article

As the global shift toward renewable energy accelerates, large-scale energy storage is essential to balance intermittent supply and growing demand. While conventional Pumped Hydro Storage remains dominant, Underground Pumped Hydro Storage (UPHS) offers a promising alternative, particularly in flat regions with ample subsurface space. Southern Ontario, Canada, underlain by thick salt formations and a history of salt mining, presents favorable conditions for UPHS development, yet relative studies remain limited. This work presents the first UPHS-specific geomechanical feasibility assessment in the Canadian Salina Group, introducing a paired-cavern layout tied to Units B and A2 and explicitly capturing both elasto-plastic and creep behavior. Using COMSOL Multiphysics 6.3, a three-dimensional numerical model was developed featuring two vertically separated cylindrical caverns located in Unit B and the lower part of Unit A2. A 24 h operating cycle was simulated over a 10-year period, incorporating elasto-plastic deformation and salt creep. Minimum working pressures were varied to evaluate long-term cavern stability. The results show that a minimum pressure of 0.3 σ_v balances structural integrity and operational efficiency, with creep strain and volumetric convergence remaining within engineering limits. Beyond previous salt-cavern studies focused on hydrogen or CAES, this study provides the first coupled elasto-plastic and creep simulation tailored to UPHS operations in bedded salt, establishing a safe operating-pressure guideline and offering site-relevant design insights for modular underground energy storage systems in sedimentary basins. Full article

This study explores the innovative use of post-mining subsurface voids by proposing a coal mine goaf-based underground reservoir energy storage system. By fully utilizing the geothermal potential and insulation properties of the mined-out coal seam, we established a finite element model considering the thermal-fluid coupling process to describe the seasonal energy storage process of the underground coal mine reservoir and analyzed the feasibility of achieving seasonal hot water storage through the underground reservoir, based on the model calculation results. By studying the temperature state of the hot water after the end of the heat storage process and the hot water output effect, the thermal energy storage and utilization potential of the underground reservoir were quantitatively analyzed using the factors of heat storage and heat production. The research results have clarified the feasibility of using coal mine underground reservoirs for cross-seasonal heat storage applications. The results of this study can provide new ideas for the utilization of coal mine goaf areas and underground goaf residual spaces and serve as a reference for the development and design of new energy storage facilities. Full article

The development of underground space, as a critical strategy for enhancing urban land use efficiency, requires careful consideration of the effects that new construction may have on existing foundations and structures to prevent safety hazards such as foundation damage. This paper investigates the influence of shield tunnel construction on the pile foundations of adjacent bridges. Based on the shield tunnel project intersecting the Haiqin Bridge pile foundations along a segment of the Guangzhou–Zhuhai Intercity Railway as a case study, a finite element (FE) model was developed. The validity of the numerical method was confirmed through comparison with existing model test results. Building on this foundation, this paper analyzed the impact patterns of shield tunnel construction on existing bridge pile foundations. Additionally, the model was employed to assess how variables such as the relative spatial positioning between the pile foundations and the tunnel, as well as the stiffness coefficient of the pile foundations, affect the structural response of the piles. The findings reveal that shield tunnel construction crossing adjacent bridge pile foundations induces bending deformation of the piles toward the tunnel side. The maximum horizontal displacement and internal forces occur near the tunnel axis, whereas the peak vertical displacement is observed at the pile head. The zone most affected by tunnel excavation extends approximately one tunnel diameter (1D) before and after the pile foundation location. The vertical relative position between the tunnel and pile foundation governs the relative displacement behavior between the pile and surrounding soil during excavation. Specifically, when the pile toe moves downward relative to the tunnel, the excavation’s influence on the pile foundation shifts from being dominated by negative skin friction and settlement to positive skin friction and rebound, leading to substantial changes in the force distribution and displacement patterns within the pile. As the horizontal clearance between the tunnel and pile foundation increases, the internal forces and displacements within the pile foundation progressively diminish and eventually stabilize. Furthermore, an increase in pile stiffness coefficient decreases the maximum pile displacement and increases internal forces in the pile shaft. Pile diameter has a greater influence than Young’s modulus, which exhibits a relatively minor effect. Full article

As renewable energy adoption intensifies, the demand for efficient and large-scale storage technologies such as compressed air energy storage (CAES) has become critical. Abandoned mine caverns present a cost-effective and sustainable option for CAES, enabling the reuse of existing underground spaces while minimizing new excavation. This study aims to quantitatively evaluate the stability of abandoned mine caverns for CAES under varying burial depths (150 m, 300 m, 450 m), cavern geometries (rectangular, trapezoidal, straight-wall arch, and circular) and sealing layer (steel, polymer) in Class II rock mass conditions. Finite element modelling employing ABAQUS was employed to simulate excavation, lining installation, and high-pressure gas storage, incorporating an analysis of surrounding rock strain, plastic zone development, and sealing layer performance. Results indicate that geometry and burial depth are dominant factors controlling deformation, with straight-wall arch caverns inducing relatively minimal disturbance to the ground surface after excavation and lining, and circular caverns showing the highest stability after pressurization. Steel sealing layers significantly improve structural performance, while polymer layers have a limited effect. The findings provide engineering guidance for the safe retrofit and design of CAES facilities in abandoned mines. Full article

Underground spaces hold significant potential for enhancing urban resilience against disasters, a key dimension of sustainable urban development. However, due to persistent associations of underground environments with negative psychological perceptions, these spaces—despite their superior protective advantages—are often overlooked as viable refuge options during emergencies. Guided by the theoretical framework of environmental psychology, this research focuses on underground parking garages in Hangzhou, China as its primary research object. The target participants are residents of Hangzhou aged 18–58 years (encompassing diverse occupations such as students, office workers, and service industry employees), who represent potential users of such spaces as refuges. To explore human behavioral patterns, psychological responses, and needs related to underground refuge spaces, we employed a two-phase methodology: first, a questionnaire survey to capture broader behavioral tendencies and subjective perceptions; complementing this, Virtual Reality (VR) experiments—a more immersive method—utilizing semantic analysis and the Likert scale to assess psychological indicators influenced by underground environments. The experimental data were analyzed via mean analysis, correlation analysis, and multiple linear regression analysis to identify the key environmental factors that influence psychological responses, as well as their optimal design parameters. These analyses reveal significant correlations between various environmental factors and psychological indicators. This research synthesizes individuals’ psychological tendencies in underground environments and proposes quantitative physical design guidelines to meet fundamental psychological needs. The findings provide theoretical and practical support for the design of underground space for refuge and the development of sustainable urban emergency shelter systems, thereby contributing to resilient and sustainable urban development. Full article

With rapid urbanization, the development of Urban Underground Space (UUS) has become essential to addressing various urban challenges. However, the accelerated expansion of UUS has also introduced problems such as duplicated infrastructure, functional deficiencies, and underutilized spaces. Fundamentally, these issues result from imbalances between the supply and demand for UUS, a phenomenon particularly pronounced in the central areas of major cities. Therefore, employing scientific methods to accurately identify and quantify these gaps is crucial. Leveraging recent advances in remote sensing and point-of-interest (POI) data, this study constructs a multi-source data-driven framework for assessing UUS supply–demand relationships, applied using a grid-based analysis to the central urban area of Nanjing. The results indicate that both the highest supply capacity and demand intensity occur in Xinjiekou Street in Nanjing’s Old City. Most high and medium–high supply and demand zones are concentrated in the Old City. Areas with prominent supply–demand conflicts are identified and classified into five types using the Jenks natural breaks method, further categorized into three groups based on their spatial characteristics, with tailored development strategies proposed accordingly. The proposed evaluation framework provides a robust scientific approach for analyzing UUS supply–demand relationships, offering significant theoretical and practical value for refined urban governance in large cities with extensive data availability. Full article

Urban tree planting on single-family-home lots represents a critical yet underexplored component of municipal greening strategies. This study examines residents’ perceptions of tree planting in Westpointe, a diverse neighborhood in Salt Lake City, Utah, as part of the city’s Reimagine Nature Public Lands Master Plan development effort. Through a mixed-methods approach combining qualitative interviews (n = 24) and a tree signup initiative extended to 86 residents, with 51 participating, this research explores the complex interplay of demographic, economic, social, and infrastructure factors influencing residents’ willingness to plant trees on single-family-home lots. The findings reveal significant variations based on gender, with women expressing more positive environmental and aesthetic motivations, while men focused on practical concerns including maintenance and property damage. Age emerged as another critical factor, with older adults (65+) expressing concerns about long-term maintenance capabilities, while younger families (25–44) demonstrated future-oriented thinking about shade and property values. Property characteristics, particularly yard size, significantly influenced receptiveness, with owners of larger yards (>5000 sq ft) showing greater willingness compared to those with smaller properties, who cited space constraints. Additional barriers, i.e., maintenance, financial, and knowledge barriers, included irrigation costs, lack of horticultural knowledge, pest concerns, and proximity to underground utilities. Geographic analysis revealed that Spanish-speaking social networks were particularly effective in promoting tree planting. The study contributes to urban forestry literature by providing nuanced insights into single-family homeowners’ tree-planting decisions and offers targeted recommendations for municipal programs. These include gender-specific outreach strategies, age-appropriate support services, sliding-scale subsidy programs based on property size, and comprehensive education initiatives. The findings inform evidence-based approaches to increase urban canopy coverage through private property plantings, ultimately supporting climate resilience and environmental justice goals in diverse urban neighborhoods. Full article