Search Results (491)

Due to the long operation period of Beijing Metro Line 2 and the complex surrounding building environment, this paper comprehensively studied the mechanical properties of new tunnels using close-fitting undercrossing based on pre-support technology. To control structural deformation caused by the expansion project, methods such as laboratory tests, numerical simulation, and field tests were adopted to systematically analyze the tunnel mechanics during the undercrossing of existing metro lines. First, field tests were carried out on the existing Line 2 and Line 3 tunnels during the construction period. It was found that the close-fitting construction based on pre-support technology caused small deformation displacement in the subway tunnels, with little impact on the smoothness of the existing subway rail surface. The fluctuation range was −1 to 1 mm, ensuring the safety of existing subway operations. Then, a refined finite difference model for the close-fitting undercrossing construction process based on pre-support technology was established, and a series of field and laboratory tests were conducted to obtain calculation parameters. The reliability of the numerical model was verified by comparing the monitored deformation of existing structures with the simulated structural forces and deformations. The influence of construction methods on the settlement changes of existing line tracks, structures, and deformation joints was discussed. The research results show that this construction method effectively controls the settlement deformation of existing lines. The settlement deformation of existing lines is controlled within 1~3 cm. The deformation stress of the existing lines is within the concrete strength range of the existing structure, and the tensile stress is less than 3 MPa. The maximum settlement and maximum tensile stress of the station in the pre-support jacking scheme are −5.27 mm and 2.29 MPa. The construction scheme with pre-support can more significantly control structural deformation, reduce stress variations in existing line structures, and minimize damage to concrete structures. Based on the monitoring data and simulation results, some optimization measures were proposed. Full article

Settlement analyses of foundation soils are very important for the investigation, design, and construction of buildings. However, due to complex natural sedimentary processes, soil-forming environments, and geological tectonic stress histories, settlement properties show obvious spatial variability and autocorrelation. Moreover, measurement data on the physical and mechanical parameters of building foundation soils are limited. This limits the accuracy of formation stability analyses and safety evaluations. In this study, a series of field tests of building foundation soils were carried out, and the statistical physical and mechanical properties of the clay strata were obtained. A random field method and copula functions of uncertain geotechnical properties with limited survey data are proposed. A dual-yield surface constitutive model of the soil properties and a stability analysis method for uncertain deformation were developed. The detailed analytical procedures for soil deformation and stratum settlement are presented. The reliability functions and failure probabilities of variable settlement processes are calculated and analyzed. The impact of the spatial variation and cross-correlation of geotechnical properties on the probabilistic stability of variable land subsidence is discussed. This work presents an innovative analysis approach for evaluating the variable settlement properties of building foundation soils. The results show that the four different mechanical parameters can be regressed to linear equations. The horizontal fluctuation scale is significantly larger than the vertical scale. Copula theory provides a powerful framework for modeling limited geotechnical parameters. The bootstrap approach avoids parametric assumptions, leveraging empirical data to enhance the reliability analysis of variable settlement. The variability parameter exerts a greater influence on land subsidence processes than the correlation structure. The failure probabilities of variable stratum settlement for different cross-correlations of building foundation soils are different. These results provide an important reference for the safety of building engineering. Full article

Jacking-pipe construction has the advantages of high mechanization, low environmental impact and fast construction speed. It is widely used in the project of underground pipeline under river. However, jacking-pipe grouting under shallow burial conditions is prone to cause surface bubbling problems. Based on the jacking-pipe project of Meichong Lake in Changfeng County, Hefei, this paper discussed the mechanism of grouting surface leakage, and defined the relationship between the critical pressure of jacking-pipe grouting and the ultimate pressure of shear damage of mud jacket. Mechanical model of surface leakage from shallow buried jacking-pipe grouting was established. A general mathematical expression for the grouting critical pressure was derived and a sensitivity analysis was performed. A numerical model was established based on the background engineering, and multiple sets of grouting pressure conditions for simulation and analysis were set up. The results showed that the cohesive force $c$, the angle of internal friction $\phi$, and the overburden thickness $h_s$ were all approximately linearly and positively correlated with the critical pressure of grouting. When the grouting pressure was less than 197.54 kPa the surface settlement increased. When this value was exceeded the surface displacement changed from settlement to uplift and the risk of slurry bubbling increased significantly. The theoretical calculation matched the value of grouting critical pressure from numerical simulation. The actual grouting pressure in the project was lower than the theoretical grouting critical pressure value and no slurry bubbling occurred during construction, which had verified the reliability of the theoretical model. This study can provide theoretical basis and investigation ideas for the setting of reasonable grouting pressure in similar projects. Full article

While existing analytical methods provide solutions for calculating vertical pressures in soil, calculating lateral stresses remains a critical challenge. Therefore, experimentally measuring stress values is essential, considering the various factors influencing these stresses. This study investigates the lateral stress variations occurring beneath foundations placed on sandy soil and assesses the ultimate bearing capacity and settlement behavior of these foundations. Additional lateral stresses were measured beneath square shallow foundations on the sand with varying relative densities. The model tests were conducted in a square-sectioned sand tank. The results revealed that the lateral stress values tended to increase with both the foundation size and soil density, with this effect being most pronounced at a relative density of 90%. Furthermore, the lateral stresses decreased with increasing depth beneath the foundation for all foundation sizes. Loading tests were performed on square foundations of various sizes placed on sand prepared at different relative densities. A significant increase in the ultimate bearing capacity was noted as the foundation size and relative density of the soil increased. The measured lateral stresses were compared with theoretical predictions, and it was found that the values derived from the theoretical equations aligned well with the experimental results. In the second part of the study, a regression analysis was conducted to predict the lateral stresses within the soil. It was concluded that lateral stresses can be estimated with a high degree of accuracy using the proposed regression model (R² = 0.982). Full article

The site selection and spatial arrangement of rural settlements embody the ethnic characteristics and cultural heritage of ethnic minority groups. Investigating their spatial layout features and underlying determinants can provide both theoretical foundations and practical methodologies for the conservation and development planning of these settlements. This paper takes the representative ethnic minority villages in the first batch of key traditional villages in Liuzhou, Guangxi, as the example, and employs a combination of qualitative and quantitative methods to study the spatial layout characteristics of ethnic minority villages in southern China. This study utilizes GIS-based analytical methods to calculate quantitative indicators based on planar graphs and digital elevation model (DEM) of ethnic minority settlements. The research results show that the spatial distribution of ethnic minority villages in southern China is closely correlated with natural geographical conditions. To be specific, ethnic minority villages in southern China generally distribute in accordance with the terrain and form specific spatial relationships with roads, topography, mountains, and water. Regardless of whether minority residents live on mountain tops or in valleys, they generally prefer gently sloping terrain. In addition, factors such as natural environment (sunshine and water sources, etc.) and traffic conditions are considered comprehensively in the settlement location. On this basis, the spatial layout features of rural settlement are extracted, and corresponding characteristic maps are constructed. The construction framework of the spatial characteristics map established based on “overall layout, architecture, roads and architecture-natural pattern” in this paper can be applied to general rural settlements. The findings can provide both theoretical foundations and practical references for the planning and development of rural settlements across different regions and ethnic groups. Full article

The quality of life in both urban and rural areas is highly dependent on the availability of services of general interest. This study examines the provision and accessibility of 41 types of point-specific services, divided into 10 categories, within the functional urban region of Zagreb, Croatia, characterized by a declining population, despite being the most populous area in Croatia. This study adopts a multi-service rather than a single-service research approach, providing a more comprehensive understanding of the phenomenon. Using GIS composite indices for service provision and accessibility by car (cumulative opportunities) were calculated. Cluster analysis (Ward method, quadratic Euclidean distance) revealed seven different geographical patterns. The results show different patterns of service provision and accessibility throughout the urban region. Two specific areas were highlighted: traditional and inner peripheral areas with low levels of both service provision and accessibility, and suburban areas with very good accessibility but very poor service provision. The results of this study are particularly valuable as they relate to a single functional urban area that includes both urban, suburban and rural settlements of different types, a spatial framework that has not been sufficiently analysed in the literature. Full article

This study presents an enhanced analytical approach for one-dimensional consolidation settlement by introducing a revised AJOP (arc joint via optimum parameters) equation assuming creep and strain rate effects can be neglected for both normally and overconsolidated clays. This modified equation integrates both curved and linear segments within a unified framework, enhancing accuracy across varying stress levels for normally consolidated clay. Additionally, the revised AJOP function, coupled with newly proposed equations for symmetrical and asymmetrical hysteresis, improves the modeling of overconsolidated clay. The findings from a comparative investigation using benchmark datasets and conventional methods, including the linear function (LF) and the curved function (CF), reveal that the revised AJOP method was found to reduce settlement prediction errors by up to 85% compared to LF method (particularly at shallow layers) and by 10–15% compared to the CF method (particularly at deep layers). The revised AJOP equation effectively resolves this error with a wide range of depths. Furthermore, results highlight the crucial impact of clay layering techniques on consolidation settlement predictions. Non-layered models yield lower settlement estimates compared to multilayer approaches, emphasizing the significance of the proper $e-log{{\mathsf{\sigma }}^{\prime }}_v$ relationship and layering techniques in enhancing prediction reliability. Full article

The analysis of the impact of the construction of the subway protection zone on the adjacent subway tunnel has become the premise on which to ensure the safe operation of the tunnel. The need for expert members to carry out safety assessments based on specific calculations to determine the impact of construction on the safety of protected tunnels is extremely inconvenient for safety management and significantly reduces management efficiency. This paper analyzes and qualitatively judges the influence range and disturbance size of pile foundation construction, shallow foundation engineering, and foundation pit excavation. Based on relevant research results from scholars and numerical simulation methods, quantitative analysis and comparison are performed on the parameter sensitivity of pile foundation engineering, shallow foundation engineering, and foundation pit engineering along the subway line, and the influence of multi-factor combination is studied and discussed to obtain the influence sensitivity of each factor. The results show that the increase in pile spacing can effectively reduce the pile group effect. The sensitivity of subway tunnel settlement displacement is mainly controlled by the settlement displacement value. The larger the settlement displacement is, the stronger the sensitivity is. The loaded pile foundation arranged along the direction of the subway tunnel has more obvious disturbance to the subway tunnel than that arranged perpendicular to the direction of the subway tunnel. Full article

Underground metal mines operated using the natural caving method often result in significant surface collapses. Key parameters such as settlement magnitude, settlement rate, settlement extent, and the influence of underground mining on surface deformation warrant serious attention. However, due to the long operational timespan of mines and incomplete data from early collapse events, coupled with the inaccessibility of collapse zones for field measurements, it is challenging to obtain accurate displacement data, thereby posing significant difficulties for follow-up research. This study employs small baseline subset InSAR (SBAS-InSAR) technology to retrieve time series data on early-stage surface displacement and deformation rates in collapse areas, thereby compensating for the lack of historical data and eliminating the safety risks associated with on-site measurements. The 5th percentile of settlement rates across all monitoring points is used to define the severe settlement threshold, determined to be −42.1 mm/year. Continuous wavelet transform (CWT) is applied to calculate the time-series power spectrum, allowing the analysis of long-term stable and periodic settlement patterns in the collapse area. The instantaneous change rate at each point in the study area is identified. Using the 97th percentile of change rates in the time series, the number of severe change events at each point is determined. High-incidence zones of sudden surface deformation are visualized through QGIS 3.16 heat map clustering. The high-risk collapse area, identified by integrating both long-term stable settlement and sudden surface deformation patterns, accounts for multiple deformation modes. This provides robust technical support for the management of mine collapse zones and offers important theoretical guidance. Full article

The rapid development of urban transportation renovation and transportation networks in China has driven the construction of an increasing number of large-span, large cross-section tunnels under sensitive environments, such as airport runways, critical infrastructure, and high-speed railways. These projects often require strict settlement control within a millimeter-level tolerance range, thus theoretical methods and key technologies for micro-settlement control have been developed. This study first derives a calculation formula for surface settlement associated with large cross-section tunnels and elucidates its correlations with factors such as pipe-roof stiffness, support system stiffness, pipe-roof construction procedures, and groundwater level changes. Theoretical approaches for controlling micro-settlement are introduced, including increasing pipe-roof stiffness, reinforcing the support system, mitigating group pipe effects, maintaining pressure and reducing resistance around the pipe, and controlling groundwater levels. A method is proposed for determining the appropriate stiffness of the pipe roof and support system. The stiffness should be selected from the transition segment between the steep decline and the gentle slope on the stiffness-settlement curves of the pipe roof and the support system. If the stiffness of the pipe roof and primary support combined with temporary support fails to meet the micro-settlement control requirements, an integrated support system with greater stiffness can be adopted. A reasonable pressure-regulating grouting technique for maintaining pressure and reducing resistance around the pipe is proposed. It is recommended that the spacing for simultaneous jacking of pipes be greater than half the width of the settlement trough. For over-consolidation-sensitive strata such as medium or coarse sands, water-blocking measures, including freezing, grouting, or a combination of both, are recommended. For over-consolidation-insensitive strata like gravels and cobbles with strong permeability, water-blocking treatments are generally unnecessary. The proposed theoretical approaches have been successfully implemented in projects such as the tunnel beneath Beijing Capital Airport runways and Taiyuan Railway Station, demonstrating their reliability. The research findings provide valuable insights into surface micro-settlement control for similar projects. Full article

Due to the imbalance between urban and rural development and improper management, the spatial forms of many heritage villages have suffered severe damage, and their landscape styles are gradually being blurred, posing serious challenges to the protection of traditional villages. Taking the traditional village of Xi Songbi in Jiexiu City, Shanxi Province, as a case study, this paper employs UAV low-altitude multi-view measurement technology to obtain high-resolution image data from different angles. Three-dimensional modeling technology is then used to construct a 3D real-world model, orthophotos, and point cloud data of the settlement. Based on these data, the weakly supervised point cloud segmentation method, DDLA, is further applied to finely segment and classify the acquired point cloud data, accurately extracting key spatial elements such as buildings, roads, and vegetation, thereby enabling a comprehensive and quantitative analysis of the spatial morphology of traditional villages. The results of the study show the following: (1) The use of UAVs for low-altitude multi-view measurement not only greatly improves the efficiency of data acquisition but also provides millimeter-level precision spatial data in a short time through the constructed 3D models and orthophotos. (2) The acquired point cloud data can be processed through the DDLA, which effectively differentiates building contours from other environmental elements. (3) The calculation and analysis of the segmented point cloud data can accurately quantify key spatial morphology elements, such as the dimensions of traditional village buildings, spacing, and road widths, ensuring the scientific rigor and reliability of the data. (4) The comprehensive application of digital technology and point cloud segmentation methods provides clear expectations and solid technical support for the quantitative study of the spatial morphology of traditional villages, laying a scientific foundation for the protection and sustainable development of cultural heritage. Full article

Throughout human settlement history, the pursuit of durability has been a paramount objective in building construction. The emphasis on durability has resulted in the construction of buildings designed to outlast human lifespans. However, the lack of consideration for building demolition and disposal during the design and construction phases has created challenges for future generations. This oversight contributes to the environmental impact of structures after demolition, which is a significant concern given that the construction industry is a major contributor to energy consumption, CO₂ emissions, and solid waste production. In fact, in recent decades, there has been an increasing demand for temporary constructions, driven by factors such as migration phenomena, natural disasters, and the COVID-19 pandemic, but also in sectors like agriculture, where seasonality and annual variations in activities require adaptable structures such as warehouses, barns, livestock shelters, and food storage facilities. Unlike traditional constructions, these temporary buildings must be assembled and disassembled multiple times during their lifespan. The challenge lies in ensuring the structural integrity, adaptability to varying conditions, and compliance with specific requirements to extend their usability and postpone the disposal phase. This study focuses on the design of a novel type of temporary structures intended for temporary needs such as emergencies and planned agricultural activities, resulting in a European patent. The structure is based on a glulam frame inside two OSB panels—that work as structural bracing, creating a hollow, resistant, light structure—connected with external steel connections. This work reports results of mechanical simulations and thermal transmittance calculations. Specifically, it demonstrates the building maintains structural strength through multiple usages and its thermal characteristics can be easily adapted to the context. These are the first steps for a resilient and sustainable building. Full article

This paper presents two innovative procedures developed for rural electrification planning. To address the challenges of processing vast geospatial data, handling complex and computationally intensive network design, and making detailed yet accessible economic assessments, this work introduces a Buffering plugin for community identification and a Grid Routing and Cost Allocation plugin for network design and economic assessment, both integrated into the open-source QGIS platform. The first enables the identification of potential electrification zones through dual methodologies, while the second introduces three key processes: hierarchical clustering, a modified minimum spanning tree, and a novel cost allocation methodology that provides village-specific LCOE calculations. Testing in Zambia has proven that this approach is not only effective but also—compared to existing tools—offers significant advantages in terms of computational efficiency and accessibility, while providing practical solutions to large-scale challenges. This synergistic approach enables planners to move from granular geospatial data to actionable electrification decisions through a streamlined process. The analysis covered over 3 million buildings, grouped into 162,142 settlement clusters, and subsequently determined optimal electrification strategies for 3025 villages—40.4% connected to grid extensions and 59.6% to mini-grids—serving a total population of 18 million people. Full article

The construction of urban subway tunnels typically induces soil settlement within a specific radius of the surrounding area. However, the accuracy of current methods for predicting ground deformation curves corresponding to the excavation of double-track tunnels with small spacing remains insufficient. Most studies simplify this problem by modeling it as a two-dimensional plane problem; however, the actual ground deformation exhibits pronounced three-dimensional characteristics. Consequently, studying the ground settlement patterns caused by the construction of small-spacing double-track tunnels is crucial. This study is based on the Peck formula, used to calculate surface settlement caused by the excavation of single-track tunnels. By incorporating the maximum settlement offset e and the soil loss rate η(y), the soil displacement calculation formula is derived for small-spacing double-track tunnel excavation. The accuracy of the derived formula is then validated through a case study. The findings provide a theoretical reference for predicting surface settlement induced by the excavation of small-spacing double-track tunnels. Furthermore, the influence of different parameters on ground settlement patterns is explored. The results indicate that appropriately increasing the tunnel spacing, increasing burial depth, and adopting a sequential excavation method for the two tunnels help reduce ground settlement. Full article

In order to address the issue of surface deformation in wintering foundation pits in seasonal frozen soil areas due to excavation and freeze–thaw, an indoor scale model test was conducted to examine the displacement relationship between pit wall soil and supporting structures under freeze–thaw conditions, as well as the temperature change and water migration of soil surrounding the foundation pit. The distribution mode of surface settlement under excavation and freeze–thaw conditions was examined and a surface settlement calculation model was established based on the maximum value of surface settlement. The water will move from the frozen to the unfrozen region as a result of the freeze–thaw cycle. About 1.1 m is the freezing depth. An increase in surface settlement will result from the coordination of deformation between the soil and the supporting structure during freezing and thawing. The greatest surface settlement value following the initial freeze–thaw cycle is 1.082 mm, which is around 215% greater than that of excavation. The skewed distribution is comparable to the surface settlement curves produced by excavation and freeze–thaw cycles. The calculated model’s results and the measured settlement values agree rather well. Full article