Search Results (182)

With the rapid advancement of urban underground space development, shield tunnel construction has seen a significant increase. However, at the initial launching stage of shield tunnels in shallow-buried weak strata, engineering risks such as face instability and sudden surface settlement frequently occur. At present, there are relatively few studies on the reinforcement technology of the initial section of shield tunnel in shallow soft ground and the evolution law of ground disturbance. This study takes the launching section of the Guanggang New City depot access tunnel on Guangzhou Metro Line 10 as the engineering background. By applying MIDAS/GTS numerical simulation, settlement monitoring, and theoretical analysis, the reinforcement technology at the tunnel face, the spatiotemporal evolution of ground settlement, and the mechanism of soil disturbance transmission during the launching process in muddy soil layer are revealed. The results show that: (1) the reinforcement scheme combining replacement filling, high-pressure jet grouting piles, and soil overburden counterpressure significantly improves surface settlement control. The primary influence zone is concentrated directly above the shield machine and in the forward excavation area. (2) When the shield machine reaches the junction between the reinforced and unreinforced zones, a large settlement area forms, with the maximum ground settlement reaching −26.94 mm. During excavation in the unreinforced zone, ground deformation mainly occurs beneath the rear reinforced section, with subsidence at the crown and uplift at the invert. (3) The transverse settlement trough exhibits a typical Gaussian distribution and the discrepancy between the measured maximum settlement and the numerical and theoretical values is only 3.33% and 1.76%, respectively. (4) The longitudinal settlement follows a trend of initial increase, subsequent decrease, and gradual stabilization, reaching a maximum when the excavation passes directly beneath the monitoring point. The findings can provide theoretical reference and engineering guidance for similar projects. Full article

African cities are experiencing rapid, unregulated growth, characterized by high land pressure and growing demand for housing and urban infrastructure. New arrivals often settle in vulnerable areas (wetlands, hills, flood) where land is cheaper and unregulated by public authorities. This type of settlement is accompanied by numerous land conflicts, exacerbated by the coexistence of formal and customary land tenure systems, which struggle to harmonize. In this context, public land regulation policies often remain centralized and ill-adapted, revealing their limitations in ensuring equitable and sustainable management of urban land. Faced with this gap, our systematic study explores the socio-environmental dynamics of this normative pluralism in land governance within Cameroonian cities. Our findings highlight the tensions and opportunities of this complex coexistence, which vary significantly according to city size (small, medium, and large), the colonial heritage (Francophone and Anglophone), and the dominant legal framework (civil law and common law). The analysis highlights the need to take into account historical, linguistic, and politico-administrative roots, which profoundly influence local forms of the institutionalization of normative pluralism and the associated socio-environmental vulnerabilities. This normative plurality underlines the importance of a hybrid system of land governance capable of integrating local specificities while ensuring land security for all. Future research will include comparisons with other African countries in order to understand transferable mechanisms for better land governance. Full article

The Yellow River Basin features a unique geographical environment with challenges like seawater erosion and soft soil. In this context, the construction of foundation pits can significantly impact the settlement of adjacent structures. Grounded in a real-world project, this study employs the finite element software Midas GTS to construct a 3D interaction model between foundation pit excavation and nearby buildings. Through this model, we analyze the settlement patterns of adjacent buildings influenced by variables such as foundation soil strength, slope gradient, and construction sequence. By integrating orthogonal experimental design and range analysis, we identify the sensitive factors affecting the settlement deformation and stability of foundation pits. Our analysis reveals that among the factors significantly influencing settlement deformation at the foundation pit base, groundwater levels and internal friction angles are the most critical. Slope gradient and soil cohesion also play substantial roles, whereas the compressive modulus of soil shows relatively less impact. However, a comparison with actual engineering data indicates that groundwater factors considerably affect slope deformation, underscoring the necessity for stringent control of groundwater level fluctuations. Full article

This study investigates co-seismic landslides triggered by the 1 January 2024 Mw 7.6 Noto Peninsula earthquake in Japan using LiDAR differentiation and a modified Savage–Hutter model. By analyzing pre- and post-earthquake high-resolution topographic data from 13 landslides in a geologically homogeneous area of the peninsula, we characterized distinct landslide morphologies and dynamic behaviours. Our approach combined static morphological analysis from LiDAR data with simulations of granular flow mechanics to evaluate landslide mobility. Results revealed two distinct landslide types: those with clear erosion-deposition zonation and complex landslides with discontinuous topographic changes. Landslide dimensions followed power-law relationships (H = 7.51L^0.50, R² = 0.765), while simulations demonstrated that internal deformation capability (represented by the μ parameter) significantly influenced runout distances for landslides terminating on low-angle surfaces but had minimal impact on slope-confined movements. These findings highlight the importance of integrating both static topographic parameters and dynamic flow mechanics when assessing co-seismic landslide hazards, particularly for predicting potential runout distances on gentle slopes where human settlements are often located. Our methodology provides a framework for improved landslide susceptibility assessment and disaster risk reduction in seismically active regions. Full article

The development trend of urban underground space towards deep and large three-dimensional foundation pit projects in complex environments faces the challenges of deformation and instability of supporting structures, strong sensitivity of the surrounding environment, and significant limitations of the traditional design theory. Based on the ultra-long/deep foundation pit project at the Shenzhen Airport East Station, a refined three-dimensional finite element simulation is used to systematically study the deformation mechanism of the supporting structures of deep and large foundation pits under a complex environment and investigate the influence on the neighbouring buildings. In this study, a three-dimensional finite element model is constructed considering the soil–structure coupling effect, and the mechanical response law of the foundation pit under the compliant–inverse combination method is revealed. Based on ABAQUS 6.14, a 10 m wide strip-shaped model of the central island area and an environmental risk source model including an underground station and group pile foundation are established. The analysis shows the following: the lateral shift in the ground wall is distributed in a ‘convex belly’ shape, with a maximum displacement of 29.98 mm; the pit bottom is raised in the shape of the bottom of a rebutted pot, and the settlement behind the wall has an effect ranging up to 3.8 times the depth of the excavation; the lateral shift in the side wall of the neighbouring underground station and the differential settlement of the group piles validate the predictive ability of the model on the complex-environment coupling effect. The research results can provide guidance for the design and construction of support structure projects and similar projects. Full article

With the increasing construction of engineering structures on soft soils, accurately assessing their consolidation behavior has become crucial. To address this, Terzaghi’s one-dimensional consolidation model was revisited. The elastic behavior of soil skeleton was modified by incorporating viscous effects using the fractional derivative Merchant model (FDMM), while the linear Darcy’s law governing flux–pressure relations was extended by introducing time memory formalism through the fractional derivative Darcy model (FDDM). The governing equation is derived by incorporating the resulting constitutive behavior of both the soil skeleton and water flow into the Terzaghi’s formulation of the poroelasticity problem. The proposed rheological consolidation model is solved by a forward time-centered space scheme (FTCS). After verifying the numerical procedure with published data, the influence of parameters on both the average degree of settlement and the pressure was comprehensively studied. Full article

In the case of a high-risk infectious disease affecting two distinct (without demographic interactions) human populations, e.g., differentiated by their settlement areas, we assume the implementation of a health non-pharmaceutical mitigation policy. However, this policy is based solely on indicators from one of the populations. Using a mathematical model that integrates $\beta (·)$-SIR representations—where $\beta (·)$ is a variable specific to each population and is governed by a dynamic law (a differential equation coupled to state variables)—the dynamic consequences of the epidemiological processes in both populations are explored and compared analytically and numerically. Mainly, it studies the role of the so-called reaction (intensity of the mitigation) and restitution factor (human compliance). Full article

This Study delves on changes in the extent of mangroves over a 42 years span in the Douala-Edea NP, Cameroon. Mangroves are valuable ecosystems that provide significant biological, environmental, ecological, and cultural functions. To inform the development of management plans for the ecosystem’s sustainability, it is crucial to evaluate how their land cover, levels of degradation, and phases of restitution have changed. GIS and remote sensing techniques were used to classify and analyze Landsat images from 1980 to 2022 categorized into nine classes: bare ground, Nypa palms, settlements, coastal sedimentation, river sedimentation, regeneration, matured mangroves, dense forest, and water body. Using the Markovian chain approach, the changes noted during the period were utilized to forecast future trends up to 2052. Findings demonstrated that the mature mangrove area decreased throughout the study. The surface area covered by mature mangroves was 80,628.78 hectares in 1980, which decreased by 7.31%, 1.51%, 3.70%, and by 17% for the overall period of 42 years. Additionally, a gain of 6.84% from 1980 to 2022 was observed, probably from artificial mangrove regeneration. Settlements, invasive Nypa palms, bare ground (resulting from over-exploitation), and the sedimentation of rivers and coast primarily replaced mangroves. The prediction derived indicated the continuous decline in mangroves if not fully protected by law. The gazettement to National Park and recent promulgation of two laws are steps in providing the needed protection. These results provide vital information to direct future mangrove conservation actions in the recently gazetted Douala-Edea National Terrestrial and Marine Park and other mangrove blocks along the Gulf of Guinea. Full article

Ground fissures are extraordinary urban geological disasters, and their harmful effects on underground structures have been highlighted in many cities. Differential settlements between strata can cause a void phenomenon at the bottom of a pipe gallery structure, significantly threatening the project’s construction and operation. This study analyzes the void phenomenon at the bottom of a pipe gallery structure, and a calculation method for the bottom void range is proposed. Through a model test, the stress and deformation laws of the pipe gallery structure under the conditions of orthogonal (90°) and oblique (45°) ground fissure displacements are analyzed. The results show that, owing to the dislocation of the ground fissure, the bottom void range of the pipe gallery is 2.87–3 times the length of the bottom edge of the pipe gallery section under the orthogonal condition and 3.125–3.5 times the length under the oblique condition. Under the dislocation of the ground fissure, the top plate of the structure is under tension; the bottom plate is under compression, and the strains on the side plates are significantly less than those on the top and bottom plates. The maximum contact pressure between the structure and the surrounding soil is distributed on the top plate of the hanging wall and the bottom plate of the footwall near the ground fissure. This study provides a theoretical basis for the optimal design of pipe gallery structures crossing ground fissures and has theoretical significance and application value. Full article

There is growing awareness that there is a link between climate change and human influence and that human activities contribute to the warming of the atmosphere. The research identifies two ways to prepare cities to meet the challenges: the first is to optimize the way the urban organism functions by containing CO₂ emissions and consumption of nonrenewable resources by indicating strategies to regenerate the existing city according to an ecosystem approach; the second is to preserve the natural areas of the peri-urban area through graded forms of protection and enhancement by curbing the settlement thrusts of the existing city. The article illustrates two case studies for comparison (Reggio Calabria and Enna) chosen in the context of two Italian regions. Both have urban planning laws that provide for new urban planning instruments sensitive to these aspects. The two case studies were selected because of the similarity of their physical characteristics and the types of agricultural production affecting large areas of land, which has been partially compressed over the years. The respective regional regulations provide solutions to increase protection while allowing for better sustainable use and enhancement. Full article

The relevant value standards for reserved deformation of tunnels with different types of loess soil are not yet perfect. Through mathematical statistics, literature research, and other methods, 148 monitoring sections of loess tunnels with different soil types were investigated. Pearson, Kendall, and Spearman correlation coefficients were used to analyze the influence of surrounding rock grade, moisture content, and burial depth on the deformation law of tunnels, providing reference for the value of reserved deformation for loess tunnels. The research results indicate that: (1) The correlation between soil type and convergence around the tunnel is strong, followed by excavation span, and the correlation between moisture content and burial depth is weak. Therefore, the design of reserved deformation should focus on considering the soil type and excavation span. (2) For loess tunnel sections with class IV surrounding rock, the deformation allowance for cohesive loess and silty loess tunnel sections can be set within 15 cm, and for sandy loess, it can be set within 15–20 cm. (3) For the loess tunnel section with V-grade surrounding rock, the deformation margin can be determined as follows: viscous loess within 15–20 cm, silty loess within 15 cm, and sandy loess within 35–47.5 cm. (4) The moisture content is mainly distributed between 11% and 23%. It is worth noting that in sandy loess sections, the influence of moisture content on tunnel arch settlement is more significant compared to cohesive loess and silty loess sections. (5) The settlement of the arch crown is affected by changes in coverage depth and has discreteness. When the deformation margin is set to 16 cm, the assurance rate can reach 84.6%. Finally, the rationality of the proposed reserved deformation amount was verified through engineering practice. The research results can provide reference for related similar projects. Full article

In this study, the evolution process of a landslide model under continuous rainfall conditions with a rainfall intensity of 30 mm/h is studied in depth based on an outdoor rainfall model test of a colluvial slope as the research material. The response law of pore water pressure and settlement amount is also obtained, and the influence of bedrock inclination angle on the development and deformation failure of the colluvial landslide is discussed. When the dip angle of the bedrock is 40°, it is prone to sudden slip-type landslides, and the evolution process is as follows: tensile cracks appear at the trailing edge, and these cracks continue to increase, leading to overall sliding. When the bedrock dip angle is 30°, traction landslides are prone to occur, and the evolution process is as follows: there is sliding at the foot of the slope, tensile cracks appear in the middle, sliding occurs in the middle, and tensile cracks appear in the upper part, leading to overall sliding. Before the landslide starts, the pore water pressure rises significantly. In the process of landslide evolution, the fine particles move to the foot of the slope with the rainwater, and the larger the angle of the slope, the greater the number of fine particles that accumulate at the foot of the slope, and the higher the elevation and the larger the scale of the trailing edge of the sliding body during sliding. Full article

To investigate the mechanism by which clay shock slurry fills excavation gaps and reduces ground layer deformation during shield tunneling, we conducted a study using the project example of Beijing Metro Line 19 from Youanmenwai Station to Niujie Station, which passes through Guang’anmennei Station to CaiShiKou Station of Beijing Metro Line 7 at a close distance. We employed physical and mechanical testing, numerical simulation calculations, and other methods to examine the deformation law and mechanism of the clay shock method in shield tunneling construction. Our results indicate that (1) as the mass concentration of clay shock slurry increases, its permeability decreases significantly; at a mass concentration of 400 kg/m³, clay shock slurry can prevent synchronous grouting slurry from flowing forward, providing optimal filling and support for excavation gaps. (2) Clay shock slurry can reduce friction between the shield shell and soil body by 50%, avoiding super-consolidation, shear damage, and volumetric expansion of the surrounding soil body. (3) Radial grouting with a two-fluid slurry of cement–water glass at a 1:1 ratio within 15 rings after shield tail removal effectively reduces settlement of the existing tunnel. (4) Numerical simulations demonstrate that using clay shock slurry to fill shield tunnel gaps not only significantly reduces construction settlement but also effectively inhibits strata displacement along the tunnel axis. Full article

Among the most significant impacts related to the spread of settlements and the densification of urban areas, the reduction in the availability of public green spaces plays a central role in the definition of livable cities, in terms of the environment and social cohesion, interaction, and equality. In the framework of target 11.7 of the Sustainable Development Goals (SDG) 11, the United Nations has established the objective of ensuring universal, safe, and inclusive access to public spaces by 2030, for women, children, the elderly, and people with disabilities. This study proposes the evaluation of this objective for the urban area of the 14 Italian metropolitan cities, as defined by EUROSTAT and adopted by the United Nations and the Nature Restoration Law (NRL). A methodology based on open-source data and network analysis tools is tested for the provision of an unprecedented mapping of the availability and accessibility to green urban public spaces, which shows that less than 30% of metropolitan city residents have access to a green space within 300 m on foot, according to OpenStreetMap data (less than one in five for the Urban Atlas data). Furthermore, a critical analysis on the geometric and semantic definition of green urban public spaces adopted by the main European and international tools is carried out, which underlines the strategic role of crowdsourcing but also the need for mapping rules that make the data more consistent with the monitoring objectives set at the institutional level. Full article

In this paper, an investigation was conducted to characterize the behavior of weakly cohesive soil subjected to vibratory compaction. Thus, the authors developed a model for weakly cohesive soils, defined by inter-parametric laws that consider their initial state and predict the evolution of state parameters resulting from static and vibratory compaction processes, depending on the number of equipment passes. Four types of soil were proposed for testing, with different initial characteristics such as dry density, longitudinal modulus, and moisture content. Some correlations between main parameters involved in the compaction process were established, considering soil mechanical properties, compaction equipment, and in situ technology applied. The results obtained in the computational environment were implemented to predict the performance compaction process for an overall assessment. This research contributes to database development by offering valuable insights for specialists aiming to apply Industry 4.0 digitalization practices, which stipulate the use of predictability laws in pre-assessing the degree of soil compaction (or settlement) to estimate and maximize the efficiency of road construction or foundation works. These insights help optimize design processes, enhance functional performance, improve resource utilization, and ensure long-term sustainability in large infrastructure projects built on these soils. Full article