bluuebunny/crossref_metadata_2025_split huggingface dataset:
Firefighters’ behavior via vertical shafts in natural-ventilated tunnels
Authors: Zhang Y , Rui Y , Zhu H , Yan Z 
Published: May 2024

Abstract
Tunnel load traffic flows day and night, and is highly susceptible to catching tunnel fires. When a tunnel is on fire, occupants are endangered by the rapid deterioration of the tunnel environment during burning, and their self-evacuation is limited by their unfamiliarity with tunnels. Therefore, efficient and effective firefighting and rescue methods are urgently required to guarantee the safety of occupants during tunnel fires. During firefighting, one of the most important issues is that a fire brigade may encounter difficulties identifying the fire source. They have to deal with congestion and navigate cars piling into the tunnel, which wastes significant time. Therefore, this study provides an alternative approach for firefighters to access fire sources in naturally ventilated tunnels equipped with vertical shafts. This study explored three routes for firefighters from the ground to a fire source in a tunnel. The duration and speed of taking the three routes, along with the use of facilities, firefighters’ communication, and emotions, were presented and analyzed. This indicates that firefighting and rescue via vertical shafts is a feasible and optimized method for naturally ventilated tunnels because the estimated duration decreased by 56.2% (without smoke) and 60.0% (with smoke) compared to traditional routes when the minimum distance from the fire to the nearest exit is 2000 m. In addition, the study provides field experimental data on vertical firefighting in tunnels, which are expected to be used to build and calibrate models for firefighters in future studies.
A data-informed assessment method for the urban underground complex vitality
Authors: Pan Q , Dong Y H , Peng F L 
Published: May 2024

Abstract
The urgent need for urban renewal and the rapid expansion of underground spaces has spurred the construction of urban underground complexes (UUCs). Vibrant UUCs are crucial for the efficient utilization of underground spaces and urban sustainability. Previous research on urban underground complex vitality (UUCV) has been primarily theoretical with limited reusability. In this study, we aimed to address this gap by focusing on underground functional facilities and spatial distribution characteristics to establish a UUCV indicator system based on walkability theory. We introduced a method based on exponential weighted mean for weight allocation to facilitate vitality calculations. Using the Wujiaochang UUC in Shanghai as a case study, we explored the spatial distribution mechanism of vitality and validated the feasibility of this research framework. The proposed assessment method and results obtained in this study offer valuable insights into underground space planning and design, particularly in the context of urban renewal.
Development and verification of shield thrust vector self-adaptive control technology in soft soil strata
Authors: Zhu Y T , Bi X L , Zhu Y F , Wu H M , Wang X Z , Zhang Z X , Chen J , Qin Y 
Published: May 2024

Abstract
To solve the difficulty in automatically obtaining an effective total thrust vector relative to the shield posture adjustment requirements during self-driving in soft soil strata, a shield thrust vector self-adaptive control technology for shield machines was proposed. Subsequently, a large-scale model platform was established to simulate the straight-line advancement of the testing shield machine under dynamic loads, and the feasibility of steady shield driving was verified. The test results showed that: the actual total thrust force exhibited the same variation characteristics according to load force, while a relatively fixed difference of 1000 kN between the two caused by the system friction was observed. A quick recovery after an abrupt jump of the shield speed was discovered once there was a sudden, significant change in the load. The actual resultant moment of total thrust force effectively responded to the load force, and the shield postures were maintained well. Further, the driving speed and the horizontal stroke difference were controlled in the ranges of ±3 mm/min and ±5 mm of each set values, respectively. Subsequently, this technology was applied to the Wusongkou Yangtze River Tunnel project in Shanghai, and the on-site test results verified its feasibility in actual soft soil strata. The shield speed remained stable as the actual thrust forces shared the same changing low of the target values, and a fixed difference between the two was maintained to ensure the movement of the shield machine. The variation curves of the actual steering angles in both the horizontal and vertical directions coincided with those of the target steering angles because the resultant horizontal and vertical moments of the thrust force effectively responded to each steering requirement, which was executed with high quality.
Impact of extreme rainfall on metro network resilience: Shanghai metro as an example
Authors: Feng Q K , Zhang D M , Huang Z K 
Published: May 2024

Abstract
Extreme rainfall results in urban floods that are known to occur frequently and worldwide. In particular, a metro system faces a high risk of inundation owing to its special geographical location. Consequently, metro network flood resilience has attracted increased attention. This study considered Shanghai as an example to assess the resilience of metro network under extreme rainfall. First, a resilience assessment method of metro networks under extreme rainfall conditions was proposed. This method comprised comprehensive urban waterlogging analysis, construction of a topological structure of metro networks, and resilience assessment of metro networks. Subsequently, the resilience analysis of the Shanghai metro network under extreme rainfall was conducted as a case study based on the above method. The results showed that the disruption of stations and corresponding intervals caused greater damage to network performance. Finally, based on the analysis results, suggestions were provided to improve the flood resilience of the metro network under extreme rainfall conditions.
Experimental study on the triaxial mechanical properties of hybrid steel fiber–reinforced self-compacting concrete
Authors: Gong Chenjie , Kang Lei , Ding Wenqi 
Published: May 2024

Abstract
In this study, the triaxial mechanical properties of hybrid steel fiber–reinforced self-compacting concrete (HSFRSCC) were investigated. Based on previous research, a mixture of HSFRSCC that satisfies the requirements of compression and workability performance was determined. Conventional triaxial compression tests were performed at confining pressures of 0, 4, 8, 12, and 16 MPa. The results showed that all the specimens had excellent deformation ability, and both the steel fibers and confining pressure improved the ductility of HSFRSCC. With an increase in the confining pressure, the triaxial peak stress and strain of concrete were increased. The differences in the damage characteristics of HSFRSCC and plain concrete were compared based on scanning electron microscopy test results. Finally, the applicability of the Mohr–Coulomb criterion with that of the Willam–Warnke (W–W) criteria to HSFRSCC was compared. the results showed that the nonlinear W–W criterion had a better fitting effect. Hence, the relationship between triaxial peak stress, peak strain, and confining pressure was established, and the triaxial compression meridian formula for HSFRSCC was obtained.
Deformation caused by T-shape expansion of existing metro station: complex challenges and strategies
Authors: Lin Jiangyuan , Tong Liyuan , Li Hongjiang , Qiu Tao , Wen Yingwen , Liu Songyu 
Published: May 2024

Abstract
This case study presents an investigation on existing metro station deformation characteristics during T-type expansion in Nanjing, China. A three-dimensional elastic-plastic finite element model is adopted to consider the interaction of soil, retaining structure, horizontal support system and existing station structure. The results indicate that coupling deformation of asymmetric uplift deflection and existing structure rotation occurs on existing structure. Moreover, the sensitivity of influencing factors is analyzed, including the dimension of retaining structure, the support spacing, the excavation method, the soil reinforcement depth in passive area, the width of retaining soil during excavation, the relative position between foundation pit and existing structure, the excavation depth, the existing structure rigidity. Furthermore, based on the analysis of difficulties in the T-shape expansion projects, the controlling measures for the deformation of existing metro station are proposed. The achievements of this case study can be used as a reference for similar underground expansion projects.
Optimized identification for critical metro stations from urban resilience perspective
Authors: Liu S C , Qiao Y K , Peng F L 
Published: May 2024

Abstract
Urban rail transit systems and metro-led underground space contribute to urban resilience. The critical level of metro-led underground space in a metro network demands different resilience requirements, thereby rendering the identification of critical metro stations before the evaluation of the resilience contribution essential. This study optimized the identification of critical metro stations in terms of network model construction and evaluation methods to suit urban resilience perspective. The optimized metro network model considered the influence of transfers, difference between above-ground and underground routes, and cost between adjacent stations, to construct an undirected weighted graph of a metro network. Three evaluation metrics: node betweenness, network efficiency loss, and route redundancy, were adopted for a comprehensive identification method of critical stations. The optimized identification method was applied to the Shanghai Metro network (402 stations and 481 links by 2023). The betweenness identified the downtown stations to be more critical, whereas the network efficiency loss and route redundancy identified the critical stations at downtown-suburban connections. Moreover, the vulnerability and distribution of above-ground stations influenced the identification result of critical stations. The identification results are expected to facilitate the resilience evaluation of metro-led underground space, to examine whether the contribution is balanced with the demand.
Experimental investigation of tail void grouting pressure evolution for super-large diameter shield tunnels
Authors: Zhao C , He H , Lin C , Chen Y , Lavasan A 
Published: May 2024

Abstract
The shield tunneling method is widely used in underground construction. Factors such as the variations in grouting pressure and stiffness/strength evolution over space and time directly affect ground deformation and system stability. To investigate the effect of grouting pressure variation, grouting influence zone, and hydromechanical properties on the model responses (e.g., surface settlement and lining forces), an innovative model test setup was developed to simulate the tunneling process wherein the lining could settle or float during grout injection. This setup included tunnel shrinking, loading-unloading, grout injection, and sample preparation systems. The experimental results show that the grouting pressure evolution law may be significantly affected by the tunnel translation. When the tunnel centerline was fixed in the traditional model tests, the resulting grouting pressure in the tail void was lower than that when the tunnel was free to move. This is because the tunnel translation changed the shape of the annular gap and contributed to the measured grouting pressure. The proposed setup is capable of revealing a more realistic law of grouting pressure evolution, and the subsequent spatio-temporal grouting-induced soil/lining behavior is currently being investigated.
Influence of frost heave with confining pressure under seepage on compressive strength of frozen silt in artificial ground freezing
Authors: Li Z , Zhou J , Wang J 
Published: May 2024

Abstract
Artificial ground freezing (AGF) is used for constructing subway cross passages in coastal areas. The continuous construction of complex projects (cross-sea or cross-river tunnels) has resulted in freezing environments with high groundwater seepage velocities. Seepage cannot provide an open system in soil freezing for moisture migration, resulting in large amount of frost heave owing to segregated ice compared to close freezing system. The influence of frost heave under seepage on the compressive strength of frozen silt during artificial ground freezing must be studied to ensure AGF construction safety. Thus, a unidirectional freezing device that can control seepage and confining pressure conditions during freezing was designed to prepare frozen silt samples under different seepage velocities with confining pressures and to measure the relevant segregation frost heave. Subsequently, uniaxial compression tests were performed. The compressive strength of frozen silt under the influence of frost heave and seepage conditions was analyzed. The frost heave rate, uniaxial compressive strength, and elastic modulus of frozen silt in an open freezing system were measured. The seepage velocity during freezing increased the frost heave rate of the silt; the uniaxial compressive strength and elastic modulus of the frozen silt increased subsequently. The effective confining pressure suppressed frost heave of silt and reduced the uniaxial compressive strength and elastic modulus of the frozen silt. The test results were analyzed considering the segregation frost heave formation mechanism, and a theoretical improvement model of the uniaxial compressive strength and elastic modulus of frozen silt related to the content of segregated ice was proposed. This research is significant for ensuring the AGF construction safety in cross-river or ocean tunnel engineering under seepage conditions.
Study on microscopic mechanisms of slurry infiltration in calcareous sand based on CT scanning
Authors: Yuan H , Zhang Z , Huang X 
Published: May 2024

Abstract
A novel detachable microslurry infiltration device tailored for computed tomography (CT) scanning was developed. Using this device, a series of slurry infiltration tests was conducted on calcareous and Fujian sand columns with various bentonite slurry concentrations. CT scanning technology nondestructively captured the cross-sectional image slices of each specimen for analysis. A comprehensive image processing methodology was deployed to precisely differentiate the three phases—calcareous sand, slurry, and air—enabling 3D reconstruction of the infiltrated sand column. This approach combines three techniques: threshold segmentation, the watershed algorithm, and deep learning. Distinctive particle morphologies inherent to the calcareous and Fujian sands were observed. Notably, CT scans revealed a markedly greater angularity and irregularity of the calcareous sand compared with the Fujian sand, leading to different pore characteristics. Given an identical permeability coefficient, the calcareous sand porosity exceeded that of the Fujian sands. Furthermore, image analyses revealed distinct features of filter cake formation in these two soil columns. In calcareous sands with finer grain sizes, the slurry particles were more prone to clogging because of constricted and irregular seepage pathways. Conversely, with increasing particle size, the internal pores of the calcareous sand particles augmented channels for slurry infiltration, hindering filter cake formation.
Simulation-based approach for the optimization of ground freezing in tunneling
Authors: Williams M Rodolfo J , Cao Ba-Trung , Alsahly Abdullah , Meschke Günther 
Published: May 2024

Abstract
Artificial ground freezing is used in tunnelling for temporary ground improvement primarily to control groundwater flow and provide excavation support. The principle of ground freezing is based on freeze pipes bored into the ground where a coolant flows through the freeze pipes. Eventually, the ground freezing process converts pore water into ice by withdrawing the heat from the soil. In tunneling, artificial ground freezing is applied to form a closed arch frozen ground around the tunnel. Under the presence of high seepage flow, the formation time of the frozen arch is delayed. In some cases, it cannot be formed, leading to high construction costs or unsafe temporary frozen ground support. This study proposes a strategy for systematically reducing the freezing time through an optimal design arrangement of the freeze pipes. The strategy is based on the combination of the numerical modeling of the ground freezing process using a multifield finite element model in conjunction with a surrogate model to enable real-time prediction.
Construction control technology for cutting historical anchor cables along the path of shield tunnels crossing existing tunnels at close proximity
Authors: Mu Yilong , Zhou Xiaowen , Liu Huaiyu 
Published: May 2024

Abstract
In Dongguan Metro Line 1, the new shield tunnel crosses above the existing metro tunnel at a close proximity, necessitating strict control over the displacement of the existing tunnel caused by shield construction. In addition, on the left route of the new shield tunnel, anchor cables used to strengthen the stratum during the construction of the existing tunnel remain embedded in the soil. These anchor cables must be cut off to avoid damaging the shield machine. However, cutting these anchor cables may influence the stress states of the soil and existing tunnel, resulting in additional displacements. To address these challenges, an innovative cutting method for anchor cables was employed in this project. To strictly control the induced settlements of the existing tunnel during shield tunneling, the following measures were implemented: pregrouting reinforcement of the soil above the new tunnel, numerical simulation, and displacement monitoring. The construction of the new tunnel through shield tunneling was successfully completed. The monitoring data indicated minimal displacement of the existing tunnel, demonstrating effective construction control. The control technologies introduced in this study for constructing new shield tunnels crossing an existing tunnel serve as valuable reference for similar projects in the future.
Analytical model for calculating the soil pressure on inclined shield tunnels during construction phase
Authors: Wang Z , Li H , Zhu Y , Huang J , Xie J , Huang X 
Published: May 2024

Abstract
As a new tunneling technology for shallowly buried tunnels, ground penetration shield tunneling (GPST) penetrates the ground directly without launching or receiving shafts, thereby improving the construction efficiency and land-occupation economics. Unlike traditional shield tunnels, which have a leveled or approximately leveled route, the entrance and exit sections of GPST tunnels are inclined, and the external soil and water pressures acting on the latter vary along the route. This study proposes a new loading calculation model for the GPST during the construction phase, considering the dynamically varying stress state along the route. First, a comparison was conducted to delineate the advantages of the proposed model in contrast to the modified conventional method, followed by an analysis of the potential underlying reasons. Subsequently, a parametric study is conducted to evaluate the influence of the excavation slope on the soil pressures acting on the tunnel. The results indicate that the proposed method is better suited for calculating loads at shallow burial depths in GPST.
Field-monitoring and numerical investigation of a super-large-diameter shield tunnel undercrossing existing metro tunnels
Authors: Qin P , Su Z , Zhou C , Xie J , Huang X 
Published: May 2024

Abstract
The Beiheng Expressway in Shanghai was built using a super-large shield with a diameter of 15 m, and its construction impact on adjacent underground structures cannot be overlooked. This newly built tunnel undercrossed Shanghai Metro Line 18 with a minimum distance of 7.86 m. Noticeable additional movements induced by the crossing can be observed in both lines according to in-situ data, initially manifested as slight settlement followed by atypically pronounced heave. The maximum uplifts of the up and down lines reach 7.23 and 5.09 mm, respectively. Subsequently, a numerical study was conducted on this crossing case, and its effectiveness was verified using in-situ data. The results revealed- the soil-structure interactions during the crossing period. The displacement curves in the longitudinal direction of the metro tunnels exhibited asymmetry owing to the oblique crossing, with greater deformation occurring in the region that was crossed earlier than in the region crossed later. Significant heave was also observed for the newly built segmental linings and surrounding ground, indicating pronounced floating induced by large-diameter excavation, which in turn caused the existing metro lines to move upward simultaneously.
Longitudinal structural behavior of shield tunnel with large diameter and small curvature
Authors: Song Q Y , Zhang M X , Ding W J , Wu H M , Zhang Y C 
Published: May 2024

Abstract
The structural mechanism of a large-diameter curved tunnel is introduced in detail because no relevant calculation method is available. A longitudinal discontinuous contact model is established based on the newly built North Highway Tunnel in Shanghai, China. First, the load-spreading mechanism of circumferential joints was considered. Second, the distribution laws of the longitudinal internal force, settlement, and joint deformation of curved and straight tunnels under the same load were analyzed and compared. Finally, a model test is conducted to verify the effectiveness of the discontinuous contact model. The results indicated that with an increase in the radius of curvature, the maximum internal force and deformation decreased. The internal forces and deformations of straight and curved tunnels are quite different; therefore, the design method for a straight tunnel cannot be used in the design of curved tunnels. The overall and local deformations of the curved tunnel were affected by end displacement.
Study on anti-seepage mechanism of attapulgite-modified loess in Northwest China
Authors: Zhang Zhengrui , Zhang Lili , Ahad Aminipishro , Siti Jahara Matlan , Wang Hao 
Published: May 2024

Abstract
Loess is distributed widely in the arid areas in northwest China. Lanzhou city is located on the loess plateau, covered by a large area of deep collapsible Malan loess. Collapsible loess is a soft soil in engineering. It has a specific bearing capacity under dry conditions but will collapse after being immersed in water, which is unfavorable to engineering construction. This paper used the attapulgite abundant in the Zhangye City of Gansu Province as a modifier to improve the loess. The permeability test tested the permeability coefficient of the specimens under different dosages of attapulgite. The anti-permeability principle of attapulgite-modified loess was analyzed from the microscopic perspective by electron microscopy scanning (EMS) and nuclear magnetic resonance (NMR). The test results show that the permeability coefficient of attapulgite-modified loess decreases significantly compared with pure loess, but the permeability coefficient decreases gently when the content of attapulgite exceeds 10%. It was found that the anti-permeability mechanism of the modified loess was that the cohesive attapulgite particles filled the macropores of the loess particles, and the acicular attapulgite combined the loess particles to form a sheet structure, which reduced the porosity and permeability of the modified soil.