Pub Date : 2024-11-23DOI: 10.1016/j.tust.2024.106191
Kun He , Fei Ren , Jian Li , Xiaodong Qian , Junyi Li , Yao Hong , Wei Cong , Yanan Hou
Multiple fire source fires in a tunnel may cause serious fire consequences. In the present study, the flame properties and maximum ceiling smoke temperature for two asymmetric fire sources in the tunnel with natural ventilation are studied in detail. A large number of model-scale fire experiments are performed, considering energy release rate ratio ratio and fire source spacing. The results show that the smaller fire has a larger flame inclination angle and the flame inclination angle of the smaller fire increases with energy release rate ratio. In contrast, the flame tilt angle of the larger fire becomes slightly smaller with the energy release rate ratio. When mean flames merge vertically, the flame height becomes higher when the energy release rate ratio increases. A revised model based on the air entrainment perimeter is proposed to calculate the height of the merged flame. When mean flames cannot merge vertically, a non-dimensional correlation is also developed. With a longer fire source spacing, the maximum ceiling smoke temperature decreases first and then remains unchanged. According to the relative position of the flame tip and tunnel ceiling height, a model is developed to calculate the maximum ceiling smoke temperature. The results of this paper are significant to the fire detection and structure protection for the possibility of two asymmetric fire sources in a tunnel with natural ventilation.
{"title":"Flame properties and maximum ceiling smoke temperature in tunnel fires with two asymmetric fire sources under natural ventilation","authors":"Kun He , Fei Ren , Jian Li , Xiaodong Qian , Junyi Li , Yao Hong , Wei Cong , Yanan Hou","doi":"10.1016/j.tust.2024.106191","DOIUrl":"10.1016/j.tust.2024.106191","url":null,"abstract":"<div><div>Multiple fire source fires in a tunnel may cause serious fire consequences. In the present study, the flame properties and maximum ceiling smoke temperature for two asymmetric fire sources in the tunnel with natural ventilation are studied in detail. A large number of model-scale fire experiments are performed, considering energy release rate ratio ratio and fire source spacing. The results show that the smaller fire has a larger flame inclination angle and the flame inclination angle of the smaller fire increases with energy release rate ratio. In contrast, the flame tilt angle of the larger fire becomes slightly smaller with the energy release rate ratio. When mean flames merge vertically, the flame height becomes higher when the energy release rate ratio increases. A revised model based on the air entrainment perimeter is proposed to calculate the height of the merged flame. When mean flames cannot merge vertically, a non-dimensional correlation is also developed. With a longer fire source spacing, the maximum ceiling smoke temperature decreases first and then remains unchanged. According to the relative position of the flame tip and tunnel ceiling height, a model is developed to calculate the maximum ceiling smoke temperature. The results of this paper are significant to the fire detection and structure protection for the possibility of two asymmetric fire sources in a tunnel with natural ventilation.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106191"},"PeriodicalIF":6.7,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106232
Hong He , Ling-Yi Diao , Wei-Chao Yang , Jun-Jie Liu , Yi-Kang Liu , E Deng
The lateral force exerted when two trains pass each other can adversely affect train safety, and this adverse effect becomes more pronounced as the train speed increases. When trains cross paths in tunnels, the aerodynamics differ from those in open lines due to the restrictive nature of tunnel walls. Utilizing the Renormalization Group (RNG) k-ε turbulence model and the “Mosaic” grid method, this research examines changes in aerodynamic load of the train and ride comfort during a intersection at 400 km/h in a tunnel and contrasts this with conditions at 350 km/h. The results indicate that the change in aerodynamic load on each carriage is more pronounced when the head train of the oncoming train passes than when its tail train passes, with the largest variation observed during the passing of both the head and tail trains. This alteration in aerodynamic load is primarily attributed to the air being pushed in the locomotive area and the negative pressure from the vortex structure between trains. When the speed is increased from 350 km/h to 400 km/h, the aerodynamic load on the train increases by approximately 20 % to 40 %, and the acceleration of the head train grows by 20 % to 50 %. The most noticeable decrease in ride comfort is observed in the head train, with the highest increase in the head train’s Overall Vibration Total Value (OVTV), which rises by 30.1 %.
{"title":"Abrupt changing aerodynamic loads resulting in diminished ride comfort when two high-speed trains intersect in a tunnel","authors":"Hong He , Ling-Yi Diao , Wei-Chao Yang , Jun-Jie Liu , Yi-Kang Liu , E Deng","doi":"10.1016/j.tust.2024.106232","DOIUrl":"10.1016/j.tust.2024.106232","url":null,"abstract":"<div><div>The lateral force exerted when two trains pass each other can adversely affect train safety, and this adverse effect becomes more pronounced as the train speed increases. When trains cross paths in tunnels, the aerodynamics differ from those in open lines due to the restrictive nature of tunnel walls. Utilizing the Renormalization Group (RNG) <em>k-ε</em> turbulence model and the “<em>Mosaic</em>” grid method, this research examines changes in aerodynamic load of the train and ride comfort during a intersection at 400 km/h in a tunnel and contrasts this with conditions at 350 km/h. The results indicate that the change in aerodynamic load on each carriage is more pronounced when the head train of the oncoming train passes than when its tail train passes, with the largest variation observed during the passing of both the head and tail trains. This alteration in aerodynamic load is primarily attributed to the air being pushed in the locomotive area and the negative pressure from the vortex structure between trains. When the speed is increased from 350 km/h to 400 km/h, the aerodynamic load on the train increases by approximately 20 % to 40 %, and the acceleration of the head train grows by 20 % to 50 %. The most noticeable decrease in ride comfort is observed in the head train, with the highest increase in the head train’s Overall Vibration Total Value (<em>OVTV</em>), which rises by 30.1 %.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106232"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106229
Junchen Zhang , Qixiang Yan , Yu Zhao , Minghui Sun , Chaofan Yao , Hongbin Xu
Dislocations of circumferential joints are commonly prevalent in shield tunnels. Generally, the displacement space of bolt in rigid segment joint is very small. When the dislocation of the circumferential joint is large, plastic deformation of the bolts or concrete crushing is inevitable, which will affect the service life of the shield tunnel. The flexibility of the joint can be achieved by embedding in a dowel, which can reduce the damage of the segment joint during the misalignment of the circumferential joint. However, the addition of the dowel changes the structure of the circumferential joint. At present, the shear bearing capacity of the circumferential joint, affecting the design, safety verification, and service performance evaluation, cannot be accurately calculated through the existing mechanical models. Therefore, the envelope curves of the shear bearing capacity of the circumferential joint with dowel were investigated in this paper. Firstly, a series of shear resistance experiments were conducted to clarify the failure characteristics of the circumferential joint with the dowel. Subsequently, based on the experimental results, several shear mechanical calculation models for the circumferential joint were proposed. And the analytical method for the envelope curves between axial force (N) and shear force (Q) was derived. Finally, the accuracy of the analytical method was verified, and corresponding optimization methods to improve the bearing performance of the circumferential joint were proposed. The research results indicate that the circumferential joint with dowel has both concrete shear stage and steel rebars shear stage. The N-Q envelope curves is determined by the combination of concrete, connectors (including the dowel and the bolt), and steel rebars, and the leading factor can be clarified by the proposed method. A constructive conclusion has been found that the optimization design of the circumferential joint must consider the axial force in order to effectively improve its shear bearing performance. The research results can serve the joint optimization, load-bearing verification during design process, and the physical model in big data analysis during the operation and maintenance of the shield tunnel.
{"title":"Compression-shear capacity of circumferential joint with dowel in shield tunnel: From experiments to analytical solution","authors":"Junchen Zhang , Qixiang Yan , Yu Zhao , Minghui Sun , Chaofan Yao , Hongbin Xu","doi":"10.1016/j.tust.2024.106229","DOIUrl":"10.1016/j.tust.2024.106229","url":null,"abstract":"<div><div>Dislocations of circumferential joints are commonly prevalent in shield tunnels. Generally, the displacement space of bolt in rigid segment joint is very small. When the dislocation of the circumferential joint is large, plastic deformation of the bolts or concrete crushing is inevitable, which will affect the service life of the shield tunnel. The flexibility of the joint can be achieved by embedding in a dowel, which can reduce the damage of the segment joint during the misalignment of the circumferential joint. However, the addition of the dowel changes the structure of the circumferential joint. At present, the shear bearing capacity of the circumferential joint, affecting the design, safety verification, and service performance evaluation, cannot be accurately calculated through the existing mechanical models. Therefore, the envelope curves of the shear bearing capacity of the circumferential joint with dowel were investigated in this paper. Firstly, a series of shear resistance experiments were conducted to clarify the failure characteristics of the circumferential joint with the dowel. Subsequently, based on the experimental results, several shear mechanical calculation models for the circumferential joint were proposed. And the analytical method for the envelope curves between axial force (<em>N</em>) and shear force (<em>Q</em>) was derived. Finally, the accuracy of the analytical method was verified, and corresponding optimization methods to improve the bearing performance of the circumferential joint were proposed. The research results indicate that the circumferential joint with dowel has both concrete shear stage and steel rebars shear stage. The <em>N-Q</em> envelope curves is determined by the combination of concrete, connectors (including the dowel and the bolt), and steel rebars, and the leading factor can be clarified by the proposed method. A constructive conclusion has been found that the optimization design of the circumferential joint must consider the axial force in order to effectively improve its shear bearing performance. The research results can serve the joint optimization, load-bearing verification during design process, and the physical model in big data analysis during the operation and maintenance of the shield tunnel.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106229"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106225
Dongwei Wu , Lei Zhou , Fukuan Nie , Feng Dai , Meng Wang , Bang Liu
Multitudinous natural human-induced flaws exist in the rock mass, which could pose potential risks to the safety of tunnel engineering. To study the dynamic failure properties of the tunnel with a crack in the surrounding rock mass, a series of typical split Hopkinson pressure bar (SHPB) dynamic fracture tests were conducted. A high-speed camera was utilized to record the failure process and digital image correlation (DIC) techniques were applied to analyze the evolution law of strain field in the surrounding rock mass. Numerical simulations were performed using LS-DYNA software after calibrating the parameters of the Riedel-Hiermaier-Thoma (RHT) model. The findings of this study indicate that far-field cracks could contribute to tensile crack propagation from the tunnel vault and tunnel floor. In addition, simulations are highly consistent with model experiments, which proves its practicability and accuracy. These results could provide significant references for more secure, economical and efficient support solutions for engineering. The study also promotes the application of the RHT model to the dynamic response behavior of defected rock-like materials.
{"title":"Experimental and numerical investigation on the failure behavior of far-field-crack-tunnel rock mass under dynamic loads","authors":"Dongwei Wu , Lei Zhou , Fukuan Nie , Feng Dai , Meng Wang , Bang Liu","doi":"10.1016/j.tust.2024.106225","DOIUrl":"10.1016/j.tust.2024.106225","url":null,"abstract":"<div><div>Multitudinous natural human-induced flaws exist in the rock mass, which could pose potential risks to the safety of tunnel engineering. To study the dynamic failure properties of the tunnel with a crack in the surrounding rock mass, a series of typical split Hopkinson pressure bar (SHPB) dynamic fracture tests were conducted. A high-speed camera was utilized to record the failure process and digital image correlation (DIC) techniques were applied to analyze the evolution law of strain field in the surrounding rock mass. Numerical simulations were performed using LS-DYNA software after calibrating the parameters of the Riedel-Hiermaier-Thoma (RHT) model. The findings of this study indicate that far-field cracks could contribute to tensile crack propagation from the<!--> <!-->tunnel vault and tunnel floor. In addition, simulations are highly consistent with model experiments, which proves its practicability and accuracy. These results could provide significant references for more secure, economical and efficient support solutions for engineering. The study also promotes the application of the RHT model to the dynamic response behavior of defected rock-like materials.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106225"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106233
Zheng Chen , Shulei Zhao , Chen Dong , Shuaishuai Wang , Yabin Guo , Xuan Gao , Bing Sun , Wengan Chen , Chun Guo
In extra-long tunnels, the dust generated by blasting excavation is difficult to discharge through ventilation, which can easily lead to secondary dust generation, severely affecting the health of construction personnel inside the tunnel and potentially increasing the construction interval. To shorten the dust removal time and enhance efficiency during tunnel blasting, this study utilized a single-hole single-track railway tunnel to conduct on-site measurements and numerical simulations of blasting dust. The effectiveness of the dust mist coupling model was validated through indoor model experiments, showing a maximum deviation of 16.94 % between the average concentration at numerical simulation monitoring points and that from model test measurements. Additionally, the model’s stability was assessed using three grid sizes: coarse, medium, and fine, with the maximum relative change in dust removal rate reaching 14.75 %. In combination with the original forced ventilation system, a three-section spray dedusting method was designed. The first nozzle was positioned at the center of the forced air duct outlet, with a nozzle diameter of SH2.4 mm. The second section, located 50 m from the tunnel face, contained two nozzles placed at the top and bottom of the section. The third section, situated approximately 100 m from the tunnel face, featured two X-core circular nozzles with a diameter of 2 mm, operating at a spray pressure of 8 MPa. Nine groups of orthogonal experiments were designed using CFD, identifying the spray angle, compressed air duct volume, and spray ring spacing as the most influential factors in dust removal time. Through the addition of Experiment 10 to the orthogonal set and subsequent comparisons, the optimal spray parameters were determined to be a spray angle of 15°, a compressed air duct air volume of 26 m3/s, and a spray ring spacing of 50 m. Based on the analysis of numerical results, it can be concluded that the spray dust reduction measures effectively reduced the dust concentration within 200 m of the tunnel face to a safe level 900 s after blasting.
{"title":"Spray dust control measures of tunnel blasting dust based on CFD dust-droplet coupling model and orthogonal test","authors":"Zheng Chen , Shulei Zhao , Chen Dong , Shuaishuai Wang , Yabin Guo , Xuan Gao , Bing Sun , Wengan Chen , Chun Guo","doi":"10.1016/j.tust.2024.106233","DOIUrl":"10.1016/j.tust.2024.106233","url":null,"abstract":"<div><div>In extra-long tunnels, the dust generated by blasting excavation is difficult to discharge through ventilation, which can easily lead to secondary dust generation, severely affecting the health of construction personnel inside the tunnel and potentially increasing the construction interval. To shorten the dust removal time and enhance efficiency during tunnel blasting, this study utilized a single-hole single-track railway tunnel to conduct on-site measurements and numerical simulations of blasting dust. The effectiveness of the dust mist coupling model was validated through indoor model experiments, showing a maximum deviation of 16.94 % between the average concentration at numerical simulation monitoring points and that from model test measurements. Additionally, the model’s stability was assessed using three grid sizes: coarse, medium, and fine, with the maximum relative change in dust removal rate reaching 14.75 %. In combination with the original forced ventilation system, a three-section spray dedusting method was designed. The first nozzle was positioned at the center of the forced air duct outlet, with a nozzle diameter of SH2.4 mm. The second section, located 50 m from the tunnel face, contained two nozzles placed at the top and bottom of the section. The third section, situated approximately 100 m from the tunnel face, featured two X-core circular nozzles with a diameter of 2 mm, operating at a spray pressure of 8 MPa. Nine groups of orthogonal experiments were designed using CFD, identifying the spray angle, compressed air duct volume, and spray ring spacing as the most influential factors in dust removal time. Through the addition of Experiment 10 to the orthogonal set and subsequent comparisons, the optimal spray parameters were determined to be a spray angle of 15°, a compressed air duct air volume of 26 m<sup>3</sup>/s, and a spray ring spacing of 50 m. Based on the analysis of numerical results, it can be concluded that the spray dust reduction measures effectively reduced the dust concentration within 200 m of the tunnel face to a safe level 900 s after blasting.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106233"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106212
Yimo Zhu, Qian-Bing Zhang
Underground infrastructures are the essential assets to the transport, energy storage, and utilities. However, with the deepening development of urbanisation and modernisation, the safety of underground infrastructure is threatened by various natural or human-induced hazards. In the construction and operation phases, hazards can be single, cascade or combined in their origin and effects, the combined or potential interrelated effects of them may exacerbate consequences, leading to higher loss of functionality and cost of restoration. Determining the post-hazard capacity and recovery ability of these infrastructures in a quantitative approach remains ongoing research priority. This paper proposes a unified approach of implementing a quantified resilience assessment of underground infrastructures subjected to multiple hazards. Embedding potential abrupt hazards into long-term deterioration of a circular tunnel, coupled with modelling of restoration, the lifecycle performance is presented. The results show that the disturbance caused by excavation construction has an influence on the performance of subsequent operation phase. The deterioration hazards including ageing and corrosion of structure and creep deformation of rock mass during the whole service life continuously decreases the functionality of the tunnel. While abrupt hazards, such as earthquake and blasting, lead to a sharp decline in functionality in a short period of time. Continuous evolution over time of deformation and damage caused by various hazards, whether deteriorated or abrupt, will be inherited and accumulated. Timely repair, such as pretensioned bolts and grouting can effectively restore the bearing capacity of the infrastructure to a specific extent. Through this numerical approach, the restoration time can be estimated by the functionality recovered and unit consumed time. The dimensionless resilience index is then calculated for the post-hazard functionality based on the specific hazard scenarios and restoration solutions.
{"title":"Modelling and assessing lifetime resilience of underground infrastructure to multiple hazards: Toward a unified approach","authors":"Yimo Zhu, Qian-Bing Zhang","doi":"10.1016/j.tust.2024.106212","DOIUrl":"10.1016/j.tust.2024.106212","url":null,"abstract":"<div><div>Underground infrastructures are the essential assets to the transport, energy storage, and utilities. However, with the deepening development of urbanisation and modernisation, the safety of underground infrastructure is threatened by various natural or human-induced hazards. In the construction and operation phases, hazards can be single, cascade or combined in their origin and effects, the combined or potential interrelated effects of them may exacerbate consequences, leading to higher loss of functionality and cost of restoration. Determining the post-hazard capacity and recovery ability of these infrastructures in a quantitative approach remains ongoing research priority. This paper proposes a unified approach of implementing a quantified resilience assessment of underground infrastructures subjected to multiple hazards. Embedding potential abrupt hazards into long-term deterioration of a circular tunnel, coupled with modelling of restoration, the lifecycle performance is presented. The results show that the disturbance caused by excavation construction has an influence on the performance of subsequent operation phase. The deterioration hazards including ageing and corrosion of structure and creep deformation of rock mass during the whole service life continuously decreases the functionality of the tunnel. While abrupt hazards, such as earthquake and blasting, lead to a sharp decline in functionality in a short period of time. Continuous evolution over time of deformation and damage caused by various hazards, whether deteriorated or abrupt, will be inherited and accumulated. Timely repair, such as pretensioned bolts and grouting can effectively restore the bearing capacity of the infrastructure to a specific extent. Through this numerical approach, the restoration time can be estimated by the functionality recovered and unit consumed time. The dimensionless resilience index is then calculated for the post-hazard functionality based on the specific hazard scenarios and restoration solutions.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106212"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106226
Haitong Sui , Kensuke Asaba , Kazuo Sakai , Syuntaro Miyanaga , Ying Cui
A novel method for quantitatively describing the distribution of point clouds in tunnels is introduced to optimize tunnel scanning schemes. The method uses point cloud spacing and thickness to represent the density and unevenness of the point cloud, respectively. Point cloud spacing is categorized into point spacing and ring spacing based on the scanning trajectory, and these metrics are calculated using coordinates from a regularly distributed point cloud. Point cloud thickness is derived by combining the measurement error range in the laser incidence direction with the laser incidence angle. The above calculation method has been validated through tunnel field tests. The quantitative characterization method evaluates the effects of resolution, station spacing, and linearity error on point cloud spacing and thickness. It helps determine the necessary resolution, station spacing, and TLS scanner specifications to ensure that point cloud spacing and thickness meet the requirements for tunnel health assessment. By addressing the lack of comprehensive quantitative consideration of point cloud distribution in selecting scanning parameters, this method provides a robust framework for optimizing scanning schemes, ensuring accurate and reliable point cloud data for tunnel inspection.
{"title":"Quantitative characterization method of point cloud distribution in tunnel for optimizing TLS scanning plan","authors":"Haitong Sui , Kensuke Asaba , Kazuo Sakai , Syuntaro Miyanaga , Ying Cui","doi":"10.1016/j.tust.2024.106226","DOIUrl":"10.1016/j.tust.2024.106226","url":null,"abstract":"<div><div>A novel method for quantitatively describing the distribution of point clouds in tunnels is introduced to optimize tunnel scanning schemes. The method uses point cloud spacing and thickness to represent the density and unevenness of the point cloud, respectively. Point cloud spacing is categorized into point spacing and ring spacing based on the scanning trajectory, and these metrics are calculated using coordinates from a regularly distributed point cloud. Point cloud thickness is derived by combining the measurement error range in the laser incidence direction with the laser incidence angle. The above calculation method has been validated through tunnel field tests. The quantitative characterization method evaluates the effects of resolution, station spacing, and linearity error on point cloud spacing and thickness. It helps determine the necessary resolution, station spacing, and TLS scanner specifications to ensure that point cloud spacing and thickness meet the requirements for tunnel health assessment. By addressing the lack of comprehensive quantitative consideration of point cloud distribution in selecting scanning parameters, this method provides a robust framework for optimizing scanning schemes, ensuring accurate and reliable point cloud data for tunnel inspection.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106226"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.tust.2024.106241
Mukhtiar Ali Soomro , Shaokai Xiong , Zhen-Dong Cui , Chenyang Zhao , Naeem Mangi
The escalation in infrastructure such as highways and high-speed railways has necessitated construction on soft and compressible ground, prompting the adoption of innovative solutions like piled-supported embankments. With the surge in tunnelling for transportations projects, the necessity of constructing tunnels in close proximity to piled embankments has become apparent. This study examines into settlement and load transfer mechanisms in piled-embankments affected by tunnel excavation at varying depths relative to pile lengths, employing a hypoplastic model to capture the nonlinear behaviour of soft soil. The findings indicate that the deepest tunnel caused the largest settlement, while the shallowest tunnel in led to the smallest settlement in the embankment due to pile settlements playing a significant role. The pile-soil stress ratio near the tunnel increased significantly when excavated close to pile shaft, contrasting substantially with decreased ratio in the tunnelling beneath the piled-embankment case. The bending moments in the piles exhibited differing behaviours in each case, with distinct trends observed in lateral movement and stress-induced responses. The axial load changes were influenced by factors such as negative skin friction, positive shaft resistance, and embankment weight transfer through arching, leading to unique load patterns along the pile length caused by the shallowest tunnel.
{"title":"Piled-supported embankment responses to tunnelling in soft ground: An investigation of settlement and load transfer mechanisms","authors":"Mukhtiar Ali Soomro , Shaokai Xiong , Zhen-Dong Cui , Chenyang Zhao , Naeem Mangi","doi":"10.1016/j.tust.2024.106241","DOIUrl":"10.1016/j.tust.2024.106241","url":null,"abstract":"<div><div>The escalation in infrastructure such as highways and high-speed railways has necessitated construction on soft and compressible ground, prompting the adoption of innovative solutions like piled-supported embankments. With the surge in tunnelling for transportations projects, the necessity of constructing tunnels in close proximity to piled embankments has become apparent. This study examines into settlement and load transfer mechanisms in piled-embankments affected by tunnel excavation at varying depths relative to pile lengths, employing a hypoplastic model to capture the nonlinear behaviour of soft soil. The findings indicate that the deepest tunnel caused the largest settlement, while the shallowest tunnel in led to the smallest settlement in the embankment due to pile settlements playing a significant role. The pile-soil stress ratio near the tunnel increased significantly when excavated close to pile shaft, contrasting substantially with decreased ratio in the tunnelling beneath the piled-embankment case. The bending moments in the piles exhibited differing behaviours in each case, with distinct trends observed in lateral movement and stress-induced responses. The axial load changes were influenced by factors such as negative skin friction, positive shaft resistance, and embankment weight transfer through arching, leading to unique load patterns along the pile length caused by the shallowest tunnel.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106241"},"PeriodicalIF":6.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.tust.2024.106147
Bryan A. McCabe , Kevin G. O’Dwyer , Brian B. Sheil
In long pipe-jacking drives used for installing utility pipelines, field experience has shown that transient peaks in skin friction arise upon recommencement of jacking after stoppages; these forces are often very large and difficult to predict, presenting a significant risk for contractors. In this paper, the problem is replicated in the laboratory using direct shear interface tests with a concrete specimen in one half of the apparatus and various sand/bentonite slurry mixtures in the other. Once critical state conditions were reached in these tests, stoppages of various durations (from 30 mins up to ≈2 weeks) were incorporated and the increase in shear stress upon recommencement of shearing was noted. The experimental results revealed that these increases are dependent on bentonite slurry content, and there appears to be a threshold stoppage duration beyond which the skin friction increase appears to plateau, suggestive of a time-limited process within the bentonite. Shearometer tests measuring the gel strength of aged bentonite slurry samples, in addition to small and erratic (in time) consolidation magnitudes during the direct shear test stoppages together suggest that bentonite thixotropy is a key contributor to the stoppage-induced skin friction increases. A simple model capturing this behaviour provided a safe upper bound to the stoppage-induced skin friction increases extracted from a selection of field data, offering much better jacking force predictions than standard prediction models used in industry.
{"title":"Skin friction increases associated with pipe-jacking stoppages modelled using direct shear interface tests","authors":"Bryan A. McCabe , Kevin G. O’Dwyer , Brian B. Sheil","doi":"10.1016/j.tust.2024.106147","DOIUrl":"10.1016/j.tust.2024.106147","url":null,"abstract":"<div><div>In long pipe-jacking drives used for installing utility pipelines, field experience has shown that transient peaks in skin friction arise upon recommencement of jacking after stoppages; these forces are often very large and difficult to predict, presenting a significant risk for contractors. In this paper, the problem is replicated in the laboratory using direct shear interface tests with a concrete specimen in one half of the apparatus and various sand/bentonite slurry mixtures in the other. Once critical state conditions were reached in these tests, stoppages of various durations (from 30 mins up to ≈2 weeks) were incorporated and the increase in shear stress upon recommencement of shearing was noted. The experimental results revealed that these increases are dependent on bentonite slurry content, and there appears to be a threshold stoppage duration beyond which the skin friction increase appears to plateau, suggestive of a time-limited process within the bentonite. Shearometer tests measuring the gel strength of aged bentonite slurry samples, in addition to small and erratic (in time) consolidation magnitudes during the direct shear test stoppages together suggest that bentonite thixotropy is a key contributor to the stoppage-induced skin friction increases. A simple model capturing this behaviour provided a safe upper bound to the stoppage-induced skin friction increases extracted from a selection of field data, offering much better jacking force predictions than standard prediction models used in industry.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106147"},"PeriodicalIF":6.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.tust.2024.106239
Zheng-Wei Chen , Zhan-Hao Guo , Yi-Qing Ni , Zi-Jian Guo , Tian-Tian Wang , En-Ze Rui , Guang-Zhi Zeng
Sudden pressure changes and strong micro-pressure waves are critical issues in the train/tunnel aerodynamics during high-speed maglev trains traveling through tunnels, as they can significantly influence the safety, and comfort of the passengers. This paper focuses on the application of suction actuators to alleviate these issues and explores the influence of various suction parameters through simulations, such as suction positions, shapes, and areas, on pressure waves. Furthermore, it compares the mitigating effects of the suction method with those of the tunnel hood. The results show: (i) the alleviating effects are superior when suction actuators are installed at the middle of the tunnel compared to those installed at the entrance or exit; (ii) suction shapes have minimal influence on their mitigating effects, while increasing the size of the suction slots enhances these effects; the suction size reaches a threshold at approximately 1.00 m in width, achieving reductions of 15.76 % and 14.84 % in the micro-pressure wave at distances of 20 m and 50 m from the exit, respectively; (iii) the mitigating effects of the suction method and the tunnel hood are different; the suction method focuses on reducing the overall pressure in high-pressure regions within the tunnel, whereas the tunnel hood primarily mitigates micro-pressure waves; (iv) combining passive and active mitigation methods does not significantly enhance their alleviating effects due to their different mechanisms; in fact, their combined effects may worsen. All these results can serve as a valuable reference for mitigating train/tunnel aerodynamics.
{"title":"Parametric investigation of suction actuators on the tunnel wall for alleviating pressure interactions in high-speed maglev train/tunnel system","authors":"Zheng-Wei Chen , Zhan-Hao Guo , Yi-Qing Ni , Zi-Jian Guo , Tian-Tian Wang , En-Ze Rui , Guang-Zhi Zeng","doi":"10.1016/j.tust.2024.106239","DOIUrl":"10.1016/j.tust.2024.106239","url":null,"abstract":"<div><div>Sudden pressure changes and strong micro-pressure waves are critical issues in the train/tunnel aerodynamics during high-speed maglev trains traveling through tunnels, as they can significantly influence the safety, and comfort of the passengers. This paper focuses on the application of suction actuators to alleviate these issues and explores the influence of various suction parameters through simulations, such as suction positions, shapes, and areas, on pressure waves. Furthermore, it compares the mitigating effects of the suction method with those of the tunnel hood. The results show: (i) the alleviating effects are superior when suction actuators are installed at the middle of the tunnel compared to those installed at the entrance or exit; (ii) suction shapes have minimal influence on their mitigating effects, while increasing the size of the suction slots enhances these effects; the suction size reaches a threshold at approximately 1.00 m in width, achieving reductions of 15.76 % and 14.84 % in the micro-pressure wave at distances of 20 m and 50 m from the exit, respectively; (iii) the mitigating effects of the suction method and the tunnel hood are different; the suction method focuses on reducing the overall pressure in high-pressure regions within the tunnel, whereas the tunnel hood primarily mitigates micro-pressure waves; (iv) combining passive and active mitigation methods does not significantly enhance their alleviating effects due to their different mechanisms; in fact, their combined effects may worsen. All these results can serve as a valuable reference for mitigating train/tunnel aerodynamics.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"156 ","pages":"Article 106239"},"PeriodicalIF":6.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号