Pub Date : 2024-12-16DOI: 10.1016/j.undsp.2024.11.001
Shuhong Wang , Bowen Han , Jianhui Jiang , Natalia Telyatnikova
To comply with the requirements of sustainable energy development, China has proposed the strategic goal of achieving dual carbon. Systematic and scientific development and utilization of urban underground space will provide critical support for reducing carbon emissions and enhancing carbon sink capacity. This paper examines the transmission and distribution ring pit project of Fuzhou Binhai New City, China, divided into four regions, where the selection of the support system is determined by the project’s characteristics. Stability is analyzed using in-situ monitoring data from the R4 area, and the deformation of the support system is predicted using machine learning. The predicted maximum lateral deformation of the support system may reach the warning value, necessitating corrections to the existing support parameters. On this basis, the deformation during foundation pit excavation is simulated, and the effects of key factors such as pile geometric parameters, pile penetration depth, and anchor cable insertion ratio on the deformation are analyzed. The study shows that pile deformation control is optimal when the support parameters include a 1.3 insertion ratio, a 20° anchor cable angle, and a 200 kN prestressing force, enabling the construction of the remaining three areas. This study can serve as a valuable reference for the design and analysis of deep foundation pits under special stratigraphic conditions in coastal areas.
{"title":"Machine learning and FEM-driven analysis and optimization of deep foundation pits in coastal area: A case study in Fuzhou soft ground","authors":"Shuhong Wang , Bowen Han , Jianhui Jiang , Natalia Telyatnikova","doi":"10.1016/j.undsp.2024.11.001","DOIUrl":"10.1016/j.undsp.2024.11.001","url":null,"abstract":"<div><div>To comply with the requirements of sustainable energy development, China has proposed the strategic goal of achieving dual carbon. Systematic and scientific development and utilization of urban underground space will provide critical support for reducing carbon emissions and enhancing carbon sink capacity. This paper examines the transmission and distribution ring pit project of Fuzhou Binhai New City, China, divided into four regions, where the selection of the support system is determined by the project’s characteristics. Stability is analyzed using in-situ monitoring data from the R4 area, and the deformation of the support system is predicted using machine learning. The predicted maximum lateral deformation of the support system may reach the warning value, necessitating corrections to the existing support parameters. On this basis, the deformation during foundation pit excavation is simulated, and the effects of key factors such as pile geometric parameters, pile penetration depth, and anchor cable insertion ratio on the deformation are analyzed. The study shows that pile deformation control is optimal when the support parameters include a 1.3 insertion ratio, a 20° anchor cable angle, and a 200 kN prestressing force, enabling the construction of the remaining three areas. This study can serve as a valuable reference for the design and analysis of deep foundation pits under special stratigraphic conditions in coastal areas.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 55-76"},"PeriodicalIF":8.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512391","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 : 2024-12-04DOI: 10.1016/j.undsp.2024.10.001
Tao Yan , Shui-Long Shen , Annan Zhou
This paper proposed a framework for muck types identification based on data augmentation-assisted image recognition during shield tunnelling. The muck pictures were collected from the shield monitoring system above the conveyor belt. The data augmentation operations were then used to increase the quality of the original images. Furthermore, the Bayesian optimisation algorithm was employed to adjust the parameters of augmenters and highlight the features of the photos. The deep image recognition algorithms (AlexNet and GoogLeNet) were trained and enhanced by the augmentation images, which were used to establish the muck types identification models and assessed by the evaluation indices. Model efficiency was analysed through the performance and time cost of training and validation processes to select the optimal model for muck types identification. Results showed that the performance of identification models could be highly increased by data augmentation with Bayesian optimisation, and the enhanced GoogLeNet performed the highest efficiency for muck types identification.
{"title":"Data augmentation-assisted muck image recognition during shield tunnelling","authors":"Tao Yan , Shui-Long Shen , Annan Zhou","doi":"10.1016/j.undsp.2024.10.001","DOIUrl":"10.1016/j.undsp.2024.10.001","url":null,"abstract":"<div><div>This paper proposed a framework for muck types identification based on data augmentation-assisted image recognition during shield tunnelling. The muck pictures were collected from the shield monitoring system above the conveyor belt. The data augmentation operations were then used to increase the quality of the original images. Furthermore, the Bayesian optimisation algorithm was employed to adjust the parameters of augmenters and highlight the features of the photos. The deep image recognition algorithms (AlexNet and GoogLeNet) were trained and enhanced by the augmentation images, which were used to establish the muck types identification models and assessed by the evaluation indices. Model efficiency was analysed through the performance and time cost of training and validation processes to select the optimal model for muck types identification. Results showed that the performance of identification models could be highly increased by data augmentation with Bayesian optimisation, and the enhanced GoogLeNet performed the highest efficiency for muck types identification.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 370-383"},"PeriodicalIF":8.2,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147149","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 : 2024-11-30DOI: 10.1016/j.undsp.2024.09.003
Hao Luo , Ming Tao , Zhixian Hong , Gongliang Xiang , Chengqing Wu
The dynamic response and failure characteristics of tunnels vary significantly under various dynamic disturbances. These characteristics are crucial for assessing structural stability and designing effective support for surrounding rock. In this study, the theoretical solution for the dynamic stress concentration factor (DSCF) of a circular tunnel subjected to cylindrical and plane P-waves was derived using the wave function expansion method. The existing equivalent blast stress wave was optimized and the Ricker wavelet was introduced to represent the seismic stress waves. By combining Fourier transform and Duhamel’s integral, the transient response of the underground tunnel under near-field blasts and far-field earthquakes was determined in both the frequency and time domains. The theoretical results were validated by comparing them with those obtained from numerical simulations using ANSYS LS-DYNA software. Numerical simulations were conducted to further investigate the damage characteristics of the underground tunnel and evaluate the effect of initial stress on structural failure under both types of disturbances. The theoretical and numerical simulation results indicated that the differences in the dynamic response and damage characteristics of the underground tunnel were primarily due to the curvature of the stress waves and transient load waveform. The locations of the maximum DSCF values differed between near-field blasts and far-field earthquakes, whereas the minimum DSCF values occurred at the same positions. Without initial stress, the blast stress waves caused spalling damage to the rock mass on the wave-facing side. Shear failure occurred near the areas with maximum DSCF values, and tensile failure occurred near the areas with minimum DSCF values. In contrast, damage occurred only near the areas with maximum DSCF values under seismic stress waves. Furthermore, the initial stress exacerbated spalling and shear damage while suppressing tensile failure. Hence, the blast stress waves no longer induced tensile failure on the tunnel sidewalls under initial stress.
{"title":"Analysis of the dynamic response and damage characteristic for the tunnel under near-field blasts and far-field earthquakes","authors":"Hao Luo , Ming Tao , Zhixian Hong , Gongliang Xiang , Chengqing Wu","doi":"10.1016/j.undsp.2024.09.003","DOIUrl":"10.1016/j.undsp.2024.09.003","url":null,"abstract":"<div><div>The dynamic response and failure characteristics of tunnels vary significantly under various dynamic disturbances. These characteristics are crucial for assessing structural stability and designing effective support for surrounding rock. In this study, the theoretical solution for the dynamic stress concentration factor (DSCF) of a circular tunnel subjected to cylindrical and plane P-waves was derived using the wave function expansion method. The existing equivalent blast stress wave was optimized and the Ricker wavelet was introduced to represent the seismic stress waves. By combining Fourier transform and Duhamel’s integral, the transient response of the underground tunnel under near-field blasts and far-field earthquakes was determined in both the frequency and time domains. The theoretical results were validated by comparing them with those obtained from numerical simulations using ANSYS LS-DYNA software. Numerical simulations were conducted to further investigate the damage characteristics of the underground tunnel and evaluate the effect of initial stress on structural failure under both types of disturbances. The theoretical and numerical simulation results indicated that the differences in the dynamic response and damage characteristics of the underground tunnel were primarily due to the curvature of the stress waves and transient load waveform. The locations of the maximum DSCF values differed between near-field blasts and far-field earthquakes, whereas the minimum DSCF values occurred at the same positions. Without initial stress, the blast stress waves caused spalling damage to the rock mass on the wave-facing side. Shear failure occurred near the areas with maximum DSCF values, and tensile failure occurred near the areas with minimum DSCF values. In contrast, damage occurred only near the areas with maximum DSCF values under seismic stress waves. Furthermore, the initial stress exacerbated spalling and shear damage while suppressing tensile failure. Hence, the blast stress waves no longer induced tensile failure on the tunnel sidewalls under initial stress.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 331-351"},"PeriodicalIF":8.2,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143146750","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 : 2024-11-26DOI: 10.1016/j.undsp.2024.08.008
Yu Miao, Han-Wen Ji, Yang Shi
Assembled monolithic subway station partly synthesizes the advantages of cast-in-place and precast subway stations. However, the related seismic response analysis considering the influences of vertical ground motion and aboveground structure is still scant. In this study, we firstly performed the statistical analysis on bidirectional bedrock ground motion parameters (response spectrum, duration and envelope function) using KiK-net data, and obtained some suggested values of the above parameters. Then, four sets of artificial bedrock ground motions with statistical meanings were generated and a three-dimensional finite element analysis of the seismic response of an existing two-story three-span subway station was conducted. The main results are summarized below. (1) The significant damage to assembled monolithic station under far-field strong motion firstly occurred at side middle slab; middle slab, upper column and related grouting sleeve joints were more damage-prone. (2) When horizontal peak ground acceleration stayed constant, overall the damage of far-field motion was stronger than that of near-fault motion. (3) Vertical ground motion obviously accelerated the damage progresses of various structural members at various positions, then aboveground structure further enhanced the damages and vertical displacement responses of parts of top slab. (4) For the axial force time-history of upper column during far-field strong motion, aboveground structure uplifted the baseline, and vertical ground motion increased the amplitude and advanced the obvious drop of the baseline, among which the latter effect of vertical ground motion on assembled monolithic station was stronger than that on cast-in-place station. (5) Vertical ground motion enhanced inter-story displacement during far-field strong motion, among which the influence on the upper story of assembled monolithic station could be obviously amplified by aboveground structure, and the amplification effect lagged behind the influence of vertical ground motion. Based on the results of this study, some suggestions for the seismic design of subway station are also provided.
{"title":"Bidirectional seismic response of assembled monolithic subway station-aboveground structure system under artificial bedrock ground motions","authors":"Yu Miao, Han-Wen Ji, Yang Shi","doi":"10.1016/j.undsp.2024.08.008","DOIUrl":"10.1016/j.undsp.2024.08.008","url":null,"abstract":"<div><div>Assembled monolithic subway station partly synthesizes the advantages of cast-in-place and precast subway stations. However, the related seismic response analysis considering the influences of vertical ground motion and aboveground structure is still scant. In this study, we firstly performed the statistical analysis on bidirectional bedrock ground motion parameters (response spectrum, duration and envelope function) using KiK-net data, and obtained some suggested values of the above parameters. Then, four sets of artificial bedrock ground motions with statistical meanings were generated and a three-dimensional finite element analysis of the seismic response of an existing two-story three-span subway station was conducted. The main results are summarized below. (1) The significant damage to assembled monolithic station under far-field strong motion firstly occurred at side middle slab; middle slab, upper column and related grouting sleeve joints were more damage-prone. (2) When horizontal peak ground acceleration stayed constant, overall the damage of far-field motion was stronger than that of near-fault motion. (3) Vertical ground motion obviously accelerated the damage progresses of various structural members at various positions, then aboveground structure further enhanced the damages and vertical displacement responses of parts of top slab. (4) For the axial force time-history of upper column during far-field strong motion, aboveground structure uplifted the baseline, and vertical ground motion increased the amplitude and advanced the obvious drop of the baseline, among which the latter effect of vertical ground motion on assembled monolithic station was stronger than that on cast-in-place station. (5) Vertical ground motion enhanced inter-story displacement during far-field strong motion, among which the influence on the upper story of assembled monolithic station could be obviously amplified by aboveground structure, and the amplification effect lagged behind the influence of vertical ground motion. Based on the results of this study, some suggestions for the seismic design of subway station are also provided.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 291-312"},"PeriodicalIF":8.2,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147148","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 : 2024-11-20DOI: 10.1016/j.undsp.2024.08.007
Haoyu Wang , Jichen Xie , Jinyang Fu , Cong Zhang , Dingping Chen , Zhiheng Zhu , Xuesen Zhang
Small-section hydraulic tunnels are characterized by small spaces and various section forms, under complex environments, which makes it difficult to carry out an inspection by the mobile acquisition equipment. To resolve these problems, an arbitrarily adjustable camera module deployment method and the corresponding automatic image acquisition equipment with multi-area array cameras are proposed and developed. Such method enables the acquisition of full-length surface images of the hydraulic tunnels with different cross-section forms and diameters by a one-way travel, and the overlap rate and accuracy of the acquired image sets meet the requirements of three-dimensional reconstruction and panoramic image generation. In addition, to improve the speed and accuracy of traditional algorithms for tunnel surface defects detection, this paper proposes an improved YOLOv5s-DECA model. The algorithm introduces DenseNet to optimize the backbone feature extraction network and incorporates an efficient channel attention ECA module to make a better extraction of features of defects. The experimental results show that mAP, and F1-score of YOLOv5-DECA are 73.4% and 74.6%, respectively, which are better than the common model in terms of accuracy and robustness. The proposed YOLOv5-DECA has great detection performance for targets with variable shapes and can solve the problem of classification imbalance in surface defects. Then, by combining YOLOv5-DECA with the direction search algorithm, a “point-ring-section” method is established to allow rapid identification of common surface defects by detecting them layer by layer with the bottom image of the stitched panorama as the seed. The presented method in this paper effectively solves the problem that a single image fails to show the overall distribution of the defects and their accurate positioning in a whole large tunnel section and the effective features of defects in an excessively large panoramic image size are difficult to be captured by the neural network. Field applications demonstrated that the presented method is adequate for high-precision and intelligent surface defect detection and positioning for different small-section hydraulic tunnels such as circular, arch-wall, and box-shaped hydraulic tunnels.
{"title":"Rapid acquisition and surface defects recognition based on panoramic image of small-section hydraulic tunnel","authors":"Haoyu Wang , Jichen Xie , Jinyang Fu , Cong Zhang , Dingping Chen , Zhiheng Zhu , Xuesen Zhang","doi":"10.1016/j.undsp.2024.08.007","DOIUrl":"10.1016/j.undsp.2024.08.007","url":null,"abstract":"<div><div>Small-section hydraulic tunnels are characterized by small spaces and various section forms, under complex environments, which makes it difficult to carry out an inspection by the mobile acquisition equipment. To resolve these problems, an arbitrarily adjustable camera module deployment method and the corresponding automatic image acquisition equipment with multi-area array cameras are proposed and developed. Such method enables the acquisition of full-length surface images of the hydraulic tunnels with different cross-section forms and diameters by a one-way travel, and the overlap rate and accuracy of the acquired image sets meet the requirements of three-dimensional reconstruction and panoramic image generation. In addition, to improve the speed and accuracy of traditional algorithms for tunnel surface defects detection, this paper proposes an improved YOLOv5s-DECA model. The algorithm introduces DenseNet to optimize the backbone feature extraction network and incorporates an efficient channel attention ECA module to make a better extraction of features of defects. The experimental results show that mAP, and F1-score of YOLOv5-DECA are 73.4% and 74.6%, respectively, which are better than the common model in terms of accuracy and robustness. The proposed YOLOv5-DECA has great detection performance for targets with variable shapes and can solve the problem of classification imbalance in surface defects. Then, by combining YOLOv5-DECA with the direction search algorithm, a “point-ring-section” method is established to allow rapid identification of common surface defects by detecting them layer by layer with the bottom image of the stitched panorama as the seed. The presented method in this paper effectively solves the problem that a single image fails to show the overall distribution of the defects and their accurate positioning in a whole large tunnel section and the effective features of defects in an excessively large panoramic image size are difficult to be captured by the neural network. Field applications demonstrated that the presented method is adequate for high-precision and intelligent surface defect detection and positioning for different small-section hydraulic tunnels such as circular, arch-wall, and box-shaped hydraulic tunnels.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 270-290"},"PeriodicalIF":8.2,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147147","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 : 2024-11-15DOI: 10.1016/j.undsp.2024.08.006
Ziqi Liu , Xiaohui Cheng , Jie Xiao
A thermal–hydraulic-mechanical (THM) field coupling three-dimensional (3D) finite element (FE) program is developed for complex THM coupled problems in engineering practice. This 3D program incorporates a thermo-mechanical coupled constitutive model known as Tsinghua-Thermo-Soil. The program solves the hydraulic and mechanical fields together and the thermal field separately (i.e., the T-HM scheme). Validation is done against the analytical solutions of one-dimensional (1D) steady-state forced convection-conduction and 1D thermo-elastic consolidation processes. Additionally, effects of the dynamic viscosity coefficient and thermal expansion coefficient of water are analyzed for 1D thermo-elastic consolidation coupled problem. It is revealed that for soils in long-term consolidation and under high loading levels, convective effect is significant and the temperature distribution differs from that obtained by considering only heat conduction. A coupled THM problem of foundations involving an actual engineering energy raft is analyzed. The response of a linear elastic foundation under the combined effect of assumed long-term cyclic thermal loading and mechanical loading process is studied. The results demonstrate that heating leads to the locally accumulation of excess pore pressure and reduces settlement and differential settlement, while cooling has the opposite effects. Due to the heat injected into the foundation exceeding the heat extracted, the ground temperature within several meters of burial depth gradually increases over time, meanwhile the average differential settlement decreases.
{"title":"Development of an innovative THM fully coupled three-dimensional finite element program and its applications","authors":"Ziqi Liu , Xiaohui Cheng , Jie Xiao","doi":"10.1016/j.undsp.2024.08.006","DOIUrl":"10.1016/j.undsp.2024.08.006","url":null,"abstract":"<div><div>A thermal–hydraulic-mechanical (THM) field coupling three-dimensional (3D) finite element (FE) program is developed for complex THM coupled problems in engineering practice. This 3D program incorporates a thermo-mechanical coupled constitutive model known as Tsinghua-Thermo-Soil. The program solves the hydraulic and mechanical fields together and the thermal field separately (i.e., the T-HM scheme). Validation is done against the analytical solutions of one-dimensional (1D) steady-state forced convection-conduction and 1D thermo-elastic consolidation processes. Additionally, effects of the dynamic viscosity coefficient and thermal expansion coefficient of water are analyzed for 1D thermo-elastic consolidation coupled problem. It is revealed that for soils in long-term consolidation and under high loading levels, convective effect is significant and the temperature distribution differs from that obtained by considering only heat conduction. A coupled THM problem of foundations involving an actual engineering energy raft is analyzed. The response of a linear elastic foundation under the combined effect of assumed long-term cyclic thermal loading and mechanical loading process is studied. The results demonstrate that heating leads to the locally accumulation of excess pore pressure and reduces settlement and differential settlement, while cooling has the opposite effects. Due to the heat injected into the foundation exceeding the heat extracted, the ground temperature within several meters of burial depth gradually increases over time, meanwhile the average differential settlement decreases.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 352-369"},"PeriodicalIF":8.2,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143146710","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 : 2024-11-07DOI: 10.1016/j.undsp.2024.08.005
Sihan Li , Fei Ye , Caifei Zhang , Yong Yang , Tianhan Xia , Yin Jiang , Xingbo Han
Loess is a special type of soil whose properties are significantly affected by water. However, the grout diffusion law for backfill grouting in loess shield tunnels remains unknown. Based on a visual model experimental device, three experiments were conducted with 10%, 20%, and 30% loess moisture. A finite discrete element method was used to verify the grout diffusion mode, and parameters such as the tunnel buried depth, grout viscosity, and elastic modulus were considered to analyse the grout diffusion law. Experiments and numerical simulations show that the screening diffusion of grout occurs at low loess moisture, whereas splitting diffusion occurs at high loess moisture. The farthest splitting diffusion distance decreases as the tunnel buried depth, grout viscosity, and elastic modulus increase. In addition, based on capillary theory and geotechnical strength criteria, screening diffusion and splitting diffusion models were established. This study investigated the grout diffusion law and grout diffusion model, providing a reference for the design and construction of loess shield tunnels.
{"title":"Diffusion law and diffusion model for backfill grouting in loess shield tunnel at different soil moisture","authors":"Sihan Li , Fei Ye , Caifei Zhang , Yong Yang , Tianhan Xia , Yin Jiang , Xingbo Han","doi":"10.1016/j.undsp.2024.08.005","DOIUrl":"10.1016/j.undsp.2024.08.005","url":null,"abstract":"<div><div>Loess is a special type of soil whose properties are significantly affected by water. However, the grout diffusion law for backfill grouting in loess shield tunnels remains unknown. Based on a visual model experimental device, three experiments were conducted with 10%, 20%, and 30% loess moisture. A finite discrete element method was used to verify the grout diffusion mode, and parameters such as the tunnel buried depth, grout viscosity, and elastic modulus were considered to analyse the grout diffusion law. Experiments and numerical simulations show that the screening diffusion of grout occurs at low loess moisture, whereas splitting diffusion occurs at high loess moisture. The farthest splitting diffusion distance decreases as the tunnel buried depth, grout viscosity, and elastic modulus increase. In addition, based on capillary theory and geotechnical strength criteria, screening diffusion and splitting diffusion models were established. This study investigated the grout diffusion law and grout diffusion model, providing a reference for the design and construction of loess shield tunnels.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 313-330"},"PeriodicalIF":8.2,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147792","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 : 2024-10-29DOI: 10.1016/j.undsp.2024.05.005
Shouzhong Feng , Deyuan Kan , Long Zhou , Xianling Liu , Cunyu Du , Weixing Mao
The tunnel pavement is generally made of asphalt or concrete. Due to the relatively fixed material of pavement, the effect of tunnel pavement setting on the lighting environment and visual performance of drivers has not received sufficient attention, especially the impact on the visual performance of drivers during driving has not been revealed. Therefore, experimental research on the visual recognition performance of an obstacle on asphalt and concrete pavements inside tunnels during dynamic driving was conducted in this study. The results indicate that under the same pavement illumination, the luminance on concrete pavement is higher than that on asphalt pavement due to the higher reflectance of concrete. The visible distance of the human eyes for a gray obstacle with a reflectance of 0.2 on the concrete pavement is greater than that on the asphalt pavement, and the visible distance of the obstacle on the concrete pavement increases by more than 28%. When the color of the obstacle and the pavement are close, it can be challenging for observers to recognize the obstacle, and the pavement and obstacle need to have a higher level of luminance for the recognition. During dynamic driving, the visible distance at a speed of 60 km/h is 1.2 to 1.4 times that at a speed of 80 km/h, which means the influence of vehicle speed on the human eye’s recognition of obstacles on asphalt and concrete pavements should be taken into consideration in the design of road tunnel lighting. The correlated color temperature and S/P value of LED light have little impact on the visible distance of human eyes to the obstacle on the asphalt and concrete pavements, but it does create different visual perceptions. As the correlated color temperature and S/P value increase, the lighting environment of the tunnel gradually gives a brighter feeling to drivers.
{"title":"Experimental study on effect of pavement background on obstacle visibility in LED lighting environment of road tunnel","authors":"Shouzhong Feng , Deyuan Kan , Long Zhou , Xianling Liu , Cunyu Du , Weixing Mao","doi":"10.1016/j.undsp.2024.05.005","DOIUrl":"10.1016/j.undsp.2024.05.005","url":null,"abstract":"<div><div>The tunnel pavement is generally made of asphalt or concrete. Due to the relatively fixed material of pavement, the effect of tunnel pavement setting on the lighting environment and visual performance of drivers has not received sufficient attention, especially the impact on the visual performance of drivers during driving has not been revealed. Therefore, experimental research on the visual recognition performance of an obstacle on asphalt and concrete pavements inside tunnels during dynamic driving was conducted in this study. The results indicate that under the same pavement illumination, the luminance on concrete pavement is higher than that on asphalt pavement due to the higher reflectance of concrete. The visible distance of the human eyes for a gray obstacle with a reflectance of 0.2 on the concrete pavement is greater than that on the asphalt pavement, and the visible distance of the obstacle on the concrete pavement increases by more than 28%. When the color of the obstacle and the pavement are close, it can be challenging for observers to recognize the obstacle, and the pavement and obstacle need to have a higher level of luminance for the recognition. During dynamic driving, the visible distance at a speed of 60 km/h is 1.2 to 1.4 times that at a speed of 80 km/h, which means the influence of vehicle speed on the human eye’s recognition of obstacles on asphalt and concrete pavements should be taken into consideration in the design of road tunnel lighting. The correlated color temperature and S/P value of LED light have little impact on the visible distance of human eyes to the obstacle on the asphalt and concrete pavements, but it does create different visual perceptions. As the correlated color temperature and S/P value increase, the lighting environment of the tunnel gradually gives a brighter feeling to drivers.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 124-136"},"PeriodicalIF":8.2,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579938","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 : 2024-10-29DOI: 10.1016/j.undsp.2024.05.004
Wei Yu , Zhi-Yi Chen , Zhi-Qian Liu
This paper proposes an innovative method for selecting the severest design ground motions based on overall damage characterization of underground structures. The selection procedure is elaborated using 4749 ground motions, exemplifying various forms of underground structures in class III sites. Initially, an overall damage index, predicated on dual-parameters of deformation and hysteretic energy dissipation, is proposed as an engineering demand parameter to quantitatively depict the failure state of underground structures. Subsequently, given the inadequacy of a single intensity measure in evaluating the damage of underground structures, composite intensity measures with higher correlation to the index are constructed using partial least squares regression method. The composite intensity measures served as the damage potential characterization parameter for ground motions concerning underground structures. Consequently, alternative databases of severest design ground motions are derived through these composite intensity measures. The ground motions in this alternative database are employed as inputs for nonlinear dynamic analysis of underground structures. The severest design ground motions are identified by ranking the overall damage index to underground structures. Finally, a comparison with traditional selecting method demonstrates that the proposed method yields more accurate results.
本文提出了一种基于地下结构总体破坏特征的最严重设计地面运动选择创新方法。利用 4749 次地面运动对选择程序进行了阐述，这些地面运动体现了 III 类场地中各种形式的地下结构。首先，提出了基于变形和滞回耗能双重参数的整体损伤指数，作为工程需求参数，定量描述地下结构的破坏状态。随后，考虑到单一强度指标在评估地下结构破坏方面的不足，采用偏最小二乘回归法构建了与指数相关性更高的复合强度指标。综合烈度指标可作为地下结构地震动的潜在破坏特征参数。因此，通过这些综合烈度量度得出了最严重设计地面运动的替代数据库。该替代数据库中的地面运动可用作地下结构非线性动态分析的输入。通过对地下结构的总体破坏指数进行排序，确定最严重的设计地面运动。最后，通过与传统的选择方法进行比较，证明所提出的方法能得到更准确的结果。
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Pub Date : 2024-10-28DOI: 10.1016/j.undsp.2024.08.004
Guanyu Yan , Chengshun Xu , Zihong Zhang , Xuelai Wang , Xiuli Du
Due to the planning of the subway route, it is difficult to avoid crossing soft soil site conditions at subway stations. The seismic response of subway station structures is closely related to the surrounding soil site. In this paper, centrifuge shaking table tests were designed and carried out for subway station structures at three typical soft soil sites (all-clay site, liquefiable interlayer site, and fully liquefiable site). The test results are as follows. The structure is most severely damaged in all-clay site, while the damage is low in liquefiable interlayer site and fully liquefiable site. For liquefiable sites, site liquefaction results in a lower soil-structure stiffness ratio. Thus liquefiable interlayer site and fully liquefiable site provide a natural seismic isolation system for structures compared to all-clay site. The limits of the inter-story drift ratio of the structure were used to evaluate the post-earthquake performance stages of the model structure in the three sites. In all-clay site, the structure is in the “immediately operational” stage after the loading condition of 0.1g and 0.32g, and in the “reparable operational” stage after the loading condition of 0.52g and 0.72g. In the liquefiable interlayer site and full liquefiable site, the underground structure is in the “normal operational” stage after the loading condition of 0.1g and in the “immediately operational” stage after the loading condition of 0.32g–0.72g.
{"title":"Series of centrifuge shaking table tests study on seismic response of subway station structures in soft soil sites","authors":"Guanyu Yan , Chengshun Xu , Zihong Zhang , Xuelai Wang , Xiuli Du","doi":"10.1016/j.undsp.2024.08.004","DOIUrl":"10.1016/j.undsp.2024.08.004","url":null,"abstract":"<div><div>Due to the planning of the subway route, it is difficult to avoid crossing soft soil site conditions at subway stations. The seismic response of subway station structures is closely related to the surrounding soil site. In this paper, centrifuge shaking table tests were designed and carried out for subway station structures at three typical soft soil sites (all-clay site, liquefiable interlayer site, and fully liquefiable site). The test results are as follows. The structure is most severely damaged in all-clay site, while the damage is low in liquefiable interlayer site and fully liquefiable site. For liquefiable sites, site liquefaction results in a lower soil-structure stiffness ratio. Thus liquefiable interlayer site and fully liquefiable site provide a natural seismic isolation system for structures compared to all-clay site. The limits of the inter-story drift ratio of the structure were used to evaluate the post-earthquake performance stages of the model structure in the three sites. In all-clay site, the structure is in the “immediately operational” stage after the loading condition of 0.1<em>g</em> and 0.32<em>g</em>, and in the “reparable operational” stage after the loading condition of 0.52<em>g</em> and 0.72<em>g</em>. In the liquefiable interlayer site and full liquefiable site, the underground structure is in the “normal operational” stage after the loading condition of 0.1<em>g</em> and in the “immediately operational” stage after the loading condition of 0.32<em>g</em>–0.72<em>g</em>.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"21 ","pages":"Pages 232-251"},"PeriodicalIF":8.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705116","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}
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