Pub Date : 2026-01-10DOI: 10.1016/j.trgeo.2026.101898
Hao Liu , Yiheng Pan , Xinqiang Gao , Song Hu
Researchers had presumed different failure mechanisms for calculating the load on culverts, but the research on summarizing, comparing, and evaluating these failure mechanisms was limited. This paper estimates the failure surface and shear stress along the failure surface by numerical analysis, following a brief summary of the methods for calculating the load on the culvert. From the simulation, three types of failure surfaces, i.e., internal, vertical, and external failure surfaces, were observed in the fill. Among them, the dominant surface depended on the friction angle and height. In addition, the lateral earth pressure coefficient at the vertical and dominant failure surface decreased with the fill height and friction angle, contrary to the assumption that the lateral earth pressure coefficient was only influenced by the fill friction angle. Furthermore, when the external and dominant failure surface was simplified as the vertical failure surface with an equivalent settlement surface (ESS), the vertical earth pressure in the interior fill could be accurately calculated if an appropriate value for the ESS height was chosen.
{"title":"Vertical load on embankment-installed rigid culvert buried by cohesionless fill","authors":"Hao Liu , Yiheng Pan , Xinqiang Gao , Song Hu","doi":"10.1016/j.trgeo.2026.101898","DOIUrl":"10.1016/j.trgeo.2026.101898","url":null,"abstract":"<div><div>Researchers had presumed different failure mechanisms for calculating the load on culverts, but the research on summarizing, comparing, and evaluating these failure mechanisms was limited. This paper estimates the failure surface and shear stress along the failure surface by numerical analysis, following a brief summary of the methods for calculating the load on the culvert. From the simulation, three types of failure surfaces, i.e., internal, vertical, and external failure surfaces, were observed in the fill. Among them, the dominant surface depended on the friction angle and height. In addition, the lateral earth pressure coefficient at the vertical and dominant failure surface decreased with the fill height and friction angle, contrary to the assumption that the lateral earth pressure coefficient was only influenced by the fill friction angle. Furthermore, when the external and dominant failure surface was simplified as the vertical failure surface with an equivalent settlement surface (ESS), the vertical earth pressure in the interior fill could be accurately calculated if an appropriate value for the ESS height was chosen.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101898"},"PeriodicalIF":5.5,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The dynamic interaction between pile and saturated soil governs pile settlement in soft soil foundation, which is strictly controlled in high-speed railways. However, the underlying mechanisms governing the transformation of dynamic load within the pile-soil system and their evolution over time remain inadequately understood. Therefore, conventional design methods that rely solely on static pile capacity and neglect dynamic interaction effects are inapplicable. In this study, a series of centrifuge modelling tests were conducted using a self-developed dynamic loading device and an instrumented model pile. The setup adequately satisfied the similitude requirements for intensified loading frequency and stress wave propagation along pile. Various static and dynamic loads were applied to the pile embedded in saturated silty soil, with frequencies reaching 360 Hz and cycles up to 5 × 105. Complementary numerical analyses were also performed to elucidate the mechanisms of dynamic pile-soil interaction. Experimental and numerical results demonstrate that stress waves propagated from the pile shaft into the surrounding soil in the form of Mach cone, driven by the differences in wave velocities between pile and soil. Moreover, soil vibration attenuated with increasing distance from the pile, a trend predictable using Bornitz’s approach even under loading frequencies as high as 360 Hz. The evolution of pore water pressure and the corresponding redistribution of axial force along the pile reveal distinct pile-soil interaction responses under different loading amplitudes: (1) Under low-amplitude loads (CLR ≤ 0.3), pore water pressure accumulation was negligible, shaft resistance carried most of the pile-head load without significant degradation, and base resistance remained minimal; (2) Under moderate loads (0.4 ≤ CLR ≤ 0.5), pore pressure accumulated noticeably, shaft resistance gradually degraded, axial force was transmitted to deeper pile segments, and base resistance increased but remained below its ultimate threshold; (3) Under high-amplitude loads (CLR ≥ 0.6), buildup of pore water pressure was most pronounced, shaft resistance degradation was substantial, base resistance increased significantly compared with moderate load levels, and deformation of the soil beneath the pile tip accumulated rapidly. Ultimately, these micromechanical processes led to distinct macro-scale settlement behaviours, i.e., stable, metastable, and unstable developments, which can be consistently explained by the evolving dynamic pile-soil interaction.
{"title":"Load transfer mechanism and interaction evolution in pile-soil system to high-frequency axial load: Centrifuge modelling and numerical analysis","authors":"Feng Qin , Xuecheng Bian , Zizhuang Yan , Yu Zhao , Chuang Zhao","doi":"10.1016/j.trgeo.2026.101904","DOIUrl":"10.1016/j.trgeo.2026.101904","url":null,"abstract":"<div><div>The dynamic interaction between pile and saturated soil governs pile settlement in soft soil foundation, which is strictly controlled in high-speed railways. However, the underlying mechanisms governing the transformation of dynamic load within the pile-soil system and their evolution over time remain inadequately understood. Therefore, conventional design methods that rely solely on static pile capacity and neglect dynamic interaction effects are inapplicable. In this study, a series of centrifuge modelling tests were conducted using a self-developed dynamic loading device and an instrumented model pile. The setup adequately satisfied the similitude requirements for intensified loading frequency and stress wave propagation along pile. Various static and dynamic loads were applied to the pile embedded in saturated silty soil, with frequencies reaching 360 Hz and cycles up to 5 × 10<sup>5</sup>. Complementary numerical analyses were also performed to elucidate the mechanisms of dynamic pile-soil interaction. Experimental and numerical results demonstrate that stress waves propagated from the pile shaft into the surrounding soil in the form of Mach cone, driven by the differences in wave velocities between pile and soil. Moreover, soil vibration attenuated with increasing distance from the pile, a trend predictable using Bornitz’s approach even under loading frequencies as high as 360 Hz. The evolution of pore water pressure and the corresponding redistribution of axial force along the pile reveal distinct pile-soil interaction responses under different loading amplitudes: (1) Under low-amplitude loads (CLR ≤ 0.3), pore water pressure accumulation was negligible, shaft resistance carried most of the pile-head load without significant degradation, and base resistance remained minimal; (2) Under moderate loads (0.4 ≤ CLR ≤ 0.5), pore pressure accumulated noticeably, shaft resistance gradually degraded, axial force was transmitted to deeper pile segments, and base resistance increased but remained below its ultimate threshold; (3) Under high-amplitude loads (CLR ≥ 0.6), buildup of pore water pressure was most pronounced, shaft resistance degradation was substantial, base resistance increased significantly compared with moderate load levels, and deformation of the soil beneath the pile tip accumulated rapidly. Ultimately, these micromechanical processes led to distinct macro-scale settlement behaviours, i.e., stable, metastable, and unstable developments, which can be consistently explained by the evolving dynamic pile-soil interaction.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101904"},"PeriodicalIF":5.5,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-08DOI: 10.1016/j.trgeo.2026.101900
Yafei Jia , Chuan-Bao Xu , Jun Zhang , Jun-Jie Zheng , Hanjiang Lai , Yewei Zheng
This study develops discrete element method (DEM) models to investigate the soil arching and membrane effects in geosynthetic reinforced, pile-supported (GRPS) embankments under cyclic loading. The model was validated against large-scale physical model tests to ensure reliability. Using the validated DEM, the evolution of contact force chains, fabric tensors, and average contact force ratios (ACFRs) was analyzed to elucidate the microscopic mechanisms of load transfer and degradation. The results reveal that cyclic loading leads to progressive degradation of soil arching in unreinforced embankments, initiating from the bottom and propagating upward. In contrast, the presence of geogrid reinforcement effectively stabilizes the soil arching structure, enhances load transfer to the pile caps, and reduces the contact force transmitted to the underlying soft soil. The geogrid exhibits a distinct membrane effect characterized by catenary deflection and localized tensile strain, particularly during the early cycles. Parametric analyses further demonstrate that higher trough values, larger load amplitudes, and higher loading frequencies accelerate the degradation of soil arching, while an intermediate loading area and moderate embankment porosity yield the most stable load transfer. Although thicker soft soil foundations initially enhance soil arching, they are more susceptible to degradation under repeated loading.
{"title":"DEM Analysis of Load Transfer Mechanisms in Pile-Supported Embankments under Cyclic Traffic Loading","authors":"Yafei Jia , Chuan-Bao Xu , Jun Zhang , Jun-Jie Zheng , Hanjiang Lai , Yewei Zheng","doi":"10.1016/j.trgeo.2026.101900","DOIUrl":"10.1016/j.trgeo.2026.101900","url":null,"abstract":"<div><div>This study develops discrete element method (DEM) models to investigate the soil arching and membrane effects in geosynthetic reinforced, pile-supported (GRPS) embankments under cyclic loading. The model was validated against large-scale physical model tests to ensure reliability. Using the validated DEM, the evolution of contact force chains, fabric tensors, and average contact force ratios (ACFRs) was analyzed to elucidate the microscopic mechanisms of load transfer and degradation. The results reveal that cyclic loading leads to progressive degradation of soil arching in unreinforced embankments, initiating from the bottom and propagating upward. In contrast, the presence of geogrid reinforcement effectively stabilizes the soil arching structure, enhances load transfer to the pile caps, and reduces the contact force transmitted to the underlying soft soil. The geogrid exhibits a distinct membrane effect characterized by catenary deflection and localized tensile strain, particularly during the early cycles. Parametric analyses further demonstrate that higher trough values, larger load amplitudes, and higher loading frequencies accelerate the degradation of soil arching, while an intermediate loading area and moderate embankment porosity yield the most stable load transfer. Although thicker soft soil foundations initially enhance soil arching, they are more susceptible to degradation under repeated loading.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101900"},"PeriodicalIF":5.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-08DOI: 10.1016/j.trgeo.2026.101899
Shunshun Qi , Guoyu Li , Jiawei Yang , Qingsong Du , Kai Gao , Dun Chen , Mingtang Chai , Anshuang Su , Miao Wang
Permafrost-related deformation of highway embankments is a major constraint on the long-term serviceability of the Qinghai–Tibet Highway (QTH). Freeze–thaw cycles, water migration and heavy traffic loads produce rutting, corrugation and differential settlement at the surface, but their relationship to subsurface anomalies is not yet fully understood. This study combines unmanned aerial vehicle (UAV) photogrammetry with ground-penetrating radar (GPR) to examine coupled pavement–subgrade behaviour on three permafrost sections of the QTH. UAV-derived digital surface models are used to quantify rut depth, roughness and longitudinal/transverse elevation differentials, whereas 2D GPR profiles and depth-dependent reflection-intensity maps are interpreted to identify stratigraphic undulations, localised loosening and the position of the permafrost table. The joint analysis shows that sections with large elevation differentials and roughness systematically coincide with zones of strong GPR anomalies, and that the three sites exhibit contrasting deformation patterns ranging from severe settlement with rutting and cracking to pseudo-corrugations and localised depressions. Vertically continuous bands of anomalous reflections indicate that, in some cases, weaknesses extend from the active layer into the embankment body, providing a plausible link between subsurface degradation and surface distress under combined freeze–thaw and traffic loading. The case study suggests that integrating established UAV and GPR techniques offers a practical, non-destructive means of characterising pavement–subgrade deformation in permafrost highways and can inform the early identification of problematic sections and the planning of maintenance strategies.
{"title":"Assessment of pavement–subgrade deformation in permafrost highways using UAV photogrammetry and ground-penetrating radar: Case study of Qinghai–Tibet highway","authors":"Shunshun Qi , Guoyu Li , Jiawei Yang , Qingsong Du , Kai Gao , Dun Chen , Mingtang Chai , Anshuang Su , Miao Wang","doi":"10.1016/j.trgeo.2026.101899","DOIUrl":"10.1016/j.trgeo.2026.101899","url":null,"abstract":"<div><div>Permafrost-related deformation of highway embankments is a major constraint on the long-term serviceability of the Qinghai–Tibet Highway (QTH). Freeze–thaw cycles, water migration and heavy traffic loads produce rutting, corrugation and differential settlement at the surface, but their relationship to subsurface anomalies is not yet fully understood. This study combines unmanned aerial vehicle (UAV) photogrammetry with ground-penetrating radar (GPR) to examine coupled pavement–subgrade behaviour on three permafrost sections of the QTH. UAV-derived digital surface models are used to quantify rut depth, roughness and longitudinal/transverse elevation differentials, whereas 2D GPR profiles and depth-dependent reflection-intensity maps are interpreted to identify stratigraphic undulations, localised loosening and the position of the permafrost table. The joint analysis shows that sections with large elevation differentials and roughness systematically coincide with zones of strong GPR anomalies, and that the three sites exhibit contrasting deformation patterns ranging from severe settlement with rutting and cracking to pseudo-corrugations and localised depressions. Vertically continuous bands of anomalous reflections indicate that, in some cases, weaknesses extend from the active layer into the embankment body, providing a plausible link between subsurface degradation and surface distress under combined freeze–thaw and traffic loading. The case study suggests that integrating established UAV and GPR techniques offers a practical, non-destructive means of characterising pavement–subgrade deformation in permafrost highways and can inform the early identification of problematic sections and the planning of maintenance strategies.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101899"},"PeriodicalIF":5.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Groundwater level fluctuation-induced collapse in deep loess threatens the long-term safety of deep-buried metro tunnels. A field sand-well immersion test is conducted along a Xi’an metro line, employing a water-level control system to regulate the leaching exploratory well water level precisely. This experimental setup simulates the wetting-induced deformation process under bottom-up infiltration with constant overburden stress, and a computational model for deep loess collapse deformation is established by considering the hydro-mechanical path. Results demonstrated an inverted-funnel-shaped moisture diffusion pattern in deep loess, with the saturation front diffusion angle measuring approximately 90° within 2 m of the well, decreasing to 50° at distances of 2–6 m, and increasing to 73° beyond 6 m. During immersion, the deep loess exhibits three-stage deformation behavior: collapse governed by structural strength degradation, rebound dominated by unloading due to cavity formation with a positive correlation to water level height, and compression from residual structural strength failure with a negative correlation to water level height. Post-immersion consolidation settlement is also observed. Collapse and rebound develop from deep to shallow layers and from inner to outer zones, whereas consolidation settlement propagates from shallow to deep layers and from outer to inner areas. Based on the wetting-unloading hydro-mechanical path during bottom-up infiltration, a collapse deformation model is developed. Using a degree of wetting η1 = 0.8 combined with actual unloading ratios, the model achieves a relative error of only 8.85 %. This study provides valuable insights for evaluating collapsibility in deep loess foundations within groundwater fluctuation zones.
{"title":"Collapse deformation characteristics and computational model for loess sites under bottom-up field immersion","authors":"Xin Huang , Jianguo Zheng , Yongtang Yu , Weiwei Zhang , Chunjie Yan","doi":"10.1016/j.trgeo.2025.101890","DOIUrl":"10.1016/j.trgeo.2025.101890","url":null,"abstract":"<div><div>Groundwater level fluctuation-induced collapse in deep loess threatens the long-term safety of deep-buried metro tunnels. A field sand-well immersion test is conducted along a Xi’an metro line, employing a water-level control system to regulate the leaching exploratory well water level precisely. This experimental setup simulates the wetting-induced deformation process under bottom-up infiltration with constant overburden stress, and a computational model for deep loess collapse deformation is established by considering the hydro-mechanical path. Results demonstrated an inverted-funnel-shaped moisture diffusion pattern in deep loess, with the saturation front diffusion angle measuring approximately 90° within 2 m of the well, decreasing to 50° at distances of 2–6 m, and increasing to 73° beyond 6 m. During immersion, the deep loess exhibits three-stage deformation behavior: collapse governed by structural strength degradation, rebound dominated by unloading due to cavity formation with a positive correlation to water level height, and compression from residual structural strength failure with a negative correlation to water level height. Post-immersion consolidation settlement is also observed. Collapse and rebound develop from deep to shallow layers and from inner to outer zones, whereas consolidation settlement propagates from shallow to deep layers and from outer to inner areas. Based on the wetting-unloading hydro-mechanical path during bottom-up infiltration, a collapse deformation model is developed. Using a degree of wetting <em>η</em><sub>1</sub> = 0.8 combined with actual unloading ratios, the model achieves a relative error of only 8.85 %. This study provides valuable insights for evaluating collapsibility in deep loess foundations within groundwater fluctuation zones.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101890"},"PeriodicalIF":5.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-06DOI: 10.1016/j.trgeo.2026.101897
Wenyun Ding , Shunguo Wang , Zude Ding , Yongfa Guo , Zhigang Song , Shangze Feng
Focusing on the core issue of safety impacts during the construction of large-section high-speed railway tunnels adjacent to karst caves, this study comprehensively applied theoretical analysis, orthogonal numerical experiments, and multiple regression methods to systematically investigate the stability of the cave-tunnel system. A predictive model for the critical safety distance was established, and a zoning standard for construction safety influence was developed. The research shows that the surrounding rock grade and the lateral pressure coefficient have a highly significant influence on the critical safety distance, with their impact exceeding that of the geometric parameters of the karst cave and the tunnel burial depth. Through range analysis and analysis of variance, the primary and secondary order of influencing factors under different karst cave locations was clarified, and multiple regression prediction expressions for the critical safety distance were established for five typical karst cave locations: above the vault, outside the spandrel, outside the sidewall, outside the wall foot, and below the invert. The most critical conditions occur when the karst cave is located outside the tunnel wall foot or spandrel. Based on the criteria of plastic zone connectivity and energy mutation, a comprehensive discriminant standard centered on the critical safety distance was constructed, classifying the impact of karst caves on tunnel construction into strong, moderate, and weak influence zones. Combining the conditions of the supporting project, the influence zoning ranges for typical tunnel sections were determined, resulting in the zoning for the Changshui Airport Tunnel under Grade IV and Grade V surrounding rock conditions with cave sizes of 0.2D, 0.4D, 0.6D, and 0.8D. As the cave size increases from 0.2D to 0.8D, the extent of the strong influence zone expands from 0.33D–0.94D to 0.80D–2.23D in Grade IV surrounding rock, and from 0.97D–1.44D to 1.34D–3.47D in Grade V surrounding rock. This demonstrates a significant amplification effect of cave size on the disturbance range imposed on the tunnel. Compared to Grade IV surrounding rock, the influence zone induced by karst caves in Grade V rock is substantially larger and more sensitive to changes in cave size. The validity and engineering applicability of the proposed model and zoning criteria were verified using the case study of the Changshui Airport Tunnel. This research provides a theoretical basis and practical reference for the safe design and construction of similar tunnel projects in karst areas.
{"title":"Predictive modeling and risk zoning for safety of large-section high-speed railway tunnels adjacent to karst caves: a case study of the Chongqing-Kunming high-speed railway tunnel","authors":"Wenyun Ding , Shunguo Wang , Zude Ding , Yongfa Guo , Zhigang Song , Shangze Feng","doi":"10.1016/j.trgeo.2026.101897","DOIUrl":"10.1016/j.trgeo.2026.101897","url":null,"abstract":"<div><div>Focusing on the core issue of safety impacts during the construction of large-section high-speed railway tunnels adjacent to karst caves, this study comprehensively applied theoretical analysis, orthogonal numerical experiments, and multiple regression methods to systematically investigate the stability of the cave-tunnel system. A predictive model for the critical safety distance was established, and a zoning standard for construction safety influence was developed. The research shows that the surrounding rock grade and the lateral pressure coefficient have a highly significant influence on the critical safety distance, with their impact exceeding that of the geometric parameters of the karst cave and the tunnel burial depth. Through range analysis and analysis of variance, the primary and secondary order of influencing factors under different karst cave locations was clarified, and multiple regression prediction expressions for the critical safety distance were established for five typical karst cave locations: above the vault, outside the spandrel, outside the sidewall, outside the wall foot, and below the invert. The most critical conditions occur when the karst cave is located outside the tunnel wall foot or spandrel. Based on the criteria of plastic zone connectivity and energy mutation, a comprehensive discriminant standard centered on the critical safety distance was constructed, classifying the impact of karst caves on tunnel construction into strong, moderate, and weak influence zones. Combining the conditions of the supporting project, the influence zoning ranges for typical tunnel sections were determined, resulting in the zoning for the Changshui Airport Tunnel under Grade IV and Grade V surrounding rock conditions with cave sizes of 0.2D, 0.4D, 0.6D, and 0.8D. As the cave size increases from 0.2D to 0.8D, the extent of the strong influence zone expands from 0.33D–0.94D to 0.80D–2.23D in Grade IV surrounding rock, and from 0.97D–1.44D to 1.34D–3.47D in Grade V surrounding rock. This demonstrates a significant amplification effect of cave size on the disturbance range imposed on the tunnel. Compared to Grade IV surrounding rock, the influence zone induced by karst caves in Grade V rock is substantially larger and more sensitive to changes in cave size. The validity and engineering applicability of the proposed model and zoning criteria were verified using the case study of the Changshui Airport Tunnel. This research provides a theoretical basis and practical reference for the safe design and construction of similar tunnel projects in karst areas.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101897"},"PeriodicalIF":5.5,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-03DOI: 10.1016/j.trgeo.2026.101891
Jun Fang , Qiyu Zhao , Chunfa Zhao , Zaigang Chen , Jizhong Yang , Qian Xiao , Zhihui Chen , Guojun Yang
Mountainous rack railways face significant operational challenges on steep gradients, where the dynamic stability of ballasted tracks under traction loads is crucial to ensuring operational safety. Existing studies, mostly based on multibody dynamics or finite element methods, have limited capability in revealing the microscopic mechanical behavior of ballast. In this study, a coupled vehicle–track dynamic model for rack railways was developed. Fastener forces on the rail and rack were extracted using Simpack and subsequently applied to a 3-D discrete element model to simulate the structural response of the track. The model was validated against field measurements obtained from a 120 ‰ gradient section, and then employed to systematically analyze the dynamic response characteristics of the track under varying traction forces (50 %, 75 %, 100 %), vehicle loads (AW0–AW3), and gradients (50 ‰–400 ‰). Results indicate that traction force is the dominant factor governing the longitudinal response of the track; its increase markedly amplifies sleeper longitudinal displacement (up to 115 %) and ballast particle migration, far exceeding the vertical response (increase of 44.1 %). Moreover, the influence of rack bogies is greater than that of conventional wheel–rail systems. When the gradient exceeds 200‰, track dynamic responses deteriorate sharply, with sleeper longitudinal acceleration and inter-sleeper displacement difference increasing to 198.8 % and 187 %, respectively, and deep ballast movement becoming significantly intensified. Increased vehicle load primarily raises ballast contact forces and vertical sleeper displacement, with the most pronounced effects occurring beneath the rails. Ballast movement patterns exhibit marked spatial variability: beneath the rack, longitudinal downslope migration predominates, while beneath the rail, more complex local uplift and upslope movement trends are observed. This study elucidates the macro–micro dynamic response mechanisms of steep-gradient ballasted rack railway tracks under traction loads, highlighting the pronounced longitudinal force transmission and ballast instability risks when gradients exceed 200‰, and providing a theoretical basis for track structure optimization and refined maintenance strategies.
{"title":"Dynamic stability and ballast movement characteristics of steep-gradient rack railway track under traction load","authors":"Jun Fang , Qiyu Zhao , Chunfa Zhao , Zaigang Chen , Jizhong Yang , Qian Xiao , Zhihui Chen , Guojun Yang","doi":"10.1016/j.trgeo.2026.101891","DOIUrl":"10.1016/j.trgeo.2026.101891","url":null,"abstract":"<div><div>Mountainous rack railways face significant operational challenges on steep gradients, where the dynamic stability of ballasted tracks under traction loads is crucial to ensuring operational safety. Existing studies, mostly based on multibody dynamics or finite element methods, have limited capability in revealing the microscopic mechanical behavior of ballast. In this study, a coupled vehicle–track dynamic model for rack railways was developed. Fastener forces on the rail and rack were extracted using Simpack and subsequently applied to a 3-D discrete element model to simulate the structural response of the track. The model was validated against field measurements obtained from a 120 ‰ gradient section, and then employed to systematically analyze the dynamic response characteristics of the track under varying traction forces (50 %, 75 %, 100 %), vehicle loads (AW0–AW3), and gradients (50 ‰–400 ‰). Results indicate that traction force is the dominant factor governing the longitudinal response of the track; its increase markedly amplifies sleeper longitudinal displacement (up to 115 %) and ballast particle migration, far exceeding the vertical response (increase of 44.1 %). Moreover, the influence of rack bogies is greater than that of conventional wheel–rail systems. When the gradient exceeds 200‰, track dynamic responses deteriorate sharply, with sleeper longitudinal acceleration and inter-sleeper displacement difference increasing to 198.8 % and 187 %, respectively, and deep ballast movement becoming significantly intensified. Increased vehicle load primarily raises ballast contact forces and vertical sleeper displacement, with the most pronounced effects occurring beneath the rails. Ballast movement patterns exhibit marked spatial variability: beneath the rack, longitudinal downslope migration predominates, while beneath the rail, more complex local uplift and upslope movement trends are observed. This study elucidates the macro–micro dynamic response mechanisms of steep-gradient ballasted rack railway tracks under traction loads, highlighting the pronounced longitudinal force transmission and ballast instability risks when gradients exceed 200‰, and providing a theoretical basis for track structure optimization and refined maintenance strategies.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101891"},"PeriodicalIF":5.5,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-03DOI: 10.1016/j.trgeo.2026.101893
Chengping Zhang, Shiqin Tu, Tongxin Liu, Wei Li
The high-temperature water inrush geo-hazards are often encountered during the construction of deep tunnels recently. The stability of the water-resistant rock mass of tunnel face under the high-temperature and high-pressure conditions plays an important role for the prevention of water inrush disaster, which has been paid little attention to in existing researches. In order to investigate the stability of water-resistant rock mass of water-rich fault tunnels under high temperature and high pressure conditions, a thermal–hydraulic-mechanical coupled model is established to simulate the failure of water-resistant rock mass during the tunnel excavation. Then a series of experiments are conducted using the self-developed model test device of tunnel water inrush with high temperature and high pressure. The validity of the numerical model is proved by comparing the results obtained from model test and numerical simulation. The results show that the thermal–mechanical coupling effect not only intensifies the instability of surrounding rock but also redirects the failure kinematics of water-resistant rock mass, resulting a more significant downward deflection of the velocity of failure zone. In addition, the thermal–mechanical or thermal–hydraulic-mechanical coupling effects significantly alter the stress path at which the water-resistant rock mass reaches the failure state, while the hydraulic-mechanical coupling effect merely accelerates the failure of the water-resistant rock mass along the original stress path. The results of this study can provide useful guidance for preventing water inrush of deep tunnels in water-rich stratum with high temperature and pressure.
{"title":"Stability of water-resistant rock mass of fault tunnels under high-temperature and high-pressure conditions","authors":"Chengping Zhang, Shiqin Tu, Tongxin Liu, Wei Li","doi":"10.1016/j.trgeo.2026.101893","DOIUrl":"10.1016/j.trgeo.2026.101893","url":null,"abstract":"<div><div>The high-temperature water inrush geo-hazards are often encountered during the construction of deep tunnels recently. The stability of the water-resistant rock mass of tunnel face under the high-temperature and high-pressure conditions plays an important role for the prevention of water inrush disaster, which has been paid little attention to in existing researches. In order to investigate the stability of water-resistant rock mass of water-rich fault tunnels under high temperature and high pressure conditions, a thermal–hydraulic-mechanical coupled model is established to simulate the failure of water-resistant rock mass during the tunnel excavation. Then a series of experiments are conducted using the self-developed model test device of tunnel water inrush with high temperature and high pressure. The validity of the numerical model is proved by comparing the results obtained from model test and numerical simulation. The results show that the thermal–mechanical coupling effect not only intensifies the instability of surrounding rock but also redirects the failure kinematics of water-resistant rock mass, resulting a more significant downward deflection of the velocity of failure zone. In addition, the thermal–mechanical or thermal–hydraulic-mechanical coupling effects significantly alter the stress path at which the water-resistant rock mass reaches the failure state, while the hydraulic-mechanical coupling effect merely accelerates the failure of the water-resistant rock mass along the original stress path. The results of this study can provide useful guidance for preventing water inrush of deep tunnels in water-rich stratum with high temperature and pressure.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101893"},"PeriodicalIF":5.5,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-03DOI: 10.1016/j.trgeo.2026.101892
Jiafeng Tan , Deyi Jiang , Rong Liu , Yi He , Jinyang Fan , Jianyu Liang , Cheng Qian , Hanlin He , Hong Zheng
The potential danger of tunnel gas hazards increases with the complexity of geological conditions, resulting in major casualties, huge economic losses and seriously affecting the normal construction progress of tunnels. Addressing the core issues of the lagging nature of static prediction and the weak mechanistic research in dynamic models in existing early warning methods, a new idea of gas disaster early warning that integrates geological damage evolution and multi-physics coupling is proposed. Based on the coal-rock damage-seepage synergistic evolution mechanism, a multi-field coupled control equation considering dynamic excavation effect, Klinkenberg effect and gas desorption characteristics was constructed, and a damage-seepage coupled numerical model was established based on COMSOL. By simulating the whole excavation process of the tunnel through the coal, the spatial and temporal evolution of the gas dynamic outflow is revealed: with the increase of the excavation distance, the gas pressure perturbation shows obvious nonlinear characteristics, and the cumulative outflow is regulated by the multifactorial nonlinearities of the coal seam gas pressure, the thickness of the coal seam, the depth of the tunnel, and the excavation step spacing. Engineering validation demonstrates that the model has a prediction average relative error rate of 2.1%, which is considered to be an effective reflection of the gas outflow pattern in actual projects. The resultant framework provides a mechanism-rich yet practical tool for dynamic risk assessment of gas disasters in deep tunnels, with direct implications for the development of reliable early-warning systems.
{"title":"Mechanisms of failure and permeability evolution in gas-bearing strata under tunnel-induced stress paths","authors":"Jiafeng Tan , Deyi Jiang , Rong Liu , Yi He , Jinyang Fan , Jianyu Liang , Cheng Qian , Hanlin He , Hong Zheng","doi":"10.1016/j.trgeo.2026.101892","DOIUrl":"10.1016/j.trgeo.2026.101892","url":null,"abstract":"<div><div>The potential danger of tunnel gas hazards increases with the complexity of geological conditions, resulting in major casualties, huge economic losses and seriously affecting the normal construction progress of tunnels. Addressing the core issues of the lagging nature of static prediction and the weak mechanistic research in dynamic models in existing early warning methods, a new idea of gas disaster early warning that integrates geological damage evolution and multi-physics coupling is proposed. Based on the coal-rock damage-seepage synergistic evolution mechanism, a multi-field coupled control equation considering dynamic excavation effect, Klinkenberg effect and gas desorption characteristics was constructed, and a damage-seepage coupled numerical model was established based on COMSOL. By simulating the whole excavation process of the tunnel through the coal, the spatial and temporal evolution of the gas dynamic outflow is revealed: with the increase of the excavation distance, the gas pressure perturbation shows obvious nonlinear characteristics, and the cumulative outflow is regulated by the multifactorial nonlinearities of the coal seam gas pressure, the thickness of the coal seam, the depth of the tunnel, and the excavation step spacing. Engineering validation demonstrates that the model has a prediction average relative error rate of 2.1%, which is considered to be an effective reflection of the gas outflow pattern in actual projects. The resultant framework provides a mechanism-rich yet practical tool for dynamic risk assessment of gas disasters in deep tunnels, with direct implications for the development of reliable early-warning systems.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"57 ","pages":"Article 101892"},"PeriodicalIF":5.5,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2026-01-01DOI: 10.1016/j.trgeo.2025.101840
Yingnan Liu , Huayang Lei , Mengting Wang , Hongwei Huang
Tunnel face stability plays a decisive role in construction safety, particularly in sand-clay composite strata where the risks are significantly heightened. A thorough understanding of the instability evolution mechanism is therefore essential. Existing studies have not adequately revealed the internal instability evolution process under such composite strata conditions. In this study, accurately formulated transparent soil was employed in model tests at ambient temperature of 20 °C and constant humidity of 60 % RH, combined with discrete element method (DEM) simulations, to investigate the failure modes, evolution process, support pressure, and soil arching effect of tunnel face in sand-clay composite strata. The results demonstrate that the failure mode shows a basin-shaped global failure under shallow burial conditions, while a teardrop-shaped local failure under deep burial conditions. The soil arching effect restrains failure propagation toward the ground surface. Three critical ratios of tunnel face movement (s) to tunnel diameter (D) were identified at s/D = 3.0 %, 6.0 %, and 12.0 %, corresponding to initial instability, accelerated instability, and complete instability, respectively. The support pressure variation resembles that observed in pure clay, characterized by a rapid decline phase followed by a slow decline phase, with their intersection defining the limit support pressure. At the microscopic level, the deflection of principal stress direction dominates the soil arching effect. The arching zone in the composite strata spans approximately 0.94D. Furthermore, the soil arching effect intensifies as the stratum interface locates closer to the tunnel. The findings in this paper provide theoretical and practical insights into instability mechanisms and safety control for shield tunnelling in sand-clay composite strata.
{"title":"Internal instability evolution mechanism of tunnel face in sand-clay composite strata: Transparent soil model tests and DEM simulations","authors":"Yingnan Liu , Huayang Lei , Mengting Wang , Hongwei Huang","doi":"10.1016/j.trgeo.2025.101840","DOIUrl":"10.1016/j.trgeo.2025.101840","url":null,"abstract":"<div><div>Tunnel face stability plays a decisive role in construction safety, particularly in sand-clay composite strata where the risks are significantly heightened. A thorough understanding of the instability evolution mechanism is therefore essential. Existing studies have not adequately revealed the internal instability evolution process under such composite strata conditions. In this study, accurately formulated transparent soil was employed in model tests at ambient temperature of 20 °C and constant humidity of 60 % RH, combined with discrete element method (DEM) simulations, to investigate the failure modes, evolution process, support pressure, and soil arching effect of tunnel face in sand-clay composite strata. The results demonstrate that the failure mode shows a basin-shaped global failure under shallow burial conditions, while a teardrop-shaped local failure under deep burial conditions. The soil arching effect restrains failure propagation toward the ground surface. Three critical ratios of tunnel face movement (<em>s</em>) to tunnel diameter (<em>D</em>) were identified at <em>s</em>/<em>D</em> = 3.0 %, 6.0 %, and 12.0 %, corresponding to initial instability, accelerated instability, and complete instability, respectively. The support pressure variation resembles that observed in pure clay, characterized by a rapid decline phase followed by a slow decline phase, with their intersection defining the limit support pressure. At the microscopic level, the deflection of principal stress direction dominates the soil arching effect. The arching zone in the composite strata spans approximately 0.94<em>D</em>. Furthermore, the soil arching effect intensifies as the stratum interface locates closer to the tunnel. The findings in this paper provide theoretical and practical insights into instability mechanisms and safety control for shield tunnelling in sand-clay composite strata.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"56 ","pages":"Article 101840"},"PeriodicalIF":5.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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