Pub Date : 2026-02-05DOI: 10.1016/j.tafmec.2026.105495
Weimin Song
Fatigue cracking in asphalt pavements stems from the complex, nonlinear accumulation of damage, a process further complicated by the use of reclaimed asphalt pavement (RAP) and fiber reinforcements. Traditional fatigue characterization, focusing on macroscopic endpoints, failing to capture the intrinsic dynamic patterns of damage evolution. This study proposes a paradigm shift by conceptualizing fatigue damage accumulation as a nonlinear dynamical system. From stiffness degradation time series, this investigation developed a novel framework that extracts dynamic signatures, including approximate entropy (ApEn), the maximum Lyapunov exponent (λ), and damage rate fluctuation (DRF). These signatures quantitatively describe the complexity, predictability, and stability of the damage process itself. Applying this framework to four types of asphalt mixtures with different contents of RAP and glass fiber tested under direct tension reveals that: 1) incorporating 25% RAP enhances fatigue life by 130% and increases damage complexity (ApEn); 2) an optimal 0.1% glass fiber content maximizes fatigue life (a 214% increase over H-25R) by significantly stabilizing the damage process (lowest DRF); 3) fatigue life correlates strongly with these dynamic signatures. Crucially, a multilinear regression model integrating ApEn and DRF provides accurate fatigue life prediction, resolving the paradoxical roles of damage complexity (beneficial) and instability (detrimental). The framework moves beyond correlation by offering a quantitative, systems-based language to describe damage evolution, thereby providing a critical link between macroscopic performance and the underlying dynamical behavior of the material, and guiding future micromechanical investigations.
{"title":"From stiffness degradation to fatigue life prediction: A nonlinear dynamic signature-based framework for asphalt mixtures","authors":"Weimin Song","doi":"10.1016/j.tafmec.2026.105495","DOIUrl":"10.1016/j.tafmec.2026.105495","url":null,"abstract":"<div><div>Fatigue cracking in asphalt pavements stems from the complex, nonlinear accumulation of damage, a process further complicated by the use of reclaimed asphalt pavement (RAP) and fiber reinforcements. Traditional fatigue characterization, focusing on macroscopic endpoints, failing to capture the intrinsic dynamic patterns of damage evolution. This study proposes a paradigm shift by conceptualizing fatigue damage accumulation as a nonlinear dynamical system. From stiffness degradation time series, this investigation developed a novel framework that extracts dynamic signatures, including approximate entropy (ApEn), the maximum Lyapunov exponent (λ), and damage rate fluctuation (DRF). These signatures quantitatively describe the complexity, predictability, and stability of the damage process itself. Applying this framework to four types of asphalt mixtures with different contents of RAP and glass fiber tested under direct tension reveals that: 1) incorporating 25% RAP enhances fatigue life by 130% and increases damage complexity (ApEn); 2) an optimal 0.1% glass fiber content maximizes fatigue life (a 214% increase over H-25R) by significantly stabilizing the damage process (lowest DRF); 3) fatigue life correlates strongly with these dynamic signatures. Crucially, a multilinear regression model integrating ApEn and DRF provides accurate fatigue life prediction, resolving the paradoxical roles of damage complexity (beneficial) and instability (detrimental). The framework moves beyond correlation by offering a quantitative, systems-based language to describe damage evolution, thereby providing a critical link between macroscopic performance and the underlying dynamical behavior of the material, and guiding future micromechanical investigations.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105495"},"PeriodicalIF":5.6,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189095","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 : 2026-02-05DOI: 10.1016/j.tafmec.2026.105460
F. Núñez , K. Saavedra , A. Olivos , R. Valle
This study investigates Mode I fracture of Chilean Chilean Pinus radiata D. Don using double-cantilever beam (DCB) tests. Some mechanical properties were first determined by compression, tension, shear, and bending tests. The latter provide the modulus of elasticity (MOE), proportional (TLS), and modulus of rupture (MOR). Although the main objective was to identify cohesive parameters for bilinear, trilinear, and potential laws under mode I loading, evaluating which best represents crack propagation in the TL and RL planes through Equivalent Linear Elastic Fracture Mechanics. The results show that the potential law most accurately reproduces the experimental load–displacement response. The results obtained, in relation to other species of timber studied mainly in Europe, show that the energy release rate is lower compared to species such as Eucalyptus globulus Labill, while being comparable to Picea abies (L.) H. Karst., Pinus pinaster Aiton and untreated pine.
本研究采用双悬臂梁（DCB）试验研究智利智利辐射松（Pinus radiata D. Don）的I型骨折。一些机械性能首先通过压缩、拉伸、剪切和弯曲试验来确定。后者提供弹性模量（MOE）、比例模量（TLS）和断裂模量（MOR）。虽然主要目的是确定双线性、三线性和I型载荷下的潜在规律的内聚参数，但通过等效线弹性断裂力学来评估哪一个最能代表TL和RL平面上的裂纹扩展。结果表明，势律最准确地再现了试验荷载-位移响应。所获得的结果，与主要在欧洲研究的其他树种相比，表明能量释放率低于桉树（Eucalyptus globulus Labill）等树种，而与云杉（Picea abies） （L.）相当。h .岩溶。、Pinus pinaster和未经处理的松。
{"title":"Fracture behavior of Chilean Pinus radiata D. Don: Experimental and numerical identification through LEFM R-curves","authors":"F. Núñez , K. Saavedra , A. Olivos , R. Valle","doi":"10.1016/j.tafmec.2026.105460","DOIUrl":"10.1016/j.tafmec.2026.105460","url":null,"abstract":"<div><div>This study investigates Mode I fracture of Chilean Chilean <em>Pinus radiata</em> D. Don using double-cantilever beam (DCB) tests. Some mechanical properties were first determined by compression, tension, shear, and bending tests. The latter provide the modulus of elasticity (MOE), proportional (TLS), and modulus of rupture (MOR). Although the main objective was to identify cohesive parameters for bilinear, trilinear, and potential laws under mode I loading, evaluating which best represents crack propagation in the TL and RL planes through Equivalent Linear Elastic Fracture Mechanics. The results show that the potential law most accurately reproduces the experimental load–displacement response. The results obtained, in relation to other species of timber studied mainly in Europe, show that the energy release rate is lower compared to species such as <em>Eucalyptus globulus</em> Labill, while being comparable to <em>Picea abies</em> (L.) H. Karst., <em>Pinus pinaster</em> Aiton and <em>untreated pine</em>.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105460"},"PeriodicalIF":5.6,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189099","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 : 2026-02-05DOI: 10.1016/j.tafmec.2026.105489
Florian Paysan, David Melching, Eric Breitbarth
The link between microscopic mechanisms and macroscopic behaviour, represented by the curve, plays an increasingly important role in relating the fatigue crack growth curve required for component design to the underlying physics. High-resolution digital image correlation (HR-DIC) allows for in-depth analysis of microscopic fatigue crack growth mechanisms, but is rarely used to determine the SIF of the crack tip. This paper examines the applicability of the interaction integral in HR-DIC data and identifies factors that should be considered when evaluating the integral results.
A major influence is the integration near the PZ, which leads to an erroneous increase in the calculated SIF result. In addition, the large integration path gaps required in HR-DIC around the crack path significantly hinder accurate results. The effect of the crack face contact is overall small. While it slightly increases the SIF result, it does not correlate with the crack opening load .
{"title":"Advanced crack tip stress analysis using interaction integrals in high-resolution digital image correlation fields","authors":"Florian Paysan, David Melching, Eric Breitbarth","doi":"10.1016/j.tafmec.2026.105489","DOIUrl":"10.1016/j.tafmec.2026.105489","url":null,"abstract":"<div><div>The link between microscopic mechanisms and macroscopic behaviour, represented by the <span><math><mrow><mi>d</mi><mi>a</mi><mo>/</mo><mi>d</mi><mi>N</mi><mo>−</mo><mi>Δ</mi><mi>K</mi></mrow></math></span> curve, plays an increasingly important role in relating the fatigue crack growth curve required for component design to the underlying physics. High-resolution digital image correlation (HR-DIC) allows for in-depth analysis of microscopic fatigue crack growth mechanisms, but is rarely used to determine the SIF of the crack tip. This paper examines the applicability of the interaction integral in HR-DIC data and identifies factors that should be considered when evaluating the integral results.</div><div>A major influence is the integration near the PZ, which leads to an erroneous increase in the calculated SIF result. In addition, the large integration path gaps required in HR-DIC around the crack path significantly hinder accurate results. The effect of the crack face contact is overall small. While it slightly increases the SIF result, it does not correlate with the crack opening load <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>op</mi></mrow></msub></math></span>.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105489"},"PeriodicalIF":5.6,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189094","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 : 2026-02-04DOI: 10.1016/j.tafmec.2026.105491
Jian Hua, Lei Zhou, Fukuan Nie, Hongdan Zhang, Yao Li, Meng Wang
To examine the effects of elliptical cavities on the dynamic stability and failure patterns of straight-walled arched tunnels, this study utilizes a modified drop-weight impact test apparatus for dynamic experiments and performs numerical simulations via AUTODYN software. The research examines stress wave attenuation, energy dissipation, and the evolving characteristics of the stress field around the elliptical cavity through both experimental and numerical approaches. The findings reveal that elliptical cavities significantly obstruct stress wave propagation, resulting in considerable attenuation of peak stress amplitude and notable energy dissipation. The crack coalescence is observed between the tunnel crown and the rock bridge beneath the elliptical cavity, which leads to shifts in the stress field. Notably, the location of maximum circumferential stress deviates by approximately 10° for the inclination angle of θ = 45°. The results are indicative of the fact that the stability of the tunnel is highest under horizontal stress waves (θ = 90°) and lowest at θ = 45°, where damage initiation and stress concentration primarily occur at the haunches. Further, the dominant coalescence modes vary with cavity inclination: crown crack coalescence at θ = 0° and 15°, shoulder crack coalescence at θ = 30°, 45°, and 60°, and sidewall crack coalescence at θ = 75° and 90°. The tunnel shoulders and sidewalls represent the most vulnerable zones, exhibiting the highest susceptibility to failure.
{"title":"Examination of the impact of elliptical cavities on the propagation law of stress waves within the tunnel surrounding rock","authors":"Jian Hua, Lei Zhou, Fukuan Nie, Hongdan Zhang, Yao Li, Meng Wang","doi":"10.1016/j.tafmec.2026.105491","DOIUrl":"10.1016/j.tafmec.2026.105491","url":null,"abstract":"<div><div>To examine the effects of elliptical cavities on the dynamic stability and failure patterns of straight-walled arched tunnels, this study utilizes a modified drop-weight impact test apparatus for dynamic experiments and performs numerical simulations via AUTODYN software. The research examines stress wave attenuation, energy dissipation, and the evolving characteristics of the stress field around the elliptical cavity through both experimental and numerical approaches. The findings reveal that elliptical cavities significantly obstruct stress wave propagation, resulting in considerable attenuation of peak stress amplitude and notable energy dissipation. The crack coalescence is observed between the tunnel crown and the rock bridge beneath the elliptical cavity, which leads to shifts in the stress field. Notably, the location of maximum circumferential stress deviates by approximately 10° for the inclination angle of θ = 45°. The results are indicative of the fact that the stability of the tunnel is highest under horizontal stress waves (θ = 90°) and lowest at θ = 45°, where damage initiation and stress concentration primarily occur at the haunches. Further, the dominant coalescence modes vary with cavity inclination: crown crack coalescence at θ = 0° and 15°, shoulder crack coalescence at θ = 30°, 45°, and 60°, and sidewall crack coalescence at θ = 75° and 90°. The tunnel shoulders and sidewalls represent the most vulnerable zones, exhibiting the highest susceptibility to failure.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105491"},"PeriodicalIF":5.6,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189020","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 : 2026-02-04DOI: 10.1016/j.tafmec.2026.105470
Chao Wang, Kaiyun Wang, Tao Zhu, Jingke Zhang, Bing Yang, Shoune Xiao, Guangwu Yang
The surface fatigue crack growth mechanism of welded structures under random loads in service is complex, and the assessment method based on failure life lacks an effective description of the crack growth process. This study investigates the surface crack evolution mechanism in welded joints under random fatigue loading. First, a series of experiments were conducted to determine the through-thickness crack growth rate parameters of aluminum alloy butt joints. These experiments revealed the influence of thickness and stress ratio on the fatigue crack growth rate. The normalization of the growth rate of surface cracks under variable fatigue loading was achieved through the introduction of the constraint factor of surface cracks and the crack closure function(ΔKeff-da/dN). Moreover, the effect of mean stress on the crack growth threshold was considered to describe the crack growth behavior of welded joints more accurately under near-threshold conditions and at high stress ratios. Furthermore, a two-stage model for surface fatigue crack growth in welded joints under variable-amplitude loading is proposed. The random load was converted into an equivalent variable-amplitude load spectrum, enabling a dynamic calculation of the surface fatigue crack growth life. Finally, this model significantly narrows the prediction error for test fatigue life from −25% ∼ 45% under the BS7910 standard analytical method to within −15% ∼ 25%, verifying the effectiveness of the proposed life assessment method for variable-amplitude fatigue crack growth in welded joints.
{"title":"Equivalent fatigue crack growth rate model and life assessment method for the surface of welded joints under variable amplitude loading","authors":"Chao Wang, Kaiyun Wang, Tao Zhu, Jingke Zhang, Bing Yang, Shoune Xiao, Guangwu Yang","doi":"10.1016/j.tafmec.2026.105470","DOIUrl":"10.1016/j.tafmec.2026.105470","url":null,"abstract":"<div><div>The surface fatigue crack growth mechanism of welded structures under random loads in service is complex, and the assessment method based on failure life lacks an effective description of the crack growth process. This study investigates the surface crack evolution mechanism in welded joints under random fatigue loading. First, a series of experiments were conducted to determine the through-thickness crack growth rate parameters of aluminum alloy butt joints. These experiments revealed the influence of thickness and stress ratio on the fatigue crack growth rate. The normalization of the growth rate of surface cracks under variable fatigue loading was achieved through the introduction of the constraint factor of surface cracks and the crack closure function(Δ<em>K</em><sub>eff</sub>-d<em>a</em>/d<em>N</em>). Moreover, the effect of mean stress on the crack growth threshold was considered to describe the crack growth behavior of welded joints more accurately under near-threshold conditions and at high stress ratios. Furthermore, a two-stage model for surface fatigue crack growth in welded joints under variable-amplitude loading is proposed. The random load was converted into an equivalent variable-amplitude load spectrum, enabling a dynamic calculation of the surface fatigue crack growth life. Finally, this model significantly narrows the prediction error for test fatigue life from −25% ∼ 45% under the BS7910 standard analytical method to within −15% ∼ 25%, verifying the effectiveness of the proposed life assessment method for variable-amplitude fatigue crack growth in welded joints.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105470"},"PeriodicalIF":5.6,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189016","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 : 2026-02-03DOI: 10.1016/j.tafmec.2026.105493
Min Lou , Gezhanpeng Li , Yangyang Wang , Bin Wu , Siyuan Wen , Chen Zhang
The fatigue behavior of the X80 pipeline steel under variable amplitude loading (VAL) in marine environments is critical for safely operating the offshore oil and gas transportation pipelines, such as risers. Therefore, a macro–micro multiscale analysis model (MMMA), which integrated crystal plasticity finite element method (CPFEM) and extended finite element method (XFEM), was proposed to characterize crack-tip plasticity and the associated micro-scale deformation mechanisms during VAL-induced crack growth. The macroscopic FCP characteristics of X80 pipeline steel under VAL were experimentally validated. This study clarified the macroscale evolution of the crack-tip plastic zone and the associated residual-stress field under VAL, and investigated the subgrain-scale distribution of intragranular slip-induced damage ahead of the crack tip, thereby elucidating overload retardation and its loading-sequence sensitivity through a consistent macro–micro linkage. The results demonstrated that overload induces residual plastic deformation and a compressive residual-stress field at the crack tip, leading to crack-growth retardation. Increasing the overload ratio (Rol) aggravates strain and intragranular slip heterogeneity, which strengthens the overload retardation. Different loading sequences determine retardation by altering slip tendency and recovery rates, with the single-peak overload followed by underload (OL–UL) more effectively suppressing overload-enhanced intragranular slip and reducing retardation than the single-peak underload followed by overload (UL–OL).
{"title":"Multiscale characterization of crack-tip plasticity and overload retardation in X80 pipeline steel under variable amplitude loading","authors":"Min Lou , Gezhanpeng Li , Yangyang Wang , Bin Wu , Siyuan Wen , Chen Zhang","doi":"10.1016/j.tafmec.2026.105493","DOIUrl":"10.1016/j.tafmec.2026.105493","url":null,"abstract":"<div><div>The fatigue behavior of the X80 pipeline steel under variable amplitude loading (VAL) in marine environments is critical for safely operating the offshore oil and gas transportation pipelines, such as risers. Therefore, a macro–micro multiscale analysis model (MMMA), which integrated crystal plasticity finite element method (CPFEM) and extended finite element method (XFEM), was proposed to characterize crack-tip plasticity and the associated micro-scale deformation mechanisms during VAL-induced crack growth. The macroscopic FCP characteristics of X80 pipeline steel under VAL were experimentally validated. This study clarified the macroscale evolution of the crack-tip plastic zone and the associated residual-stress field under VAL, and investigated the subgrain-scale distribution of intragranular slip-induced damage ahead of the crack tip, thereby elucidating overload retardation and its loading-sequence sensitivity through a consistent macro–micro linkage. The results demonstrated that overload induces residual plastic deformation and a compressive residual-stress field at the crack tip, leading to crack-growth retardation. Increasing the overload ratio (<em>R</em><sub>ol</sub>) aggravates strain and intragranular slip heterogeneity, which strengthens the overload retardation. Different loading sequences determine retardation by altering slip tendency and recovery rates, with the single-peak overload followed by underload (OL–UL) more effectively suppressing overload-enhanced intragranular slip and reducing retardation than the single-peak underload followed by overload (UL–OL).</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105493"},"PeriodicalIF":5.6,"publicationDate":"2026-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189097","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 : 2026-02-03DOI: 10.1016/j.tafmec.2026.105480
Dejun Liu , Hai Pu , Xiaoding Xu , Yunhui Fan , Kangsheng Xue , LuluLiu , Hao Zhang , Qingyu Yi
Understanding the coupled influence of material brittleness and fracture geometry on the mechanical degradation and failure behavior of fractured rock is critical for assessing instability in deep underground engineering. In this study, sandstone specimens with two distinct levels of brittleness were prepared with prefabricated fractures characterized by varying inclination angles and rock-bridge angles. A multiscale experimental framework integrating AE-DIC monitoring was employed to systematically investigate damage evolution and fracture mechanisms. To quantitatively characterize mechanical weakening, strength-degradation and elastic-modulus-degradation indices were proposed. The results show that prefabricated fractures significantly reduce the peak strength of sandstone. Increasing the fracture inclination angle leads to higher peak strength, whereas increasing the rock-bridge angle results in a non-monotonic decrease–increase trend. High-brittleness sandstone exhibits larger fluctuations in strength and stiffness under geometric disturbance, indicating stronger sensitivity to fracture-induced heterogeneity. AE-DIC results demonstrate that fracture inclination primarily controls the orientation and intensity of strain localization, while the rock-bridge angle governs the complexity of crack coalescence. High-brittleness specimens develop more concentrated and rapidly evolving strain localization bands, ultimately leading to abrupt mixed tensile–shear failure. Higher brittleness accelerates damage accumulation and promotes shear-dominated microcrack activity, particularly under high fracture inclination and large rock-bridge angles. In contrast, low-brittleness sandstone is characterized by a higher proportion of tensile microcracks and smoother b-value evolution, reflecting more progressive damage development. The degradation indices further reveal that strength deterioration is more pronounced in high-brittleness sandstone, whereas elastic modulus degradation shows greater sensitivity to brittleness reduction in low-brittleness sandstone. Overall, the findings highlight a coupled degradation mechanism in which fracture geometry controls the spatial evolution of damage, while material brittleness governs the rate and severity of mechanical degradation.
{"title":"Coupled effects of brittleness and fracture geometry on the damage evolution and mechanical degradation of sandstone","authors":"Dejun Liu , Hai Pu , Xiaoding Xu , Yunhui Fan , Kangsheng Xue , LuluLiu , Hao Zhang , Qingyu Yi","doi":"10.1016/j.tafmec.2026.105480","DOIUrl":"10.1016/j.tafmec.2026.105480","url":null,"abstract":"<div><div>Understanding the coupled influence of material brittleness and fracture geometry on the mechanical degradation and failure behavior of fractured rock is critical for assessing instability in deep underground engineering. In this study, sandstone specimens with two distinct levels of brittleness were prepared with prefabricated fractures characterized by varying inclination angles and rock-bridge angles. A multiscale experimental framework integrating AE-DIC monitoring was employed to systematically investigate damage evolution and fracture mechanisms. To quantitatively characterize mechanical weakening, strength-degradation and elastic-modulus-degradation indices were proposed. The results show that prefabricated fractures significantly reduce the peak strength of sandstone. Increasing the fracture inclination angle leads to higher peak strength, whereas increasing the rock-bridge angle results in a non-monotonic decrease–increase trend. High-brittleness sandstone exhibits larger fluctuations in strength and stiffness under geometric disturbance, indicating stronger sensitivity to fracture-induced heterogeneity. AE-DIC results demonstrate that fracture inclination primarily controls the orientation and intensity of strain localization, while the rock-bridge angle governs the complexity of crack coalescence. High-brittleness specimens develop more concentrated and rapidly evolving strain localization bands, ultimately leading to abrupt mixed tensile–shear failure. Higher brittleness accelerates damage accumulation and promotes shear-dominated microcrack activity, particularly under high fracture inclination and large rock-bridge angles. In contrast, low-brittleness sandstone is characterized by a higher proportion of tensile microcracks and smoother b-value evolution, reflecting more progressive damage development. The degradation indices further reveal that strength deterioration is more pronounced in high-brittleness sandstone, whereas elastic modulus degradation shows greater sensitivity to brittleness reduction in low-brittleness sandstone. Overall, the findings highlight a coupled degradation mechanism in which fracture geometry controls the spatial evolution of damage, while material brittleness governs the rate and severity of mechanical degradation.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105480"},"PeriodicalIF":5.6,"publicationDate":"2026-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189015","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 : 2026-02-01DOI: 10.1016/j.tafmec.2026.105488
Jiajun Ding , Jianhua Yang , Zhiwei Ye , Da Liu , Chi Yao , Xiaobo Zhang , Yongli Ma
The pilot tunnel expansion method has emerged as a crucial technique for constructing deep large-section tunnels. However, under high in-situ stress conditions, the dynamic response mechanisms and fracture characteristics of rock around a pilot tunnel subjected to blasting-induced impact loads remain insufficiently understood, limiting excavation efficiency and construction safety. To address this, this study investigates the dynamic response and fracture characteristics of granite containing a pilot tunnel using a modified true triaxial split Hopkinson pressure bar (SHPB) system combined with digital image correlation (DIC) technology. Additionally, smoothed particle hydrodynamics-finite element method (SPH-FEM) coupled numerical simulations were conducted to analyze three-dimensional damage evolution and energy dissipation characteristics. The results demonstrate that axial prestress accelerates fracture initiation and promotes fragmentation, whereas lateral prestress suppresses fracture propagation and enhances structural stability. Increasing the pilot tunnel diameter triggers a transition in failure mode from tensile to shear, accompanied by intensified spalling and localized shear strain. Furthermore, a novel quantitative indicator, damage volume-specific energy (DVSE), is proposed to evaluate fragmentation efficiency. Analysis shows that larger diameters and higher axial prestress reduce DVSE, indicating improved fragmentation efficiency. Building on these mechanisms, an innovative sequential blasting scheme is developed that prioritizes detonation along the major principal stress direction. This strategy effectively utilizes the in-situ stress to assist rock breaking, achieving superior fragmentation compared to conventional schemes. These findings provide theoretical guidance for improving blasting design efficiency and safety in deep tunnel construction using the pilot tunnel expansion method.
{"title":"Dynamic impact responses and fracture characteristics of rock around a pilot tunnel under in-situ stress","authors":"Jiajun Ding , Jianhua Yang , Zhiwei Ye , Da Liu , Chi Yao , Xiaobo Zhang , Yongli Ma","doi":"10.1016/j.tafmec.2026.105488","DOIUrl":"10.1016/j.tafmec.2026.105488","url":null,"abstract":"<div><div>The pilot tunnel expansion method has emerged as a crucial technique for constructing deep large-section tunnels. However, under high in-situ stress conditions, the dynamic response mechanisms and fracture characteristics of rock around a pilot tunnel subjected to blasting-induced impact loads remain insufficiently understood, limiting excavation efficiency and construction safety. To address this, this study investigates the dynamic response and fracture characteristics of granite containing a pilot tunnel using a modified true triaxial split Hopkinson pressure bar (SHPB) system combined with digital image correlation (DIC) technology. Additionally, smoothed particle hydrodynamics-finite element method (SPH-FEM) coupled numerical simulations were conducted to analyze three-dimensional damage evolution and energy dissipation characteristics. The results demonstrate that axial prestress accelerates fracture initiation and promotes fragmentation, whereas lateral prestress suppresses fracture propagation and enhances structural stability. Increasing the pilot tunnel diameter triggers a transition in failure mode from tensile to shear, accompanied by intensified spalling and localized shear strain. Furthermore, a novel quantitative indicator, damage volume-specific energy (DVSE), is proposed to evaluate fragmentation efficiency. Analysis shows that larger diameters and higher axial prestress reduce DVSE, indicating improved fragmentation efficiency. Building on these mechanisms, an innovative sequential blasting scheme is developed that prioritizes detonation along the major principal stress direction. This strategy effectively utilizes the in-situ stress to assist rock breaking, achieving superior fragmentation compared to conventional schemes. These findings provide theoretical guidance for improving blasting design efficiency and safety in deep tunnel construction using the pilot tunnel expansion method.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105488"},"PeriodicalIF":5.6,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189100","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 : 2026-01-30DOI: 10.1016/j.tafmec.2026.105461
Saber Fallah-Valukolaee, Ali Hasan-Ghasemi, Mahdi Nematzadeh
<div><div>Evaluating the performance of self-compacting concrete (SCC) at elevated temperatures significantly contributes to understanding the behavior of structures during fire. The inclusion of polyethylene terephthalate (PET) as a partial replacement of fine aggregates in SCC addresses environmental challenges while modifying the failure behavior. However, the failure performance and thermal response of self-compacting concrete (SCC) containing PET at elevated temperatures are still not fully understood. Understanding the changes in toughness, ductility, and fracture energy of this type of concrete at elevated temperatures is essential for the safe design of concrete structures. In this study, to assess the effect of shredded PET sheets as a partial replacement for natural fine aggregates, self-compacting concrete mixtures incorporating 0, 5, 10, and 15% PET by volume were produced, and their fracture behavior and ductility were investigated under unheated conditions and following thermal exposure at 200, 400, and 600 °C through three-point flexural loading applied to notched beam specimens. The results showed that the characteristic crack length as a ductility index (<span><math><msubsup><mi>α</mi><mo>∞</mo><mo>∗</mo></msubsup></math></span>), the fracture toughness (<span><math><msub><mi>K</mi><mi>IC</mi></msub></math></span>), the initial fracture energy (<span><math><msub><mi>G</mi><mi>f</mi></msub></math></span>), and the size independent fracture energy (<span><math><msub><mi>G</mi><mi>F</mi></msub></math></span>) decreased by approximately 7.5, 20, 22, and 27%, respectively, for the concrete specimens compared with the reference sample (without PET and without heating) as the PET replacement ratio increased to 15%. In addition, exposure of the specimens to 600 °C resulted in the greatest reduction in the investigated parameters compared with the other temperature levels. Analysis of the fracture parameters using the BEM method indicated that, in PET-free concrete and PET-containing concretes subjected to heating, the fracture energies and fracture toughness decreased by about 26 to 50% and 38 to 47%, respectively. Conversely, increasing the temperature within the range of 20 to 600 °C resulted in a reduction observed in both groups, with the difference that PET-containing concretes exhibited considerably more ductile behavior than PET-free concrete at high temperatures. Examination of the design criterion indicated that the fracture behavior of SCC becomes more consistent with linear elastic fracture mechanics (LEFM) with a rise in temperature, such that the design criterion at higher temperatures, with greater initial notch depth, conforms to LEFM. Finally, based on the achieved results and the experimental variables, multivariable equations were created to predict PET fracture parameters containing self-compacting concrete exposed to high temperatures. Evaluating these models against the present experimental findings, as well as with
{"title":"BEM investigation of fracture characteristics in polyethylene terephthalate-modified self-compacting concrete after thermal exposure","authors":"Saber Fallah-Valukolaee, Ali Hasan-Ghasemi, Mahdi Nematzadeh","doi":"10.1016/j.tafmec.2026.105461","DOIUrl":"10.1016/j.tafmec.2026.105461","url":null,"abstract":"<div><div>Evaluating the performance of self-compacting concrete (SCC) at elevated temperatures significantly contributes to understanding the behavior of structures during fire. The inclusion of polyethylene terephthalate (PET) as a partial replacement of fine aggregates in SCC addresses environmental challenges while modifying the failure behavior. However, the failure performance and thermal response of self-compacting concrete (SCC) containing PET at elevated temperatures are still not fully understood. Understanding the changes in toughness, ductility, and fracture energy of this type of concrete at elevated temperatures is essential for the safe design of concrete structures. In this study, to assess the effect of shredded PET sheets as a partial replacement for natural fine aggregates, self-compacting concrete mixtures incorporating 0, 5, 10, and 15% PET by volume were produced, and their fracture behavior and ductility were investigated under unheated conditions and following thermal exposure at 200, 400, and 600 °C through three-point flexural loading applied to notched beam specimens. The results showed that the characteristic crack length as a ductility index (<span><math><msubsup><mi>α</mi><mo>∞</mo><mo>∗</mo></msubsup></math></span>), the fracture toughness (<span><math><msub><mi>K</mi><mi>IC</mi></msub></math></span>), the initial fracture energy (<span><math><msub><mi>G</mi><mi>f</mi></msub></math></span>), and the size independent fracture energy (<span><math><msub><mi>G</mi><mi>F</mi></msub></math></span>) decreased by approximately 7.5, 20, 22, and 27%, respectively, for the concrete specimens compared with the reference sample (without PET and without heating) as the PET replacement ratio increased to 15%. In addition, exposure of the specimens to 600 °C resulted in the greatest reduction in the investigated parameters compared with the other temperature levels. Analysis of the fracture parameters using the BEM method indicated that, in PET-free concrete and PET-containing concretes subjected to heating, the fracture energies and fracture toughness decreased by about 26 to 50% and 38 to 47%, respectively. Conversely, increasing the temperature within the range of 20 to 600 °C resulted in a reduction observed in both groups, with the difference that PET-containing concretes exhibited considerably more ductile behavior than PET-free concrete at high temperatures. Examination of the design criterion indicated that the fracture behavior of SCC becomes more consistent with linear elastic fracture mechanics (LEFM) with a rise in temperature, such that the design criterion at higher temperatures, with greater initial notch depth, conforms to LEFM. Finally, based on the achieved results and the experimental variables, multivariable equations were created to predict PET fracture parameters containing self-compacting concrete exposed to high temperatures. Evaluating these models against the present experimental findings, as well as with ","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105461"},"PeriodicalIF":5.6,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189102","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 : 2026-01-29DOI: 10.1016/j.tafmec.2026.105484
Wenhui Sun , Yifei Li , Xiaodong Ge , Xiaojian Cao , Xianzheng Zhu , Haizhou Zhou , Shuyang Yu
Fissures in natural rock masses severely weaken bearing capacity and threaten deep engineering stability. Grouting reinforcement is an effective method for restoring integrity and inhibiting crack propagation. In this study, the mechanical properties and fracture mechanisms of 3D-printed rock-like specimens with resin-filled dual flaws under three-point bending are investigated. Digital Image Correlation (DIC) and two-dimensional Particle Flow Code (PFC2D) numerical simulations were integrated to analyze crack evolution under varying inclination angles (α). Resin filling fundamentally reconfigures the failure mechanism, shifting crack propagation from low-energy shear slip to high-energy matrix tension. Unlike unfilled specimens where increasing inclination (α) degrades strength and stress blocking effects as α increased, resin filling restored stress transmission continuity. To quantitatively elucidate this reinforcement, we analyze the mechanism of stress transfer restoration and evaluate the energy evolution using a normalized energy dissipation ratio (Kd). Analysis of the Kd ratio reveals that resin filling stabilizes the energy conversion rate between 70% and 74%, effectively overcoming the brittle collapse observed in unfilled samples. Crucially, at the critical 60° angle, the resin optimizes the energy evolution process by enforcing a transition from interface slip to matrix fracture, providing a theoretical basis for stability assessment in deep engineering projects.
{"title":"Fracture mechanisms of rock-like specimens containing double resin-infilled fissures under three-point bending loading: Sand-based 3D printing experiments and discrete element numerical simulations","authors":"Wenhui Sun , Yifei Li , Xiaodong Ge , Xiaojian Cao , Xianzheng Zhu , Haizhou Zhou , Shuyang Yu","doi":"10.1016/j.tafmec.2026.105484","DOIUrl":"10.1016/j.tafmec.2026.105484","url":null,"abstract":"<div><div>Fissures in natural rock masses severely weaken bearing capacity and threaten deep engineering stability. Grouting reinforcement is an effective method for restoring integrity and inhibiting crack propagation. In this study, the mechanical properties and fracture mechanisms of 3D-printed rock-like specimens with resin-filled dual flaws under three-point bending are investigated. Digital Image Correlation (DIC) and two-dimensional Particle Flow Code (PFC2D) numerical simulations were integrated to analyze crack evolution under varying inclination angles (<em>α</em>). Resin filling fundamentally reconfigures the failure mechanism, shifting crack propagation from low-energy shear slip to high-energy matrix tension. Unlike unfilled specimens where increasing inclination (<em>α</em>) degrades strength and stress blocking effects as <em>α</em> increased, resin filling restored stress transmission continuity. To quantitatively elucidate this reinforcement, we analyze the mechanism of stress transfer restoration and evaluate the energy evolution using a normalized energy dissipation ratio (<em>K</em><sub>d</sub>). Analysis of the <em>K</em><sub><em>d</em></sub> ratio reveals that resin filling stabilizes the energy conversion rate between 70% and 74%, effectively overcoming the brittle collapse observed in unfilled samples. Crucially, at the critical 60° angle, the resin optimizes the energy evolution process by enforcing a transition from interface slip to matrix fracture, providing a theoretical basis for stability assessment in deep engineering projects.</div></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":"143 ","pages":"Article 105484"},"PeriodicalIF":5.6,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078167","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}
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