Transportation Geotechnics最新文献

{"title":"Genetic programming-based closed-form solutions for predicting the compressive strength of cement-treated soils","authors":"Muhammad Hasnain Ayub Khan ,&nbsp;Akbar A. Javadi ,&nbsp;Adel Abdallah ,&nbsp;Olivier Cuisinier","doi":"10.1016/j.trgeo.2026.101949","DOIUrl":"10.1016/j.trgeo.2026.101949","url":null,"abstract":"<div><div>This study presents closed-form predictive models for estimating the unconfined compressive strength (UCS) of cement-treated soils using two genetic programming techniques i.e., Gene Expression Programming (GEP) and Multi Expression Programming (MEP), addressing the limitations of existing closed-form predictive models that are often overly simplified, rely on a narrow set of input variables, or are tailored to specific soil types, thereby restricting their general applicability. An extended dataset comprising 328 data points was compiled from existing literature, covering both coarse- and fine-grained soils and incorporating key geotechnical and treatment-related parameters such as liquid limit (LL), fine content (FC), normalized compaction parameters (ρ_norm, w_norm), cement dosage (C), curing time (T), and porosity-to-volumetric cement ratio (η/C_iv). The dataset was pre-processed using min–max normalization and split evenly into training and testing sets. Through a systematic trial-and-error process, optimal configurations for GEP and MEP were identified. The optimal GEP and final MEP models demonstrated high predictive accuracy, achieving coefficients of determination (R²) of 0.86 and 0.92, respectively, and were further corroborated by low error room-mean-squared error, and mean absolute error. Closed-form mathematical expressions were derived from both models. Performance evaluation, including monotonicity and sensitivity analyses, confirmed the physical relevance of the models, with GEP showing higher physical consistency than MEP. Notably, feature importance varied between models: ρ_norm was most influential in MEP, while FC had the highest impact in GEP. Overall, the developed models offer accurate and physically meaningful tools for predicting UCS in cement-stabilized soils, contributing to improved design practices in cement-soil stabilization applications.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"59 ","pages":"Article 101949"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175336","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}

{"title":"Railway ballast fouling detection using thermal imaging: integration of LSTM and XGBoost","authors":"Mehdi Koohmishi ,&nbsp;David P. Connolly","doi":"10.1016/j.trgeo.2025.101889","DOIUrl":"10.1016/j.trgeo.2025.101889","url":null,"abstract":"<div><div>This paper presents an artificial intelligence (AI)-based approach to automate the structural health monitoring (SHM) of railway ballast through the fusion of long short-term memory and XGBoost (LSTM-XGB) to surface temperature data derived from infrared thermal images. In this context, machine learning models are trained using remotely acquired surface temperature data to classify fouling index based on thermal variations within ballast aggregates captured from thermograms. The long short-term memory (LSTM) component processes sequential time-series thermal data to predict preceding values, and the XGBoost (XGB) component classifies fouled ballast conditions based on identified patterns of surface temperature variations measured via infrared thermography (IRT). The results confirm the capability of the LSTM component to capture the time-series variations of a specimen’s surface temperature in a shorter timeframe as well as the superior performance of XGBoost compared to a random forest (RF) approach, in classifying fouled ballast conditions. Therefore, the LSTM-XGB model demonstrates higher efficiency compared to the standalone XGBoost model, since the predictive nature of LSTM over time-series temperature data enables capturing shorter time window for measuring ballast surface temperature and identifying patterns. Moreover, establishing a coarser classification of ballast fouling (categorized into three groups instead of five) significantly improves the model capability for accurate assessment of the ballast fouling conditions.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"59 ","pages":"Article 101889"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146162176","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}

{"title":"Brittle failure evaluation of rocks under freeze–thaw cycles based on an energy-based method","authors":"Tao Wen ,&nbsp;Wanying Huang ,&nbsp;Bocheng Zhang ,&nbsp;Ningsheng Chen ,&nbsp;Fengyun Wang","doi":"10.1016/j.trgeo.2026.101940","DOIUrl":"10.1016/j.trgeo.2026.101940","url":null,"abstract":"<div><div>The importance of the evaluation of the brittleness under freeze–thaw cycle is reflected in the slope stability and the safety construction of infrastructure in cold region. There are few studies on rock brittleness in various engineering applications under freeze–thaw (F-T) cycles in cold regions. Herein, existing methods for rock brittleness evaluation are concluded and their limitations are identified. To address these limitations, a novel brittleness index (BI) that comprehensively considers the energy evolution throughout the entire stages is proposed. The effectiveness of the proposed BI is verified the suitability of proposed BI in different rock types by utilizing four datasets of varying rock compositions. Afterwards, the samples collected from the Qinghai-Tibet Plateau were subjected to the F-T test, the proposed BI is validated by comparing it with four existing BIs using the data of F-T cycle tests on conglomerate and sandstones. The results demonstrate that with increasing confining pressure (CP), all selected BIs exhibit a downward trend under the same F-T cycle. Moreover, different F-T cycles have significant influence on rock failure under the same CP, and the proposed BI exhibiting a more pronounced trend compared to other BIs. These findings provide valuable support for research on the rock brittleness in resource exploration and engineering construction assessment especially in cold regions.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"59 ","pages":"Article 101940"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146162177","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}

{"title":"Hydro-mechanical responses of irregular twin tunnels with unequal burial depths in anisotropic soil layer","authors":"Senlin Xie ,&nbsp;Zhen Huang ,&nbsp;Changqing Xia ,&nbsp;Hao Zhang ,&nbsp;Jie Shi ,&nbsp;Xiangsheng Chen","doi":"10.1016/j.trgeo.2026.101933","DOIUrl":"10.1016/j.trgeo.2026.101933","url":null,"abstract":"<div><div>Understanding the seepage-mechanical behavior of tunnels with complex geometries and layouts is essential for the safety and durability of underground structures in anisotropic soils. However, most existing studies focus on single circular tunnels under idealized conditions, while multi-tunnel interference, unequal burial depths, and noncircular sections-common in practical engineering-remain insufficiently addressed. This study develops a hybrid Physics-Informed Neural Network (with hard constraints)-Finite Element Method (PINN-FEM) framework to analyze the steady-state seepage and stress fields of anisotropic foundations containing dual-line tunnels with unequal depths and noncircular cross sections. The seepage continuity equation is first solved by the PINN to capture pore pressure distribution without mesh generation, and the predicted field is then interpolated and incorporated into the FEM as an external input to compute the stress-displacement response. This hybrid strategy combines the flexibility of PINN with the numerical robustness of FEM, achieving a balance between computational efficiency and physical accuracy. Results show that the PINN-predicted pore pressure agrees closely with reference solutions, confirming its effectiveness for complex boundary conditions. Results show that the PINN-predicted pore-pressure field agrees closely with reference solutions, achieving a global average L₂ error of 0.055 and a maximum relative error on the order of 10⁻³, demonstrating high accuracy under complex boundary conditions. A domain-size sensitivity analysis reveals that lateral boundary effects cannot be reliably assessed using a single universal criterion; however, a lateral extent of approximately five times the tunnel diameter provides a reasonable reference for preliminary model setup.tunnel number and burial-depth asymmetry dominate the hydro-mechanical response, producing changes of more than 60% in displacement and up to approximately 80% in stress components. Permeability anisotropy results in moderate variations (typically 15–40%) in stresses and displacements, whereas changes in cross-sectional shape mainly amplify local stress concentrations rather than global deformation. In addition, comparisons between constraint strategies confirm that hard-constrained PINNs markedly improve convergence stability and physical consistency relative to soft-constraint formulations. The proposed PINN–FEM framework provides an efficient and reliable tool for parametric and comparative hydro-mechanical analysis of complex tunnel systems in anisotropic soils.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"59 ","pages":"Article 101933"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146162175","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}

{"title":"Biocementation of road pavements: An experimental investigation through physical modeling and accelerated testing","authors":"Tianzheng Fu,&nbsp;Stuart Kenneth Haigh","doi":"10.1016/j.trgeo.2026.101913","DOIUrl":"10.1016/j.trgeo.2026.101913","url":null,"abstract":"<div><div>Biocementation, owing to its non-intrusive nature, holds great promise as a non-disruptive solution for improving road pavements, particularly for rehabilitating those experiencing deterioration. The present study provides a direct proof of concept for this application. Full-depth physical models of a three-layer pavement structure, uncemented and biocemented, were constructed and subjected to accelerated testing under increasing wheel loads, with laser scanning and particle image velocimetry (PIV) combined to monitor surface and subsurface deformation. The results showed that both models exhibited a depression in the wheel path and an upheave on the side. The enhanced structural integrity of the biocemented model allowed it to experience significantly reduced deformation while sustaining higher loads. PIV analysis of subsurface displacement and strain fields revealed distinct deformation mechanisms. The uncemented model experienced localized failure within the poorly compacted base with a predominantly contractive response, while the biocemented model involved an active, vertically displacing zone beneath the wheel that underwent volumetric dilation, which was laterally confined by a passive zone on the side. These findings clearly demonstrate the effectiveness of biocementation in improving the structural performance of pavements. However, low treatment efficiency under unsaturated conditions presents a critical challenge for field implementation and warrants further investigations.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101913"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080494","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}

{"title":"Direct shear–DEM evaluation of basic oxygen furnace (BOF) slag for railway ballast","authors":"Elijah Adebayonle Aremu,&nbsp;Doszhan Tuzelbayev,&nbsp;Jong Kim,&nbsp;Sung-Woo Moon","doi":"10.1016/j.trgeo.2026.101938","DOIUrl":"10.1016/j.trgeo.2026.101938","url":null,"abstract":"<div><div>Integrated large-scale direct shear tests and discrete element method (DEM) simulations were used to evaluate basic oxygen furnace (BOF) slag as a sustainable partial replacement for natural crushed-stone ballast. Laboratory tests provided validation targets for a specific BOF source under low confinement (30–70kPa), while DEM reproduced the gradation and angular shapes using clumped particles. The simulations were calibrated to the measured shear stress–strain curves and then used to probe micromechanics, including coordination number, strong/weak contact partition, and fabric anisotropy. Across 0–100% BOF by volume, peak shear strength and peak friction angle decreased with increasing BOF; however, mixtures with 20–40% BOF retained performance only marginally below natural stone. Microstructurally, BOF addition reduced coordination and peak fabric deviator, shortened force chains, and increased contact-orientation randomness—features that explain the strength reductions. A compact pre-peak constitutive relation between fabric deviator and stress ratio, <span><math><mrow><msub><mi>ϕ</mi><mi>d</mi></msub><mo>=</mo><mi>a</mi><msup><mrow><mo>(</mo><mi>τ</mi><mo>/</mo><msub><mi>σ</mi><mi>n</mi></msub><mo>)</mo></mrow><mi>b</mi></msup></mrow></math></span>, provided excellent fits for the overall and strong contact networks. These results offer mechanism-based guidance for mixture design: limited BOF substitution (20–40%) provides a practical balance supporting material-circularity potential while maintaining shear capacity within a narrow penalty band. The study demonstrates how DEM-informed fabric metrics, interpreted alongside large-scale testing, can support the adoption of industrial by-products in railway ballast without compromising key mechanical requirements.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101938"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190528","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}

{"title":"Numerical investigation of train-induced ground vibrations in ballastless embankment considering wheel–rail geometric nonlinearity","authors":"Zihao Jin ,&nbsp;Wei Zhang ,&nbsp;Xueyu Geng","doi":"10.1016/j.trgeo.2026.101934","DOIUrl":"10.1016/j.trgeo.2026.101934","url":null,"abstract":"<div><div>Predicting train-induced ground vibrations is essential for assessing the environmental impact of high-speed rail systems. However, many existing numerical models rely on simplified wheel–rail interaction formulations, which can lead to unreliable predictions due to inaccurate representation of the excitation source. In this study, a novel three-dimensional (3D) Vehicle–Track–Embankment–Ground (VTEG) finite element (FE) model is developed, explicitly incorporating rail irregularities and fully coupled wheel–rail geometric interaction. The proposed model is validated against field measurements in terms of subgrade dynamic soil stresses and ground surface vibration velocities. A parametric case study identifies two characteristic velocities. Critical Velocity I (CV I) closely corresponds to the Rayleigh wave velocity of the weakest supporting soil layer, whereas Critical Velocity II (CV II), associated with the peak maximum dynamic displacement (MDD) of track, lies between the Rayleigh wave velocities of the softest ground layer and the embankment base. Comparative analyses show that a conventional 2.5D linear FE model provides adequate accuracy under weakly dynamic conditions (V ≤ CV I) but progressively underestimates the track MDD as train speed approaches CV II. At CV II, the peak MDD is underestimated by approximately 14.6% relative to the proposed 3D nonlinear model, with about 54% of this discrepancy attributable to reduced model dimensionality and the remaining 46% to linear wheel–rail contact assumptions. Furthermore, foundation reinforcement markedly increases both CV I and CV II and reduces the peak MDD by approximately 43.5%, thereby effectively mitigating resonance-like behaviour at ultra-high train speeds. In addition, foundation reinforcement significantly suppresses ground-borne vibrations and modifies the characteristics of surface wave propagation, producing more circular wavefronts within the reinforced zone while maintaining Mach-cone-type features outside. These findings provide quantitative guidance for vibration assessment, modelling strategy selection and mitigation design in high-speed railway engineering.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101934"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189908","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}

{"title":"DIC-Based Investigation into Failure Mechanisms and Geogrid Optimization of Eccentrically Loaded Footings above Void","authors":"Changjie Liu ,&nbsp;Heng Zhao ,&nbsp;Zeyu Xu ,&nbsp;Gaoqiao Wu ,&nbsp;Yunhao Chen ,&nbsp;Biao Luo ,&nbsp;Chuhan Xie ,&nbsp;Jie Xu ,&nbsp;Minlong Zhou","doi":"10.1016/j.trgeo.2026.101937","DOIUrl":"10.1016/j.trgeo.2026.101937","url":null,"abstract":"<div><div>Ground loss from road tunnelling beneath surface buildings can generate localized subsurface voids, threatening the serviceability and safety of shallow foundations. This study performs DIC-assisted laboratory model tests to investigate the bearing response of an eccentrically loaded strip footing in sand above a tunnelling-induced void, with geogrid reinforcement adopted as a mitigation measure. The experimental program is organized by the following dimensionless groups: the eccentricity ratio <em>e</em>/B, the void burial depth <em>H</em>/D, the void horizontal position <em>S</em>/D and the geogrid embedment and length ratios <em>u</em>/B and <em>L</em>/B. Full-field DIC observations clearly reveal the evolution of failure paths and disturbed zones and provide the first comprehensive set of full-field displacement maps for the coupled footing–void–geogrid system under eccentric loading. The results show that increasing <em>e</em>/B reduces the ultimate bearing capacity, intensifies footing rotation,　and shifts the disturbed zone toward the unloaded side. The failure mode is governed by the combined effects of the void and the footing influence zone. For example, when the footing influence zone overlaps with the void, the stress path tends to develop toward the void, and the ultimate bearing capacity decreases accordingly. When the cover thickness or the void’s horizontal offset exceeds the footing influence zone, the failure mode can be approximated as a “no-void” condition.Geogrid reinforcement markedly improves the capacity and exhibits optima in <em>u/</em>B and <em>L/</em>B: a distinct optimal <em>u</em>/B appears at larger e/B, whereas a plateau-type optimal range emerges at smaller <em>e</em>/B, the required <em>L</em>/B increases with <em>e</em>/B. Under the present conweuration, void effects become negligible when <em>H</em>/B≈3. For geogrid mitigation, the recommended embedment depth is <em>u</em>/B≈0.2–0.4 for <em>e</em>/B≳0.3 (with <em>u</em>/B≈0.2 at <em>e</em>/B = 0.4), and the plateau range is <em>u</em>/B≈0.6–1.2 for <em>e</em>/B ≤ 0.1, a practical reinforcement length is <em>L</em>/B≈8.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101937"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189911","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}

{"title":"Efficient improvement of physicochemical properties and plant growth in sandy ecological substrates: performance and mechanisms of biochar-based materials","authors":"Daxiang Liu ,&nbsp;Yexiong Zhou ,&nbsp;Zhihai Xu ,&nbsp;Qiangbing Song ,&nbsp;Yuliang Qin ,&nbsp;Zuosen Luo ,&nbsp;Yao Xiao ,&nbsp;Xudong Hu ,&nbsp;Dong Xia ,&nbsp;Liming Liu ,&nbsp;Mingtao Zhou ,&nbsp;Huafeng Deng ,&nbsp;Wennian Xu ,&nbsp;Yueshu Yang","doi":"10.1016/j.trgeo.2026.101901","DOIUrl":"10.1016/j.trgeo.2026.101901","url":null,"abstract":"<div><div>Engineering damaged exposed slopes often experience severe soil degradation, with soils predominantly composed of weathered bedrock. When such soils are used as ecological slope protection substrates, they commonly exhibit inadequate geotechnical strength and low fertility, which severely restrict the effectiveness and long-term durability of ecological slope protection engineering. Addressing this challenge, this study investigates the potential of combining biochar (BC) and microbially induced calcium precipitation (MICP) to enhance the structural and ecological performance of sandy ecological substrates (SSs). A series of pumping-grouting and plant cultivation experiments were conducted to evaluate the individual and synergistic effects of BC and MICP. Results showed that BC improved porosity and plant growth but reduced dry density, shear strength, and disintegration resistance. MICP significantly increased mechanical strength but inhibited plant growth. When combined, BC facilitated microbial adhesion and CaCO₃ precipitation, enhancing MICP performance while reducing BC degradation. However, excessive BC content negatively impacted substrate strength and mineralization efficiency. Optimization experiments identified ideal conditions: 1-2% BC by mass, bacterial concentration at OD₆₀₀ = 1.0, and calcium acetate and urea at 1.0 mol/L. This optimized scheme significantly improves the structural and ecological performance of SSs with minimal adverse effects on vegetation, demonstrating strong potential for practical ecological slope engineering applications.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101901"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190112","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}

{"title":"Mechanistic evaluation of reclaimed asphalt pavement (RAP) as base course: the role of binder aging in the response of RAP-virgin aggregate blends","authors":"Saad Ullah ,&nbsp;Adnan Sadiq ,&nbsp;Asad Mehmood ,&nbsp;Debanjana Ghosh ,&nbsp;Burak F. Tanyu","doi":"10.1016/j.trgeo.2026.101925","DOIUrl":"10.1016/j.trgeo.2026.101925","url":null,"abstract":"<div><div>This study investigates the influence of binder properties of reclaimed asphalt pavement (RAP) specifically binder content and oxidative aging on the performance of RAP-virgin aggregate (VA) blends through repeated load triaxial (RLT) testing. RAP samples from four regional sources were characterized using standard index property tests, binder content determination, and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy to quantify binder aging via an aging index. RAP-VA blends were prepared at as-is gradations in proportions of 20%, 30%, 60%, and 80% RAP, and tested under stress conditions representing higher, medium, and low traffic pavement structures representative of Illinois pavement and traffic conditions. Results demonstrate that PD performance depends on the interplay between binder content and aging index, rather than binder content alone. RAP with higher aging indices consistently exhibited superior resistance to deformation, even at high RAP contents. The threshold RAP content for deformation resistance at optimum moisture and maximum dry density, beyond which permanent deformation begins to increase, was found to vary depending on the pavement structure and traffic level typically ranging from 20 to 40% for pavements with thicker asphalt layers (high-volume roads) and 20–80% for thinner asphalt layers (medium- to low-volume sections). This variation arises primarily from differences in the binder characteristics of each RAP source, including binder content and aging index. RAP with higher binder content or a more oxidized (aged) binder tends to exhibit a stiffer yet more brittle response, which alters the blend’s deformation behavior and shifts the threshold RAP content at which performance begins to decline.</div></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":"58 ","pages":"Article 101925"},"PeriodicalIF":5.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189913","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}