Transportation Geotechnics最新文献

{"title":"Hybrid artificial neural network models for bearing capacity evaluation of a strip footing on sand based on Bolton failure criterion","authors":"","doi":"10.1016/j.trgeo.2024.101347","DOIUrl":"10.1016/j.trgeo.2024.101347","url":null,"abstract":"<div><p>This paper employs the Bolton failure criterion, incorporating strength-dilatancy relationships, to analyze the bearing capacity factor of a strip footing on dense sand. Utilizing finite element limit analysis (FELA) based on the lower and upper bound theorems, the study presents the results as average bound solutions. By using the Bolton model, the <em>b</em> parameter is first calibrated and found that it should be about 3.50 to align the ultimate bearing capacity (<em>q_u</em>) from FELA to have a good agreement with that from experimental test results from previous studies. The influence of parameters relevant to the Bolton failure criterion is analysed, showing that an increase in relative density (<em>D_R</em>) significantly affects the variation in the bearing capacity factor (<em>N</em>_γ) at higher <em>Q</em> values, while lower <em>Q</em> values inhibit dilatancy due to soil crushing. The width of the strip footing (<em>B</em>) has a decreasing effect on <em>N</em>_γ at higher <em>Q</em> values, and the unit weight (<em>γ</em>) changes minimally impact <em>N</em>_γ within the range of 16–22 kN/m³. Additionally, an increase in the critical state friction angle (<em>ϕ_cv</em>) consistently increases <em>N</em>_γ, highlighting its direct correlation with soil shear strength. A hybrid artificial neural network (ANN) model integrates machine learning with four optimization algorithms: Imperialist Competitive Algorithm (ICA), Ant Lion Optimization (ALO), Teaching Learning Based Optimization (TLBO), and New Self-Organizing Hierarchical Particle Swarm Optimizer with Jumping Time-Varying Acceleration Coefficients (NHPSO-JTVAC). Comparative rank analysis of hybrid ANN models based on the selection of the optimal number of hidden neurons demonstrates that the ANN-TLBO model excels in predicting the bearing capacity factor, achieving a score of 48. This conclusion is corroborated by an error heatmap matrix, which indicates a minimized percentage of error relative to other hybrid ANN models. Importance analysis identifies particle crushing strength (<em>Q)</em> as the most significant factor influencing the bearing capacity factor (<em>N</em>_γ).</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142096379","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":"Small-strain stiffness of compacted loess upon wetting, drying and loading: Experiments and model interpretation","authors":"","doi":"10.1016/j.trgeo.2024.101341","DOIUrl":"10.1016/j.trgeo.2024.101341","url":null,"abstract":"<div><p>Stiffness of soil at very small strains <em>G</em>₀ is mainly affected by void ratio, effective stress and suction. Empirical equations considering those factors have been proposed to estimate <em>G</em>₀. However, for collapsible soil like loess, variations in suction might induce changes in void ratio of soil. The combined effect of these two factors poses challenges in accurately estimating of <em>G</em>₀. This paper first presents an experimental study on the <em>G</em>₀ of collapsible loess under various conditions, including as-compacted states, wetting/drying and K₀ loading. <em>G</em>₀ is estimated from shear wave velocity obtained with bender element technique. The changes of <em>G</em>₀ with respect to void ratio, suction, effective stress, and wetting under K₀ stress conditions are evaluated. Test results reveal that power relationships can be defined between <em>G</em>₀ and void ratio, suction and effective stress, respectively. The changes in <em>G</em>₀ along wetting/drying shows an “S” shape due to the different dominant effects on soil structure, as well as the induced non-uniform volume changes when suction change at different zones. Under K₀ loading, <em>G</em>₀ decreases upon wetting at stresses below the compaction stress, while it increases upon wetting at stresses above the compaction stress, due to the combined effects of densification caused by volume collapse during wetting and softening induced by suction decrease. Finally, a <em>G</em>₀ model considering net stress and suction as independent stress variable is proposed. This model could effectively capture the change of <em>G</em>₀ during wetting, drying and loading, as well as upon wetting under K₀ loading for collapsible loess.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142136819","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":"Physical model investigation of a hybrid GRS integral bridge abutment under cyclic thermal stresses","authors":"","doi":"10.1016/j.trgeo.2024.101348","DOIUrl":"10.1016/j.trgeo.2024.101348","url":null,"abstract":"<div><p>GRS integral bridge abutments develop large lateral earth pressure on the facing during seasonal/diurnal thermal expansion/contraction, causing significant surface settlements. To mitigate these issues, researchers prefer the use of different kinds of facing to withstand lateral pressure in conjunction with reinforcing of backfill to reduce surface settlement. The present research investigates the performance of a hybrid integral abutment under lateral movement of the facing due to cyclic thermal expansion/contraction of the bridge deck through scaled down <em>1 g</em> physical model tests. Using the optimized facing and reinforcement configuration, an integral abutment model was proposed and analyzed under varying rate of loading and different loading offsets for three displacement modes till 100 cycles of excitation. The assessment included the development of lateral pressure on facing, surface settlement, magnitude and location of peak reinforcement forces, followed by evaluating long-term performance in terms of permanent strains, stiffness degradation, and strain energy dissipation. The observations revealed that the proposed model having strong connection between the reinforcement and facing along with inclusion of secondary reinforcements along the entire height of abutment in the bearing zone exhibits rapid dissipation of accumulated strain energy, leading to a 48 % reduction in surface settlement under cyclic thermal stresses.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142096401","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":"A novel large-scale direct shear apparatus considering size effects on strength of frozen coarse-grained soils","authors":"","doi":"10.1016/j.trgeo.2024.101365","DOIUrl":"10.1016/j.trgeo.2024.101365","url":null,"abstract":"<div><p>As engineering activities in cold regions expand and the application of artificial ground freezing technology in constructions grows, understanding the strength of frozen coarse-grained soils has become imminently crucial. While existing research and testing methods have provided valuable opinions into the behavior of coarse-grained materials in frozen states, there is a recognized need to enhance and expand these methods to gain a more comprehensive understanding of how size effects influence the strength of these materials. To further investigate this issue, a novel large-scale direct shear apparatus was employed to determine the shear strength of frozen coarse-grained soil materials. The apparatus features a unique design capable of accommodating square specimens with five different section lengths: 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm. Depending on the maximum load requirements and budget constraints of the experiment, the equipment can provide a maximum normal stress of 5.5–50 MPa and a maximum shear stress of 3.5–30 MPa for different sample sizes, along with precise temperature control down to −30 °C. The efficacy of the device is validated through experiments conducted on frozen coarse-grained soil samples with specific particle size distributions. This study presents the technological details involved in the development of the apparatus and offers preliminary insights into the strength characteristics of frozen coarse-grained soils, highlighting the influence of size effects. The innovative features of the apparatus help the geotechnical community to comprehensively understand the strength characteristics of this complex material, thereby improving the reliability of engineering practices that involve it.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142136820","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":"Finite-Element modelling of axial movements of polyethylene pipes in dense sand","authors":"","doi":"10.1016/j.trgeo.2024.101366","DOIUrl":"10.1016/j.trgeo.2024.101366","url":null,"abstract":"<div><p>The current design guidelines (e.g., ALA 2005) have been reported to underpredict the axial pullout resistance measured in laboratory and field tests for pipes buried in dense sand. The higher pullout resistances in the tests were believed to be due to the shearing-induced soil dilation at the pipe–soil interface. However, the mechanism of soil dilation could not be measured during the tests. In the current study, three-dimensional finite-element (FE) analysis was employed to examine the mechanism, which revealed that the effect of shearing-induced dilation could be insignificant, depending on the magnitude of the earth pressures. For pipes buried at shallow depths, the compaction-induced lateral earth pressures significantly contributed to higher interface normal stresses and the increase of normal stress due to shear-induced dilation, resulting in relatively higher pullout resistances. The stiffness of the pipe and soil also influenced the interface normal stress. The compaction-induced lateral earth pressure increase was modelled using equivalent temperature loads in the FE analysis that successfully simulated the measured pipe responses. Based on the findings, a modification to the current design equation to calculate the maximum axial spring force was proposed, incorporating the compaction-induced lateral earth pressure and a normal stress adjustment factor.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142149064","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":"A data-driven approach to quantify track buckling strength through the development and application of a Track Strength Index (TSI)","authors":"","doi":"10.1016/j.trgeo.2024.101359","DOIUrl":"10.1016/j.trgeo.2024.101359","url":null,"abstract":"<div><p>Railroads are increasingly adopting advanced technologies to enhance safety and state of good repair of their track infrastructure, some of which employ artificial intelligence-based inspection methods. The objectivity of these inspection techniques, along with their detailed measuring capabilities, has created opportunities for railroads to improve both inspection and operational efficiency. This is achieved through more frequent and precise track data collections and technical data aggregations. This paper explores the potential of these track inspection methods to address one of the few drawbacks of continuous welded rail (CWR): track buckling. While track buckling mechanics and prevention have been the subject of numerous studies, the need for a practical and objective method to assess resistance to buckling remains. Numerous track health indices for geometry parameters and some for railway components have been developed and utilized in various applications. Yet, the opportunity exists to develop a metric that combines geometric parameters with the condition levels of railway components, particularly designed to quantify the resistance of track to buckling. Such a holistic view of the track and network-wide time series analyses of the proposed metric demonstrate whether the buckling resistance improves, remains in a steady state, or declines. In this study, a sensitivity analysis conducted using CWR-Risk software identified misalignment amplitude, track curvature, lateral resistance, torsional resistance, and longitudinal resistance as the main factors contributing to buckling resistance. Based on the sensitivity study and with a focus on the capacity side of the track buckling equation, a methodology was proposed for converting inspection data into 10-point scales that were combined through weighted averaging into a single Track Strength Index (TSI) to quantitatively assess the resistance to buckling at a track-system level. The influence of ballast condition on TSI output was evaluated using 15 ballast configuration scenarios, ensuring that the index accurately reflects ballast deficiencies in a proportionate manner. Lastly, the proposed metric was tested leveraging revenue service data collected from a Class I railroad mainline in the United States.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2214391224001806/pdfft?md5=31f13c7b808e0f1517f15d4098cc9f71&pid=1-s2.0-S2214391224001806-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laboratory characterisation of sand-tyre mix as bedding material for buried structures","authors":"","doi":"10.1016/j.trgeo.2024.101355","DOIUrl":"10.1016/j.trgeo.2024.101355","url":null,"abstract":"<div><p>Bedding material directly interacts with buried structures and supports to sustain external loadings such as traffic and overburden soil pressure. Therefore, soil-structure interaction plays an essential role in the stability and safety of buried structures. In particular focusing on underground pipelines, the annual rate of failures in Australia is around 19 % per 100 km of pipeline and can cost millions of Australian dollars in maintenance. Of these annual failures, ground vibrations from heavy traffic and construction activities are a major cause. In order to reduce such effects of ground vibrations on buried structures, this paper presents the possible application of sand-rubber mixes as a bedding material, where rubber is sourced from recycled tyres. The performance of sand-tyre mixes with regard to the potential for vibration reduction is assessed through this experimental study which comprises of particle size distribution, standard proctor compaction, permeability test, direct shear test, California Bearing Ratio and Repeated Load Test. From these tests, it was found that sand mixed with up to 20 % recycled tyre rubber was the most suitable mix for use as a bedding material.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2214391224001764/pdfft?md5=0b6ac1c15198ff7b26a232732f6002d1&pid=1-s2.0-S2214391224001764-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142096376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative study on dynamic responses of ballasted and ballastless tracks at critical velocity","authors":"","doi":"10.1016/j.trgeo.2024.101354","DOIUrl":"10.1016/j.trgeo.2024.101354","url":null,"abstract":"<div><p>High-speed railways are becoming ubiquitous worldwide, demanding increased operational speeds. Yet, as trains near critical speeds, dynamic stress and embankment displacement escalate, jeopardizing safety. While significant strides have been made in studying these critical speeds, capturing the dynamic characteristics of all track responses remains elusive. This study presents a coupled train-track-ground model employing a 2.5D finite element approach integrated with a nonlinear soil model to investigate the influence of embankment and foundation properties on the critical speeds for both ballasted and ballastless tracks. The research resulted in the development of unified Dynamic Amplification Factor curves that consistently represent the dynamic behavior of various tracks as observed in multiple studies. Additionally, the applicability of simplified theoretical models for calculating critical speeds, such as the elastic half-space foundation and track-foundation models, was assessed. The findings suggest that the simplified models are suitable only under specific conditions. This research provides valuable perspectives on optimizing train speeds and ensuring the safety of diverse track types.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142096402","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":"Optimization of mixtures of soil, construction and demolition waste, and steel slag using the simplex-extreme vertices method","authors":"","doi":"10.1016/j.trgeo.2024.101361","DOIUrl":"10.1016/j.trgeo.2024.101361","url":null,"abstract":"<div><p>In the present study, a simplex-extreme vertices methodology was applied to investigate the optimal proportions of recycled aggregates from construction and demolition waste (CDWr) and fines of electric arc furnace oxidizing slag (FS) for the stabilization of two distinct tropical soils, enabling their use in structural pavement layers. The influence of mixture components content on the unconfined compressive strength (UCS) and California Bearing Ratio (CBR) was investigated using regression analyses and response surfaces. UCS and CBR were optimized, based on the application of the Desirability function approach for determination of the best mixture compositions. The regression models yielded high coefficients of determination (R² ≥ 0.83). The optimization methodology demonstrated that the best dry mass composition was 80 % soil, 0 % CDWr, and 20 % FS for the sandy soil; and 18 % soil, 62 % CDWr, and 20 % FS for the clayey soil. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed the formation of typical products of pozzolanic reactions after a 28-day curing period. Incorporating wastes and extending the curing period caused a decrease in expansion and an enhancement in the UCS and CBR values of the soils.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142130213","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":"Thermo-mechanical response of sand-silt mixtures","authors":"","doi":"10.1016/j.trgeo.2024.101342","DOIUrl":"10.1016/j.trgeo.2024.101342","url":null,"abstract":"<div><p>The thermo-mechanical response under undrained conditions is crucial in evaluating the mechanical behaviors of sand-silt mixtures. A series of consolidated undrained triaxial shear tests were conducted to investigate the mechanical response of sand-silt mixtures with different fines contents, temperatures, and initial mean effective stresses. The results showed that the volume shrinkage was observed in all specimens during heating. The amplitudes of volume shrinkage were dependent on the fines content and initial mean effective stress. Moreover, the fines content and temperature significantly influence the peak strength, flow behavior, stress ratio at the undrained instability state, and collapsibility index. Furthermore, a unified critical state line has been established in the compression plane for both clean sand and binary mixture under different temperatures and fines contents. It is reliable and suitable to use the equivalent skeleton void ratio to illustrate the thermo-mechanical response of sand-silt mixtures under undrained conditions.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142117546","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}