Transportation Geotechnics最新文献

{"title":"Revealing the mechanisms of water permeability enhancement of urban loess subgrades due to vibration application","authors":"","doi":"10.1016/j.trgeo.2024.101346","DOIUrl":"10.1016/j.trgeo.2024.101346","url":null,"abstract":"<div><p>Urban loess subgrades are affected by considerable vibrations from traffic, especially when the underground pipelines leak, and seepage under vibrations often causes road damage. However, the influence of vibrations on the water permeability of loess subgrades remains elusive. Here we address this issue by performing vibration-assisted permeability tests and scanning electron microscopy, mercury intrusion porosimetry, and suction–nuclear magnetic resonance measurements. This allowed the evolution of the saturated hydraulic conductivity (<em>K</em>_s), water-air migration, soil microstructure, and pore water forms to be evaluated. The water permeability of the loess subgrade is promoted by vibrations due to the increase in <em>K</em>_s, the acceleration of wet front migration, and the escape of entrapped air. Moreover, the value of <em>K</em>_s under vibration is 3–14 times greater than that without vibration, and the maximum increase occurs at a vibration frequency near the natural frequency of the loess. Furthermore, a theoretical framework of loess vibration permeability is proposed, and the mechanisms by which vibration accelerates the permeability behavior of the loess subgrade are revealed. Vibration promotes the expansion of soil pores, a decrease in the binding capacity of pore water, the mobilization of fine particles, and the formation of local low-permeability layer. Moreover, it accelerates the opening of entrapped air bubbles and the displacement of water-air, the reduction in seepage resistance. Thus, seepage water flows rapidly along infiltration channels. These findings are highly important for the road safety performance and the sustainable development of the traffic environment in loess regions.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142058470","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":"Parametric optimization of Cement-based solidification combined with vacuum-assisted filtration","authors":"","doi":"10.1016/j.trgeo.2024.101351","DOIUrl":"10.1016/j.trgeo.2024.101351","url":null,"abstract":"<div><p>This study delves into the parametric optimalization of cement-based stabilized soft clays (CBSC) combined vacuum-assisted filtration (VAF) technique on for engineering applications, focusing on the influence of the retarder, calcium source and intermittent time etc. Key findings include VAF benefiting CBSC’s strength for water discharge from the paste, where the UCS of CBSC treated with VAF can increase more than ten times higher than the untreated samples (e.g., 767 kPa versus 60 kPa). The added retarders extend the initial setting time, thus facilitating the removal of excessive water, that the 0.2 % addition of calcium lignosulfonate causes 6.5 % increment of dewatering mass. Especially, calcium lignosulfonate, working as a versatile agent of imparting significant improvements in the rheological properties of cement mixtures and augmenting the structural integrity of clayey soils, was found to significantly enhance the VAF efficiency and the UCS, of which 28-day’s UCS further increases comparing to referential group after VAF. The study also reveals that calcium sources, such as desulfurized ash and lime, are also vital in replenishing calcium ions lost during VAF and maintaining a strong alkaline environment, significantly contributing to the strength enhancement. Additionally, the intermittent timing is also critical to the filtration efficiency, where the intermittent time was recommended within two hours post-mixing. These findings offer valuable insights for the practical application of CBSC by the VAF assistance, particularly involving soft clays with high water content.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142048952","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":"Mechanical and hydraulic characteristics of unvegetated or vegetated loess soils amended with xanthan gum","authors":"","doi":"10.1016/j.trgeo.2024.101350","DOIUrl":"10.1016/j.trgeo.2024.101350","url":null,"abstract":"<div><p>With the development of western and central China, the increasing construction of transportation infrastructures (e.g., roads, railways, etc.) has been producing a large number of man-made slopes in loess regions. Biopolymer as an eco-friendly stabilizing material, has a great potential to amend soils for the purpose of ground improvement and slope stabilization, with its application in vegetated soils particularly at the initial growing stage to support vegetation growth as well as offer reinforcement to unprotected soils being reported recently. In the current study, the contribution of xanthan gum (XG) to both mechanical and hydraulic behaviors of the unvegetated and vegetated loess soils subjected to climatic wetting–drying cycles under the impacts of degree of compaction and biopolymer content are explored, whilst the effectiveness of the two XG-based soil reinforcing methods (with and without vegetation) are compared. Results indicate that XG treatment improved the water-retention capacity of loess soils to an extent that even the degradation of water retention upon initial wetting–drying cycles could be mitigated particularly at higher degrees of compaction. The strengthened shear resistance of loess soils was observed, mainly attributed to the increased soil cohesion, whilst the friction angle remained almost constant. The unvegetated loess soils basically had an increased cohesion proportional to the XG content up to 1.00% of the dry soil mass, whilst the vegetated soils had the highest soil cohesion at a fixed XG content of 0.50% which corresponded to the mostly promoted vegetation growth. Although a dense soil structure inhibited the seed germination and growth of sprouts and roots, it contributed to the overall shear strength of the vegetated soils similar to its effect on the unvegetated soils. XG amendment outperformed planting vegetation at enhancing soil shear strength at a degree of compaction of 95% (comparable to those adopted for design of highway subgrade), whilst providing XG in combination with vegetation was able to result in a more sizable strength increment over the summation of gains in strength by utilizing XG and vegetation separately, suggesting the considerable potential of XG in assisting vegetated soils for ecological slope stabilization. The results obtained from the current research support the broader usage of biopolymers (either used alone or in combination with vegetation) as reliable geotechnical engineering materials in practical implementations.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084149","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":"Evaluation of sensor-enabled piezoelectric geoelectric cable in cyclic shear tests of subgrade soil under vertical cyclic loads","authors":"","doi":"10.1016/j.trgeo.2024.101357","DOIUrl":"10.1016/j.trgeo.2024.101357","url":null,"abstract":"<div><p>Of late, deformation of subgrade soil has led to an increasing number of road subsidence diseases. Real-time monitoring of subgrade deformation is critical to ensure the safety of subgrade operations. In this paper, a sensor-enabled piezoelectric geoelectric cable (SPGC) with impedance strain effect and piezoelectric effect is tested. The SPGC impedance and voltage signals obtained by cyclic shear test under vertical static load and cyclic shear test under vertical cyclic load are used to evaluate the monitoring effect. The results showed that normal stress had the greatest effect on the shear strength of the soil, whereas the normal stress and horizontal shear displacement amplitude significantly influenced the strain in the soil. Varying the normal and horizontal shear frequencies had little effect on the shear strength and strain of the soil. The normalized impedance and voltage of the SPGC, respectively, decreased and increased rapidly during the initial stage of the shear cycle; these changes were relatively small during the middle and late stages of the shear cycle. The SPGC voltage waveform revealed the changes in the shear stress and vertical displacement under different normal and horizontal shear frequencies, from which the stability of the subgrade soil under the aforementioned conditions could be evaluated. The variations in the SPGC impedance and effective voltage from the cyclic shear tests under both vertical static and vertical cyclic loads remained essentially consistent with the number of cycles. However, there was a difference in that the trough of the SPGC impedance under the vertical cyclic load was larger than that under the vertical static load; likewise, the effective SPGC voltage under the cyclic load was larger than that under the static load. Through an analysis of the SPGC impedance and voltage signals in the subgrade soil, the consistency of the SPGC-normalized impedance and effective voltage with shear stress was clarified; this helped us evaluate the health of the subgrade and monitor the characteristics of the precursor signals before a slide were to occur, thereby affording us an opportunity to issue timely warnings.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084169","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":"Development of insulating backfill materials produced from the ternary mixtures of red mud, fly ash and preformed foam","authors":"","doi":"10.1016/j.trgeo.2024.101339","DOIUrl":"10.1016/j.trgeo.2024.101339","url":null,"abstract":"<div><p>Many public utility lines to transport power, water, natural gas, water, sewer, and communication are placed beneath trafficable areas. However, insufficient or inadequate backfill induces sudden subsidence, damage, or pothole on the road. This study aims to develop lightweight controlled low-strength materials (CLSM) with low thermal conductivity using the ternary mixtures of red mud to replace aggregate sand, high carbon fly ash, and preformed foam. Changes in flow consistency, air void characteristics, bulk unit weight, unconfined compressive strength (UCS), and thermal conductivity (<em>k</em>) of the tested materials with varying red mud contents were investigated as a function of the foam volume ratio (<em>FVR</em>). The results demonstrate that the UCS and <em>k</em> of tested materials decreased with increasing <em>FVR</em> due the decrease in unit weight, and a greater UCS but smaller <em>k</em> was observed at a given <em>FVR</em> with increasing red mud content because the inclusion of red mud in the lightweight CLSM mix design helps improve the stability of air bubbles and achieve uniform distribution of air voids. In addition, the red mud can act as a NaOH supplier, leading to the developed material had additional strength gain from the alkali activation. Thus, the developed insulating backfill material showed 43 % decrease in <em>k</em> while maintaining UCS similar to non-foam CLSM without red mud.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142041128","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":"Semi-Conv-DETR: A railway ballast bed defect detection model integrating convolutional augmentation and semi-supervised DETR","authors":"","doi":"10.1016/j.trgeo.2024.101334","DOIUrl":"10.1016/j.trgeo.2024.101334","url":null,"abstract":"<div><p>Railway ballast bed defects, including subsidence, mud pumping, and abnormal water, pose significant safety risks by destabilizing the railway ballast beds. Timely detection and repair of railway ballast bed defects are vital for safeguarding the security of both the trains and their passengers. Ground-Penetrating Radar (GPR) is widely used for railway ballast beds inspection and evaluation owing to its high speed and non-destructive characteristics. However, GPR image data contain considerable noise, and the distinct shapes and sizes of each ballast bed defect renders it challenging to apply a unified data annotation standard, which hampers the development of railway ballast bed defect detection models. Considering the distinct wave-like characteristics of GPR data and the vaguely contours of the defects to be identified, we propose a convolutional augmentation operation tailored for GPR images. Furthermore, we also investigate Semi-Supervised Learning by employing limited annotated railway ballast bed inspection data along with a vast amount of unlabeled data to joint train the DETR detection model. To sum up, we proposed a semi-supervised DETR model supplemented with convolutional augmentation for railway ballast bed defect detection, termed as Semi-Conv-DETR model. Experimental outcomes indicate that Semi-Conv-DETR shows an improvement of 58.6 % in accuracy when compared to the classical Faster-RCNN model.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142048949","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":"Confinement effect of geocell on the mechanical characteristics of reinforced sand subgrade","authors":"","doi":"10.1016/j.trgeo.2024.101336","DOIUrl":"10.1016/j.trgeo.2024.101336","url":null,"abstract":"<div><p>Geocell has a confinement effect, limiting the deformation of soil and enhancing the strength of reinforced soil, and has a wide range of application prospects in traffic transportation subgrade engineering. To investigate the confinement effect of geocell on the mechanical characteristics of reinforced sand subgrade, this paper analyzes the macro-mechanical properties of reinforced sand subgrade using triaxial tests, investigates the micro-reinforcement mechanism employing discrete element method (DEM)-based simulations. The potential macro–micro linkages are studied. The experimental results revealed that the volumetric strain of the geocell-reinforced samples increased with the material’s elastic modulus, exhibiting a shear shrinkage phenomenon. The deformation pattern of the reinforced samples presented “segmental deformation,” which differed from that of the unreinforced sand samples. The geocell enhanced the cohesion intercept of the sand samples while having a minimal impact on friction angle. Through the analysis of numerical simulation results, it was found that the geocell constrained the displacement of the soil particles, altering the shear band development trend of the sample and resulting in “segmental deformation”. The geocell facilitated the concentration of force chains, enhancing their stability and resulting in improving the strength in the macro. Additionally, it was observed that the confinement effect of the geocell significantly reduced the fabric and force anisotropy of the granular soil, promoting consistent vertical alignment of force chains. This, in turn, enhanced the vertical force transmission capacity of the sample, explaining the micro-mechanism by which the confinement effect of the geocell increases the peak shear strength of the samples.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985180","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":"Prediction of thermal regime and frost heave deformations of subgrade soils during non-stationary heat and moisture transfer","authors":"","doi":"10.1016/j.trgeo.2024.101338","DOIUrl":"10.1016/j.trgeo.2024.101338","url":null,"abstract":"<div><p>In order to ensure the safe operation of high-speed trains in cold regions, frost heave is one of the basic problems in the research for prediction and control roadbed deformation in such regions. In this paper, based on the classical hydrodynamic model we developed a method of studying thermal regime of soils and predicting frost heave deformations of subgrade soils. Our coupling model takes into account the mutual influence of temperature and soil moisture during non-stationary processes of heat and moisture transfer, calculation of frost heave deformation based on calculated result of the temperature and moisture fields of the roadbed. We have also observed the change of the soil temperatures and frost heave deformation in a freezing-thawing cycle at the geodesic center of PGUPS. The field observation results show that the soil temperature variations amplitude decreases with depth. The simulation verification results and the field observation data show good reproducibility, thus the reliability of the model is confirmed. At last, the paper presents the application of the method in improving high speed railway lines (HSRL) subgrade design in order to reduce frost heave deformations. Based on the results of calculations, it is recommended to lay a thermal insulation layer at the depth of 0.2 m below the subgrade and on the slopes to reduce frost depth and frost heave deformations of subgrade soils.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997249","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":"Enhancing sand liquefaction resistance through microbial-induced partial saturation: An experimental study","authors":"","doi":"10.1016/j.trgeo.2024.101337","DOIUrl":"10.1016/j.trgeo.2024.101337","url":null,"abstract":"<div><p>The liquefaction potential of saturated sand can be significantly reduced by inducing partial saturation in the soil. Conventional soil liquefaction mitigation methods, namely soil densification, drainage, cementing, and groundwater lowering, pose environmental concerns and are challenging to apply to pre-existing structures. However, the microbially induced partial saturation (MIPS) method is emerging as a novel and eco-friendly approach to mitigate liquefaction. The MIPS method involves microbial denitrification, which produces nitrogen gas and results in a desaturating effect in the saturated soil. The current study conducted a series of stress-controlled undrained cyclic triaxial tests on saturated sandy soil and microbially-desaturated sandy soil under different relative densities and loading conditions. In addition, the study systematically analyzed the effects of temperature and pH on bacterial activity and the denitrification process. Batch experiments were conducted to establish a relationship between the initial nitrate concentration in the bacterial media and the resulting desaturation.Comprehensive analyses of cyclic resistance curves were performed to gain a thorough understanding. Additionally, the study conducts detailed analyses of the accumulation of excess pore pressure and the resulting axial strains and deformation patterns in both treated and untreated sand. This study demonstrates that the MIPS treatment considerably enhances the liquefaction resistance of treated sand.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142012245","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":"Hydraulic influences on the long-term performance of tunnels: A review","authors":"","doi":"10.1016/j.trgeo.2024.101329","DOIUrl":"10.1016/j.trgeo.2024.101329","url":null,"abstract":"<div><p>Long-term performance of tunnels usually depends on their interaction with surrounding environment induced by various internal and external, natural and anthropogenic factors. Understanding these long-lasting impacts is paramount and crucial for the sustainable lifelong management of tunnel infrastructures. Considering prolonged rainfall, sea level rise and other extreme geohazards partly due to climate change, this paper specifically reviews previous studies examining the hydraulic influences on the long-term performance of tunnels. The variation in groundwater levels, changes in the hydraulic permeability of the surrounding ground and tunnel linings, water leakage, and tunnel deterioration are key hydraulic factors that critically affect the long-term performance of tunnels. The primary objective is to identify research gaps and limitations and provide insights for future research directions to improve our understanding of the long-term performance of tunnels under hydraulic influences. It is found that previous studies often fail to quantify these effects, exemplified by subjectively varying groundwater levels, ground and tunnel permeability and assuming random distribution of tunnel deteriorations. Therefore, future research should focus on adopting laboratory/field data-based, realistic assumptions, aiming to advance the understanding of the performance of tunnels across their lifespan and eventually enhance the principles of tunnel design, construction, and maintenance.</p></div>","PeriodicalId":56013,"journal":{"name":"Transportation Geotechnics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2214391224001508/pdfft?md5=4a6058743867ee2bca921976d13c55f1&pid=1-s2.0-S2214391224001508-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141930754","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}