Analysis of Roadbed Splicing at Hub Interchanges

This article discusses the roadbed splicing for hub interchanges.The article starts with a description of the characteristics of junction roadbed splicing.The application of splicing technology is explained using a subgrade splicing scheme of a project.Roadbed splicing involves stepwise excavation and preparative measures like surface cleaning and backfilling.This article serves to provide a valuable reference for road and bridge construction and improve the quality of China’s road and bridge projects,so as to achieve sustainable development of the road and bridge engineering industry.

Reinforcement Technology for Soft Soil Roadbed in the Widened Section of Expressway Expansion

This article examines the soft soil roadbed reinforcement technology for widened sections of highways in a specific project.It provides an overview of the project,the principles of soft soil roadbed reinforcement technology for wide sections,and its practical application.The analysis aims to offer guidance on applying soft soil roadbed wide section reinforcement technology and enhancing the overall quality of similar projects.

Settlement Control Standards of Construction and Expansion for Mountainous Highway Roadbeds

This article analyzes the differential settlement of new and old roadbeds after widening and its characteristics based on a highway reconstruction and expansion project case study.The research proposes a subgrade settlement control standard that states that the maximum differential settlement value should be less than 5 cm when the embankment fill height exceeds 20 m.Similarly,the maximum differential settlement value should be less than 10 cm when the embankment fill height does not exceed 20 m.The findings of the study can provide a useful reference for the design of roadbed widening in highway reconstruction and expansion projects.

Analysis of Roadbed Pavement Designs for Highway Reconstruction and Upgrading

This paper focuses on the route and roadbed pavement design in highway reconstruction and upgrading projects.It discusses the importance of project design for highway reconstruction and upgrading,highlighting key aspects of route design and roadbed pavement design.The analysis reveals that the main design considerations in these projects include controlling factors of route reconstruction,expansion,and upgrading,as well as route plan design and longitudinal section design combined with roadbed pavement.In roadbed pavement design,it is crucial for designers to thoroughly collect existing data and make reasonable use of the current roadbed and pavement to develop a comprehensive design scheme.This analysis aims to provide a reference for the reasonable design of such projects.

Soil erosion and its causes in high-filling body:A case study of a valley area on the Loess Plateau,China

Large-scale land consolidation projects(LCPs)have been carried out on the Loess Plateau to increase the area of agriculture land.The newly created land is prone to soil erosion under the effects of water and gravity.Taking a typical high-filling body(HFB)formed by LCPs in Yan’an,China as the subject,this study comprehensively investigated the types and causes of soil erosion with multiple methods of field investigation,on-site monitoring and laboratory tests.Results showed that the HFB presented a composite pattern of soil erosion with multiple types mainly including underground erosion,mixed water-gravity erosion,seepage erosion,and scouring erosion.The type of erosion varied spatially in different parts of the HFB depending on the dominant factors,mainly including the groundwater state,rainfall,runoff,gravity action,topography,and soil erodibility.The underground erosion mainly occurred at the positions with higher groundwater level and larger hydraulic gradient,while scouring erosion mainly occurred at the positions with extensive interactions of surface runoff,channel slope gradient and soil properties.And near the leading edge of the top of the slope,a band of mixed watergravity erosion occurred owing to the effects of water and gravity.In addition,nearly saturated soils at the toe of HFB displayed groundwater exfiltration and slope-face slumping.Based on our findings on the causes and variation of soil erosion for the HFB,we proposed the following erosion prevention and control measures to protect the LCPs on the Loess Plateau:to construct drainage ditches and blind ditches to form a complete drainage system,plant alfalfa on the top platform to increase rainfall interception and reduce surface runoff,set seepage ditches and plant deep-rooted plants at the toe of the slope to improve slope toe stability,monitor groundwater level and slope deformation to learn the erosion dynamics and slope stability,and optimize the geometry of HFB such as the slope gradient and slope steps to reduce soil erosion.

Stress distribution in roadbeds of slab tracks with longitudinal discontinuities

Stress concentration occurs in the foundations of railway tracks where discontinuous components are located.The exacerbated stress under the expansion joints in slab tracks may trigger foundation failures such as mud pumping.Although the higher stress due to the discontinuities of track structures has been discussed in past studies,few focused on the stress response of roadbeds in slab tracks and quantitatively characterized the stress pattern.In this paper,we performed a dynamic finite element analysis of a track-formation system,incorporating expansion joints as primary longitudinal discontinuities.The configurations of CRTS Ⅲ slab tracks and the contact conditions between concrete layers were considered.Numerical results show that longitudinal influencing length of induced stress on roadbed under wheel load relates to the contact conditions between concrete layers,increasing nonlinearly at a larger coefficient of friction.Given a measured coefficient of friction of 0.7,the calculated longitudinal influencing length(9.0 m) matches with field data.The longitudinal influencing length is not affected with the increasing velocity.As stress concentration arises with expansion joints,the worstcase scenario emerges when double-axle loads are exerted immediately above the expansion joints between concrete bases.A stress concentration factor Cvon the roadbed is proposed;it increases with the increasing velocity,changing from 1.33 to 1.52 at velocities between 5 and 400 km/h.The stress distribution on roadbeds transforms from a trapezoid pattern at continuous sections to a triangle pattern at points with longitudinal discontinuities.An explicit expression is finally proposed for the stress pattern on roadbed under expansion joints.Although structural discontinuities induce stress raiser,the extent of concentration is mitigated with increasing depth at different velocity levels.

Wireless remote spatiotemporal monitoring of high-fill foundation deformation

The spatial and temporal deformation patterns and deformation control indicators of highfill foundations directly affect the design,construction and operational safety of high-fill projects.In situ monitoring can comprehensively reflect the deformation of high-fill during and after construction.In this paper,we have first designed and installed an integrated wireless remote monitoring system for high-fill to achieve real-time dynamic monitoring of settlement,pore water pressure and soil pressure of the fill foundation.Based on the monitoring results of nearly one year of the construction period and two years after construction,it was found that the deformation amount and deformation rate of the high-fill foundation showed a non-linear growth relationship with the filling rate and filling height.The settlement deformation of the high-fill foundation during the loading period was mainly dominated by the original foundation soil,accounting for 54.4%of the total settlement on average;the settlement deformation during the post-construction period was mainly dominated by the filling body,accounting for 77.04%of the total settlement on average,and the settlement deformation during the post-construction period mainly occurred in the first year after construction.The analysis of the deformation mechanism suggests that the deformation of the filling body is dominated by exhaust consolidation during the loading period and drainage consolidation during the post-construction period;the deformation of the original foundation soil is dominated by drainage consolidation during the loading period and drainage consolidation develops slowly during the post-construction period.It is recommended that the original foundation should be reinforced before the large area filling construction,and that the filling rate should be strictly controlled during construction.The research results can provide a scientific basis for deformation calculation and stability assessment of high-fill foundations.

Analysis of Highway Roadbed Performance Evaluation Technology

With the continuous development of China,the requirements for road construction are also increasing.Among them,strengthening the performance of roadbed test can effectively improve road construction.Besides,it is also crucial to perform suitable tests in a timely manner.Therefore,highway inspection technology should be improved for the continuous development of highway construction,which will be explained in this paper,in hopes of improving the construction of highway in China.

Permafrost Characteristics of the Qinghai-Tibet Plateau and Methods of Roadbed Construction of Railway

Permafrost along the Qinghai-Tibet railway is featured by abundant ground ice and high ground temperature. Under the influence of climate warming and engineering activities, the permafrost is under degradation process. The main difficulty in railway roadbed construction is how to prevent thawing settlement caused by degradation of permafrost. Therefore the proactively cooling methods based on controlling solar radiation, heat conductivity and heat convection were adopted instead of the traditional passive methods, which is simply increasing thermal resistance. The cooling methods used in the Qinghai-Tibet railway construction include sunshine-shielding roadbeds, crushed rock based roadbeds, roadbeds with rock revetments, duct-ventilated roadbeds, thermosyphon installed roadbeds and land bridges. The field monitored data show that the cooling methods are effective in protecting the underlying permafrost, the permafrost table was uplifted under the embankments and therefore the roadbed stability was guaranteed.

Numerical simulation of roadbed slope under seismic action in permafrost regions

The deformation and strength characteristics of roadbed slope under seismic loading in permafrost regions are simulated numerically. The seismic response of roadbed at different positions and inclinations of a slope section was analyzed. Results show that, roadbed slope damage is mainly led by lateral displacement, and the deformation gradually decreases with increasing depth; roadbed and foundation displacement and plastic strain increases with the magnitude of slope angle, hence the roadbed safety factor will be reduced.

Roadbed, embankment, tower support and culvert stability problems on permafrost

The history of railway and highway construction in permafrost zones in Russia, the United States, Canada, and China spans more than 110 years. Nonetheless, no railway track or highway has yet been built in such area that is impervious to deformation caused by subsidence resulting from the thawing of ice-rich subgrade soils. This paper presents data on the roadbed states of the Trans- baikalian and the Baikal-Amur Railways as well as the Russian ＂AMUR＂ Chita-Khabarovsk Highway. It also discusses the feasi- bility of roadbed stability maintenance using methods based on the reduction of the mean annual ground temperature and roadbed preservation in a permafrost state by means of the natural cooling and heating factors ratio regulation resulting in a reduction of the heat generation in the roadbed and the adjoining area accompanied by an increase of heat consumption with help of the sun-precipitation protective sheds （awnings）, rock covers, dolomite powder （reflective paint）, cooling tube and thermosyphons as well as tower supports and corrugated pipe culverts stability.

Applying the AHP-FUZZY method to evaluate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau: a case study of Chaidaer-Muli Railway

This article attempts to investigate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau. As a case study, Chaidaer-Muli Railway is used to evaluate the measure effect of rubble roadbed engineering in permafrost regions. The AHP(Analytic Hierarchy Process) method is thus employed to establish the evaluation indicator system. The evaluation factor is selected by analyzing the mutual relation between the permafrost environment and roadbed engineering. Thus, a hierarchical structure model is established based on the selected evaluation indices. Each factor is weighted to determine the status in the evaluation system, and grading standards are built for providing a basis for the evaluation. Then, the fuzzy mathematical method is introduced to evaluate the measure effect of rubble roadbed engineering in permafrost regions along the Chadaer-Muli Railway. Results show that most of the permafrost roadbed is in a preferable condition(b) along the Chaidaer-Muli Railway due to rubble engineering measures. This proportion reaches to 86.1%. The proportion in good(a), general(c) and poor states(d) are 0.0%, 7.5% and 6.4%, respectively, in all the evaluation sections along the Chaidaer-Muli Railway. Ground-temperature monitoring results are generally consistent with AHP-FUZZY evaluation results. This means that the AHP-FUZZY method can be applied to evaluate the effect of rubble roadbed engineering measures in permafrost regions. The effect evaluation of engineering measures will provide timely and effective feedback information for further engineering design. The series of engineering measures will more effectively protect permafrost stability.

Roadbed behavior subjected to tilting-train loading at rail joint and continuous welded rail

The tilting-train is very attractive to the railroad users in the world due to the advantage of high speed in curved track using pre-existing infrastructure of railway.Tilting-train has a unique allowable speed and mechanism especially in curved track.In this work,when tilting-train is operated with the allowable speed,the behavior of roadbed is evaluated by examining its settlement and bearing capacity.Additionally,the stability of roadbed is estimated as the roadbed is in the condition of soft soil influenced by the weather effects and cyclic train loading.Numerical results show that the roadbed settlement satisfies the allowable settlement when the elastic moduli of upper roadbed and in-situ soil are greater than 3800 and 4600 kN/m2 for rail joint and 2300 and 3300 kN/m2 for continuous welded rail(CWR).

Design method of pile-slab structure roadbed of ballastless track on soil subgrade

堆积平板结构路基是为高速度铁路的无碎石的轨道的一种新形式。由于相应设计代码的缺乏，基于它的结构特征和应用程序要求的分析，根据最终的限制状态和有用性限制状态执行负担效果联合被建议，并且每个状态的最相反的联合被选择为堆积平板结构完成设计计算。堆积平板结构的空间模型能作为一个飞机框架模型被简化，由用直角的测试方法，和堆积平板的设计参数，结构被优化。而且基于 Suining 重庆高速度的铁路的设计背景，堆积平板结构路基的动态变丑特征被继续室内的动态模型测试进一步研究。测试结果证明在路基的建设以后的解决满足解决控制的要求为高速度的铁路在土壤路基上造无碎石的轨道。当负担从平板被传给堆积，平板结构起拱门壳的作用，并且路基土壤的垂直动态压力是近似有深度的 K 形式分发。应力是的堆积的分发仔细与土壤特征，它有一个不安的三角形有关塑造大动态压力在顶在哪儿。与土壤份额相比堆很有活力的应力。堆积结构扩展路基的动态反应的深度并且改进火车的路基土壤，和速度的压力在动态反应上限制了效果。这些结果能为在土壤路基上使用的堆积平板结构路基提供科学基础。

Mechanism and calculation method of rheological settlement of high-filled embankment

The characteristics of high-filled embankment rheological settlement were analyzed;mechanical calculation model of high-filled embankment rheological settlement during constructing and running period was also put forward.Combining the macroscopic and microscopic deformation properties of the engineering soil grain,its constitutive model was set up and its characters were fully revealed,at the same time,its practical calculation formula under the action of dead-weight load was derived,which is feasible by analysis and comparison.

Roadbed Subsidence Mechanisms under the Driven of Penetration-Soak Coupling

Roadbed subsidence is one of the main types of highway flood damage, the periodic fluctuation of the river water level and the softening of the subgrade soils by the river water immersion for a long time are the main inducement factors of the subgrade subsidence. Based on the theory of absorbing water infiltration in unsaturated soil, calculation formula of dynamic stability coefficient of subgrade is established by using the Swedish arc method. Example analysis shows that, soil roadbed suffers the water permeability-soak, road-bed’s stability reduce with the time, and leads to roadbed subsidence. Research results for improving roadbed subsidence water logging mechanism understanding level have a positive meaning.

THE APPLICATION OF GROUND PENETRATING RADAR IN THE HIGHWAY ROADBED INVESTIGATION

Ground penetrating radar (GPR) is a new nondestructive geophysical method for road quality investigation. In this article, a section of the highway joints with the third Yangtze Bridge in Wuhan have been investigated using the RAMAC/GPR system developed by the MAL? GeoScience Company. Various antennas with different frequency were used in the exploration. And the data gathered by the unshielded antenna with frequency in 400 MHz is very well. Then the field data was processed using methods such as trace equalization, F K filtering, deconvolution filtering and so on. Through the processing, the GPR profile shows the underground structure more clearly. From the processed GPR profile, the sinking and slipping condition of the roadbed can be easily found. Most parts of the roadbed are well, but several parts of the roadbed have sunken or slipped seriously. Contrasts to the shallow seismic section, the GPR profile accords with it very well. It indicates that the GPR method is available and has the high efficiency in the highway roadbed investigation.

A Roadbed Cooling Approach for the Construction of Qinghai-Tibet Railway

Over one half of the permafrost along the Qinghai-Tibet Railway is “warm" and approximately 40% ice-rich. Under global warming, the construction of the Qinghai-Tibet Railway needs to consider climate changes over the next 50～100 years. Recent estimates indicate that the air temperature on the plateau will increase by 2.2～2.6℃ by 2050. Thus, the key to the success of the railway construction lies in preventing the permafrost underlying roadbeds from thawing. It has been more than 100 years since the first railway was build over permafrost. A frost damage ratio of greater than 30% has been reported for all the railroads built in permafrost regions. Based upon the experience and lessons learned from roadway constructions over permafrost, this paper proposes a more proactive design approach for the construction of the Qinghai-Tibet Railway. This approach focuses on cooling down the roadbed by lowering the ground temperature and is different from the passive method of preventing permafrost from thawing by simply increasing thermal resistance (e.g., increasing embankment height and using insulating materials). This “roadbed cooling" design approach is especially relevant to “warm" and ice-rich permafrost areas. A number of measures can be taken to cool down the roadbed, including proper selection of roadbed material, and configurations to adjust solar radiation, heat convection, and heat conduction patterns in and/or around the roadbed.

广西大新红黏土工程地质特性及路基处治措施

研究目的:红黏土因其特殊的工程性质,容易引起边坡出现裂隙、垮塌、不均匀沉降等病害,对工程质量、安全、造价造成极大影响。本文对红黏土进行详细室内土工试验,分析研究红黏土的物理力学性特征,从而为红黏土边坡防护及填料利用提供相应的处治措施建议,以指导工程实践。研究结论:(1)该地区红黏土显示出高含水率、高饱和度、高孔隙比、高液限、高塑性、压缩性较小、黏聚力高、弱~中膨胀性的特征;(2)随深度增加,含水率、液限、孔隙比、液性指数、压缩系数逐渐增大,而黏聚力、压缩模量逐步降低,形成上硬下软的特征;(3)对红黏土路堑,提出采用“缓边坡、宽平台、固坡脚”的设计原则;(4)针对红黏土填料,提出根据击实后50 kPa下膨胀总率判定填料膨胀性,采取包边、加筋、设置垫层、无机结合料改良处治后用于路基填料;(5)本研究成果对广西红黏土地区勘察设计具有一定的参考价值。

基于CiteSpace知识图谱的冻土路基研究现状与趋势分析

冻土路基的稳定性对于寒区公路与铁路的安全运营至关重要。为全面了解冻土路基领域的研究现状及发展趋势,利用知识图谱工具CiteSpace对中国知网和Web of Science数据库中冻土路基相关文献进行了可视化分析。检索时间范围为2000年1月1日—2023年8月31日,共纳入1 027篇中文文献和854篇英文文献。结果表明:自2000年以来,冻土路基研究的发文量总体呈增长趋势;从2017年开始,英文文献的发布数量逐渐超过中文文献,其中我国学者在国际期刊的发文量占到80%左右;国内研究机构之间合作较为密切,以中国科学院西北生态环境资源研究院和北京交通大学为核心的科研机构及院校在冻土路基的研究中起着主导作用,而国际机构间的合作还有待加强。关键词聚类与突现图谱表明,冻土路基的研究主要围绕多年冻土路基的稳定性、路基病害与补强措施、季节冻土路基的病害防治展开。近几年,冻土专家学者们聚焦于新型路基稳定措施,路基的水、汽迁移机理,以及高铁路基的冻胀防治研究,新材料、新技术及新结构不断被引入到冻土路基研究。未来随着新能源、材料学、人工智能、合成孔径雷达干涉测量(InSAR)等新一代技术与机械化的融合,冻土路基的稳定性补强措施和季节冻土路基的防冻胀措施会在提高效果的同时更加注重环保理念,冻土路基的施工、管理及监测也会不断向着数字化和智能化发展。