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.

Structural Design of Roadbed and Pavement in Transition Section of Roads and Bridges

As the lifeline of social development,road and bridge projects are the main channel to realize resource transportation and economic circulation.Ensuring the quality of road and bridge project construction is crucial for the development of society,the economy,and people’s livelihoods.This paper studies the design of roadbed pavement structures in road and bridge transition sections.It aims to provide technical references and significance for China’s road and bridge engineering design and construction units,promoting scientific and standardized design in these actions.This will contribute to the safety and stable operation of road and bridge projects,offering effective technical support.Furthermore,it seeks to foster the sustainable and healthy development of China’s road and bridge engineering on a macro level.

Mechanical properties of fiber and cement reinforced heavy metal-contaminated soils as roadbed filling

The treatment of contaminated soil is a crucial issue in geotechnical and environmental engineering.This study proposes to incorporate appropriate polypropylene fibers and cements as an effective method to treat heavy metal contaminated soil(HMCS).The objective of this paper is to investigate the effects of fiber content,fiber length,cement content,curing time,heavy metal types and concentration on the mechanical properties of soils.To this end,a series of direct shear test,unconfined compression strength(UCS)test,dry-wet cycle and freeze-thaw cycle test are performed.The results confirm that the appropriate reinforcement of polypropylene fibers and cement is an effective way to recycle HMCS as substitutable fillers in roadbed,which exhibits benefits in environment and economy development.

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.

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

Pile-slab structure roadbed is a new form of ballastless track for high speed railway. Due to lack of corresponding design code, based on the analysis of its structure characteristics and application requirements, it is proposed to carry out load effect combination according to ultimate limit state and serviceability limit state, and the most unfavorable combination of each state is chosen to carry through design calculation for pile-slab structure. Space model of pile-slab structure can be simplified as a plane flame model, by using the orthogonal test method, and the design parameter of pile-slab structure is optimized. Moreover, based on the engineering background of Suining-Chongqing high-speed railway, the dynamic deformation characteristics of pile-slab structure roadbed are further researched by carrying on the indoor dynamic model test. The test results show that the settlement after construction of subgrade satisfies the requirement of settlement control to build ballastless track on soil subgrade for high-speed railway. Slab structure plays the role of arch shell as load is transmitted from slab to pile, and the vertical dynamic stress of subgrade soil is approximately of ＂K＂ form distribution with the depth. The distribution of pile stress is closely related to soil characteristics, which has an upset triangle shape where the large dynamic stress is at the top. Pile compared with soil shares most dynamic stress. Pile structure expands the depth of the dynamic response of subgrade has limited effect on dynamic response. These results can provide subgrade. and improves the stress of subgrade soil, and the speed of train scientific basis for pile-slab structure roadbed used on soil

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.

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).

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.

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.

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.

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.

重力挡墙结构在陡坡回填路基土中的应用研究

为了探究高陡坡路基填筑施工填筑作用下路基路面沉降变形情况,基于ABAQUS有限元软件建立了挡墙、土工格栅与地基路基的数值模型,模型计算研究了挡墙与路基填筑建造工后引起路基路面的沉降与挡墙水平变形以及应力的分布。其数值计算表明:未进行铺设土工格栅时,路基路面工后最大沉降值未23.45 cm,挡墙侧向位移最大值为9.59 cm,挡墙最大主应力值为33.85 kPa;当在原方案基础,对路基内铺设土工格栅后,路基路面最大沉降值为13.6 cm,较原设计方案最大沉降(23.45 cm)减少了9.85 cm,并满足了工程经验对路基路面横向沉降变形差控制要求。

盾构下穿高速公路对既有平行通道桥的影响规律

为探讨盾构下穿高速公路对既有平行通道桥的影响规律,以韩江榕江练江水系连通后续优化工程盾构隧道穿越G78汕昆高速公路路堤为背景,建立三维有限元模型,分析盾构施工对地表沉降、高速公路路基、既有平行通道桥桩基的影响规律。结果表明:1)盾构隧道开挖对地层的影响范围大致为隧道直径的4倍;2)隧道轴线正上方地表沉降值最大,达到5.6 mm,路基最大沉降值发生在隧道轴线正上方,约为5 mm;3)通道桥桩基竖向位移均表现为沉降,靠近盾构侧桩基沉降大于远侧,其中桩基Z1沉降值最大,达到2.4 mm;4)隧道埋深顶面处对应的桩基水平位移较大,受盾构掘进叠加影响,桩基Z1水平位移最大,约为0.37 mm;5)弯矩的最大值出现在隧道埋深位置附近,轴力的最大值出现在桩身中点位置,桩基Z1弯矩和轴力最大。

道路路基工程施工中的软基处理技术研究

软土是由水环境下沉积而成,包括泥炭、淤泥质土和淤泥等,具有高含水、大孔隙、低透水和抗剪力弱的特点。对软土地基进行有效处理,能显著提升道路路基的承载力和稳定性,从而有效解决其沉降和不稳定问题。鉴于软基处理在道路总造价中占比较高,达到15%~30%,因此,如何在保证路基质量的同时降低软基处理造价,已成为研究热点。本文以商周高速公路周口段为例,深入探讨了道路软基处理设计方案的比选、优化及施工验证过程。通过实践经验总结,旨在为同类项目提供有价值的参考,以期在保障路基质量的基础上,实现造价的优化降低。