Numerical simulation of flow field deposition and erosion characteristics around bridge-road transition section

Wind-sand flow generates erosion and deposition around obstacles such as bridges and roadbeds, resulting in sand damage and endangering railway systems in sandy regions. Previous studies have mainly focused on the flow field around roadbeds, overlooking detailed examinations of sand particle erosion and deposition patterns near bridges and roadbeds. This study employs numerical simulations to analyze the influence of varying heights and wind speeds on sand deposition and erosion characteristics at different locations: the bridge-road transition section(side piers), middle piers, and roadbeds. The results show that the side piers, experience greater accumulation than the middle piers. Similarly, the leeward side of the roadbed witnesses more deposition compared to the windward side. Another finding reveals a reduced sand deposition length as the vertical profile, in alignment with the wind direction, moves further from the bridge abutments at the same clearance height. As wind speeds rise, there’s a decline in sand deposition and a marked increase in erosion around the side piers, middle piers and roadbeds. In conclusion, a bridge clearance that’s too low can cause intense sand damage near the side piers, while an extremely high roadbed may lead to extensive surface sand deposition. Hence, railway bridges in areas prone to sandy winds should strike a balance in clearance height. This research provides valuable guidelines for determining the most suitable bridge and roadbed heights in regions affected by wind and sand.

Design Strategy of Highway Speed Transition Section

In this paper,combined with the relevant speed theory and characteristics of the law,the current highway speed transition design problems are studied and analyzed.In the process of specific analysis,mainly combined with the characteristics of different types of highway speed changes and road section design requirements,this paper studies and analyzes the design methods of different types of highway speed transition section.And on this basis,according to the design principles and requirements of highway operation speed transition section,the paper summarizes the matters needing attention in the design of highway operation speed transition section,in order to provide certain reference value for relevant personnel.

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.

Distress Characteristics in Embankment‑Bridge Transition Section of the Qinghai‑Tibet Railway in Permafrost Regions

The Qinghai-Tibet Railway has been operating safely for 16 years in the permafrost zone and the railroad subgrade is generally stable by adopting the cooling roadbed techniques.However,settlement caused by the degradation of subgrade permafrost in the embankment-bridge transition sections(EBTS)is one of the most representative and severe distresses.A feld survey on 440 bridges(including 880 EBTSs)was carried out employing terrestrial laser scanning and ground-penetrating radar for comprehensively assessing all EBTSs in the permafrost zone.The results show that the types of distresses of EBTSs were diferential settlement,upheaval mounds of the protection-cone slopes,subsidence of the protection-cone slopes,surface cracks of the protection cones and longitudinal and transverse dislocation of the wing walls.The occurrence rates of these distresses were 78.93,3.47,11.56,3.36,21.18 and 4.56%,respectively.The most serious problem was diferential settlement,and the average diferential settlement amount(ADSA)was 15.3 cm.Furthermore,the relationships between diferential settlement and 11 infuencing factors were examined.The results indicate that ADSA is greater on the northern side of a bridge than on the southern side and on the sunny slope than on the shady slope.It is also greater in the high-temperature permafrost region than in the low-temperature permafrost region and in the high-ice content area than in the low-ice content area.The EBTSs are more infuenced by ice content than by ground temperature.The ADSA increases when the embankment height increases,the particle size of subgrade soil decreases and the surface vegetation cover decreases.