Fig 6 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Distress distribution of protection-cone slopes and wing walls along the Qinghai-Tibet railway (QTR). a Upheaval mounds of the protection-cone slopes; b cracks on the surface of the protection cones; c subsidence of the protection-cone slopes; d longitudinal displacement of the wing walls and beams; e transverse displacement of
Source publication
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 distre...
Contexts in source publication
Context 1
... mounds of the protection-cone slopes, cracks on the surface of the protection cones and subsidence of the protection-cone slopes. This survey focused on the four cones of each bridge. Crack damage affected 203 cones in varying degrees, frequently in the direction of the slope surface, making it the most common distress of the protection cone (Fig. 6b). Despite occurring less frequently, upheaval mounds and subsidence of the protection-cone slopes have a greater impact on the structure of the protection cone (Fig. 6a and ...
Context 2
... of each bridge. Crack damage affected 203 cones in varying degrees, frequently in the direction of the slope surface, making it the most common distress of the protection cone (Fig. 6b). Despite occurring less frequently, upheaval mounds and subsidence of the protection-cone slopes have a greater impact on the structure of the protection cone (Fig. 6a and ...
Context 3
... direct contact between the wing wall and the beam results from the movement of the wing wall toward the beam body and even the subsidence joints vanish. Figure 6d demonstrates the prevalence of this type of distress along the QTR in the permafrost zone, with an occurrence rate of up to 21.18%. Another type of distress that could result in rail bending is the transverse displacement of the wing wall. ...
Context 4
... zone, with an occurrence rate of up to 21.18%. Another type of distress that could result in rail bending is the transverse displacement of the wing wall. Compared with the first type of distress, the transverse displacement of the wing wall occurs less frequently and is mostly concentrated from the Hoh Xil Mountain area to the Chiqu valley (Fig. 6e). It can be seen that the cracks of the protection-cone surface and the longitudinal dislocation of the wing walls are widely distributed along the QTR. The Beilu River basin to the Chiqu valley, the Kaixinling Mountains area and the Tanggula Mountains area are the concentrated development sections of these five types of ...
Citations
... The study area is located between 92°16′19" E to 93°15′24" E and 34°05′32" N to 35°18′17" N, with a total area of about 3.45 × 10 3 km². The region is characterized by a cold and dry continental climate [32], with monthly average temperatures ranging from -17.4°C to 5.9°C, and monthly average precipitation ranging from 247 mm to 357 mm [3]. The altitude ranges from 4370 m to 5281 m, with an average altitude of about 4827 m ( Fig. 1(c)). ...
Global warming is accelerating the permafrost degradation along the Qinghai-Tibet Railway (QTR), causing the surface deformation (SD) of the railway subgrade. Especially in the Salt Lake to Wuli section of the QTR, the permafrost is widely distributed, and the SD has been the most serious. However, the spatio-temporal characteristics and mechanism of SD are still unclear. In addition, it is very important to predict the future trend of SD. Therefore, we acquired time series SD results from 2019 to 2022 based on Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) and analyzed the spatio-temporal characteristics and mechanism of SD in the Salt Lake to Wuli section. Subsequently, the EnvCA-GRU model for SD prediction was developed, integrating the Multi-Head Cross-Attention (MHCA) mechanism and Gated Recurrent Unit (GRU) to account for changes in environmental factors (EFs). The model was then employed to forecast SD trends over the next two years. Our results showed that the SD was uneven in the Salt Lake to Wuli section of the QTR from 2019 to 2022, there were six typical deformation areas, and the maximum cumulative ground subsidence reached 126.79 mm. The SD velocity of the sunny slope was higher than that of the shady slope, and the closer to the QTR, the greater the ground subsidence. Land surface temperature (LST), normalized difference vegetation index (NDVI), and precipitation are the main factors affecting SD. Our proposed EnvCA-GRU prediction model fusing NDVI, LST, and precipitation showed an RMSE of 0.153 and an R² of 0.991, the proposed model was reliable. The maximum cumulative ground subsidence of six typical areas by July 2024 reached 177.52, 268.08, 287.73, 270.99, 190.70, and 211.89 mm, respectively. The results of this study can play a guiding role in the early warning and mitigation of ground subsidence disasters along the QTR.
... The 583 mainly caused by hydrothermal impact. For the vast dry bridges along the QTR, the factors causing 585 permafrost degradation are mainly related to its unique thermal environment (He et al., 2023) because, 586 compared with standard roadbeds, the increased heating surface provided by bridge structures and 587 protection cones, coupled with the higher thermal boundaries of concrete bridges and the larger surface 588 area of the protection cone, contribute to significantly higher net annual heat absorption in the transition 589 zones, which results in severe permafrost degradation in these regions . Permafrost 590 degradation not only reduces the bearing capacity of the deep soils but also weakens the freezing force 591 between the pile side and the permafrost layer, significantly reducing the capability of the foundations to 592 resist deformation (Shang et al., 2024). ...
... In order to reduce the occurrence of melt subsidence disasters, traditional permafrost subgrade insulation measures follow the principles of "active cooling" and "passive protection" [10,11]; however, these measures can only be applied in an environment where future temperature increases remain within 1 • C. With global warming, the protective effect on an existing embankment will be weakened, the effect on the WFS area will not be obvious, and the WFS area will continue to increase. Therefore, these methods also have certain limitations, and there is an urgent need to develop new methods for WFS embankment reinforcement. ...
Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai–Tibet Railway (QTR) is continuously decreasing, and melting subsidence damage to existing warm frozen soil (WFS) embankments is constantly occurring, thus seriously affecting the stability and safety of the existing WFS embankments. In this study, in order to solve the problems associated with the melting settlement of existing WFS embankments, a novel reinforcement technology for ground improvement, called an inclined soil–cement continuous mixing wall (ISCW), is proposed to reinforce embankments in warm and ice-rich permafrost regions. A numerical simulation of a finite element model was conducted to study the freeze–thaw process and evaluate the stabilization effects of the ISCW on an existing WFS embankment of the QTR. The numerical investigations revealed that the ISCW can efficiently reduce the melt settlement in the existing WFS embankment, as well as increase the bearing capacity of the existing WFS embankment, making it favorable for improving the bearing ability of composite foundations. The present investigation breaks through the traditional ideas of “active cooling” and “passive protection” and provides valuable guidelines for the choice of engineering supporting techniques to stabilize existing WFS embankments along the QTR.
Embankment–bridge transition sections (EBTSs) suffer from diverse engineering diseases that have escalated into one of the most severe issues along the Qinghai‐Tibet Railway (QTR). Nevertheless, the causes and mechanisms of engineering diseases in EBTSs remain limited. This study employed a methodological approach to conduct field surveys in the Tuotuo River Basin in the hinterland of the Qinghai‐Tibet Plateau (QTP). Borehole investigations and nuclear magnetic resonance (NMR) techniques accurately determined the permafrost characteristics, enabling the correction of electromagnetic wave velocity and acquisition of resistivity threshold. Ground‐penetrating radar (GPR) and quasi‐3D electrical resistivity tomography (ERT) were combined to indicate permafrost resistivity above 200 Ω‐m. It reveals that the permafrost is relatively stable across a large area on the shaded side, whereas the permafrost degradation is more pronounced on the sunny side, where the maximum active layer thickness (ALT) reaches 5.2 m. Notable permafrost degradation and substantial increases in ALT were observed near the EBTS resulting from heat absorption and thermal erosion of the groundwater. Terrestrial laser scanning (TLS) captured time‐series deformation highlights the specific displacements of the EBTS, demonstrating that the displacement is the rotational behavior of wing walls. The severe heat absorption and groundwater thermal erosion around the EBTS result in permafrost degradation and the expansion of the thawing bulbs to increased structural deformation and even failure. It was shown that permafrost degradation, moisture influence, and heat transfer characteristics are the primary contributing factors to the disease's continued deterioration, and thus reinforcement measures for existing structures need to address these three issues. The mechanisms of disease development revealed in this paper provide new insights into EBTS dynamics for the EBTS design and maintenance in permafrost regions.
Research in geocryology is currently principally concerned with the effects of climate change on permafrost terrain. The motivations for most of the research are (1) quantification of the anticipated net emissions of CO 2 and CH 4 from warming and thaw of near‐surface permafrost and (2) mitigation of effects on infrastructure of such warming and thaw. Some of the effects, such as increases in ground temperature or active‐layer thickness, have been observed for several decades. Landforms that are sensitive to creep deformation are moving more quickly as a result, and Rock Glacier Velocity is now part of the Essential Climate Variable Permafrost of the Global Climate Observing System. Other effects, for example, the occurrence of physical disturbances associated with thawing permafrost, particularly the development of thaw slumps, have noticeably increased since 2010. Still, others, such as erosion of sedimentary permafrost coasts, have accelerated. Geochemical effects in groundwater from trace elements, including contaminants, and those that issue from the release of sediment particles during mass wasting have become evident since 2020. Net release of CO 2 and CH 4 from thawing permafrost is anticipated within two decades and, worldwide, may reach emissions that are equivalent to a large industrial economy. The most immediate local concerns are for waste disposal pits that were constructed on the premise that permafrost would be an effective and permanent containment medium. This assumption is no longer valid at many contaminated sites. The role of ground ice in conditioning responses to changes in the thermal or hydrological regimes of permafrost has re‐emphasized the importance of regional conditions, particularly landscape history, when applying research results to practical problems.
Permafrost is sensitive to both climate warming and engineering disturbance on the Qinghai–Tibet Plateau (QTP). These factors degrade the stability of infrastructure built on permafrost and reduce its service life. To counter these effects, cooling of the subgrade to lower permafrost temperature forms part of the engineering design on the QTP. Proactive cooling of the subgrade has been used in construction of the Qinghai–Tibet Railway (QTR), the Chaidaer–Muli Railway, the Qinghai–Tibet DC Power Transmission Line, and the Gonghe–Yushu Express Highway. As a consequence, there has been significant ground cooling and little permafrost thaw beneath these infrastructure projects. However, the QTR has experienced some problems, such as in the stability of transitions at bridge abutments, reductions to the convective capacity of crushed rock structures from infilling by eolian sand, and freeze–thaw damage. A monitoring network has been established to examine the influence of climate change for engineering stability on the QTP. Climate warming on the plateau will present significant challenges for engineering of proposed oil and gas pipelines, express highways and the high‐speed railway from Golmud to Lhasa.
