Typical embankment settlement/heave patterns of the Qinghai–Tibet highway in permafrost regions: Formation and evolution

International Journal of Damage Mechanics

et al. 2017

A series of multistage triaxial compression, creep, and stress relaxation tests were conducted on frozen loess at the temperature of −6℃ in order to study the damage evolution and recrystallization enhancement of mechanical properties during deformation process. The effect of strain rate, confining pressure, and hydrostatic stress history in the degradation laws of mechanical properties is investigated further. The strain rate has a significant influence on the stress–strain curve which dominates the evolution trend of mechanical properties. The mechanical behaviors (strength, stiffness, and viscosity) of frozen loess all exhibit evident response for the consolidation and pressure melting phenomenon caused by the confining pressure. The multistage loading tests under different hydrostatic stresses are capable of differentiating the development characteristics of mechanical properties during axial loading and hydrostatic compression process, respectively. The testing results indicated that the recrystallization of the ice particle in the frozen soils is an important microscopic factor for enhancement behaviors of mechanical parameters during the deformation process. This strengthening degree of mechanical properties is determined by temperature, duration time, deformation degree, and stress state during the recrystallization process. The phase transformation led by pressure melting and ice recrystallization is a nonnegligible changing pattern of frozen soils microstructure, which has apparent role in the damage evolution of mechanical properties.

Section: Introductionmentioning

confidence: 99%

Damage evolution and recrystallization enhancement of frozen loess

Zhou

International Journal of Damage Mechanics

et al. 2017

“…ough some countermeasures, such as elevating embankment height, constructing thermal insulation berm, and placing insulation materials in the embankment, were used to reinforce the embankments based on the principle of permafrost protection or thawing rate control, some damages to the embankments occurred subsequently [43]. At present, the subgrade distress mainly results from differential settlement [16,42], and the pavement damages are characterized by transverse cracking, potholes, and longitudinal cracking [30]. Until now, pavement damages along the QTH have not been entirely solved, and large-scale rehabilitations and remedies still need to be carried out every 2-3 years [44,45].…”

Section: Ermomechanical Stability Of Existing Linear Projectsmentioning

confidence: 99%

“…Now, the existing linear projects, such as the Qinghai-Tibet Highway (QTH), the Qinghai-Tibet Railway (QTR), the Golmud-Lhasa oil product pipeline, and the optical cable from Lanzhou to Lhasa, are all located in the QTEC within a width of less than 10 km [9,15]. During the operation of the QTH and the QTR, remarkable settlement of the embankments occurred in warm and ice-rich permafrost regions [16,17], posing an adverse effect on the traffic safety. With the design and construction of major projects along the QTEC, it is urgent to formulate the proper engineering design principles and develop the valid engineering supporting techniques.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Necessity and Feasibility for Ground Improvement in Warm and Ice‐Rich Permafrost Regions

Wang

Advances in Civil Engineering

Chai

et al. 2022

Characterized by low bearing capacity and high compressibility, warm and ice-rich frozen soil is a kind of problematic soil, which makes the original frozen ground formed by of that unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. With the design and construction of major projects along the Qinghai-Tibet Engineering Corridor (QTEC), such as expressway and airport runway, it is a great challenge to favor the stability of overlying structures by formulating the proper engineering design principles and developing the valid engineering supporting techniques. The investigations carried out in recent years indicated that warm and ice-rich permafrost foundations were widespread, climate warming was significant, and the stability of existing engineering structures was poor, along the QTEC. When the warm and ice-rich frozen ground is used as the foundation soil, the implementation of ground improvement is an alternative measure to enhance the bearing capacity of foundation soil and eliminate the settlement of structures during operation, in order to guarantee the long-term stability of the structures. Based on the key factors determining the physicomechanical properties of frozen soil, an innovative idea of stabilizing the warm and ice-rich frozen soil based on chemical stabilization is proposed in this study, and then, an in situ ground improvement technique is introduced. This study intends to explore the feasibility of ground improvement in warm and ice-rich permafrost regions along the QTEC based on in situ chemical stabilization and provide the technical support and scientific reference to prevent and mitigate the hazards in the construction of major projects in the future.

“…Therefore, the cloud model is utilized to handle the randomness and fuzziness in the process of highway distresses prediction, which can reflect the actual situation. According to the relevant research results and literature data, the higher annual average ground temperature in permafrost regions is the primary cause of subsoil ice melting and thaw slumping, as well as the subgrade uneven deformation and subgrade settlement [28]. With the increase in the annual average ground temperature in permafrost regions, the stability of frozen soil becomes worse, and the highway distress degree increases.…”

Section: Analysis Of Influence Factors Of Highway Distresses Inmentioning

confidence: 99%

Novel Prediction Method for Highway Distresses in Permafrost Regions Based on Qualitative Reasoning of Multidimensional and Multirules Cloud Model

Mathematical Problems in Engineering

et al. 2019

Highway in permafrost regions has numerous diseases during operation, due to instability and degradation of permafrost. To predict distress sections of a newly built highway in permafrost regions, we proposed a new method based on the multidimensional and multirules reasoning cloud model. Herein, the evaluation parameters affecting the highway distresses in permafrost regions, i.e., annual average ground temperature, ice content, and frozen-heave factor, were as the data input, whereas the distress degree was as the data output; all of the aforementioned were described by a cloud model. Based on the analysis of distress large data, inference rules and a cloud reasoning prediction model were established. Subsequently, distress degrees of the 10 equidistance highway sections were predicted on the Qinghai-Tibet highway by using the cloud model, and actual distress degree and predicted distress degree were compared by using the regression analysis algorithm. The results showed that the relevance between the actual distress degree and the predicted distress degree was 0.738. The study provides a feasible and effective method to predict the potential distress sections of the newly built highway and better plan infrastructure project on permafrost regions.