Changes in permafrost environments caused by construction and maintenance of Qinghai-Tibet Highway

The sideward permafrost along the Qinghai-Tibet Highway (QTH) contains massive ground-ice and is at a relatively high temperature.Under the influence of the steady increase of human activities,the permafrost environment has been changed greatly for a long time.At present,the permafrost becomes warm and rapidly degenerates,including the decline of the permafrost table,rising of the ground temperature,shortening of the length of frozen section,and extension of range of melting region.Some thaw hazards (e.g.thaw slumping and thermokarst pond) have widely occurred along both sides of the roadbed.In addition,due to the incomplete construction management,the vegetation adjacent to the highway is seriously damaged or eradicated,resulting in the land desertification and ecosystem out of balance.The dust,waste and garbage brought by drivers,passengers,maintenance workers,and transportations may also pollute the permafrost environment.

The status evaluation of the permafrost environment along the Chaida'er-Muli Railway in southern Qilian Mountains in northern Qinghai Province,China

Engineering construction has major influence on the permafrost environment.This paper analyzes the interaction between engineering construction and permafrost environment along the Chaidaer-Muli Railway(simply,CMR) based on the press-state-response(PSR) framework.The permafrost environmental system is divided into three subsystems,consisting of permafrost thermal stability,proneness to the freeze-thawing erosion and permafrost ecological fragility.Each subsystem considers its most important influencing factors.Catastrophe Progression Method(CPM) is applied to calculate the current environment condition along the railway.The result indicates that:(1) as far as the thermal stability is concerned,most sections along the CMR are mainly concentrated in rank Ⅲ(fair situation),and a few in Ⅱ(good situation) and Ⅳ(bad situation),respectively;(2) for the proneness tothe freeze-thawing erosion,the entire railway route falls largely in rank Ⅱ(good situation);(3) along the CMR,the ecological fragility of the permafrost environment is in rank Ⅱ(good situation),or slightly fragile;(4) overall,the permafrost environments along the CMR are in rank Ⅲ(fair situation) or Ⅱcondition(good situation).In general,the permafrost environment along the CMR is fair.It is mainly because a series of active measures of protecting permafrost were taken for stabilizing the CMR foundation soils.On the one hand,we should try our best to minimize the influences that engineering activities have exerted on ecology and environment,on the other hand,the positive measures have made improvements to prevent the permafrost environment from deterioration.

Thermal and hydrological processes in permafrost slope wetlands affect thermosyphon embankment stability

To ensure the long-term service performance of infrastructure such as railways,highways,airports and oil pipelines built on permafrost slope wetland sites,it is imperative to systematically uncover the long-term heat-water changes of soil in slope wetlands environment under climate warming.More specifically,considering valuable field data from 2001 to 2019,the long-term heat and water changes in active layers of the slope wetland site along the Qinghai-Xizang Railway(QXR)are illustrated,the effect of thermosyphon measures in protecting the permafrost environment is evaluated,and the influences of climate warming and hydrological effects on the stability of slope wetland embankments are systematically discussed.The permafrost at the slope wetland site is rapidly degrading,demonstrating a reduction in active layer thickness of>3.7 cm per year and a permafrost temperature warming of>0.006℃ per year.The thermosiphon embankment developed by QXR has a specific cooling period;thus,to mitigate the long-term impacts of climate warming on the thermal stability of permafrost foundation,it is essential to implement strengthening measures for the thermosiphon embankment,such as adding a crushed-rock layer or sunshade board on the slope of thermosiphon embankment to creating a composite cooling embankment.Short-term seasonal groundwater seepage intensifies frost damage to the slope wetland embankment,while long-term seasonal supra-permafrost water and groundwater seepage exacerbates uneven transverse deformation of slope wetland embankment.Long-term climate warming and slope effects have altered the surface water and groundwater hydrological processes of slope wetlands,potentially leading to an increased occurrence of slope embankment instability.These results are crucial for improving our understanding of heat and water variation processes in the active layer of slope wetland sites located in permafrost regions and ensuring long-term service safety for the QXR.

Permafrost environment monitoring on the Qinghai-Tibet Plateau using time series ASAR images

The permafrost in Qinghai-Tibet Plateau(QTP)has long been the focus of many researchers.In this study,we first use the method that integrates synthetic aperture radar(SAR)intensity and phase information to monitor permafrost environment in the Beiluhe Region,using time series advanced SAR images.The backscattering coefficients(σ^(0))and deformation were extracted for the main features,and the influences of meteorological conditions to them were also quantified.The results show that both the change inσ^(0)and surface deformation are closely related to the active layer,and the deformation is also affected by the permafrost table.First,over meadow and sparse vegetation regions,σ^(0)rose about 6.9 and 4 dB from the freezing to thawing period,respectively,which can be mainly attributed to the thaw of the active layer and increased precipitation.Second,seasonal deformation,derived from the freeze-thaw cycle of the active layer,was characteristic of frost heave and thaw settlement and exhibited a negative correlation with air temperature.Its magnitude was larger than 1 cm in a seasonal cycle.Last,significant secular settlement was observed,with rates ranging from-16 to 2 mm/a,and it was primarily due to the thaw of the permafrost table caused by climate warming.