Fujun Niu - Academia.edu (original) (raw)

Papers by Fujun Niu

Cold Regions Science and Technology, 2014

ABSTRACT Harbin to Dalian passenger dedicated line (HDPDL) was the first high-speed railway in th... more ABSTRACT Harbin to Dalian passenger dedicated line (HDPDL) was the first high-speed railway in the moderately deep seasonally frozen regions in the Northeast China. The roadbed-culvert transition section (RCTS) was paid special attention, as it was prone to uneven deformation. In this paper, the temperature field and its changing process of a typical RCTS at Siping site along HDPDL was discussed based on monitoring data. The results showed that during the freezing period (from November, 2010 to March, 2011), the thinner layer fill on the culvert, the higher temperature amplitude appeared in the RCTS. Due to the solar radiation difference on the sunny and shady slopes, the temperature in the sunny-slope was 1 ~ 3 °C higher than that in the shady-slope, and the difference increased as roadbed height increase. However, the culvert serves as a large ventilation duct, exchanging the amount of thermal rotation and weakening the temperature difference between the two sides. Numerical simulation of the temperature fields were carried out for discussing roadbed fill materials and culvert structures. The results indicated that, under the current design conditions, a pipe-style culvert shows a more stable thermal regime in the freezing period, while a box-styled culvert showed a more stable thermal regime in the thawing period. The anti-frost and insulation engineering measures were also discussed, and several critical design parameters were proposed and optimized. At last, it was found that the most suitable configuration was a box culvert with one section transiting to embankments, and this configuration was recommended for construction of high-speed railway in the seasonal frozen regions.

Landslides, 2006

ABSTRACT Permafrost covers a significant area of the Qinghai-Tibet Plateau. Slope instability pro... more ABSTRACT Permafrost covers a significant area of the Qinghai-Tibet Plateau. Slope instability problem in the region was often neglected, though it plays important roles in engineering construction and landform processes. In this paper, the slope instability phenomena in the permafrost regions on the plateau are discussed. The slope failures often occur in the forms of thaw-induced landslides and gelifluction. Thaw-induced landslides are closely related to active layer detachment and changes of permafrost conditions. Such landslides include retrogressive flow and thaw slump and are hazardous to engineering constructions. Gelifluction includes deep-seated movement and surface movement. It is an important factor in landform planation because it may spread over a large area and remain active for a long period of time.

Environmental Geology, 2014

ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between so... more ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between soil and atmosphere caused changes in the thermal and mechanical stability of permafrost beneath the railway embankment. Monitoring from 2005 to 2010 indicated 12 sections of embankment that experienced more than 5 cm of settlement, with three showing deformations of more than 10 cm and signs of continuing settlement. Embankment stability is closely related to permafrost changes beneath the embankment. Large-scale deformations have contributed to permafrost thaw and artificial permafrost table deepening, and this deformation has not stabilized over the short term. In contrast, small-scale deformations have contributed to a warming of the permafrost that has gradually stabilized as soil temperature decreases. Only three sections of the Qinghai–Xizang Railway have exhibited settlement deformation that exceeds 10 cm, through a deepening of the artificial permafrost table and a gradual increase in permafrost thawing result in embankment settlement deformation. However, with climate warming trends and the long-term operation of the railway, the long-term thermal and mechanical stability of the embankment needs to be carefully monitored to ensure the safe operation of the Qinghai–Xizang Railway.

Extremophiles, 2016

Permafrost on the Qinghai-Tibet Plateau is one of the most sensitive regions to climate warming, ... more Permafrost on the Qinghai-Tibet Plateau is one of the most sensitive regions to climate warming, thus characterizing its microbial diversity and community composition may be important for understanding their potential responses to climate changes. Here, we investigated the prokaryotic diversity in a 10-m-long permafrost core from the Qinghai-Tibet Plateau by restriction fragment length polymorphism analysis targeting the 16S rRNA gene. We detected 191 and 17 bacterial and archaeal phylotypes representing 14 and 2 distinct phyla, respectively. Proteobacteria was the dominant bacterial phylum, while archaeal communities were characterized by a preponderance of Thaumarchaeota. Some of prokaryotic phylotypes were closely related to characterized species involved in carbon and nitrogen cycles, including nitrogen fixation, methane oxidation and nitrification. However, the majority of the phylotypes were only distantly related to known taxa at order or species level, suggesting the potential of novel diversity. Additionally, both bacterial α diversity and community composition changed significantly with sampling depth, where these communities mainly distributed according to core horizons. Arthrobacter-related phylotypes presented at high relative abundance in two active layer soils, while the deeper permafrost soils were dominated by Psychrobacter-related clones. Changes in bacterial community composition were correlated with most measured soil variables, such as carbon and nitrogen contents, pH, and conductivity.

Journal of Mountain Science, 2012

On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sich... more On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this earthquake is currently hotly debated. We suppose that it is a special type of intraplate earthquake called an activenappe-type earthquake. Using a holistic methodology, incorporating rockmass structure cybernetics and Byerlee's law, we present a comprehensive study on the geological origin of macroseisms in the Longmen Shan area and the seismic origin of the 2008 Wenchuan earthquake. Previous studies of neotectonic activity indicate that the Longmen Shan nappe moves at a rate of 1~3 mm/yr, due to horizontal compressive stress from the Tibetan Plateau. The difference between movement rates in the Bayankala block, Longmen Shan nappe and Sichuan Basin cause slow shear stress and strain accumulation in the Longmen Shan nappe. It is exhibited a relatively simple linear relations for the shear strength and the buried depth of the structural planes, and the detachment layer of the nappe has a higher shearing-sliding strength compared to the overlying fault planes and the underlying ductile shear belts, thus making it more prone to stick-slip deformation. Therefore, the detachment layer was the main section responsible for the Wenchuan earthquake. The initial rupture burst in the detachment layer under the Yingxiu-Beichuan fault, the rupture area nearly 1.4454 × 10 4 km 2 ， encompassed the cross point of the Yingxiu and the Anxian-Guanxian faults with the detachment layer, then caused the Yingxiu -Beichuan and Anxian-Guanxian faults took an active part in this earthquake, so this earthquake might consist of three chain-like earthquake stages, totally increasing the duration of this earthquake an unusually large amount, to 120 s. The focal depth spanned range of 10-20km ， consistent with the observed result of this focal depth by several agencies.

PloS one, 2015

Understanding the processes that influence the structure of biotic communities is one of the majo... more Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with so...

Environmental Earth Sciences, 2012

ABSTRACT The impacts of alpine vegetation degradation on the main soil nutrients in the permafros... more ABSTRACT The impacts of alpine vegetation degradation on the main soil nutrients in the permafrost were studied by the comparative analysis of typical plots in the source regions of the Yangtze River. It is found that vegetation degradation has a severe effect on the content of the main soil nutrients, especially in the topsoil (0–10 cm) where the soil nutrients content were changed. There are good correlations between soil organic matter (SOM) and total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in alpine soil. The change to soil nutrients increases concomitantly with the increasing intensity of vegetation degradation. Soil nutrients change dramatically in the thermokarst lakes in the surrounding area where vegetation is severely degraded. The ratio of SOM, TN, TP and TK in different soil layers of the adjacent thermokarst lakes is 5.88, 5.14, 3.86 and 4.43, respectively. The vegetation degradation accelerates the degradation of alpine soil environment in alpine frozen soil.

Cold Regions Engineering 2012, 2012

Environmental Earth Sciences, 2013

ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between so... more ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between soil and atmosphere caused changes in the thermal and mechanical stability of permafrost beneath the railway embankment. Monitoring from 2005 to 2010 indicated 12 sections of embankment that experienced more than 5 cm of settlement, with three showing deformations of more than 10 cm and signs of continuing settlement. Embankment stability is closely related to permafrost changes beneath the embankment. Large-scale deformations have contributed to permafrost thaw and artificial permafrost table deepening, and this deformation has not stabilized over the short term. In contrast, small-scale deformations have contributed to a warming of the permafrost that has gradually stabilized as soil temperature decreases. Only three sections of the Qinghai–Xizang Railway have exhibited settlement deformation that exceeds 10 cm, through a deepening of the artificial permafrost table and a gradual increase in permafrost thawing result in embankment settlement deformation. However, with climate warming trends and the long-term operation of the railway, the long-term thermal and mechanical stability of the embankment needs to be carefully monitored to ensure the safe operation of the Qinghai–Xizang Railway.

Unsaturated Soils: Research & Applications, 2014

Annals of Glaciology, 2014

ABSTRACT The ice cover on the Qinghai–Tibetan Plateau plays an important role in the environmenta... more ABSTRACT The ice cover on the Qinghai–Tibetan Plateau plays an important role in the environmental and ecological systems. We analyze the in situ measurements of ice growth and examine the thermal diffusivity of thermokarst lake ice in the Beiluhe basin. We evaluate numerically the change of thermal diffusivity of thermokarst lake ice with changing ice temperature using an optimal control model. In a higher ice temperature regime (–3 to 0°C), the thermal diffusivity of thermokarst lake ice decreases exponentially with increasing ice temperature, and approaches the thermal diffusivity value of fresh water near the freezing-point temperature. In a lower ice temperature regime (–15 to –3°C), the thermal diffusivity increases slowly with decreasing ice temperature.

Science China Earth Sciences, 2015

ABSTRACT Ten years of ground temperature data (2003-2013) indicate that the long-term thermal reg... more ABSTRACT Ten years of ground temperature data (2003-2013) indicate that the long-term thermal regimes within embankments of the Qinghai-Tibet Railway (QTR) vary significantly with different embankment structures. Obvious asymmetries exist in the ground temperature fields within the traditional embankment (TE) and the crushed-rock basement embankment (CRBE). Measurements indicate that the TE and CRBE are not conducive to maintaining thermal stability. In contrast, the ground temperature fields of both the crushed-rock sloped embankment (CRSE) and the U-shaped crushed-rock embankment (UCRE) were symmetrical. However, the UCRE gave better thermal stability than the CRSE because slow warming of deep permafrost was observed under the CRSE. Therefore, the UCRE has the best long-term effect of decreasing ground temperature and improving the symmetry of the temperature field. More generally, it is concluded that construction using the cooling-roadbed principle meets the design requirements for long-term stability of the railway and for train transport speeds of 100 km h−1. However, temperature differences between the two shoulders, which exist in all embankments shoulders, may cause potential uneven settlement and might require maintenance.

Science Bulletin, 2015

ABSTRACT This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Ti... more ABSTRACT This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Tibet Plateau over the past four decades (1969-2010) using aerial and satellite image interpretation. The results indicated that thermokarst lake activity had generally increased rapidly between 1969 and 2010. The number of thermokarst lakes had increased by approximately 534, and their coverage expanded by about 410 ha. The two main changes observed were an increase in the number of small lakes and the expansion of larger lakes. These changes are likely the result of persistent climate warming and a gradually increasing imbalance between precipitation and evapotranspiration (P-ET). However, some non-climatic factors, such as the lake-bottom substrate and local engineering activities, have also influenced the lake changes. If air temperature and P-ET continue to rise, the number of thermokarst lakes and the area they cover may continue to increase in the future.

Environmental Earth Sciences, 2013

ABSTRACT The active layer in permafrost regions plays an important role in energy exchange betwee... more ABSTRACT The active layer in permafrost regions plays an important role in energy exchange between permafrost and atmosphere. Rainfall is one of the dominant factors affecting thermal-moisture dynamics of the active layer. To better understand the thermal-moisture dynamics and the interaction between rainfall and the active layer in-detail, in situ experiment was carried out and soil temperature, soil moisture and soil heat flux of the active layer were measured from 2007 to 2009. The observation data demonstrated that the volumetric soil water content of the active layer remained fairly constant during the winter and had a notable fluctuation resulted from evapotranspiration and rewetting from rainfall events in summer. The daily variation amplitude of soil temperature and soil heat flux in summer was bigger than that in winter. Soil moisture content increased and soil temperature decreased after rainfall. Rainfall in summer led to the change of surface energy balance and caused subsurface soil cooling. The convective heat transfer from water infiltration reduced the temperature gradient along depth and changed near-surface heat fluxes. The increase in rainfall may mitigate permafrost degradation on the Tibetan Plateau.

Landslides, 2015

ABSTRACT The distribution of permafrost-related slope failures along the Qinghai-Tibet Highway fr... more ABSTRACT The distribution of permafrost-related slope failures along the Qinghai-Tibet Highway from Wuddaoliang to Fenghuoshan correlates with ice content, slope gradient, and ground temperature. Slope failures are of two types. (1) Retrogressive thaw slumps result from icy permafrost being exposed by either man-induced excavation or fluvial-thermal erosion and undercutting of basal slopes. (2) Active-layer-detachment failures are caused by thaw of icy permafrost at the active layer-permafrost interface. After initial failure, active-layer-detachment failures can lead to retrogressive thaw-slumping and localized surficial landslide. Common trigger mechanisms for failure include high summer air temperatures and heavy summer precipitation. A third possible trigger mechanism for slope failure is earthquake occurrence. A geotechnical slope stability analysis was undertaken for an active-layer-detachment failure that had progressed into a retrogressive thaw slump. A safety factor (F s ) of 1.24 for the natural slope was determined using in situ tested strength parameters. However, the slope would lose stability when either the groundwater level over the permafrost table exceeded 1.42 m or seismic acceleration reached, or exceeded, 0.03 g.

European Journal of Environmental and Civil Engineering, 2014

ABSTRACT Subsurface moisture content is one of the critical factors that control the thermal dyna... more ABSTRACT Subsurface moisture content is one of the critical factors that control the thermal dynamics of embankments. However, information on the subsurface moisture movement and distribution in embankments is still limited. To better understand the coupled water and heat transport within embankments, subsurface temperature and moisture of an asphalt pavement highway were extensively measured from 2009 to 2011. Collected data indicate that pure heat conduction is the overall main mechanism of heat transport in the embankment and heat convection plays a relatively unimportant role in heat transport. The results also indicate that subsurface moisture and temperature dynamics in the asphalt layer is strongly related to the rainfall events, while the subsurface moisture content below the road base course maintains relatively constant. Rainfall in summer leads to rapid cooling of the subsurface soil. Our results suggest that frequent and small rainfall events favour the thermal stability of the embankment due to the loss of latent heat of water evaporation. Moisture migration during freezing still occurred in the gravel fill and the water infiltrated into the active layer during thawing period. Freezing-induced water migration may result in the increase in water content of the embankment and the decrease in compactness of gravel fill.

Arctic, Antarctic, and Alpine Research, 2014

ABSTRACT In order to determine the distribution and morphometric characteristics of thermokarst l... more ABSTRACT In order to determine the distribution and morphometric characteristics of thermokarst lakes on the Qinghai-Tibet Plateau, SPOT-5 satellite images were acquired from the Chumaerhe High Plateau to Beiluhe Basin within a 10-km-wide corridor along the Qinghai-Tibet Railway. A total of 2163 water bodies, having a total area of 1.09 × 107 m2, were identified in the study area using unsupervised classification and image interpretation. Several shape metrics (area, perimeter, circularity index, elongation index, orientation of major axis, and curvature of lake shoreline) were determined for lakes from the imagery, and bathymetric profiles of lake bottoms were derived using ground-penetrating radar. The results highlighted significant morphometric differences between lakes larger than 5000 m2 among three subregions: the Chumaerhe High Plain (CHP), the Hoh Xil Hill region (HXR), and the Beluhe Basin region (BBR). The lakes in CHP usually have a more regular outline and smooth lake bottoms, while the lakes in HXR often have the greatest depths and the most complex shorelines. The most elongated and largest lakes were typically in BBR. Other than a minor NE-SE peak in HXR and BBR, the major axis orientation for lakes in the three subregions is mostly ENE-WSW. The differences in lake morphology between the three subregions are associated with differences in ground-ice content, local relief, and topography. The dominant factors controlling the development of orientated thermokarst lakes in the region are the prevailing summer wind direction and solar insolation.

Environmental Earth Sciences, 2014

ABSTRACT Thermokarst lakes have been developing recently along the Qinghai-Tibet engineering corr... more ABSTRACT Thermokarst lakes have been developing recently along the Qinghai-Tibet engineering corridor in association with increased human activity and persistent climatic warming. Based on field observations, we assessed the susceptibility of terrain to the development of thermokarst lakes between the Chumaerhe River and Fenghuoshan mountain pass. A susceptibility map of the region was created in a geographic information system by assessing seven controlling factors, ranked using the analytic hierarchy process. The resulting susceptibility values ranged between 0.1 and 0.66. These susceptibility values were divided into four classes (high, moderate, low, and lowest) according to the mutagenesis point method. Areas with values between 0.1 and 0.16 were considered to have the ‘lowest’ susceptibility, while those between 0.26 and 0.66 were considered to have ‘high’ susceptibility. Using SPOT-5 satellite data, we determined that the high-susceptibility areas contained approximately 91 % of the total thermokarst lake area in the study region, and 88 % of the number of lakes. The moderate, low, and lowest level areas accounted for about 52 % of the study region, but only contained 9 % of the total lake area and 12 % of the lakes. Finally, relations between the area of the thermokarst lakes and the main controlling factors, e.g., ground ice content, ground temperature, vegetation type, and altitude were discussed.

Cold Regions Science and Technology, 2014

ABSTRACT Harbin to Dalian passenger dedicated line (HDPDL) was the first high-speed railway in th... more ABSTRACT Harbin to Dalian passenger dedicated line (HDPDL) was the first high-speed railway in the moderately deep seasonally frozen regions in the Northeast China. The roadbed-culvert transition section (RCTS) was paid special attention, as it was prone to uneven deformation. In this paper, the temperature field and its changing process of a typical RCTS at Siping site along HDPDL was discussed based on monitoring data. The results showed that during the freezing period (from November, 2010 to March, 2011), the thinner layer fill on the culvert, the higher temperature amplitude appeared in the RCTS. Due to the solar radiation difference on the sunny and shady slopes, the temperature in the sunny-slope was 1 ~ 3 °C higher than that in the shady-slope, and the difference increased as roadbed height increase. However, the culvert serves as a large ventilation duct, exchanging the amount of thermal rotation and weakening the temperature difference between the two sides. Numerical simulation of the temperature fields were carried out for discussing roadbed fill materials and culvert structures. The results indicated that, under the current design conditions, a pipe-style culvert shows a more stable thermal regime in the freezing period, while a box-styled culvert showed a more stable thermal regime in the thawing period. The anti-frost and insulation engineering measures were also discussed, and several critical design parameters were proposed and optimized. At last, it was found that the most suitable configuration was a box culvert with one section transiting to embankments, and this configuration was recommended for construction of high-speed railway in the seasonal frozen regions.

Landslides, 2006

ABSTRACT Permafrost covers a significant area of the Qinghai-Tibet Plateau. Slope instability pro... more ABSTRACT Permafrost covers a significant area of the Qinghai-Tibet Plateau. Slope instability problem in the region was often neglected, though it plays important roles in engineering construction and landform processes. In this paper, the slope instability phenomena in the permafrost regions on the plateau are discussed. The slope failures often occur in the forms of thaw-induced landslides and gelifluction. Thaw-induced landslides are closely related to active layer detachment and changes of permafrost conditions. Such landslides include retrogressive flow and thaw slump and are hazardous to engineering constructions. Gelifluction includes deep-seated movement and surface movement. It is an important factor in landform planation because it may spread over a large area and remain active for a long period of time.

Environmental Geology, 2014

ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between so... more ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between soil and atmosphere caused changes in the thermal and mechanical stability of permafrost beneath the railway embankment. Monitoring from 2005 to 2010 indicated 12 sections of embankment that experienced more than 5 cm of settlement, with three showing deformations of more than 10 cm and signs of continuing settlement. Embankment stability is closely related to permafrost changes beneath the embankment. Large-scale deformations have contributed to permafrost thaw and artificial permafrost table deepening, and this deformation has not stabilized over the short term. In contrast, small-scale deformations have contributed to a warming of the permafrost that has gradually stabilized as soil temperature decreases. Only three sections of the Qinghai–Xizang Railway have exhibited settlement deformation that exceeds 10 cm, through a deepening of the artificial permafrost table and a gradual increase in permafrost thawing result in embankment settlement deformation. However, with climate warming trends and the long-term operation of the railway, the long-term thermal and mechanical stability of the embankment needs to be carefully monitored to ensure the safe operation of the Qinghai–Xizang Railway.

Extremophiles, 2016

Permafrost on the Qinghai-Tibet Plateau is one of the most sensitive regions to climate warming, ... more Permafrost on the Qinghai-Tibet Plateau is one of the most sensitive regions to climate warming, thus characterizing its microbial diversity and community composition may be important for understanding their potential responses to climate changes. Here, we investigated the prokaryotic diversity in a 10-m-long permafrost core from the Qinghai-Tibet Plateau by restriction fragment length polymorphism analysis targeting the 16S rRNA gene. We detected 191 and 17 bacterial and archaeal phylotypes representing 14 and 2 distinct phyla, respectively. Proteobacteria was the dominant bacterial phylum, while archaeal communities were characterized by a preponderance of Thaumarchaeota. Some of prokaryotic phylotypes were closely related to characterized species involved in carbon and nitrogen cycles, including nitrogen fixation, methane oxidation and nitrification. However, the majority of the phylotypes were only distantly related to known taxa at order or species level, suggesting the potential of novel diversity. Additionally, both bacterial α diversity and community composition changed significantly with sampling depth, where these communities mainly distributed according to core horizons. Arthrobacter-related phylotypes presented at high relative abundance in two active layer soils, while the deeper permafrost soils were dominated by Psychrobacter-related clones. Changes in bacterial community composition were correlated with most measured soil variables, such as carbon and nitrogen contents, pH, and conductivity.

Journal of Mountain Science, 2012

On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sich... more On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this earthquake is currently hotly debated. We suppose that it is a special type of intraplate earthquake called an activenappe-type earthquake. Using a holistic methodology, incorporating rockmass structure cybernetics and Byerlee's law, we present a comprehensive study on the geological origin of macroseisms in the Longmen Shan area and the seismic origin of the 2008 Wenchuan earthquake. Previous studies of neotectonic activity indicate that the Longmen Shan nappe moves at a rate of 1~3 mm/yr, due to horizontal compressive stress from the Tibetan Plateau. The difference between movement rates in the Bayankala block, Longmen Shan nappe and Sichuan Basin cause slow shear stress and strain accumulation in the Longmen Shan nappe. It is exhibited a relatively simple linear relations for the shear strength and the buried depth of the structural planes, and the detachment layer of the nappe has a higher shearing-sliding strength compared to the overlying fault planes and the underlying ductile shear belts, thus making it more prone to stick-slip deformation. Therefore, the detachment layer was the main section responsible for the Wenchuan earthquake. The initial rupture burst in the detachment layer under the Yingxiu-Beichuan fault, the rupture area nearly 1.4454 × 10 4 km 2 ， encompassed the cross point of the Yingxiu and the Anxian-Guanxian faults with the detachment layer, then caused the Yingxiu -Beichuan and Anxian-Guanxian faults took an active part in this earthquake, so this earthquake might consist of three chain-like earthquake stages, totally increasing the duration of this earthquake an unusually large amount, to 120 s. The focal depth spanned range of 10-20km ， consistent with the observed result of this focal depth by several agencies.

PloS one, 2015

Understanding the processes that influence the structure of biotic communities is one of the majo... more Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with so...

Environmental Earth Sciences, 2012

ABSTRACT The impacts of alpine vegetation degradation on the main soil nutrients in the permafros... more ABSTRACT The impacts of alpine vegetation degradation on the main soil nutrients in the permafrost were studied by the comparative analysis of typical plots in the source regions of the Yangtze River. It is found that vegetation degradation has a severe effect on the content of the main soil nutrients, especially in the topsoil (0–10 cm) where the soil nutrients content were changed. There are good correlations between soil organic matter (SOM) and total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in alpine soil. The change to soil nutrients increases concomitantly with the increasing intensity of vegetation degradation. Soil nutrients change dramatically in the thermokarst lakes in the surrounding area where vegetation is severely degraded. The ratio of SOM, TN, TP and TK in different soil layers of the adjacent thermokarst lakes is 5.88, 5.14, 3.86 and 4.43, respectively. The vegetation degradation accelerates the degradation of alpine soil environment in alpine frozen soil.

Cold Regions Engineering 2012, 2012

Environmental Earth Sciences, 2013

ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between so... more ABSTRACT After construction of the Qinghai–Xizang Railway, the resultant heat exchange between soil and atmosphere caused changes in the thermal and mechanical stability of permafrost beneath the railway embankment. Monitoring from 2005 to 2010 indicated 12 sections of embankment that experienced more than 5 cm of settlement, with three showing deformations of more than 10 cm and signs of continuing settlement. Embankment stability is closely related to permafrost changes beneath the embankment. Large-scale deformations have contributed to permafrost thaw and artificial permafrost table deepening, and this deformation has not stabilized over the short term. In contrast, small-scale deformations have contributed to a warming of the permafrost that has gradually stabilized as soil temperature decreases. Only three sections of the Qinghai–Xizang Railway have exhibited settlement deformation that exceeds 10 cm, through a deepening of the artificial permafrost table and a gradual increase in permafrost thawing result in embankment settlement deformation. However, with climate warming trends and the long-term operation of the railway, the long-term thermal and mechanical stability of the embankment needs to be carefully monitored to ensure the safe operation of the Qinghai–Xizang Railway.

Unsaturated Soils: Research & Applications, 2014

Annals of Glaciology, 2014

ABSTRACT The ice cover on the Qinghai–Tibetan Plateau plays an important role in the environmenta... more ABSTRACT The ice cover on the Qinghai–Tibetan Plateau plays an important role in the environmental and ecological systems. We analyze the in situ measurements of ice growth and examine the thermal diffusivity of thermokarst lake ice in the Beiluhe basin. We evaluate numerically the change of thermal diffusivity of thermokarst lake ice with changing ice temperature using an optimal control model. In a higher ice temperature regime (–3 to 0°C), the thermal diffusivity of thermokarst lake ice decreases exponentially with increasing ice temperature, and approaches the thermal diffusivity value of fresh water near the freezing-point temperature. In a lower ice temperature regime (–15 to –3°C), the thermal diffusivity increases slowly with decreasing ice temperature.

Science China Earth Sciences, 2015

ABSTRACT Ten years of ground temperature data (2003-2013) indicate that the long-term thermal reg... more ABSTRACT Ten years of ground temperature data (2003-2013) indicate that the long-term thermal regimes within embankments of the Qinghai-Tibet Railway (QTR) vary significantly with different embankment structures. Obvious asymmetries exist in the ground temperature fields within the traditional embankment (TE) and the crushed-rock basement embankment (CRBE). Measurements indicate that the TE and CRBE are not conducive to maintaining thermal stability. In contrast, the ground temperature fields of both the crushed-rock sloped embankment (CRSE) and the U-shaped crushed-rock embankment (UCRE) were symmetrical. However, the UCRE gave better thermal stability than the CRSE because slow warming of deep permafrost was observed under the CRSE. Therefore, the UCRE has the best long-term effect of decreasing ground temperature and improving the symmetry of the temperature field. More generally, it is concluded that construction using the cooling-roadbed principle meets the design requirements for long-term stability of the railway and for train transport speeds of 100 km h−1. However, temperature differences between the two shoulders, which exist in all embankments shoulders, may cause potential uneven settlement and might require maintenance.

Science Bulletin, 2015

ABSTRACT This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Ti... more ABSTRACT This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Tibet Plateau over the past four decades (1969-2010) using aerial and satellite image interpretation. The results indicated that thermokarst lake activity had generally increased rapidly between 1969 and 2010. The number of thermokarst lakes had increased by approximately 534, and their coverage expanded by about 410 ha. The two main changes observed were an increase in the number of small lakes and the expansion of larger lakes. These changes are likely the result of persistent climate warming and a gradually increasing imbalance between precipitation and evapotranspiration (P-ET). However, some non-climatic factors, such as the lake-bottom substrate and local engineering activities, have also influenced the lake changes. If air temperature and P-ET continue to rise, the number of thermokarst lakes and the area they cover may continue to increase in the future.

Environmental Earth Sciences, 2013

ABSTRACT The active layer in permafrost regions plays an important role in energy exchange betwee... more ABSTRACT The active layer in permafrost regions plays an important role in energy exchange between permafrost and atmosphere. Rainfall is one of the dominant factors affecting thermal-moisture dynamics of the active layer. To better understand the thermal-moisture dynamics and the interaction between rainfall and the active layer in-detail, in situ experiment was carried out and soil temperature, soil moisture and soil heat flux of the active layer were measured from 2007 to 2009. The observation data demonstrated that the volumetric soil water content of the active layer remained fairly constant during the winter and had a notable fluctuation resulted from evapotranspiration and rewetting from rainfall events in summer. The daily variation amplitude of soil temperature and soil heat flux in summer was bigger than that in winter. Soil moisture content increased and soil temperature decreased after rainfall. Rainfall in summer led to the change of surface energy balance and caused subsurface soil cooling. The convective heat transfer from water infiltration reduced the temperature gradient along depth and changed near-surface heat fluxes. The increase in rainfall may mitigate permafrost degradation on the Tibetan Plateau.

Landslides, 2015

ABSTRACT The distribution of permafrost-related slope failures along the Qinghai-Tibet Highway fr... more ABSTRACT The distribution of permafrost-related slope failures along the Qinghai-Tibet Highway from Wuddaoliang to Fenghuoshan correlates with ice content, slope gradient, and ground temperature. Slope failures are of two types. (1) Retrogressive thaw slumps result from icy permafrost being exposed by either man-induced excavation or fluvial-thermal erosion and undercutting of basal slopes. (2) Active-layer-detachment failures are caused by thaw of icy permafrost at the active layer-permafrost interface. After initial failure, active-layer-detachment failures can lead to retrogressive thaw-slumping and localized surficial landslide. Common trigger mechanisms for failure include high summer air temperatures and heavy summer precipitation. A third possible trigger mechanism for slope failure is earthquake occurrence. A geotechnical slope stability analysis was undertaken for an active-layer-detachment failure that had progressed into a retrogressive thaw slump. A safety factor (F s ) of 1.24 for the natural slope was determined using in situ tested strength parameters. However, the slope would lose stability when either the groundwater level over the permafrost table exceeded 1.42 m or seismic acceleration reached, or exceeded, 0.03 g.

European Journal of Environmental and Civil Engineering, 2014

ABSTRACT Subsurface moisture content is one of the critical factors that control the thermal dyna... more ABSTRACT Subsurface moisture content is one of the critical factors that control the thermal dynamics of embankments. However, information on the subsurface moisture movement and distribution in embankments is still limited. To better understand the coupled water and heat transport within embankments, subsurface temperature and moisture of an asphalt pavement highway were extensively measured from 2009 to 2011. Collected data indicate that pure heat conduction is the overall main mechanism of heat transport in the embankment and heat convection plays a relatively unimportant role in heat transport. The results also indicate that subsurface moisture and temperature dynamics in the asphalt layer is strongly related to the rainfall events, while the subsurface moisture content below the road base course maintains relatively constant. Rainfall in summer leads to rapid cooling of the subsurface soil. Our results suggest that frequent and small rainfall events favour the thermal stability of the embankment due to the loss of latent heat of water evaporation. Moisture migration during freezing still occurred in the gravel fill and the water infiltrated into the active layer during thawing period. Freezing-induced water migration may result in the increase in water content of the embankment and the decrease in compactness of gravel fill.

Arctic, Antarctic, and Alpine Research, 2014

ABSTRACT In order to determine the distribution and morphometric characteristics of thermokarst l... more ABSTRACT In order to determine the distribution and morphometric characteristics of thermokarst lakes on the Qinghai-Tibet Plateau, SPOT-5 satellite images were acquired from the Chumaerhe High Plateau to Beiluhe Basin within a 10-km-wide corridor along the Qinghai-Tibet Railway. A total of 2163 water bodies, having a total area of 1.09 × 107 m2, were identified in the study area using unsupervised classification and image interpretation. Several shape metrics (area, perimeter, circularity index, elongation index, orientation of major axis, and curvature of lake shoreline) were determined for lakes from the imagery, and bathymetric profiles of lake bottoms were derived using ground-penetrating radar. The results highlighted significant morphometric differences between lakes larger than 5000 m2 among three subregions: the Chumaerhe High Plain (CHP), the Hoh Xil Hill region (HXR), and the Beluhe Basin region (BBR). The lakes in CHP usually have a more regular outline and smooth lake bottoms, while the lakes in HXR often have the greatest depths and the most complex shorelines. The most elongated and largest lakes were typically in BBR. Other than a minor NE-SE peak in HXR and BBR, the major axis orientation for lakes in the three subregions is mostly ENE-WSW. The differences in lake morphology between the three subregions are associated with differences in ground-ice content, local relief, and topography. The dominant factors controlling the development of orientated thermokarst lakes in the region are the prevailing summer wind direction and solar insolation.

Environmental Earth Sciences, 2014

ABSTRACT Thermokarst lakes have been developing recently along the Qinghai-Tibet engineering corr... more ABSTRACT Thermokarst lakes have been developing recently along the Qinghai-Tibet engineering corridor in association with increased human activity and persistent climatic warming. Based on field observations, we assessed the susceptibility of terrain to the development of thermokarst lakes between the Chumaerhe River and Fenghuoshan mountain pass. A susceptibility map of the region was created in a geographic information system by assessing seven controlling factors, ranked using the analytic hierarchy process. The resulting susceptibility values ranged between 0.1 and 0.66. These susceptibility values were divided into four classes (high, moderate, low, and lowest) according to the mutagenesis point method. Areas with values between 0.1 and 0.16 were considered to have the ‘lowest’ susceptibility, while those between 0.26 and 0.66 were considered to have ‘high’ susceptibility. Using SPOT-5 satellite data, we determined that the high-susceptibility areas contained approximately 91 % of the total thermokarst lake area in the study region, and 88 % of the number of lakes. The moderate, low, and lowest level areas accounted for about 52 % of the study region, but only contained 9 % of the total lake area and 12 % of the lakes. Finally, relations between the area of the thermokarst lakes and the main controlling factors, e.g., ground ice content, ground temperature, vegetation type, and altitude were discussed.