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Heat transfer process of roadway embankments with different type and width of road surface in permafrost regions

Progress in Natural Science:Materials International 2007年第3期17卷 314-319页

作者： YU Qihao, PAN Xicai, CHENG Guodong and BAI Yang (State Key Laboratory of Frozen Soil Engineering, Cold and Arid regions Environment and Engineering Research Institute, Chinese A-cademy of Sciences, Lanzhou 730000, China) State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environment and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

The stability of roadbed in permafrost areas has become a big concern with rapid development and construction of throughways, highways and railways in these areas under the current climate change since it is governed by the thermal condition, or in other words, the heat transfer process in the embankment. We carried out a finite element analysis to analyze the effects of different types of road surface and the effect of breadth of embankment on the embankment heat transfer process. The results indicated that the mean annual heat transfer rate at the bottom of the roadway embankment with asphalt surfaces is 3 times that with sandy gravel surfaces. This means annual heat transfer rate increased by 60% when the breadth of asphalt surface was doubled. The increased heat transfer rate was mainly located at the bottom of the embankment and resulted in the effect of thermal concentration,. leading to degradation of the permafrost by as much as 1.6 times. It was also found that increasing embankment height would not reduce these increases of the heat transfer rate. Therefore both asphalt road surface and increased embankment breadth can lead to an intensified heat transfer rate in roadway embankment, consequently degradating the underlying permafrost and embankment instability.

关键词： wide road surface roadway embankment permafrost regions process of heat transfer heat flux ground temperature field.

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Thermal and mechanical characteristics of a thermal pile in permafrost regions

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Advances in Climate Change Research 2023年第2期14卷 255-266页

作者： Yun-Hu SHANG Fu-Jun NIU Kun YUAN Tian SUN Li-Bo WU State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Da Xing'anling Observation and Research Station of Frozen-Ground Engineering and Environment Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesJiagedaqi 165000China First Highway Consultants Co. Ltd.China Communications Construction Company LimitedXi'an 710075China Jiangsu Sunpower Technology Co. Ltd.Nanjing 210009China School of Civil Engineering and Hydraulic Engineering Ningxia UniversityYinchuan 750021China

Cast-in-place pile foundations are widely used in permafrost regions to support *** stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime *** degradation caused by climate change is increasing the disaster risk of castin-place pile ***,proactive cooling methods for cast-in-place pile foundations are seldom *** cold energy produced by two-phase closed thermosyphons(TPCTs)can efficiently prevent the permafrost thermal regime from being disturbed by engineering activities and climate *** were installed in a concrete pile forming a thermal ***,a model experiment was conducted to explore the thermal regime,influence scope,dissipation process of cold energy,and freezing strength of the thermal *** results indicated that the thermal pile may significantly cool the foundation *** of cold energy produced by the thermal pile dissipated during the warm period,and the cooling scope of the thermal pile can cover the area within a 40 cm(twice the pile diameter)radius around the ***,the TPCTs can significantly improve freezing strength between the thermal pile and frozen *** lesson learned from this study can provide a new approach to control the thermal regime of cast-in-place pile foundation in permafrost,which was of valuable to the construction of pile foundations in cold regions.

关键词： Pile foundation Cold energy Two-phase closed thermosyphon Freezing strength permafrost regions

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Distress Characteristics in Embankment‑Bridge Transition Section of the Qinghai‑Tibet Railway in permafrost regions

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International Journal of Disaster Risk Science 2023年第4期14卷 680-696页

作者： Peifeng He Fujun Niu Yunhui Huang Saize Zhang Chenglong Jiao State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhou 510641China South China Institution of Geotechnical Engineering School of Civil Engineering and TransportationSouth China University of TechnologyGuangzhou 510641China School of Civil Engineering Changsha University of Science and TechnologyChangsha 410114China

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 ***,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 *** 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 *** occurrence rates of these distresses were 78.93,3.47,11.56,3.36,21.18 and 4.56%,*** most serious problem was diferential settlement,and the average diferential settlement amount(ADSA)was 15.3 ***,the relationships between diferential settlement and 11 infuencing factors were *** 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 *** 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 *** EBTSs are more infuenced by ice content than by ground *** ADSA increases when the embankment height increases,the particle size of subgrade soil decreases and the surface vegetation cover decreases.

关键词： Distresses Embankment-bridge transition section permafrost regions Qinghai-Tibet railway

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Analysis of permanent deformations of railway embankments under repeated vehicle loadings in permafrost regions

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Research in Cold and Arid regions 2015年第6期7卷 645-653页

作者： Wei Ma Tuo Chen State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Science

By large-scale dynamic tests carried out on a traditional sand-gravel embankment at the Beilu River section along the Qinghai-Tibet Railroad, we collected the acceleration waveforms close to the railway tracks when trains passed. The dynamic train loading was converted into an equivalent creep stress, using an equivalent static force method. Also, the creep equation of frozen soil was introduced according to the results of frozen soil rheological triaxial tests. A coupled creep model based on a time-hardening power function rule and the Druker-Prager yield and failure criterion was estab- lished to analyze the creep effects of a plain fill embankment under repeated train loads. The temperature field of the embankment in the permafrost area was set at the current geothermal conditions. As a result, the permanent deformation of the embankment under train loading was obtained, and the permanent deformation under the train loads to the total embankment deformation was also analyzed.

关键词： vehicle load permanent deformation creep effect permafrost regions

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Discussion on the relationship between longitudinal cracks and alignment of subgrade in permafrost regions

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Research in Cold and Arid regions 2011年第2期3卷 132-136页

作者： AnHua Xu Qinghai Research Institute of Transportation Xining 810008 Qinghai China

At present, embankment longitudinal cracks are a major problem in highways through permafrost regions, and seriously affect traffic safety and the normal operations of the highway. In the past, roadbed height in permafrost regions was relatively low, and embankment cracks were rare and did not affect traffic safety. Thus, highway designers and researchers paid little attention to this problem, and they knew very little about distribution laws and mechanism of embankment longitudinal cracks. Due to this lack of knowledge, there is no uniform opinion on this problem, making it difficult to find measures that will mediate the impact of longi- tudinal crocks. Temperature is a major factor that affects and controls embankment stability in permafrost regions, especially in ice-rich and high-temperature regions, and solar radiation is the principal factor that determines surface temperatures. Under higher embankment, the difference of temperature will be larger between a sunny slope and a shady slope. Hence, the probability for longitudinal cracks generation is higher. In this paper, a survey and analysis of longitudinal cracks along the Qinghai-Tibet Highway were carried out. The longitudinal cracks are found to be related to the road strikes. Solar radiation is considered to play an important role in the generation of longitudinal cracks.

关键词： permafrost regions embankment longitudinal cracks road alignment distribution laws

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Mechanical behaviors of warm and ice-rich frozen soil stabilized with sulphoaluminate cement

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Journal of Mountain Science 2024年第1期21卷 335-345页

作者： WANG Honglei ZHANG Hu ZHANG Jianming ZHANG Qi YIN Zhenhua State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China School of Civil Engineering and Transportation Northeast Forestry UniversityHarbin 150040China National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment CCCC First Highway Consultants Co.LtdXi'an 710065China Railway Engineering Research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.

关键词： permafrost regions Frozen soil Mechanical behavior Chemical stabilization Ground improvement Ground modification

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