摘要
在全球气候变暖背景下,寒区季节冻土环境变化对陆地表面与大气之间的物质与能量交换、陆地景观格局演化的影响十分剧烈。摸清季节冻土的分布格局及其时空变化对开展寒区自然科学研究、保障生态环境和人类生产活动安全均具有重要意义。经过数十年的发展,冻土遥感技术和冻土物理学取得了长足的发展。然而,当前冻土研究成果在区域尺度下灾害风险评估与防控领域中的应用仍处于较低水平。针对冻土研究成果在应用中的短板,以青藏高原东南缘的高山峡谷区及其周边地区为研究区,重点解决地表土壤冻融循环及其水热传输过程的系统性表达,建立了适用于青藏高原高海拔冻土区的空间全分布式的冻土水热耦合过程数值模型,分析了研究区2010—2020年的冻土系统演化过程。在此基础上,构建了地表土壤冻融作用的空间参数化表征方法,提出冻融作用对土体抗剪强度的损伤系数。研究表明,青藏高原东南缘季节冻土随气温升高变化剧烈,表现出较强的空间异质性。季节冻土除了周期性冻融循环外,总体呈退化趋势,为冻融作用下岩土体结构抗剪强度的变化增加了更多不确定性。最后,利用土体抗剪强度损伤系数,从时间变化和空间分布角度揭示了地表土壤冻融作用对冻土边坡稳定性的影响程度。土体抗剪强度损伤系数可以有效刻画地表季节冻土水热过程及其冻融作用特征,为冻融灾害相关研究提供新思路,也为寒区灾害风险评估与灾害防治等领域的研究提供了冻土系统动态演化数据和技术支撑。
Under the global climate change,frozen soil regions are sensitive to changes in external hydrothermal conditions,and are tend to degrade regionally,which is mainly manifested by the thickening of permafrost ac⁃tive layer,thinning of seasonally frozen soil layer and reduction in seasonal frozen days.As an important part of the cryosphere,the direct and indirect risks of the changes or degradation of frozen soil to the ecological environ⁃ment system and the safety of human production have been gaining wide attention from scholars.The changes of surface soil in cold regions have significant impact on the evolution of the landscape pattern,and the material or energy exchange between land surface and atmosphere.Therefore,it is of great significance to monitor the distri⁃bution and spatiotemporal changes of seasonally frozen soil for carrying out natural scientific research in cold re⁃gions,or ensure the safety of ecological environment and human production activities.After several decades of development,remote sensing technology and frozen soil physics have made considerable progress.However,the application of frozen soil research results in the field of disaster risk assessment,prevention and control at re⁃gional scale is still at a low level.Aiming at the shortage of frozen soil process simulation and facing the short board in the frozen soil research results application,we focus on the systematic expression of land surface soil freeze-thaw cycle and its water and heat transfer process over the alpine canyon area and its surrounding areas on the southeastern margin of the Qinghai-Xizang(Tibet)Plateau.The dynamic balance of water and heat in vari⁃ous land surface processes such as meteorology,vegetation,snow cover and soil were considered comprehen⁃sively to establish a spatially distributed numerical model.Based on the simulated high-precision frozen soil characteristic parameters,the evolution process of the frozen soil system in the study area was analyzed deeply by using the methods of GIS spatial analysis and data processing technologies.The seasonal freeze-thaw cycle and its changing characteristics of surface frozen soil over the study area in the past decade have been analyzed,and the spatiotemporal evolution of the surface frozen soil in the complex geographical environments under cli⁃mate change has been revealed in the present study.On this basis,a parametric characterization method of sur⁃face freeze-thaw action was developed based on various frozen soil characteristic parameters of the soil hydrother⁃mal processes.Then,the damage coefficient of soil shear strength caused by freeze-thaw action is innovatively proposed by combining the relevant theories of soil shear strength and thawing stability of slopes.The results showed that surface frozen soil on southeastern of the Qinghai-Xizang Plateau changes sharply with the increase of temperature with strong spatial heterogeneity.In addition to the periodic freeze-thaw cycle,seasonally frozen soil showed a degradation trend overall.Degradations of frozen soil were mainly manifested by the increase of soil temperature and the increase of soil water content.Undoubtedly,it increases more uncertainties to the change of shear strength of rock and soil mass structure under freeze and thaw environment.Finally,influence degree of soil freeze-thaw action on slope stability in frozen regions were revealed from the perspectives of time variation and spatial distribution,based on the damage coefficient of soil shear strength that proposed in this study.The results indicated that the damage coefficient of soil shear strength could effectively express the hydrothermal process of surface frozen soil and its freeze-thaw characteristics.This study can provide new ideas for the research of frozen soil,and provide data and technical support for the dynamic evolution of frozen soil sys⁃tem for the research of disaster risk assessment and disaster prevention in cold regions.
作者
高会然
许冲
张万昌
易亚宁
肖子亢
GAO Huiran;XU Chong;ZHANG Wanchang;YI Yaning;XIAO Zikang(National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China;Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100094,China;Key Laboratory of Compound and Chained Natural Hazards Dynamics,Ministry of Emergency Management of China,Beijing 100085,China)
出处
《冰川冻土》
CSCD
北大核心
2023年第6期1859-1874,共16页
Journal of Glaciology and Geocryology
基金
应急管理部国家自然灾害防治研究院基本科研业务专项(ZDJ2022-34)资助。
关键词
青藏高原东南缘
季节冻土
冻融作用
土体损伤
数值模拟
southeast margin of the Qinghai-Xizang(Tibet)Plateau
seasonally frozen soil
freeze-thaw action
soil damage
numerical simulation
