我国东北低山区不同坡位积雪特性研究

为研究坡位对积雪性质的影响,利用Snow Fork雪特性分析仪等采集积雪物理性质（积雪深度、密度、液态水含量）数据,分析了不同坡位积雪特性的变化趋势、差异及成因。结果表明：坡位的差异可显著影响积雪,特别是积雪表层的特性,积雪表层温度与积雪反辐射强度呈显著正相关关系;阴、阳坡各坡位积雪液态水含量变化趋势一致,但阳坡液态水含量最大值出现在上坡位,阴坡则是中坡位最大;阴、阳坡各坡位在液态水含量增加的影响下雪密度也在逐渐增大,并且随着积雪深度的增加雪密度逐渐减小;试验区融雪期阳坡积雪液态水含量最先对环境变化做出响应,进而影响雪密度,深度随之响应;阴坡则是液态水含量首先响应,积雪深度次之,密度最后响应。研究结果将为融雪径流形成、融雪侵蚀防治以及季节性积雪区生态系统评估提供理论依据。     

沙漠公路风沙土路基风蚀破坏试验研究

以沙漠公路风沙土路基为研究对象,通过室内风蚀风洞试验研究路基的风蚀破坏规律,以及路基不同断面对风沙流运动的影响。以路基高度、路基边坡坡率和路基宽度作为路基断面主要设计参数,研究不同路基断面下风沙流扰动、增速、减速、恢复的过程,以及路基周围风速流场的变化特征,分析路基病害较未病害时路基周围流场的变化。试验结果表明：路基高度和边坡坡率对风沙流运动的影响较大。随路基高度增加,路基对风沙流流场扰动增强,迎风坡坡顶处吹蚀破坏和背风坡坡底处堆蚀破坏越显著,在确定的路基边坡坡率下,路基模型高度为250 mm较模型高度为60 mm时,迎风坡坡顶风速增加1.13倍,背风坡坡底风速减小2.53倍,建议沙漠公路路基高度宜小于2.5 m。进一步,在确定的路基高度下,比较不同的边坡坡率对路基沿程风速的影响,发现当路基边坡坡率为1:1.75时,路基沿程风速变化不明显,沙漠公路风沙土路基不宜被风蚀破坏。     

融雪侵蚀研究进展

融雪侵蚀在中国及世界上许多地区都有发生,其对表层土壤的破坏作用越来越为人们所认识,已成为土壤侵蚀研究中的重要问题之一。在总结相关研究成果的基础上,分析了影响积雪和融雪的气候、海拔、地形地貌及土地利用等因素。在融雪侵蚀影响因素方面,认为融雪径流、表层土壤解冻深度、解冻期表层土壤可蚀性是影响融雪侵蚀发生的特殊因素。同时指出,融雪侵蚀预报模型中冻融作用对土壤水分迁移的影响、未完全解冻层对表层土壤水分的影响以及坡面融雪过程研究是未来融雪侵蚀研究中应重点解决的问题。     

黄土坡面侵蚀产沙时空演变的REE示踪技术研究

室内交叉布设不同的稀土氧化物,通过人工模拟次降雨,在同一试验条件下,对坡面侵蚀沿顺坡方向和深度方向的演变过程同时展开研究。结果表明:REE示踪技术对定量研究土壤侵蚀具有较高的精度;降雨前期,片蚀与细沟侵蚀发育程度基本相当;后期细沟侵蚀占据坡面侵蚀的主导地位,其侵蚀平均加速度和平均侵蚀率分别是片蚀的15倍、9倍;试验结束,细沟侵蚀占据坡面总侵蚀的90%;本试验条件下,坡面下1/3区域为侵蚀活跃带。     

极端冰雪灾害条件下松散堆积体边坡演化分析

针对2008年初南方罕见的极端冰雪气候,为研究其与地质灾害的相关性,探讨了极端冰雪灾害条件下均质松散堆积体边坡的演化特征。比较了融雪与降雨触发滑坡的异同点,通过具体事例分析了融雪触发滑坡灾害的一般规律。引入度日因子与雪雨当量两个物理量,根据南方极端冰雪气候特征建立了简化的有效融雪模型,并从渗流场、稳定性及变形3个方面模拟计算在不同雨雪当量下均质松散堆积体坡体的演化特征。结果表明,一定的融雪速率与融雪量对松散堆积体边坡渗流场无影响。随着融雪的持续,非饱和区基质吸力逐渐减小,坡体整体稳定性逐渐降低。坡面上水平位移与竖向位移逐渐增大,表现为水平方向上前缘变形大于后缘,竖直方向上后缘下错与前缘隆起。在融雪持续一段时间后,坡体失稳破坏。     

路侧波形梁护栏对分离式路基风吹雪雪害影响的仿真分析北大核心CSCD

对内蒙古自治区多条公路调查发现,设置有防撞护栏的路段雪害严重。由于风吹雪现场监测受降雪量、风力、时间等诸多因素限制,因此本文采用计算机仿真“数字风洞”的方法,选择分离式路基中典型的路堤断面形式,建立路基模型和防撞护栏模型,定量分析不同防撞护栏设置参数下公路横断面风速流场特性及其影响关系。通过对路面风速控制点的数据及路面整体风速云图分析发现,防撞护栏阻碍风吹雪的流动,导致路面风速大幅度降低使大量雪粒子沉积到路面上造成道路积雪,故在风吹雪多发地区分离式路基路段可通过放缓边坡坡度或采用缆索护栏以确保路侧安全的同时消除或减少雪害的发生。本研究结果可为多雪地区公路分离式路基路侧安全设计与养护提供理论基础与参考依据。     

基于实测数据的不同雪粒径光谱分析

利用黑河流域上游冰沟流域样地的实测积雪光谱和实测雪粒径数据,对不同雪粒径的光谱曲线特征进行分析,找出位于1030 nm和1 250 nm附近对雪粒径较敏感的两个波长,定量地揭示了位于这两个波长附近处的光谱曲线特征与雪粒径的关系.1 030 nm和1 250 nm附近是雪反射光谱中两个较明显的吸收峰位置,但雪在这两处的反射率值依然较高.分别通过1 030 nm和1 250 nm附近吸收峰置差异、1 030 nm附近处的光谱吸收深度、光谱吸收面积等4种方法与雪粒径进行关系拟合.结果表明:光谱吸收面积法对雪粒径有很好的指示作用,与雪粒径的线性和指数曲线拟合效果最好.同时,1 030nm附近的波长受大气散射和衰减的影响很小,可将该方法直接运用到高光谱影像上.     

银西高铁董志塬地区边坡侵蚀特性分析

黄土坡面侵蚀特性研究对于铁路边坡及路基防护具有重要的意义。通过银西高铁董志塬段某路基护坡坡面冲刷试验,获得了不同冲刷历时、冲刷流量、坡度等条件下的坡面冲刷结果,并对坡面流水动力学特性、坡面产沙规律、坡面产沙机理进行了分析,得出以下结论:（1）坡顶和坡底比坡面中部更易受侵蚀;30°～60°斜坡在较小的冲刷强度下也能产生较明显的侵蚀沟,宜采取45°左右的多级矮坡来减弱侵蚀强度。（2）坡面流水动力学特性分析表明,试验工况水流主要处于过渡流区;平均流速与冲刷流量、坡度呈幂函数关系;达西阻力系数与冲刷流量、坡度呈负相关,且与雷诺数相关性较低。（3）平均含沙量随冲刷流量与坡度的增大而增大,随历时近似线性增加,约20 min以后,含沙量基本稳定,此过程为坡面沟道发展阶段。（4）坡面侵蚀产沙量与侵蚀切应力、有效水流功率都呈正相关,与前者近似呈线性增大关系,而与后者近似呈幂函数关系。     

风沙环境下沙漠路基风蚀破坏数值模拟研究

基于Fluent气固两相流,运用 湍流模型,对风沙环境下沙漠路基的风蚀破坏规律进行数值模拟研究。分析路基不同横断面下风沙流扰动、增速、减速、恢复的过程,以及路基障碍物的存在对风沙流扰动后造成的风速减弱区和恢复区,总结路基坡面特征点的风速变化规律,与现场实测结果作比较,二者具有很好的一致性。研究结果表明,不同路基横断面下风速减弱区和恢复区的分布对路基高度变化敏感,受边坡坡率的影响较小,不同路基高度、不同边坡坡率下路基沿程风速变化明显不同。边坡坡率一定,随路基高度的增加,路基周围流场扰动被增强,迎风坡坡顶风速增大显著,背风坡坡底风速下降愈明显;路基高度一定时,边坡坡率越小,路基沿程风速变化越平缓。当边坡坡率为1:3时,路基模型高度由1m增加到3 m时,迎风坡坡顶风速增加12%,背风坡坡底风速降低约80%。建议为避免沙漠路基的风蚀破坏,路基高度不宜太大,边坡坡率较小为宜。     

路基坡脚积水对多年冻土路基稳定性的影响研究进展

多年冻土路基的稳定性很大程度上取决于其下伏多年冻土层的热稳定性. 当融雪、降雨或人为等外界因素形成的路基坡脚积水持续一段时间后,这些积水可能通过入渗对流换热、热边界侵蚀、补给冻胀水分等方式加剧或诱发多年冻土路基热稳定性的下降和丧失. 通过回顾国内外相关文献,从影响多年冻土路基稳定性的因素、积水对路基活动层冻融过程中水分迁移的影响、热融湖塘类积水对冻土路基的热影响、降雨和融雪积水入渗对冻土路基的热影响等方面,归纳总结了坡脚积水对多年冻土路基影响方面的研究进展;在此基础上,提出了对此问题进一步深入的研究展望和探讨.     

Wind tunnel test of snow loads on a stepped flat roof using different granular materials

An accurate prediction of wind-induced redistribution of snow load on roof surfaces is vital to structural design. To represent the pattern of snow distribution caused by snowdrift in wind tunnel test, appropriate modeling particles should be selected. The particle density is the key to determine the values of several important similarity parameters. In this study, the redistribution of snow load on a stepped flat roof was simulated by means of wind tunnel test using low-density saw wood ash, medium-density polyfoam, and high-density silica sand, respectively. To ensure the comparability of the test results of the three modeling particles, the wind tunnel test results for comparison were performed under almost the same conditions of dimensionless wind velocity and dimensionless time. Then, the results of the present study were compared with those from field observations of prototypes in previous studies. The effects of wind duration, wind velocity, and roof span on the redistribution of snow on roof surfaces were investigated. The characteristics of erosion/deposition range and the location of maximum quantities of erosion/deposition under independent effects of wind duration, wind velocity, and roof span were also studied.     

青藏铁路冻土区遮挡式路基结构安全可靠性预测分析

冻土区路基的安全可靠性取决于路基地温场特征和路基面抗自然侵蚀特征。在路基基床上部修筑遮阳棚和在边坡上修筑遮阳板既可阻挡太阳对路基面和路基边坡的直接辐射,改变路基地温场形态,降低土层温度,又可防止降水渗入路基或降雪覆盖路面。这对防止冻土退化,提高冻土区铁路路基安全可靠性是一种非常有效而又简单易行的工程措施。本文以青藏铁路冻土区遮挡式路基结构路基表面温度数据和该地段气象资料为基础,运用带有相变的一维热传导方程模拟分析了青藏铁路长期运营过程中遮挡式路基结构对冻土区路基人为上限的抬升效果及对路基稳定性的影响,认为遮挡式路基结构是一种安全可靠的冻土区路基工程结构形式,同时也是未来铁路运营过程整治路基病害的一种有效工程措施。     

冰雪型地质灾害链高位萌生、动力溃散及物相转化过程剖析北大核心CSCD

受全球气候变暖对高海拔山地区气温放大效应影响,冰雪型地质灾害趋于增多,且普遍呈现链式发育特征,具有灾害类型动态转化、影响范围大、破坏程度高等特点,严重威胁区域内重大工程建设安全。基于实地考察与文献调研方式,将高寒山地区常见冰雪型地质灾害凝练为:冰岩崩、雪岩崩、冰雪型碎屑流、冰碛物堆积滑坡、冰湖溃决、冰川型泥石流6类,并分别剖析各自典型的发育特征;而后,对冰雪型地质灾害3种典型链式组合关系予以剖析,发现:冰雪型地质灾害链普遍存在“高位萌生→动力溃散→物相转化”动态演化过程;据此,对冰雪型地质灾害高位萌生、动力溃散及物相转化三阶段特征及内在机制进行分析,明确了冰雪型地质灾害的“高位萌生→位能转化→侵蚀铲刮→滑移堆积”累积链生放大机理。最后,对冰雪型地质灾害链各演化阶段进行评价模型梳理,认为:新型破碎-扩散模型、Flores接触力模型可用于评价冰雪型地质灾害高位萌生向动力溃散过程;犁切模型可较好描述其侵蚀铲刮与体积放大过程;颗粒流模型、空气润滑模型、超孔隙水压力模型可用于揭示后续的高速滑移堆积特征;而Voellmy流变模型、Bingham流体渗流模型可较好解释其灾害链条的物相转化特征。研究对于科学评价冰雪型地质灾害链动态演化过程具有基础参考价值。     

Study on the snowdrift disaster influenced by w-beam barrier used in expressway北大核心CSCD

Snowdrift is one of the most typical snow disaster forms of road traffic in Xinjiang area. Its impact on road traffic is mainly reflected in reducing driving visibility and causing traffic interruption induced by a large amount of snow on the road surface. The snowdrift disaster along the road in Xinjiang area shows the characteristics as many points,long lines and wide spread occurring with uneven distribution in time and space. Snowdrift question involves wind field,snow distribution field,temperature field and humidity field coupling,which is a very complex scientific problem. At the same time,the prevention and control of snowdrift disasters is also a practical problem that needs to be solved urgently in the construction and operation of road traffic infrastructure in cold areas. For expressways in areas of frequent snowdrift occurring,its snowdrift disaster caused by the w-beam barrier is becoming more and more obviously. But there is still a lack of in-depth research on the w-beam barrier,which is one kind of auxiliary facilities of the highway deepening the snowdrift disaster. In view of the status mentioned above and in order to explore the causes and prevention methods to snowdrift disaster by w-beam barrier,on the background of Beijing-Urumqi Expressway（G7）engineering,the field model tests of the w-beam barrier,the cable barrier and the no barrier embankment were designed. The study also combined with numerical simulation and highway field investigation and other methods in order to verify each other. In the meantime,the influence of the w-beam barrier and cable barrier on the road snowdrift disaster of the highway is studied,and the distribution law of wind field and snow field on the embankment surface with w-beam barrier and cable barrier is obtained. The results show that the snowdrift velocity increases from the foot of the embankment on the upwind side till to the w-beam barrier installed at the shoulder of or the central divider of the road. Then it moves to the road surface through the gap in the lower part of the w-beam barrier. At this time the w-beam barrier disturbs the wind field near the ground,causing a weak wind area to appear behind the beam,resulting in a large number of snow particles deposited. Especially when the lower gap of the w-beam barrier is filled with snow,the road area behind the w-beam barrier covers the driving lane with snow,which seriously affects the road capacity. While the section without setting up a barrier or setting a cable barrier is conducive to the passage of snowdrift flow. Considering the uncertainty of future climate change,in order to better prevent the impact of snowdrift on traffic operation safety,it is proposed to replace the w-beam barrier in some areas with serious wind and snow disasters with cable barrier that meet the safety requirements of expressways. Moreover,other snowdrift protection measures such as snow fences,snow barriers and snow walls can also be adopted. The research results can provide useful reference for snow removal of the expressway and new expressway construction in the windy and snow areas of Xinjiang. © 2022 Science Press (China).     

筑堤土防渗性状试验研究

结合淮河入海水道河道工程,通过渗透变形试验确定了筑堤土料的渗透变形型式、临界水力坡降和允许坡降,同时指出了采用泓道开挖土筑堤的施工控制措施、质量要求和防渗措施。     

辽宁雪灾区划及降雪影响预评估

根据1951-2014年辽宁省各市、县降雪灾害造成的经济损失、雪灾出现的频率,多年平均灾损强度及气象灾变指数,计算各市、县的气象灾损值,并依此值作为雪灾灾度指数来进行辽宁降雪灾害区划.利用1951-2014年辽宁省58个国家级气象站降雪日数(日降雪量≥5mm)资料和辽宁省降雪灾情资料,采用统计分析、百分位数等方法研究确定不同灾害分区下不同降雪阈值与降雪影响预评估的关系.结果表明:(1)灾害重度区和灾害中度区主要位于辽宁中部城市群或经济发达区域,雪灾多年平均损失为280万元以上,损失程度较重;灾害轻度区和灾害微度区主要位于辽宁东部山区及辽宁西北部山区,雪灾多年平均损失为68万元以上,损失程度较轻;雪灾对辽宁影响最大的受灾体是公路,其次为设施农业.(2)在业务使用中,应用不同灾害分区降雪致灾阈值与受灾体损毁等级的预评估关系,采用定量降水预报自动判断生成降雪灾害预评估结果,能够客观的实现降雪落区不同、服务重点不同,对提高决策气象服务的针对性具有参考作用.     

Niveo-aeolian sand deposition in subarctic dunes,eastern coast of Hudson Bay,Québec,Canada

Aeolian sand transport during winter and the snow-free season was assessed quantitatively by direct year-round field measurements along transects on the lee side of parabolic dunes in subarctic Québec. In 1987–1988, niveo-aeolian deposition was more important than aeolian sedimentation in three of the four study sites, and contributed > 75% of the total annual accumulation in exposed sites and < 25% in protected forest sites. The maximum depth of interstratified snow and sand deposits (3.5 m) was recorded in March. Semi-permanent snow lenses may persist longer than 2 years in the aeolian sediments. After dissipation of snow, 22 cm of sand (as a maximum) accumulated on the slipface of the most active dunes, whereas only minor sand accumulation occurred in distant areas from active sand erosion. Wind-driven sand was dispersed over 7.4 km² in the Whapmagoostui-Kuujjuarapik area. The acumulation of snow and sand during the snow season, together with spring thaw and collapse of the niveo-aeolian deposit, caused different types of injuries to trees, especially in 1985 and 1987 when a maximum of torn branches was recorded over the last 10 year period.     

无粘性均质土石坝漫顶溃决试验研究

针对当前土石坝溃决机理试验研究中泥沙粒径取值偏小、各砂样粒径相差不大的现状,采用粒径对比明显的两组砂样进行了土石坝漫顶溃决试验.试验表明,在给定的较强的初始冲刷条件下,粗细两种颗粒坝体的溃决过程基本一致,均是以水流的下切侵蚀为主,在坝顶下缘位置有溯源冲刷现象出现.整个溃决过程可明显分为3个阶段,第1阶段为坝顶下缘处陡坎形成阶段;第2阶段为陡坎坍塌,冲刷加剧阶段;第3阶段为出现逆行沙垄的冲刷终止阶段.试验还发现,下游坝坡对溃决过程的影响比较显著,坝坡越陡,坝顶侵蚀速率越快,洪峰值越大.另外,由于粗颗粒抗冲刷性强,同等条件下粗颗粒坝体溃决洪水过程偏矮胖,洪峰值偏小,但是值得注意的是,相比于较大的颗粒粒径差距而言,其洪峰值的差异并不是太大.     

Influence of temperate mixed and deciduous tree covers on Hg concentrations and photoredox transformations in snow

Mercury dynamics in snowpacks under forested canopy are currently unknown, even though these snowpacks may represent important Hg pools eventually released towards lakes at snowmelt. We followed Hg distribution and partitioning in snowpacks under different temperate canopy types over space and time, and conducted short-term experiments on Hg redox behaviour in these snowpacks. Hg concentrations were ca. two times higher in snow deposited under coniferous than deciduous canopies; the lowest concentrations were observed in snow over a frozen lake in the same watershed. In snow on the ground, up to 80% of the Hg was bound to particles between 10 and 70 μm. Incubations of snow in situ showed that (i) Hg photoreduction and evasion was significant in open areas (lake surface) but was greatly hampered by light attenuation under winter canopies and (ii) oxidation of newly produced Hg⁰ was a significant process in boreal snow, affecting Hg evasion to the atmosphere. We used a mass balance approach to compare Hg pools in snowpacks with wet deposition measured by precipitation collectors. A net gain of Hg was observed in snow under mixed canopies whereas, under a deciduous canopy, the pool of Hg stored at the end of the winter was comparable to that of wet deposition. Snow over lake acted as a winter source of Hg. Whereas most Hg deposited by snow on lakes is lost before snowmelt, Hg deposited on the forested watershed is largely retained in snowpacks, presenting a threat to systems receiving meltwaters.     

高温冻土区新型复合护坡降温机制研究

遮阳板碎石复合护坡是一种集碎石护坡和遮阳板护坡双重效用于一体的新型复合护坡结构,是一种很好的治理高温冻土区块碎石护坡路基病害的补强措施。基于遮阳板和块碎石单个工程措施降温机制的研究,通过对这种新型复合护坡路基的温度场和速度场特征以及降温过程的研究,提出新型复合护坡路基的降温机制。研究发现,封闭新型复合护坡的主要降温机制是：复合护坡中遮阳板有遮阳和挡风雪作用,碎石层有“热半导体”效应和“热屏蔽效应”（屏蔽遮阳板的二次辐射）;开放新型复合护坡的主要降温机制是：遮阳板有遮阳、挡风雪作用,碎石护坡有 “热屏蔽效应”（屏蔽热风和二次辐射）和“烟囱效应”,遮阳板和碎石护坡组合的通道有“虹吸效应”、“狭管效应”和 “烟囱效应”。研究成果完善和深化了新型复合护坡路基研究基础,而且对遮阳板和块碎石结构在青藏铁路或青藏公路中的应用提供科学依据和技术支撑。