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1.
The different aspects lead to great differences in the processes of water,heat,and energy balance,which further affect the soil environment and the growth of alpine plants. Based on an experimental study with eight aspects（abbreviated as octagonal platform）of Huashixia frozen soil observation base on the Qinghai-Tibet Plateau,the influence of aspects on soil environments and alpine vegetation growth was studied. The results showed that：（1）After 6 years,the soil temperature of each slope near the surface（10 cm and 30 cm depth）from high to low was as follows：south > southeast > southwest > west > east > northwest > northeast > north,that is,the relatively sunny slope（east,southeast,south and southwest）was higher than the relatively shady slope（west,northwest,north and northeast）. However,there was no significant difference in soil water con⁃ tent between the sunny slope and the shady slope at the depth of 0~30 cm. （2）The growth trend of aboveground vegetation（including plant height,coverage and aboveground biomass）on sunny slope was better than that on shady slope. The growth trend of underground vegetation（including root depth and underground biomass）on sunny slope was worse than that on shady slope. （3）In the depth of 0~10 cm,the content of soil organic carbon and total nitrogen on sunny slope was higher than that on shady slope. However,the content of total phosphorus on sunny slope was lower than that on shady slope. There was no significant difference in total potassium and available nutrients among different slopes（P>0. 05）. In general,the effect of temperature on vegetation growth and nutrient distribution is significant in alpine regions,and these findings provides an important reference for vegetation restoration and energy balance research in different aspects. © 2023 The Author(s). 相似文献
2.
冻融试验对土中含水量分布的影响 总被引：5，自引：0，他引：5
The silty clay and silty loam are two typical soil types obtained from two test sites along the Qinghai-Tibet railway. The two types of soil have been designed various initial dry densities, water eontents, temperature conditions in repeated freezing and thawing tests with free access to water at the bottom. Afterfreeze-thaw cycles, the moisture content in the freeze-thaw zone increases more than that in the unfrozen zone to the peak approximately at the top of the samples. With comparison of the water contents in the frozen and thawed states, the moisture content in the upper freeze-thaw zone in the frozen state is greater than that in the thawed state, while that in unfrozen zone in the frozen state is smaller than that in the thawed state. Within the region of the frost front, the water content in frozen state is smaller than that in thawed state. These findings help to study the freeze-thaw mechanisms deeply and perfect the forecasting module of moisture transferring in freeze-thaw cycles. 相似文献
3.
Abstract: Permafrost (perennially frozen ground) appears widely in the Golmud-Lhasa section of the Qinghai-Tibet railway and is characterized by high ground temperature (≥ ?1°C) and massive ground ice. Under the scenarios of global warming and human activity, the permafrost under the railway will gradually thaw and the massive ground ice will slowly melt, resulting in some thaw settlement hazards, which mainly include longitudinal and lateral cracks, and slope failure. The crushed rock layer has a thermal semiconductor effect under the periodic fluctuation of natural air. It can be used to lower the temperature of the underlying permafrost along the Qinghai-Tibet railway, and mitigate the thaw settlement hazards of the subgrade. In the present paper, the daily and annual changes in the thermal characteristics of the embankment with crushed rock side slope (ECRSS) were quantitatively simulated using the numerical method to study the cooling effect of the crushed rock layer and its mitigative ability. The results showed that the ECRSS absorbed some heat in the daytime in summer, but part of it was released at night, which accounted for approximately 20% of that absorbed. Within a year, it removed more heat from the railway subgrade in winter than that absorbed in summer. It can store approximately 20% of the “cold” energy in subgrade. Therefore, ECRSS is a better measure to mitigate thaw settlement hazards to the railway. 相似文献
4.
The palynomorph assemblage of lake sediments younger than 51.9 kaBP from Wulagai Gobi in Inner Mongolia was analyzed to reconstruct the vegetation and climate.From 51.9 to 30.6kaBP,the vegetation was arid to semi-arid grassland with only slight changes.According to the palynomorphs,trees and shrubs were very rare.The large number and diversity of algae indicate the presence of a lake.Quantitative climatic conditions were reconstructed using the Best Analogues Method.The results indicate that the annual mean temperature was higher than that at present.The combination of temperature and annual precipitation suggests a change in the climate from cool dry to warm dry and then cool humid.Our results show that the annual precipitation values were mostly higher than that at present but were lower than 400 mm.It infers that the study area was already within the arid to semi-arid regions but with a stronger influence of the summer monsoon during 51.9to 30.6 kaBP than at present.With slight differences mainly in time scale,the changing trend of the annual temperature curve is consistent with the other climatic records from Antarctica,Greenland,Hulu Cave(East China),and the Tibetan Plateau during the last glacial period.From 30.6 kaBP to present,very few palynomorphs were detected in the samples.Hence,no information about the vegetation and climate could be extracted.Combined with other studies during Late Pleistocene,we presume that the reason for the lack of pollen during this period was caused by an abrupt temperature fall after 30.6 kaBP or that the lacustrine conditions were unsuitable for pollen deposition.It was probably incurred by the oxidation on land prior to deposition.But for those samples only with algae,it might be caused by the fact that algae could finish their life history in a very short time in a seasonal lake. 相似文献
5.
多年冻土区热融滑塌型滑坡稳定性评价方法 总被引：1，自引：0，他引：1
Landslide of thaw-slumping in permafrost regions of the Qinghai-Tibet Plateau is studied in this paper. Thaw-slumping belongs to shallow landslide with small depth-length ratio. Therefore the infinite slope analysis method is available to be applied in the stability analysis. Considering identical seepage directions to slope surface, we deduced analytical expressions of safety factor according to the effective stress principle and plotted stability analysis chart of slopes with dry or fully saturated soils.Taking an example of landslide of thaw-slumping at the mileage of K3035 of the Qinghai-Tibet Highway, we evaluated the analytical expressions. 相似文献
6.
This paper presents probabilistic assessment of seismically-induced slope displacements considering uncertainties of seismic ground motions and soil properties.A stochastic ground motion model representing both the temporal and spectral non-stationarity of earthquake shakings and a three-dimensional rotational failure mechanism are integrated to assess Newmark-type slope displacements.A new probabilistic approach that incorporates machine learning in metamodeling technique is proposed,by combining relevance vector machine with polynomial chaos expansions(RVM-PCE).Compared with other PCE methods,the proposed RVM-PCE is shown to be more effective in estimating failure probabilities.The sensitivity and relative influence of each random input parameter to the slope displacements are discussed.Finally,the fragility curves for slope displacements are established for sitespecific soil conditions and earthquake hazard levels.The results indicate that the slope displacement is more sensitive to the intensities and strong shaking durations of seismic ground motions than the frequency contents,and a critical Arias intensity that leads to the maximum annual failure probabilities can be identified by the proposed approach. 相似文献
7.
Carbonate contourite drift at Jiuxi. Taoyuan, northern Hunan, was developed in a deepwater area ofnorthern Hunan on the margin of the Early Ordovician South China palcocontinent. The Lower Ordoviciansequence in the area is more than 350 m thick and contains well-developed contourites that can be groupedinto the following five types: the calcilutitic, the arenitic, the siltitic. the fine ruditic and the bioclastic. Thefirst three often constitute a complete or incomplete contourite succession. The arenitic contourite is nearlyuniformly distributed as interlayers throughout the succession, creating a monotonously rhythmic texture inthe contourite drift. The pattern of spatial distribution of the succession shows that the contourite drift is ahuge ridge-like sedimentary body extending along the trend of paleoslope. Numerous marks of flow direc-tion have pointed to an eastward paleoflow direction along the slope. 相似文献
8.
Using the long-term ground temperature monitoring data of the permafrost zone along the Qinghai-Tibet Railway from 2006 to 2020,three types of typical roadbed structures were analyzed. Traditional embankment（TE）,U-shaped crushed rock embankment（UCRE）and crushed rock revetment embankment（CRRE）were included the three types of typical roadbed,which were selected to the long-term monitoring sections within the warm permafrost zones. The evolution of ground temperature field,mean annual ground temperature （MAGT）and annual maximum ground temperature（AMGT）in the depth range of 20 m under the embankment were analyzed and studied since 15 years of operation. The monitoring and analysis results show that：the growth rate of MAGT under the left and right shoulders of the TE is always higher than that of the same depth in the natural site. The MAGT under the UCRE is always lower than the natural site and always maintains a certain difference,whereas,the difference in ground temperature under the left and right shoulders is also not negligible. The MAGT of the left shoulder in the CRRE is not much different from that of the natural hole,while the MAGT of the right shoulder is always lower than that of the natural hole,and the differ in ground temperature between the left and right shoulders is smaller than that of the UCRE. The artificial permafrost table（APT）under the TE is always lower than that of in the natural site. Both the UCRE and CRRE,the APT in the left and right shoulders of them has been elevated into the embankment,and the differ of APT between the left and right shoulders is about 1. 0~1. 5 m. the differ of APT between the left and right shoulders in the CRRE is slightly lower than that of UCRE. Overall,because of the influence of thermal disturbance about engineering and climate warming,the TE in the warm permafrost zones cannot keep the thermal stability of permafrost under the embankment. Some active-cooling and reinforcement measures need to be taken. Both of the UCRE and CRRE,have a certain active-cooling effect on the permafrost under embankment,but the differ in ground temperature between the left and right shoulders still needs to be taken seriously. © 2022 Science Press (China). 相似文献
9.
多年冻土地区铁路路堤北坡和南坡热状况差异分析 总被引：1，自引：2，他引：1
Based on the observational data at Beiluhe test site of Qinghai-Tibetan Railway, the difference of thermal state between south faced and north faced slope was analyzed. The results indicated that the mean annual ground temperature at the depth of 0. 5m on south faced slope was higher than that on north faced slope by over 3 ℃. The higher temperature on south faced slope was greatly attributed to the high temperature during winter time. This kind of difference in thermal state may result in asymmetric thermal regime in embankment as well as in underlying soil. As a result, the unevenly transverse deformation may appear. 相似文献
10.
The distribution of permafrost and taliks is very complex in the Tuotuo River Basin(TRB), which is located in interior of the Qinghai-Tibet Plateau. Characterizing the spatial distribution and the thermal stability of permafrost and taliks is of great significance to community activities and engineering construction in TRB. Based on the zonation of permafrost and talik distribution around TRB conducted in the 1980s, the soil temperature and its variation process of permafrost and taliks in the south and north banks of the Tuotuo River were analyzed by using the observation data of five boreholes(N1~N5)along the Qinghai-Tibet Railway in the north bank and five boreholes(S1~S5)on the first terrace in the south bank. The results showed that, under the climate warming, permafrost and taliks in the north banks experienced significant degradation and warming process. From 2005 to 2020, the permafrost at the N1 borehole has undergone a significant down-draw degradation process, from extremely unstable and high-temperature permafrost to thawed zone. From 2005 to 2013, the annual average ground temperature of the talik at N2 increased at a rate of 0. 3~0. 4 °C·(10a)-1. At Maqutang on the south bank, permafrost prevails from the first-class terrace to the gentle slope of the Kaixinling Mountain, with both through and non-through taliks on the first-class terrace. The spatial distribution and the thermal stability of permafrost and talik in the TRB are further promoted by analyzing the changes in temperatures at boreholes in the basin. However, to meet the requirements of mapping and engineering construction of permafrost and taliks in the TRB, it is still necessary to carry out geological investigation with multiple methods and in-depth research on development mechanism of taliks in the future. © 2022 Nanjing Forestry University. All rights reserved. 相似文献
11.
以青藏铁路沱沱河段路基边坡作为试验区,且在试验区路基边坡两侧种植了乡土护坡草本植物垂穗披碱草,通过对种植在试验区路基阴坡、阳坡生长5年的垂穗披碱草,做了野外原位根系拉拔试验,获得了垂穗披碱草根系抗拔力。研究表明:种植在阳坡的垂穗披碱草根系抗拔力为3088N,阴坡抗拔力为2352N,即种植在阳坡的垂穗披碱草根系抗拔力显著大于阴坡,影响其抗拔力大小的主要因素与土壤含水量及其变化有密切关系,试验区阳坡接受光照时间、程度均强于阴坡,试验区阳坡坡面土壤水分蒸发量大于阴坡这种差异形成阴坡、阳坡坡体土壤含水量不同的主要原因;垂穗披碱草根系抗拔力大小与须根数量、根径、根长、株高、根表面积、分蘖数之间均呈线性关系,其中抗拔力与须根数量之间呈显著性线性相关,阳坡垂穗披碱草抗拔力随根系数量增加的幅度显著大于阴坡,即当须根数量为40～60条时,阳坡垂穗披碱草的抗拔力集中分布在11～25N,阴坡抗拔力分布在8～15N;当须根数量为60～140条时,阳坡垂穗披碱草的抗拔力分布在30～70N,阴坡抗拔力为20～50N。根据路基边坡阴坡、阳坡垂穗披碱草根系抗拔力试验结果,评价了阴、阳两种坡向条件下垂穗披碱草根系护坡力学贡献,这对青藏铁路路基边坡种植草本植物实现该边坡与周边自然生态环境之间的协调发展具有理论指导意义。 相似文献
12.
在多年冻土区,道路工程会对周边的多年冻土产生热影响,但不同地表条件下的多年冻土对道路热影响的反馈差异尚不完全清楚。本研究基于青藏公路沿线两处监测场地的多年冻土监测数据,研究了不同地表条件下青藏公路对多年冻土的热影响差异。结果表明,青藏公路对多年冻土的热影响因地表条件的不同而存在差异。与植被覆盖率较高的监测场地相比,在植被覆盖率较低的监测场地,其多年冻土年平均地温更高、多年冻土活动层厚度更大,且青藏公路对多年冻土的水平热影响范围也相对更大。此外,在植被覆盖率较低的监测场地最靠近坡脚的位置处,由于地表条件的不同,其浅层土壤更易受到外界扰动,导致该位置浅层土壤与外界的热交换特征迥异于其他监测位置,这可能也是导致两处监测场地多年冻土的热状态存在差异的原因。目前,青藏工程走廊内各线性工程密布,工程间的相互影响及其与多年冻土间的关系已成为必须考虑的问题。本研究工作对于青藏高原多年冻土区工程走廊内线性工程之间的合理间距设定,以及即将建设的青藏高速公路双向路基间的合理距离设计都可提供参考,以达到减少工程热扰动,保障工程安全运营的目的。 相似文献
13.
国道317线鹧鸪山隧道工程引道生态护坡方案设计 总被引：2，自引：0，他引：2
鹧鸪山隧道地处高海拔的国家天然林保护区，引道边坡裸露面与周围自然环境极不协调，边坡绿化势在必行。本考在详细调查引道边坡情况的基础上，按照边坡的坡度、高度和物质组成，对边坡进行了分类。结合当地气象水文等条件．针对不同类型边坡拟定采用生态基材、三维网客土绿化、植生穴等绿化工法，提出了适宜于不同绿化地段的乔灌草配置模式和耀草配置模式，并进行了相应的物种选择。 相似文献
14.
岩石边坡生态护坡特点及其关键技术问题探讨 总被引：26，自引：0，他引：26
岩石边坡 ,尤其是坡角较大的岩石边坡 ,由于其本身地形及结构条件的限制 ,开展生态恢复与重建工作具有很大的难度。根据岩石边坡的特点 ,结合目前这类工程所存在的问题 ,对有关的关键技术问题进行了分析探讨 ,包括与生态恢复相关的坡型设计、基层结构的形成、辅助材料的运用等 ,提出了生态护坡今后应该重点研究的方向。 相似文献
15.
Failures of weak-rock slopes adjacent to roadsides in southwestern Taiwan most often occurred during or immediately after heavy rainfall. Field survey of weak rock slopes along the national South-2 Freeway conducted in this study showed that the slope protection methods employed in the study areas mainly included vegetation (82.0%), prestressed rock anchors with vegetation (6.8%), grille beam (5.9%), rock anchors with grille beam (3.6%). The highest failure rate occurred in the slopes that were protected by the vegetation method. The most frequently encountered weak rock formation along the South-2 Freeway is the alternating sandstone–shale formation (36.3%), followed in sequence by sandstone (24.4%), conglomerates (21.9%) and mudstone (17.4%). The field survey also found that the mudstone slopes present the highest failure rate among all rock types, and the most commonly encountered modes of failure were surface erosion and shallow slides. Factors affecting slope failure include inadequate drainage of storm water runoff, disparate rock types and vegetation on slope surfaces, slope angles and heights. This paper presents results of the field survey of the rate of failures of weak rock slopes in Southwestern Taiwan and examines the attributes of slope failures and the effectiveness of commonly used slope protection methods in the region. Requirements or essential features of an effective slope protection method are then presented along with the preliminary results of its field implementation. 相似文献
16.
基于青藏高原楚玛尔河地区青藏公路里程K2968+200断面浅层地温监测数据（地表下5 cm）,拟合了边界温度的回归方程,分析了公路路基及铁路路基两侧表层温度的特征.同时对路基坡面温度和理论辐射值的相关性进行了分析.结果表明：边界温度回归方程拟合程度较高,可作为冻土路基数值模拟温度边界选取的参考依据;监测断面公路和铁路路基都表现出显著的阴阳坡差异,公路左右坡面冬季温度差异达11.49℃,年均值差4.77℃,冬季铁路路基左右坡脚温度差异达到5.34℃,年均值差3.33℃,天然地表与气温的差值为5.2℃;根据融化与冻结n系数,位于阳坡一侧的冻结n系数较低且融化n系数大,表现为吸热;阴坡一侧冻结n系数较大,整体呈现出放热效应;路基边坡太阳理论辐射与温度变化趋势基本一致. 相似文献
17.
基于BP神经网络的青藏高原土壤养分评价 总被引：5，自引：1，他引：4
土壤养分在养分循环和土壤-植物关系中起着重要作用,在高海拔生态系统中,由于缺乏系统的实地观测,土壤养分在高山草原中仍然知之甚少。为了了解青藏高原多年冻土区高寒草地土壤养分的基本情况以及土壤养分的等级划分,利用青藏高原腹地西大滩至安多地区采集的154个土壤样品数据,基于BP神经网络模型建立具有3层网络,10个中间层节点的土壤养分评价模型。在MATLAB软件中进行BP神经网络的训练和验证后,对青藏高原多年冻土区高寒草地土壤养分进行综合评价。结果表明：2009年青藏高原高寒草地的土壤养分综合评价等级为4级,属于较低水平。综合评价结果与基于主成分分析方法的土壤质量指数（SQI）基本一致,说明BP神经网络模型对青藏高原土壤养分的评价结果是合理的。对评价结果与海拔、植被盖度和植被类型的关系分析表明,海拔越高或植被盖度越高,土壤养分的评价等级越高;不同植被类型的评价等级表现出高寒沼泽草甸（2级）>高寒草甸（4级）>高寒草原（5级）的趋势。BP网络作为一种简单又准确的识别方法,不仅可以评估土壤养分等级,还可以比较不同地区的土壤养分高低状况,希望为青藏高原的土地资源管理与保护提供基本的科学依据。 相似文献
18.
利用2000-2012年的MODIS 增强植被指数（Enhanced Vegetation Index,EVI）数据,结合研究区3个气象台站长期的气象数据,分析了青藏公路沿线植被变化总体趋势,以及不同整修措施对周边植被覆盖带来的不同影响.通过实地考察,选取了16个受工程活动影响的典型路边样方,3个铁路边样方和8个远离公路铁路的自然样方,对比路边和自然样方,分析植被的自我恢复能力以及4个主要影响因子.结果表明：青藏公路沿线植被覆盖变化是在整个气候变化的背景下,叠加了工程活动的影响.植被的恢复能力与其所在路段的地形、植被覆盖度、气候条件、以及工程活动的强度均有关系,抑制植被生长的因素越多,植被恢复越慢. 相似文献
19.
黔桂喀斯特山地地形复杂,植被覆盖度垂直特征分异显著,以往研究多从气候因子响应方面探讨其垂直分布差异,而研究区人地矛盾尖锐,人类活动对植被分布有重要的影响。文章以黔桂喀斯特山地为例,利用2010年MODIS13Q1 NDVI数据表征植被覆盖度,结合高程、坡度和坡向等地形特征,不同土地利用类型的分布情况,叠置分析研究区的NDVI垂直分布特征。结果表明:黔桂喀斯特山地以林地、耕地和草地为主,不同土地利用类型随海拔、坡度和坡向的变化呈现不同的分布特征。研究区NDVI平均值为0.59,其中林地NDVI最大,达到0.63,草地为0.58,耕地最小为0.54。空间分布上,贵州境内NDVI值大部分为0.5~0.6,广西境内自西北向东南NDVI值由0.8逐渐降低至0.4,以0.6~0.7为主。NDVI在垂直梯度上分布特征显著,与植被垂直地带性分布以及不同地类的垂直分布特征有密切关系。海拔分布上,NDVI在海拔小于200 m区间最小,400~600 m的区间最大;北部贵州整体海拔较高,但植被覆盖度较低;南部广西海拔较低,但植被覆盖度较高。坡度分布上,在坡度小于35°范围,随坡度增大,耕地、水域、建设用地面积迅速减少,林草地面积逐步增加,使得NDVI随坡度增大逐渐增大。坡向分布上,NDVI不随坡向变化呈现明显变化,仅偏东坡向稍大于偏西坡向。研究表明应根据海拔和坡度等地形特征,并考虑土地利用情况,因地制宜进行生态建设。 相似文献