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1.
Compacted loess is widely used as fills of road embankments in loess regions of northern China. Generally, densely-compacted loess can satisfy the requirements of embankment strength and post-construction deformation. I lowever, uneven subsidence, pavement cracks and other related damages can affect the integrity of loess subgrade after several years of operation, and even cause some hazards, especially in North China, where the strong freeze-thaw erosion occurs. In this study, cyclic freeze-thaw tests for both densely and loosely compacted loess samples were performed to determine the variation in engineering properties such as volume, void ratio, collapsible settlement, microstructure, and the related mechanisms were addressed. The experimental results showed that an obvious water migration and redistribution occurred within the samples during freeze-thaw cycles. Ice lenses and fissures could be identified in the upper frozen layers of the samples. After freeze-thaw cycles, the dry densities of the nipper layers of samples changed significantly due to strong freeze-thaw erosion. The dry densities decreased for the dense sample and increased for the loose sample. It can be found that dense samples become loose, while loose samples became dense with the increasing number of freeze-thaw cycles. Their related void ratios changed reversely. Both void ratios tended to fall into a certain range, which verified the concept of a residual void ratio proposed by Viklander. The loosening process of densely compacted samples involves the formation of large pores, volume increase and density reduction as well as the related changes in mechanical properties because freeze-thaw cycles may be important contribution to problems of loess road embankments. Adverse effects of freeze-thaw cycles, therefore, should be taken into account in selecting loess parameters for the stability evaluation of road embankment in seasonally frozen ground regions.  相似文献   

2.
Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.  相似文献   

3.
泥质砂岩残积土作为一种结构性很强的特殊土, 具有崩解性强、抗冲蚀性差以及扰动性极大的特点, 对工程建设有较大影响。为了探究泥质砂岩残积土边坡降雨冲刷机理, 设计了边坡降雨冲刷试验, 通过现场三维激光扫描技术测试分析了其表面冲刷效应; 利用高密度电法进一步明确了泥质砂岩残积土边坡的入渗特性、表面冲刷演化机制及冲刷破坏机理。结果表明: 冲刷试验的最初阶段, 降水入渗强且主要向坡脚处运移, 坡表未形成明显的细沟; 冲刷试验中期, 坡脚处土体最先达到饱和而形成坡面径流, 细沟贯通扩大形成小规模冲槽以及片蚀区; 冲刷试验后期, 坡面中部和坡脚处土体冲蚀严重, 坡脚处的冲槽向上部延伸, 片蚀区扩大, 导致表层土体结构发生变化, 渗透性差异明显; 泥质砂岩残积土坡体降雨冲刷主要划分为表层溅蚀、下层潜蚀和细沟贯通3个阶段, 坡面土体流失主要发生在最后一个阶段, 细沟率达到最高值16.9%, 细沟贯通率也高达0.74。研究结果可以为深入探讨泥质砂岩残积土边坡冲蚀防护和研究冲蚀防护机理提供基础资料。   相似文献   

4.
Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore,total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the variousindices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and-0.98, respectively,indicating that slope gradient is the major factor of affecting the development of rills. Furthermore,runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration,however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.  相似文献   

5.
The bank slopes in hydro-fluctuation areas of reservoirs or lakes suffer from severe erosion due to an absence of protection. Waves are one of the important external forces that cause bank erosion and slope failures. However, the processes and quantified impacts of wave-induced erosion on slopes remain unclear under different water level-fluctuation conditions. This paper focuses on the characteristics of wave-induced slope erosion under three conditions: water level dropping(WLD), fixed(WLF) and rising(WLR). A steel tank with glass pane was used to simulate the wave-induced slope erosion in the three treatments. The slope elevation data were collected by using the method of the pin meter for every 15 minutes from the beginning to the end, a total of 5 times during all treatments. These data were processed by using software(SURFER 9.0) to get the slope micro-topography and the erosion volume. Then the temporal and spatial change of slope erosion was analysed according to the erosion amount or erosion rate calculated based on bulk density of slope soil. The results demonstrated that the soil erosion rates for different water level changing treatments are in the following order: WLR>WLD>WLF. For the erosion spatial variation, the middle part of the slope was the major source of sediment in the WLD. The upper part of the slope was the major source of the sediment for the other two treatments. Compared with the standard deviation(SD), the coefficient of variation(CV) based on the SD is more representative of variations in the soil surface roughness(SSR). Furthermore, the good fit between the SSR and soil erosion rate have the potential to be used to predict soil erosion. Above all, the injection angle of the wave determined the rate of erosion to some extent, and the fall-back flow of the wave could also influence the extent of erosion, deposition, and bank morphology. It is vital to choose the appropriate index(SD or CV) in the three water levels to improve the prediction accuracy. This paper could provide scientific knowledge to manage reservoirs or river banks.  相似文献   

6.
高寒、高海拔地区由于反复冻融导致的岩体变形破坏,对区内工程建设有重大影响。为研究不同裂隙条件下岩体循环冻融特性,在汶马高速沿线选择具有代表性的千枚岩和砂岩,制备了不同裂隙条件（长度、张开度、裂隙组数）试样,在干燥和饱水两种状态下分别进行大温差（-20℃到20℃）循环冻融（50次）试验。试验揭示了饱水裂隙岩样冻融变形过程:冻缩→冻胀→冻缩（冻结阶段）→融胀→融缩→融胀（融化阶段）,干燥裂隙岩样冻融变形过程:冻缩（冻结阶段）→融胀（融化阶段）。进一步,选择冻胀量εd为指标,分析了两类岩样冻融循环次数与εd的关系,揭示了裂隙长度、宽度和组数对εr的影响规律;选择残余变形量εr为指标,揭示了千枚岩和砂岩试样在饱水条件下εr随εd的增加规律,获得了εd与εr间的定量关系;分析了干燥和饱水试样单轴抗压强度随冻融循环次数增加而减小规律,确定了冻融次数与试样劣化间的线性关系。最后,初步讨论了饱水条件、岩性和裂隙条件对岩体冻融循环变形的影响机制。   相似文献   

7.
Land surface temperature(LST) causes the phase change of water, links to the partitioning of surface water and energy budget, and becomes an important parameter to hydrology, meteorology, ecohydrology, and other researches in the high mountain cold regions. Unlike air temperature, which has common altitudinal lapse rates in the mountainous regions, the influence of terrain leads to complicated estimation for soil LST. This study presents two methods that use air temperature and solar position,to estimate bare LST with high temporal resolution over horizontal sites and mountainous terrain with a random slope azimuth. The data from three horizontal meteorological stations and fourteen LST observation fields with different aspects and slopes were used to test the proposed LST methods. The calculated and measured LST were compared in a range of statistical analysis, and the analysis showed that the average RMSE(root mean square error),MAD(mean absolute deviation), and R~2(correlation coefficient) for three horizontal sites were 5.09℃,3.66℃, 0.92, and 5.03℃, 3.52℃, 0.85 for the fourteen complex terrain sites. The proposed methods showed acceptable accuracy, provide a simple way to estimate LST, and will be helpful for simulating the water and energy cycles in alpine mountainous terrain.  相似文献   

8.
青藏高原作为中低纬度地区最大的高山冻土区,多年冻土和季节冻土广泛分布。高精度的地表冻融监测结果对研究该区域的水热交换、碳氮循环和土壤冻融侵蚀非常重要。本文基于4个青藏高原典型地区的土壤温湿度观测网数据,开展利用LightGBM算法和随机森林算法进行土壤冻融循环监测的研究。在构建土壤冻融监测模型的过程中,发现土壤湿度是影响冻融判别的一个关键因子。使用AMSR2亮温数据和ERA5-Land土壤湿度数据,基于两种机器学习算法判别地表冻融状态,将结果与传统冻融判别式算法进行对比分析。结果表明：相比冻融判别式算法,LightGBM算法在白天和夜间的总体判对率提高了12.09%;14.45%,随机森林算法在白天和夜间的总体判对率提高了13.23%和14.96%。近80%的错分样本分布在-4.0 ℃~4.0 ℃之间,说明2个机器学习算法能够识别出稳定的土壤冻结状态和融化状态。另外,LightGBM算法和随机森林算法得到的日冻融转换天数的平均RMSE降低了112.82和117.00;冻结天数的平均RMSE降低了47.87和53.96;融化天数的平均RMSE降低了37.10和39.80。同时,基于随机森林算法计算了2014年7月—2015年6月青藏高原冻结天数、融化天数、日冻融转换天数。得到的青藏高原冻结天数图,以中国冻土区划图为参考进行精度评价,总体分类精度为96.78%。  相似文献   

9.
Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geo-mechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG (Fiber Bragg Grating) sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from the superficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon 0.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.  相似文献   

10.
Erosion agents and patterns profoundly affect hillslope soil loss characteristics. However, few attempts have been made to analyze the effects of rainfall and inflow on soil erosion for hillslopes dominated by sheet erosion or rill erosion in the Chinese Mollisol region. The objective of this study was to discuss the erosive agent(rainfall or inflow), hillslope erosion pattern(sheet erosion or rill erosion) and slope gradient effects on runoff and soil losses. Two soil pans(2.0 m long, 0.5 m wide and 0.5 m deep) with 5° and 10° slopes were subjected to rainfall(0 and 70 mm h–1) and inflow(0 and 70 mm h–1) experiments. Three experimental combinations of rainfall intensity(RI) and inflow rate(IR) were tested using the same water supply of 70 mm by controllingthe run time. A flat soil surface and a soil bed with a straight initial rill were prepared manually, and represented hillslopes dominated by sheet erosion and rill erosion, respectively. The results showed that soil losses had greater differences among treatments than total runoff. Soil losses decreased in the order of RI70+IR70 RI70+IR0 RI0+IR70. Additionally, soil losses for hillslopes dominated by rill erosion were 1.7-2.2 times greater at 5° and 2.5-6.9 times greater at 10° than those for hillslopes dominated by sheet erosion. The loss of 0.25 mm soil particles and aggregates varying from 47.72%-99.60% of the total soil loss played a dominant role in the sediment. Compared with sheet erosion hillslopes, rill erosion hillslopes selectively transported more microaggregates under a relatively stable rill development stage, but rills transported increasinglymore macroaggregates under an active rill development stage. In conclusion, eliminating raindrop impact on relatively gentle hillslopes and preventing rill development on relatively steep hillslopes would be useful measures to decrease soil erosion and soil degradation in the Mollisol region of northeastern China.  相似文献   

11.
黄土高原边坡特征与破坏规律的分区研究   总被引：5，自引：1，他引：4  
为了研究黄土高原自然边坡的特征及破坏规律,按山系与水系或水系的分水岭、地貌单元、地层岩性特征等条件,将黄土高原划分为8个区:临洮—永靖区、天水—通渭区、兰州—会宁区、陇东区、靖边—安塞区、隰县—离石区、甘泉—吉县区和汾渭区.根据极限状态边坡的4个野外判别标准,测量了8个区510个自然极限状态黄土边坡断面,分区采用指数模型回归边坡坡高与坡宽的相关关系,计算各区20、50、100m坡高的边坡稳定系数和失效概率.结果表明:黄土高原的边坡特征与破坏形式具有分区特征,且南北差异性明显.临洮—永靖区边坡坡高与坡宽呈线性关系,表明该区边坡坡度不随坡高变化,边坡稳定性受内摩擦角控制;兰州—会宁区和靖边—安塞区高坡陡,低坡缓,高坡不稳定,易发生错落式滑坡;天水—通渭区、甘泉—吉县区和汾渭区高坡缓,低坡陡,稳定性计算结果显示高坡和低坡都较为稳定,但由于地层结构和地貌的特点,高边坡易发生低速蠕变型滑坡或高速远程滑坡;陇东区边坡整体上较为稳定;隰县—离石区受黏粒含量较高的Q1地层控制,高边坡稳定性较差;50m左右坡高的黄土边坡稳定性对强度指标内聚力、内摩擦角的敏感度都高,易于失稳.  相似文献   

12.
In this paper,the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments,considering the wind speed,blown angle of wind and soil moisture content.The results showed that the modulus of soil wind erosion increases with an increase of wind speed.When the wind speed exceeds a critical value,the soil wind erosion suddenly increases.The critical speed for both kinds of soil is within the range of 7-8m·s-1.For a constant wind speed,the rate of soil wind erosion changes from increasing to falling at a critical soil slope.The critical slope of loam soil and sandy loam soil is 20° and 10°,respectively.Soil moisture content has a significant effect on wind erosion.Soil wind erosion of both soils decreases with an increase of the soil water content in two treatments,however,for treatment two,the increasing trends of wind erosion for two soils with the falling of soil water content are no significant,especially for the loam soil,and in the same soil water content,the wind erosion of two soils in treatment one is significantly higher than treatment two,this indicates reducing the disturbance of soil surface can evidently control the soil wind erosion.  相似文献   

13.
黄土高原丘坡信息DEM提取算法的应用   总被引：3，自引：0，他引：3  
选择代表黄土地貌类型(丘陵沟壑区、梁峁区、高原丘陵过渡区)的75个样区(每个样区约4km2),以1∶1万水平分辨率为5m的DEM为研究对象,研究不同算法对提取地面坡度精度的影响。采用6种不同算法分别提取坡度。运用方差分析,对比分析,排序分析等方法,通过比较不同算法所提取坡度矩阵的平均值、最大值、标准差,以及坡度中误差等指标,认为在黄土丘陵沟壑区3类地貌类型区域如果整体考虑坡度的以上指标时选用三阶反距离平方权差分算法较为合理。在黄土高原沟壑区与丘陵沟壑区交错过渡地带也可以选用算法4提取坡度。同时,根据水土保持工作实际生产部门需要,提出并实现了对坡度信息评价时须分级别进行的思路。研究认为,在黄土丘陵沟壑区域相同的地貌类型区,算法对所获得的相同的坡度级别面积影响是不同的,并且规律不相同。在前述三种地貌类型区域,如果需要获得坡度分级面积信息,使用三阶反距离平方权差分算法和三阶反距离权差分最为理想。由于简单差分算法小于其他算法提取坡度所涉及的区域单元大小,不适宜在本区域使用。  相似文献   

14.
The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation.  相似文献   

15.
Cracks in rock or soil slopes influence the stability and durability of the slopes. Seismic forces can trigger slope disasters, particularly in the cracked slopes. Considering the nonlinear characteristics of materials, the more generalized nonlinear failure criterion proposed by Baker is adopted. The influence of non-dimensional strength parameters on the stability of cracked slopes under earthquakes is performed using the upper bound limit analysis. The seismic displacement is calculated by adopting the logarithmic spiral failure surface according to the sliding rigid block model. Based on the existing studies, two methods for the stability analysis of cracked slopes under earthquakes are introduced: the pseudo-static method(with the factor of safety(Fs) as an evaluation index), and the displacement-based method(with the seismic displacement as an evaluation index). The pseudo-static method can only determine the instantaneous stability state of the cracked slope, yet the displacement-based methodreflects the stability variation of cracked slopes during earthquakes. The results indicate that the nondimensional strength parameters affect the factor of safety and seismic displacement of slopes significantly. The non-dimensional strength parameter(n) controlling the curvature of strength function shapes on the slope stability is affected by other parameters. Owing to cracks, the effect of non-dimensional strength parameters on seismic displacement becomes more significant.  相似文献   

16.
Submarine landslides occur frequently on most continental margins. They are effective mechanisms of sediment transfer but also a geological hazard to seafloor installations. In this paper, submarine slope stability is evaluated using a 2D limit equilibrium method. Considerations of slope, sediment, and triggering force on the factor of safety (FOS) were calculated in drained and undrained (Φ=0) cases. Results show that submarine slopes are stable when the slope is <16° under static conditions and without a weak interlayer. With a weak interlayer, slopes are stable at <18° in the drained case and at <9° in the undrained case. Earthquake loading can drastically reduce the shear strength of sediment with increased pore water pressure. The slope became unstable at >13° with earthquake peak ground acceleration (PGA) of 0.5 g; whereas with a weak layer, a PGA of 0.2 g could trigger instability at slopes >10°, and >3° for PGA of 0.5 g. The northern slope of the South China Sea is geomorphologically stable under static conditions. However, because of the possibility of high PGA at the eastern margin of the South China Sea, submarine slides are likely on the Taiwan Bank slope and eastern part of the Dongsha slope. Therefore, submarine slides recognized in seismic profiles on the Taiwan Bank slope would be triggered by an earthquake, the most important factor for triggering submarine slides on the northern slope of the South China Sea. Considering the distribution of PGA, we consider the northern slope of the South China Sea to be stable, excluding the Taiwan Bank slope, which is tectonically active.  相似文献   

17.
Assessing the slope deformation is significant for landslide prediction. Many researchers have studied the slope displacement based on field data from the inclinometer in combination with complicated numerical analysis. They found that there was a shear zone above the slip surface, and they usually focused on the distribution of velocity and displacement within the shear zone. In this paper, two simple methods are proposed to analyze the distribution of displacement and velocity along the whole profile of a slope from the slip surface to the slope surface during slow movement. In the empirical method, the slope soil above the shear zone is assumed as a rigid body. Dual or triple piecewise fitting functions are empirically proposed for the distribution of velocity along the profile of a slope. In the analytical method, the slope soil is not assumed as a rigid body but as a deformable material. Continuous functions of the velocity and displacement along the profile of a slope are directly obtained by solving the Newton's equation of motion associated with the Bingham model. Using the two proposed methods respectively, the displacement and velocity along the slope profiles of three slopes are determined. A reasonable agreement between the measured data and the calculated results of the two proposed methods has been reached. In comparison with the empirical method, the analytical method would be more beneficial for slope deformation analysis in slope engineering, because the parameters are material constants in the analytical solution independent of time t, and the nonlinear viscosity of the soil can be considered.  相似文献   

18.
山西乡宁—吉县地区黄土高边坡可靠度研究   总被引：1，自引：1，他引：0  
在山西乡宁—吉县地区实测了7个具有代表性的自然极限状态黄土高边坡断面,建立边坡地层结构模型;选取研究区合理的黄土物理力学参数,并分地层年代对10个典型工点的黄土强度参数内聚力和内摩擦角的变异性进行分析;选取6组典型的强度参数变异系数组合,基于Monte Carlo法进行可靠度模拟,评价该区边坡稳定性;采用自然类比法进行边坡设计.结果表明:边坡失效概率随坡高的变化趋势一致,均是中等坡高(49.8m)的边坡失效概率较大,低坡和高坡的失效概率较低;当变异系数较小时,边坡失效概率对坡高和坡度的变化敏感,而当变异系数较大时,边坡失效概率对坡高和坡度的变化不敏感;当坡型一定、强度参数变异系数较小时,边坡的稳定系数基本不变,而当参数变异系数超过某一界限时,稳定系数随变异系数的增大而增大,二者存在非线性相关关系;研究区黄土边坡处于基本稳定状态,但其失效概率最大达69.3%,平均21.1%,介于20%~30%的比例为33.3%,大于30%的比例为14.3%,可靠度指标介于-0.5~8.5,其中小于2.7的比例为88.1%;对于坡高约为50m的黄土高边坡,若取30%作为可接受失效概率,边坡坡度需降至45°以下,如果期望可接受失效概率在10%以内,则坡度不宜超过34°.  相似文献   

19.
The three-river source region(TRSR), located in the Qinghai-Tibet Plateau in China, suffers from serious freeze-thaw(FT) erosion in China. Considering the unique eco-environment and the driving factors of the FT process in the TRSR, we introduce the driving force factors of FT erosion(rainfall erosivity and wind field intensity during FT period) and precipitation during the FT period(indicating the phase-changed water content). The objective was to establish an improved evaluation method of FT erosion in the TRSR. The method has good applicability in the study region with an overall precision of 92%. The spatial and temporal changes of FT erosion from 2000 to 2015 are analyzed. Results show that FT erosion is widely distributed in the TRSR, with slight and mild erosion being the most widely distributed, followed by moderate erosion. Among the three sub-regions, the source region of the Yellow River has the slightest erosion intensity, whereas the erosion intensity of the source region of Yangtze River is the most severe. A slight improvement can be observed in the condition of FTerosion over the whole study region from 2000 to 2015. Vegetation coverage is the dominant factor affecting the intensity of FT erosion in the zones with sparse vegetation or bare land, whereas the climate factors play an important role in high vegetation coverage area. Slopes28° also have a significant effect on the intensity of FT erosion in the zones. The results can provide a scientific basis for the prevention and management of the soil FT erosion in the TRSR.  相似文献   

20.
崾岘是将要被切穿的鞍部,是正负地形矛盾斗争的结果,也是重要的地形控制点。典型的崾岘多位于黄土高原黄土地貌区,又称黄土崾岘,其对识别沟间地与沟谷的斗争程度有一定的指示作用。本文以黄土高原样区为例,基于1:1万DEM（5 m分辨率）和影像分辨率为0.95 m的遥感影像,利用流域边界算法和缓冲区标定,分析窗口选择5×5,实现了崾岘点位的半自动化提取。并对各崾岘点位求取坡度等地形因子,总结崾岘的空间格局和地形特征。结果显示,崾岘多分布在主流域边界和垂直于主沟道的最宽部分,地形控制作用明显。崾岘的坡度、起伏度、切割深度等值均大于鞍部值,同时,高级流域区的崾岘值大于低级流域区的崾岘值,反映出崾岘具有侵蚀程度强、表层完整性低、地表破碎度高的特点。总体而言,崾岘受沟道蚕食度高,从侧面反映了黄土地貌的发育阶段,是黄土地貌发育到中期的标志性产物。  相似文献   

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