Characteristics of Soil Respiration of Terraces and Slope Farmland in Loess Hilly and Gully Regions

Soil CO_2 emissions of terraces and slope farmland in loess hilly and gully regions were measured by using Infra Red Gas Analysis(IRGA),and the diurnal variation characteristics of soil respiration rate in different slope positions of terraces and slope farmland were analyzed.The results show that the diurnal variation curves of soil respiration rate of terraces and slope farmland in loess hilly and gully regions had a single peak.The soil respiration rate of terraces reached the peak during 13:00-15:00,while the soil respiration rate of slope farmland reached the peak from 11:00 to13:00,and it was the lowest at next 07:00.The daily average of soil respiration rate in slope farmland was 0.86μmol/(m^2·s),accounting for 93.48% of that of terraces.The daily average of soil respiration rate in different slope positions of terraces and slope farmland is shown as follows:the bottom of the slope>the middle of the slope>the top of the slope.At the top of the slope,the daily averages of soil respiration rate in terraces and slope farmland were the same;at the middle and bottom of the slope,the daily average of soil respiration rate in terraces was larger than that of slope farmland.

Slope-gully erosion relationship in small catchments of the middle reaches of the Yellow River

The slope-gully erosion relationship in small catchments of the middle reaches of the Yellow River has long been a topic concerned by relevant departments in China Slope-gully relationship in typical small catchment is determined determined on the concept of net increase of sediment yield by using analytical method of sediment formation at different positions in the catchment The result shows that sediments in a small catchment in the middle reaches of the Yellow River mainly come from slopes. ms paper indicated that the sediment sources from slopes are roughly 55, 60, 78 and 85 % of the total sediment yield of a small catchment in Yangdaogou. Wangjiagou. Jiuyuangou and Nanxiaohegou, respectively, due to impacts of varying degress from slope runoff.

Interactions between water-land resources and oasis urban development at the northern slopes of the Tianshan Mountains,Xinjiang,China

Urban development in arid and semi-arid regions is largely constrained by fragile physical environ- ments. The characteristics of an urban settlement are different from those in other regions of China. This paper analyses the coupling characteristics and spatio-temporal variations for oasis urban development and water-land resources at the northern slopes of the Tianshan Mountains by principal component analysis and a coupling degree model. The result shows that the degree and change in regional use of water and land resources are different among the studied cities/counties during their development. The built-up areas of these cities/counties have changed little with increasing populations and urbanization levels, which well reflects that the urban development in arid and semi-arid regions is limited by oasis areas. Per capita amount of water supplied, however, presented a trend of slowed growth with increasing levels of urbanization. Water consumption gradually increased with urban development and the improvement of people＇s living standards, accompanied by enhanced water use efficiency. The level of urbanization can be assessed through the coupling degree between oasis urban development and the use of water and land resources. A high coupling degree represents a high level of comprehensive urban devel- opment and use of water-land resources. Alternatively, a low coupling degree denotes a low level of urban devel- opment and water-land resource use.

Application of fuzzy optimal selection of similar slopes to the evaluation of slope stability

The numerical calculation method is widely used in the evaluation of slope stability,but it cannot take the randomness and fuzziness into account that exist in rock and soil engineering objectively.The fuzzy optimization theory is thus introduced to the evaluation of slope stability by this paper and a method of fuzzy optimal selection of similar slopes is put forward to analyze slope stability.By comparing the relative membership degrees that the evaluated object sample of slope is similar to the source samples of which the stabilities are detected clearly,the source sample with the maximal relative membership degree will be chosen as the best similar one to the object sample,and the stability of the object sample can be evaluated by that of the best similar source sample.In the process many uncertain influential factors are considered and characteristics and knowledge of the source samples are obtained.The practical calculation indicates that it can achieve good results to evaluate slope stability by using this method.

Underground pressure characteristics analysis in back-gully mining of shallow coal seam under a bedrock gully slope

We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.

Integration of aspect and slope in snowmelt runoff modeling in a mountain watershed

This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.

Research on Effect of Heap Loading on Deformation and Mechanical Properties of Bridge Double Pile Foundation on Steep Slope

In order to analyze the deformation and stress characteristics of the pile foundation on the slope, this paper uses the finite element software Abaqus for numerical simulation. The displacement and stress data of pile under different working conditions (the combination of heap load and vertical load and horizontal load and inclined load) were collected;the distribution of pile displacement, axial force and bending moment were analyzed. Simulation results show that: slope top loading has little effect on vertical displacement; when the heap load exceeds 200 kPa, the horizontal displacement is greatly affected. Pile axial force decreases with pile burial depth;pile lateral resistance plays a more adequate role in the rock and soil layer. The bending moment of double pile foundation is positive at the top and negative at the bottom. Applied oblique load has obvious p-Δ effect.

Morphological characteristics and evolution model of slope units along loess gully cross section

Gully morphology is an important part of loess landform research.Along with gully development,the variation of its cross section is the most significant,and it can intuitively reflect the characteristics of the lateral widening of the gully slope.Therefore,in-depth research of the variation of the cross-sectional morphology of the gully is helpful to understanding the development process of the loess gully.Based on the DEMs(Digital Elevation Model)of nine periods of an indoor simulated loess small watershed,this paper studies the evolution model of a complete branch ditch in the watershed using the digital terrain analysis theory and method.Results show that with the development of the gully,the average gradient of the gully slope continuously decreases,and the slope morphology is mostly a concave slope along the slope direction.The degree of downward concave first increases and then gradually tends to be gentle.The gully erosion mode is gradually transformed from downward cutting erosion to lateral erosion.The more mature the gully development,the lower the depth of gully bottom cutting is compared with the width of gully widening.Furthermore,the surface cutting depth tends to be stable and the slope is stable.Then,the transformation law of the slope morphology of the gully cross section with the development of the gully is studied,and the prediction model of the transformation of the slope morphology of the gully cross section is established by using the Markov chain.The Markov model can better reflect the dynamic change of the slope morphology of the gully cross section,which is of great significance to revealing the external performance and internal mechanism of the gully morphology.

Effects of gully terrain on stress field distribution and ground pressure behavior in shallow seam mining

This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain.This approach combines numerical simulations and field tests based on the conditions of gully terrain in the Chuancao Gedan Mine.The effects of gully terrain on the in situ stress field of coal beds can be identified by the ratio of self-weight stress to vertical stress(η) at the location corresponding to the maximum vertical stress.Based on the function η =j(h),the effect of gully terrain on the stress field of overlying strata of the entire field can be characterized as a significantly affected area,moderately affected area,or non-affected area.Working face 6106 in the Chuancao Gedan Mine had a coal bed Jepth <80 m and was located in what was identified as a significantly affected area.Hence,mining may cause sliding of the gully slope and increased loading(including significant dynamic loading) on the roof strata.Field tests suggest that significant dynamic pressures were observed at the body and foot of the gully slope,and that dynamic loadings were observed upslope of the working face expansion,provided that the expanding direction of the working face is parallel to the gully.

Evaluation on Terrain-Climate Superiority Degree at County Level in Yunnan Province

Terrain slope and climate zone(heat zone)are important factors affecting land use zoning and agricultural production layout in mountainous areas.Using"weight grade method",a quantitative index of comprehensively evaluating terrain slope and climatic(thermal)conditions in mountainous areas was proposed:terrain-climate superiority degree(TCSD),and TCSD,terrain superiority degree(TSD),and climate superiority degree(CSD)in 129 counties(cities and districts)of Yunnan Province were measured and analyzed.The results showed that TCSD in 50.39%of counties of Yunnan Province was relatively better(levels I and II),and TCSD in 38.76%of counties was moderate(level III),while TCSD in 10.85%of counties was relatively poorer(levels IV and V).

融合灰关联分析和信任度的Slope One算法研究

作为一种有效的协同过滤算法,Slope One算法被广泛地应用到一些推荐系统中.但该算法在评分预测时仅根据项目之间的评分偏差以及用户的历史评分信息,未能考虑用户之间的潜在联系,而且数据稀疏性和冷启动问题也会限制算法的推荐性能.因此,为了提高算法的推荐质量,本文采用均衡接近度灰关联方法度量用户关联度,从而有效挖掘用户之间的潜在联系;并引入用户信任模型来缓解冷启动问题对算法的影响,将均衡接近度和信任度作为权重因子加权到评分预测过程.论文研究并提出了一种融合灰关联分析和信任度的Slope One算法,并通过实验验证了算法的有效性.实验结果表明,该算法可以有效地提高算法预测准确度,缓解数据稀疏性和冷启动问题对算法的影响.

Eco-environment Restoration and Regional Differentiation Characteristics Based on “Building Terrace and Returning Slope Farmland to Forests and Grass”

Based on the scientific and technological achievements in the past decade in the Loess Hilly-gully Region and the successful demonstration experience in Yan'an Yangou watershed, we summarize the characteristics of eco-environment restoration pattern based on "building terrace and returning slope farmland to forests and grass". According to the data on land use, slope farmland and the agricultural population in 1999, we calculate the area of new terrace that needs to be built, the area of garden plot that needs to be extended, vegetation restoration area and investment demand in counties (cities, districts). Establishing and using some indicators, such as basic farmland extension indicator, garden plot extension indicator, vegetation restoration index and investment demand density, we conduct type classification and analysis of regional differentiation characteristics in 55 counties (cities, districts). The results show that in the Loess Hilly-gully Region, 691 600 hm2 of new terrace needs to be built, 792 000 hm2 of economic forests and orchards need to be extended, 5 410 200 hm2 of vegetation needs to be restored, and the total investment demand is 15.82 billion yuan; in terms of geographical distribution, obviously there are two key areas for eco-environment restoration (one is located in the border area between northern Shaanxi and northwestern Shanxi, and the other is located in the eastern Gansu and southern Ningxia area); the classified regional guidance policies should be formulated as soon as possible, and the limited funds should be concentrated in the key areas.

稳定分析中滑动面构造方法分析

滑动面的构造方法是边坡稳定分析的关键课题之一。任意滑动面的构造比较复杂,基于Logistic函数积分等基函数构造的曲线可以代替传统的折线形滑动面,改善滑动面的光滑性,也有利于减少其自由度。对基于基函数的滑动面构造方法进行梳理,将其划分为基于连续函数叠加的构造方法和基于积分运算的构造方法。重点对Logistic函数及其积分的性质进行分析,得到了不同参数对曲线形态的影响规律,从而缩小了相关参数的取值范围,为减小滑动面自由度提供了依据。在此基础上也给出了一种确定给定滑动面参数初值的方法。针对两个边坡算例的计算表明,所提出的方法能够满足边坡稳定分析的要求。

基于变权理论的露天矿边坡稳定性GRA-TOPSIS评价模型研究

为使露天矿边坡稳定性评估更加科学合理,进一步提高评估结果可靠性,迫切需对现有评价模型进行优化和改进。基于变权理论、灰色关联理论(GRA)和逼近理想解法(TOPSIS),提出了露天矿边坡稳定性改进GRA-TOPSIS评价模型。从地质、环境、工程等3个方面,选取了12个典型影响因素,构建了露天矿岩质边坡稳定性综合评价指标体系;运用变权理论确定指标权重,通过计算灰色关联贴近度,实现露天矿岩质边坡稳定性综合评价。以3座矿山(K1-K3)为例,验证评价模型的适用性。结果显示:3座露天矿边坡稳定性排序为K3>K2>K1,稳定性等级分别为Ⅲ级、Ⅱ级和Ⅱ级,与边坡实际相符;通过对比改进GRA-TOPSIS模型与单独使用GRA、TOPSIS模型以及其他模型的评价结果,验证了改进GRA-TOPSIS综合评价模型在露天矿边坡稳定性评估方面的准确性和优越性,体现了研究价值,可为露天矿边坡稳定性评估提供新思路。

不同初始饱和度条件下高液限滑带土环剪试验

针对某高速公路沿线边坡滑带土,开展了一系列环剪试验研究含水率对其残余强度的影响。制作1.20 g·cm^(-3)和1.35 g·cm^(-3)两种干密度条件下初始饱和度为25%、45%、65%、85%和100%的滑带土试样,在100 kPa、200 kPa和400 kPa正应力条件下开展试验,获得了滑带土剪应力与剪切角关系曲线。根据曲线得到残余剪切强度,得出滑带土的残余强度参数。结果表明,当正应力为100 kPa时,初始饱和度对滑带土残余强度影响不明显,当正应力为200 kPa和400 kPa时,初始饱和度增大将使残余强度降低。当干密度为1.35 g·cm^(-3)时,残余黏聚力随初始饱和度增加而增加,而当干密度为1.20 g·cm^(-3)时则表现出先增后减的规律。对于两种干密度的滑带土,残余摩擦角均随初始饱和度增加而减小。低干密度条件下残余强度参数随初始饱和度的变化更敏感。

伊犁河谷不同雨型下自然与人工植被的水土流失特征

【目的】为科学防控西北干旱区草地水土流失以及比较不同雨型下植被的径流调控效果。【方法】2021—2022年雨季在伊宁市铁厂沟水土保持径流场,采用K均值方法将研究区13场侵蚀性降雨划分为3类,并监测5种自然植被(霸王、驼绒藜、伊犁绢蒿、骆驼刺、苦豆子)和3种人工植被(榆树、紫穗槐、狗牙根)的产流产沙特征,探讨不同雨型下各植被的产流产沙规律,采用灰色关联度分析雨型和植被小区对产流产沙的影响。【结果】①伊犁河谷土壤侵蚀的主导雨型是B雨型(中雨量、短历时、中雨强),对坡面产流产沙的贡献程度达到53.5%。A雨型(低雨量、长历时、低雨强)和C雨型(高雨量、长历时、高雨强)贡献率较低;②自然植被的减流减沙效益高于人工植被,自然植被在A雨型下减流减沙效益最好(87.3%~95.2%),人工植被在C雨型下减流减沙效益最差(39.2%~52.7%);③降雨量和平均雨强显著影响径流深和土壤流失量(P<0.05),灰色关联度从大到小排序为伊犁绢蒿>苦豆子>霸王>紫穗槐>骆驼刺>狗牙根>榆树>驼绒藜。【结论】伊犁河谷进行植被恢复可有效减少水土流失,不同雨型下自然植被的减流减沙效益优于人工植被,单一植被的减流减沙效益与其覆盖度有关。研究结果可为西北干旱区国土绿化、土地荒漠化和水土流失防治提供理论基础。

黄土丘陵沟壑区坡沟系统产流产沙对源-汇-路径格局的响应

坡沟系统是流域水土流失与治理的基本单元,掌握其产流产沙规律是有效解决水土流失区生态环境恢复重建的核心问题之一。该研究利用无人机遥感与地理信息系统技术对流域的土地利用进行识别,再确定5个不同坡沟系统(2个无人为干扰的退耕植被恢复+自然植被坡沟系统SG1和SG2、2个人为扰动的退耕植被恢复+自然植被坡沟系统SG3和SG4、1个果园+坡耕地的坡沟系统SG5)内泥沙源、汇及其输移路径分布特征,并在量化指标的基础上,结合2016—2022年坊塌小流域5个坡沟系统的降雨和产流产沙的监测数据,研究了不同坡沟系统的产流产沙特征及其对源-汇-路径格局的响应。结果表明:次降雨条件下,SG1和SG2的产沙模数显著低于其他坡沟系统(P<0.05),且SG3径流深和产沙模数均较大;SG2的年平均径流深显著低于SG5(P<0.05)。坡沟系统径流深分别与总坡沟系统、沟间地、沟谷地的泥沙源和汇最大斑块面积比显著正相关(P<0.05),且与沟间地泥沙源、汇指数的相关系数均要大于沟谷地,径流深与总坡沟系统路径的分岔比、沟间地与沟谷地的路径比降均呈现出显著负相关(P<0.05);产沙模数与各源汇指数之间均无显著的相关性,但与路径数量密度、长度密度、沟间地的路径分岔比呈显著正相关(P<0.05);径流深和产沙模数均与路径复杂度呈显著负相关(P<0.05)。可见,降低源/汇比例大小,适当增加泥沙输移路径的复杂度和输移距离,可有效减少坡沟系统的水土流失。研究可为坡沟系统土壤侵蚀防控以及流域生态保护和修复提供科学支撑。

降雨、汇流和坡度对黑土浅沟坡面侵蚀影响的试验研究

[目的]为研究降雨、汇流和坡度对浅沟侵蚀的影响,实施精确的水土保持措施。[方法]通过室内模拟降雨和汇流试验,设计2个降雨强度(50,100 mm/h)和2个坡度(3°,7°),并在4种降雨强度和坡度组合下设置5个依次增加的汇流强度(15,30,45,60,75 L/min),分析降雨、汇流和坡度及其交互作用对浅沟坡面侵蚀的影响,明确浅沟侵蚀对坡面侵蚀的贡献。[结果](1)坡度和汇流强度对浅沟坡面侵蚀的影响均大于降雨强度。当降雨强度由50 mm/h增加到100 mm/h时,3°和7°对应的坡面侵蚀量分别增加52.3%~81.8%和29.4%~88.4%;而当坡度从3°增大到7°,50,100 mm/h降雨强度对应的坡面侵蚀量分别增加114.3%~395.5%和130.0%~320.9%;当汇流强度由15 L/min增加至75 L/min,坡面侵蚀量增加4.6~13.5倍。同时,汇流强度的增加加剧坡度对坡面侵蚀的作用,而减弱降雨强度对坡面侵蚀的影响。(2)降雨、汇流、坡度双因子和三因子交互作用对浅沟坡面侵蚀的影响以汇流强度-坡度交互作用和降雨强度-汇流强度-坡度三者的交互作用的影响最大,其次为降雨强度-汇流强度交互作用,而以降雨强度-坡度的交互作用的影响最小。(3)不同试验条件下,浅沟侵蚀量占坡面侵蚀量的比例平均在85%以上,且其比例随汇流强度和坡度的增加呈增大趋势。(4)坡面侵蚀速率与水流流速、径流剪切力和水流功率之间均表现为极显著正相关,与阻力系数之间呈显著负相关;且坡面侵蚀速率与水流功率相关关系最优。[结论]研究结果为基于侵蚀动力因子和地形因子及其交互作用的浅沟侵蚀预测模型开发、浅沟侵蚀贡献分离和浅沟侵蚀机理研究提供了科学依据。

冷竹关沟高陡斜坡地震动响应特征

四川省泸定县冷竹关沟两岸属于高陡斜坡,距2022年5月20日汉源M_(S)4.8地震震中52 km。基于冷竹关沟监测剖面上安置的4台强震仪对汉源M_(S)4.8地震的监测数据,分析了高陡斜坡上的地震波响应规律,并与前人研究成果对比,结果显示:(1)斜坡对此次地震的地震波放大效应在水平南北向最为显著,右岸半岛状山梁处的放大作用强于左岸浑厚山体,且随着高程的增加场地的放大作用逐渐增大;(2)斜坡右岸的地震动卓越频率为2—6 Hz,左岸主要分布在7—13 Hz,冷竹关沟高陡斜坡的地震动卓越频率在半岛状山梁部位以特低频为主,在浑厚山体斜坡以中低频为主,在未来可能发生的地震中,斜坡更容易与卓越频率在此范围内的地震动记录发生共振作用,以致坡体地震动响应强烈;(3)冷竹关沟高陡斜坡存在地震波背坡效应,同时该处斜坡对地震波的放大效应还受到微地形的控制,地震波在右岸坡顶凸起地形处能量最为强烈,右岸斜坡坡顶在地震波经过时更容易发生崩塌等次生灾害。

生态建设对黄土高原丘陵沟壑区流域坡沟系统植被覆盖和侵蚀的影响

生态建设显著改变了黄土高原的下垫面状况和水动力格局,深刻影响了坡沟系统的侵蚀和泥沙来源。以黄土高原丘陵沟壑区高西沟流域为研究对象,基于Landsat TM和Landsat OLI影像,利用遥感解译和地理信息系统方法,分析了高西沟流域沟间地、沟谷地的NDVI和土地利用时空变化特征,并在此基础上研究了流域沟间地和沟谷地土壤侵蚀量的变化。结果表明:2000—2018年沟间地和沟谷地NDVI均有所增加,低等级NDVI(<0.2)面积减少,较低等级NDVI(0.2~0.4)和中等级NDVI(0.4~0.6)面积增加;沟间地和沟谷地林草地面积均有所增加,流域土地利用结构变化主要为耕地向林草地转化;沟间地平均植被覆盖度由57%增加至71%,沟谷地平均植被覆盖度由60%增加至71%;流域土壤侵蚀面积由3.81 km^(2)下降到1.77 km^(2),减少了38%,年土壤侵蚀量由3.64×10^(4)t下降至1.39×10^(4)t,降低了62%;沟间地年土壤侵蚀量减少了68%,沟谷地年土壤侵蚀量减少了47%。