Weathering of Pisha-Sandstones in the Wind-Water Erosion Crisscross Region on the Loess Plateau

Two types of pisha-sandstones of purple sandstones and gray sandstones,widely distributing in the wind-water erosion crisscross region of China,were selected and used in laboratory experiments for a better understanding of the drying-wetting-freezing weathering process resulting from the apportionment of water or salt solution to rock samples.Weathering experiments were carried out under the conditions of environment control(including temperature,moisture and salt solution).All rock samples were frequently subjected to 140 drying-wetting-freezing cycles.The influences of weathering process were evaluated.It was found that the different treatments of moisture and salt solution applications could affect the nature of the weathering products resulting from drying-wetting-freezing.It was also observed that salt solution could effectively alleviate the weathering of pisha-sandstones.Although not all the observations could be explained,it was apparent that simulated environmental factors had both direct and indirect effects on the weathering of rocks.

Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

Relationship Between Watershed Landscape Pattern Change and Runoff-Sediment in Wind-Water Erosion Crisscross Region

This paper selected the typical wind-water erosion crisscross region Xiliugou watershed for research to reveal the impact of the landscape pattern change of the underlying surface in wind-water erosion crisscross region where soil erosion is most serious on rainfall and runoff as well as erosion and sediment.Based on the Landsat TM image data and measured data of runoff-sediment in that watershed,the paper analyzed the characteristics of watershed landscape pattern change and runoff-sediment and explored the relationship between landscape index and runoff-sediment yield by means of GIS and Fragstats.The results were included as follows.(1)Grassland was the dominant landscape.In terms of the number of patches and area change rate,from 1985 to 2010,cultivated land,forest land and construction land were most stable,followed by unused land.Unused land,grassland and cultivated land experienced the most dramatic conversion and maximally affected by human activities.(2)The inter-annual difference between annual runoff and annual sediment load was significant.Compared with the annual sediment load,the trend of decreasing runoff was more obvious.The correlation coefficient of runoff-sediment was 0.67,representing a significant correlation.(3)There was a significant correlation between the landscape index and runoff-sediment.The runoff was negatively correlated with the largest patch index,patch cohesion index,aggregation index and contagion index,but positively correlated with landscape morphology index and landscape division index.And the sediment was negatively correlated with the contagion index,aggregation index and plaque cohesion index,but positively correlated with other landscape indexes.The results indicate that with the increase of the largest patch index,patch cohesion index and aggregation index,the rainfall infiltration capacity increase obviously and the soil erosion reduce significantly.Therefore,increasing the largest patch index,patch cohesion and aggregation index of the watershed landscape can enhance the function of water storage and soil conservation as well as ecological optimization in the windwater erosion crisscross region.The results can provide theoretical support for the ecological environment construction and comprehensive utilization of water and soil resources.

Effect of Alternation of Aging and Seawater Erosion on Properties of Rubber Material Used in Lead Rubber Bearing

An artificially accelerated alternation of aging and seawater erosion test of rubber materials used in lead rubber bearing(LRB)was performed,mainly to study the time-varying laws of rubber materials mechanical properties.Time-varying laws of the Mooney–Rivlin and Neo-Hookean constitutive parameters of rubber materials under the alternation of aging and seawater erosion were also analyzed.Results indicate that the rubber material mechanical properties were significantly affected by alternation of aging and seawater erosion.Hardness and elongation stress increased exponentially with test time.And 120 days after the test,the hardness increased by 14%,the maximum percentage increase in stress of 124.76%occurred at 100%constant elongation and the minimum percentage increase in stress of 68.32%occurred at 300%constant elongation;Tensile strength and elongation at break decreased by 44.96%and 53.09%.Besides,constitutive parameters of Mooney–Rivlin and Neo-Hookean all changed greatly with test duration.Finally,time-varying laws of constitutive parameters were verified by comparing the simulated and experimental results of the lead rubber bearing’s stiffness.Research results are of great significance to the seismic performance research and life-cycle performance analysis of offshore traffic engineering such as cross-sea bridges and bridges in the marine environment.

Soil erosion along a long slope in the gentle hilly areas of black soil region in Northeast China

Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on segments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and intensive precipitation, rill can be formed starting even at 15 m from the top of the slope.

Comparison of machine learning models for gully erosion susceptibility mapping

Gully erosion is a disruptive phenomenon which extensively affects the Iranian territory,especially in the Northern provinces.A number of studies have been recently undertaken to study this process and to predict it over space and ultimately,in a broader national effort,to limit its negative effects on local communities.We focused on the Bastam watershed where 9.3%of its surface is currently affected by gullying.Machine learning algorithms are currently under the magnifying glass across the geomorphological community for their high predictive ability.However,unlike the bivariate statistical models,their structure does not provide intuitive and quantifiable measures of environmental preconditioning factors.To cope with such weakness,we interpret preconditioning causes on the basis of a bivariate approach namely,Index of Entropy.And,we performed the susceptibility mapping procedure by testing three extensions of a decision tree model namely,Alternating Decision Tree(ADTree),Naive-Bayes tree(NBTree),and Logistic Model Tree(LMT).We dichotomized the gully information over space into gully presence/absence conditions,which we further explored in their calibration and validation stages.Being the presence/absence information and associated factors identical,the resulting differences are only due to the algorithmic structures of the three models we chose.Such differences are not significant in terms of performances;in fact,the three models produce outstanding predictive AUC measures(ADTree=0.922;NBTree=0.939;LMT=0.944).However,the associated mapping results depict very different patterns where only the LMT is associated with reasonable susceptibility patterns.This is a strong indication of what model combines best performance and mapping for any natural hazard-oriented application.

An experimental study on the influences of water erosion on wind erosion in arid and semi-arid regions

Complex erosion by wind and water causes serious harm in arid and semi-arid regions. The interaction mechanisms between water erosion and wind erosion is the key to further our understanding of the complex erosion. Therefore, in-depth understandings of the influences of water erosion on wind erosion is needed. This research used a wind tunnel and two rainfall simulators to investigate the influences of water erosion on succeeding wind erosion. The wind erosion measurements before and after water erosion were run on semi-fixed aeolian sandy soil configured with three slopes(5°, 10° and 15°), six wind speeds(0, 9, 11, 13, 15 and 20 m/s), and five rainfall intensities(0, 30, 45, 60 and 75 mm/h). Results showed that water erosion generally restrained the succeeding wind erosion. At a same slope, the restraining effects decreased as rainfall intensity increased, which decreased from 70.63% to 50.20% with rainfall intensity increased from 30 to 75 mm/h. Rills shaped by water erosion could weaken the restraining effects at wind speed exceeding 15 m/s mainly by cutting through the fine grain layer, exposing the sand layer prone to wind erosion to airflow. In addition, the restraining effects varied greatly among different soil types. The restraining effects of rainfall on the succeeding wind erosion depend on the formation of a coarsening layer with a crust and a compact fine grain layer after rainfall. The findings can deepen the understanding of the complex erosion and provide scientific basis for regional soil and water conservation in arid and semi-arid regions.

An experimental study on the influences of wind erosion on water erosion

In semi-arid regions, complex erosion resulted from a combination of wind and water actions has led to a massive soil loss and a comprehensive understanding of its mechanism is the first step toward prevention of the erosion. However, the mutual influences between wind erosion and water erosion have not been fully understood. This research used a wind tunnel and two rainfall simulators and simulated two rounds of alternations between wind erosion and water erosion（i.e., 1^（st） wind erosion–1^（st） water erosion and 2^（nd） wind erosion–2^（nd） water erosion） on three slopes（5°, 10°, and 15°） with six wind speeds（0, 9, 11, 13, 15, and 20 m/s） and five rainfall intensities（0, 30, 45, 60, and 75 mm/h）. The objective was to analyze the influences of wind erosion on succeeding water erosion. Results showed that the effects of wind erosion on water erosion were not the same in the two rounds of tests. In the 1^（st） round of tests, wind erosion first restrained and then intensified water erosion mostly because the blocking effect of wind-sculpted micro-topography on surface flow was weakened with the increase in slope. In the 2^（nd） round of tests, wind erosion intensified water erosion on beds with no rills at gentle slopes and low rainfall intensities or with large-size rills at steep slopes and high rainfall intensities. Wind erosion restrained water erosion on beds with small rills at moderate slopes and moderate rainfall intensities. The effects were mainly related to the fine grain layer, rills and slope of the original bed in the 2^（nd） round of tests. The findings can deepen our understanding of complex erosion resulted from a combination of wind and water actions and provide scientific references to regional soil and water conservation.

清水冲刷下顺直河道交错边滩演变过程试验研究

为进一步认识清水冲刷下顺直河道交错边滩的演变过程,基于长江中游典型边滩形态参数,采用概化水槽试验对不同流量条件下的交错边滩纵向、横向和平面冲淤变化进行了研究。结果表明:试验工况下,纵向上,沿程呈冲刷态势,流量越大,冲深越大(流量为215 L/s的深泓平均冲深约是流量为46.71 L/s的2.1倍),且大流量下深泓纵向比降变缓;横向上,边滩侧以冲刷为主,冲刷最大的位置在滩边附近,其它部位则呈冲刷—淤积—冲刷的变化规律(如流量为215 L/s时,2#断面边滩以外部分(0,2]h平均冲深约3.5 cm、(2,12]h平均淤高约0.5 cm、(12,21]h平均冲深约0.7 cm);平面上,边滩整体下移,变得细长,淤积主要发生在边滩下游1m范围内。此外,上游异岸边滩的存在初期会促使下游边滩淤积,而后加深下游边滩的冲刷,且对边滩坡脚影响最大。

The wind-water two-phase erosion and sediment-producing processes in the middle Yellow River basin, China

Based on data from the middle Yellow River basin, a wind-water two-phase mechanism for erosion and sediment-producing processes has been found. By using this mechanism, the extremely strong erosion and sediment yield in the study area can be better explained. The operation of wind and water forces is different in different seasons within a year. During winter and spring, strong wind blows large quantities of eolian sand to gullies and river channels, which are temporally stored there. During the next summer, rainstorms cause runoff that contains much fine loessic material and acts as a powerful force to carry the previously prepared coarse material. As a result, hyperconcentrated flows occur, resulting in high-intensity erosion and sediment yield.

Spatial distribution of surface rock fragment on hillslopes in a small catchment in wind-water erosion crisscross region of the Loess Plateau

The cover and size distributions of surface rock fragment in hillslopes were investigated by using digital photographing and treating technique in a small catchment in wind-water erosion crisscross region of the Loess Plateau. The results indicated that the maximal cover of rock fragment was pre-sented at mid-position in steep hillslope. Rock fragment presented a general decreasing-trend along the hillslope in gentle hillslope. Rock fragment cover was positively related to gradient, rock fragment size decreased generally along the hillslope, and the size reduced with the gradient. The mean size of rock fragment was at a range of 6―20 mm in the steep hillslope, rock fragment size > 50 mm was rarely presented. The covers of rock fragment at different positions were markedly related to the quantities of rock fragment < 40 mm. The area of rock fragment of 2―50 mm accounted for 60% or more of the total area, dominating the distribution of rock fragment in the hillslopes.

Alternate erosion and deposition in the Yangtze Estuary and the future change

The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied the erosion-deposition pattern of the entire Yangtze Estuary. An alternation between erosion and deposition was found during the past 65 years, which was in correspondence to the alternation between flood and dry periods identified by multi-year average duration days of high-level water flow (defined as discharge ≥ 60,000 m3/s, namely, D≥60,000) from the Yangtze River Basin. A quantitative relationship was further developed between the erosional/depositional rate of the Yangtze Estuary and the interpreting variables of yearly water discharge, D≥60,000 and yearly river sediment load, with contributing rates of 1%, 59% and 40%, respectively. Mechanism behind the alternate erosion and deposition pattern was analyzed by examining residual water surface slope and the corresponding capacity of sediment transport in flood and dry periods. In flood periods, a larger discharge results in steeper slope of residual water level which permits a greater capacity of sediment transport. Therefore, more bed materials can be washed to the sea, leading to erosion of the estuary. In contrast, flatter slope of residual water level occurs in dry periods, and deposition dominates the estuarine area due to the decreased capacity of sediment transport and the increased backwater effect of flood-tide. Coastal dynamics and estuarine engineering projects alter the local morphological changes, but slightly affect the total erosional/depositional rate of the whole estuarine region. Heavy sedimentation within the Yangtze Estuary after the impoundment of the Three Gorges Dam can be attributed to the reduced occurrence frequency of flood years due to water regulation by the dam, and largely (at least 36%-52%) sourced from the sea. Deposition is still possible to occur in the Yangtze Estuary in the future, because the multi-year average D≥60,000 is unlikely to exceed the critical value of 14 days/yr which corresponds to the future equilibrium state of the Yangtze Estuary, under the water regulation of the large cascade dams in the upper Yangtze. Nevertheless, the mean depositional rate will not surpass the peak value of the past years, since the total sediment load entering the Yangtze Estuary has presented a decreasing trend.

盐冻交替作用下混凝土强度与细观孔结构关系

为了探究硫酸盐溶液侵蚀和冻融循环(盐冻)交替作用下混凝土宏观强度与细观孔隙结构参数的定量关系,本文开展了盐冻交替试验、力学性能测试和孔隙结构分析等。首先,设计了不同质量分数硫酸盐和冻融循环次数的交替试验;其次,研究了盐冻作用下混凝土抗压强度、抗拉强度、灰度直方图、孔径分布、孔隙率和分形维数演变规律;最后,建立了混凝土孔隙率和孔隙分形维数与强度的定量关系。研究结果表明:在盐冻作用下,混凝土宏观强度与细观孔结构演化规律密切相关,混凝土抗压强度和劈裂抗拉强度随着盐冻交替循环次数增加而逐渐减小。相较于质量分数为3%和6%的硫酸盐溶液,9%硫酸盐溶液冻融作用对混凝土侵蚀劣化更严重,盐冻循环8次时,抗压和劈裂抗拉强度分别减小45.5%和47.5%;随着盐冻循环次数增加,混凝土CT图像灰度和孔隙分形维数逐渐降低,孔隙率逐渐增大,盐冻循环8次时,灰度均值和孔隙分形维数相比初始状态分别降低了13.82%和6.06%,孔隙率增长到7.3%。盐冻交替作用下混凝土细观孔结构与宏观强度的演化模型关联性较好,R2均大于0.887。

砒砂岩区典型小流域复合侵蚀动力特征分析

以鄂尔多斯高原砒砂岩区水力、风力、冻融交错侵蚀作用为研究对象,选择准格尔旗二老虎沟小流域作为研究流域,对侵蚀环境参数进行定位观测,统计分析水力、风力、冻融作用的年内变化过程。采用数据标准化后的层次分析法,揭示水力-风力-冻融交错作用过程,辨识高侵蚀风险发生的时阈及动力交错模式。研究表明:砒砂岩区复合侵蚀作用可分为风冻交错、风水交错和风水冻交错三个典型动力组合模式,风水交错侵蚀是该地区的主要侵蚀模式;砒砂岩区年内存在三个高侵蚀风险期,即风-冻融交错侵蚀期(2月上旬至3月中下旬),风-水交错侵蚀期(6月中上旬至8月中下旬),水-风-冻融交错侵蚀期(10月中旬至11月中下旬)。

干湿交替下干热河谷冲沟不同土层的抗侵蚀性研究

为研究"旱季高温干燥、雨季降水集中且多暴雨"的干湿交替作用对冲沟形成过程的影响,选择干热河谷区典型发育的土层剖面(由上至下依次为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅵ层),采用干湿交替原位试验,选取土体抗剪强度、抗冲系数以及崩解性指标,分析不同土层抗侵蚀的特性及差异。研究结果表明:各土层抗剪强度差异明显,其中Ⅳ层和Ⅴ层抗剪强度较大;内摩擦角随干湿交替次数增多呈波动不定趋势而粘聚力则呈显著负相关关系;各土层抗冲性差异明显,其中Ⅲ层和Ⅵ层抗冲性较小;抗冲性随干湿交替次数增多而增大、剥蚀率则随干湿交替次数增多呈波动减小趋势;各土层平均崩解速度与干湿交替次数呈显著线性相关,Ⅲ层和Ⅵ层较大、Ⅳ层和Ⅴ层较小、Ⅰ层和Ⅱ层介于二者之间。各土层具有"软硬岩层相间"的发育特征,其抗蚀性在垂直方向大致呈现"减小—增大—减小"的趋势,该研究从土壤侵蚀的角度在一定程度上揭示了冲沟发展过程。

三峡水库蓄水初期关洲分汊河段的冲淤调整特性分析

关洲分汊河段位于长江中游,其水流动力轴线年内随流量的变化在两汊间交替,为典型的年内交替型分汊河段。本文依据实测资料,分析了三峡工程蓄水运用初期关洲河段的冲淤调整情况,并着重对比分析了左右两汊冲淤调整进程的差异。研究发现,蓄水后关洲河段年际间有冲有淤,但以冲刷为主;冲淤主要表现为深泓下切及枯水河槽的冲淤调整;左右两汊冲刷进程不同,左汊为洪水期主汊,河床冲刷幅度较大,深泓平均高程连年递减,过水面积呈增大趋势,而右汊为枯水期主汊,其河床冲刷发展则相对缓慢,深泓高程变化较小。

气体钻井中钻柱力学性能及冲蚀实验研究

由于在破岩过程中受到冲击,气体钻井中的钻柱产生了交变应力,而钻柱旋转加剧了交变应力的变化,同时气体携带岩屑对钻柱产生冲蚀,加速了钻柱的失效。钻柱主要失效形式为疲劳断裂,这跟钻柱所受应力大小及变化密不可分,因此,开展气体钻井过程中钻柱力学性能和冲蚀研究,掌握钻柱应力变化规律及岩屑对钻柱的冲蚀规律,是减小和防止钻柱失效的基础工作,对增加气体钻井过程中的安全性和降低钻井成本有十分重要的意义。通过使用一种已开发出的可同时模拟气体钻井钻具振动和冲蚀的装置,进行了不同钻具组合情况下,气体钻井钻柱同时受振动和冲蚀实验。实验结果表明,气体钻井过程中,配置扶正器将使钻柱所受交变应力值变化范围降低40%以上,扶正器和减振器的配合使用将使交变应力值变化范围下降50%,因此,扶正器和减振器的配合使用,将大幅降低钻柱所受交变应力,并延长交变应力作用周期,从而降低钻柱失效的概率。

神府—东胜矿区风蚀水蚀交互作用研究

风蚀水蚀交互作用是风蚀水蚀交错带土壤侵蚀的主要过程。以神府—东胜矿区为研究范围，讨论了风蚀水蚀交互作用的时间分布规律和全矿区、小流域及坡面３种空间尺度的空间分布规律，并讨论了风蚀水蚀交互作用与坡面侵蚀和沟谷侵蚀的发育。

Cr-Ti-N系多层膜成分及周期对抗冲蚀性能的影响

苛刻环境下发动机组件存在严重的固体颗粒(SPE)冲蚀,导致其可靠性降低。为研究多层膜成分及调制周期对膜层冲蚀性能的影响,利用金属蒸发真空弧离子源(MEVVA)和磁过滤阴极真空弧复合离子束沉积技术在AM355基材表面制备交替周期分别为5、13和26的3组CrNx/TimCr1-mN、TiNy/TimCr1-mN多层膜。采用微粒喷浆冲蚀试验机、场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)等对膜层冲蚀性能、形貌及物相结构进行测试表征。结果表明:采用该技术制备的CrNx/TimCr1-mN、TiNy/TimCr1-mN多层膜结构致密、交替层变化明显。随着交替周期的增加,两体系多层膜的晶面间距减小,抗冲蚀性能得到提高,分别提高了8倍和20倍以上。

日常公共空间——公共空间的终结与重生

根据美国学者迈克尔·索金提出的"公共空间的终结"这一问题,从公共空间的历史及现存状况进行分析,认为由于政治的隔绝与全球化资本侵蚀,致使(经规划设计的正规性)公共空间不断衰落甚至面临着终结。但与此相对的是在日常生活中,人们根据个人需求不断建构的属于自己的公共空间——日常公共空间,而且这种日常公共空间已经成为都市公共空间的一个重要补充,并重新让公共空间焕发了生机。