董志塬沟头溯源侵蚀过程及崩塌中孔隙水压力变化

为研究董志塬沟头溯源侵蚀过程及孔隙水压力变化规律,采用模拟降雨+放水冲刷的方法,研究集水区坡度(1°、3°、5°、7°)和放水流量(3.0、3.6、4.8、6.0、7.2m3/h)对董志塬沟头溯源侵蚀过程和孔隙水压力特征值的影响。结果表明:1)崩塌发生频率由试验初期0～30 min时的6.29%增加到150～180 min时的27.48%。2)放水流量为3.0～7.2 m3/h时,产沙率随试验时间呈对数函数减小。产沙量随坡度和放水流量的增加而加大,建立了产沙量与二者间的多元线性回归方程。3)坡度为1°～7°时,崩塌会增加22.75%～324.59%的产沙率,产沙率突变点出现时间相较于崩塌而言存在"滞后"现象。4)孔隙水压力随试验时间呈显著线性或对数函数关系,孔隙水压力的上升是影响溯源侵蚀崩塌发生的关键因素。研究结果可为黄土高塬沟壑区生态治理提供参考。     

近40年来冷龙岭地区冰川退缩和气候变化的关系

运用比值阈值法(TM3/TM5)结合目视解译,从1973年、1999年和2010年3个时段的MSS、ETM、TM影像中提取了祁连山东段冷龙岭地区冰川的边界,并对距其较近的门源、乌鞘岭、武威和永昌4个气象站点1961—2010年的气象数据以及冰川区的气象数据进行了分析,结果表明:(1)37a来,冰川处在持续退缩状态;近10a来,冰川消融速度加快;南坡退缩较快,北坡退缩较慢,其它坡向介于二者之间;(2)该区增温趋势较明显;该区的降水虽有少量增加,但趋势却很不明显;(3)37a来,冰川退缩的主要原因是气温的升高;近10a来,冰川加速消融反映了20世纪90年代末以来的气温变化特征;南坡冰川对气候变化的反应较敏感。     

陕西省宜君县退耕还林工程后续产业发展现状与对策

退耕还林工程后续产业的实施,提高农业产业率,调整农业产业结构,增加农民收入,促进农民生活水平的提高。     

现代黄河口海岸侵蚀动力灾害预测探讨

自1976年黄河人工改道走清水沟流路以来，现代黄河口总体处于淤进状态。由于海洋动力的侵蚀作用，使得现代黄河口也产生了海岸侵蚀动力灾害，造成了水土流失。经过对河口地区1986-2004年间遥感图像进行比较分析，有关海岸位置的原始数据间存在有近似的二元一次线性相关关系，通过建立回归模型，对2005-2010年河口地区海岸侵蚀动力灾害进行了预测探讨，供有关部门参考。     

基于面向对象分类的马兰冰帽变化与气候响应

以Landsat遥感影像和数字高程数据为基础数据,利用面向对象分类方法提取了马兰冰帽1990、2000、2015年3期冰川边界,并分析了冰帽变化情况。结果表明:马兰冰帽在近25 a来一直处于退缩状态。由1990年的195.87 km~2减少到2015年的188.60 km~2,退缩了7.27 km~2,占1990年冰帽面积的3.71%,退缩速率为0.15%·a~(-1);不同时段内冰帽变化速率具有差异性,1990—2000、2000—2015年2个时段内冰帽退缩速率分别为0.16%·a~(-1)、0.14%·a~(-1),冰帽退缩速率处于减慢状态;不同朝向的冰川发育特点和变化差异显著,南坡冰川退缩速率较北坡慢。25 a来,研究区域内夏季平均气温升高了2.21℃,升温显著,增温率为0.67℃·(10a)~(-1),年降水量增加了53.52 mm,线性增加率为16.22 mm·(10a)~(-1),增加速度缓慢。由此推断,夏季气温显著升高是引起马兰冰帽持续退缩的主要原因。同时,研究发现地形条件对冰川规模变化也产生重要影响。     

贵州省威宁县退耕还林工程实施成效及存在问题分析

进一步加快退耕还林步伐,不仅对改善生态环境,建设"两江"生态屏障起着重要作用,而且对优化威宁县土地资源配置,调整农村产业结构,促进经济社会全面发展都具有十分重要的现实意义。     

Color Lapse by Halo Retreat for Night Landscape Lighting

This paper focused on making use of color change to incarnate hierarchy of floodlighting of the building facade in landscape lighting. Color lapse by halo retreat is a good method to reach this goal. The projection light source was chosen on the principle of building exterior color coordination. According to the computing method for chroma coordinates of object color, the magnitude of three stimulus values after reflection by external wall surface and the chroma coordinates were calculated. The purpose of this paper is to take account of the influence of difference between projecting light and reflecting light on external wall surface. At the same time, an approximating computing method is recommended, that is, first figure out the chroma coordinates of two points--the top and bottom points in vertical line of the building and then readjust the location of casting light lamp and lighting fitting or renewal the light source. Then let the chroma coordinate of ever point on the vertical line settle in or be near the line connecting the two points of chroma coordinates on CIE 1931 Chroma chart. It would yield good results due to the color lapse by halo retreat.     

Rainfall simulation to identify the storm-scale mechanisms of gully bank retreat

Gully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil material by splash and by water running along gully banks (runoff), during rainfall events. The study was conducted in the sloping lands of the KwaZulu-Natal province, a region that is highly affected by gully erosion. Artificial rain was applied at 60 mm h⁻¹ for 45 min at the vertical wall of a gully bank typical to the area. The splash material was collected by using a network of 0.045 m² buckets. The sediments in the running water were assessed by sampling the runoff collected from a microplot inserted within the base of the bank, and collecting the fallen aggregates after the rainfall simulation was complete. Results indicated that the overall erosion for the simulation was 721 g m⁻² h⁻¹. Runoff erosion proved to be the dominant mechanism and amounted to 450 g m⁻² h⁻¹, followed by splash and fall down of aggregates (about 170 g m⁻² h⁻¹). Gully bank retreat occurred at a rate of 0.55 mm h⁻¹ and assuming that the soil bulk density is 1.3 g cm⁻³, this corresponds to a retreat of 8.8 mm y⁻¹. Extrapolations to the watershed level, where about 500 m² of gully bank are observed per hectare, would lead to an erosion rate of 4.8 t ha⁻¹ y⁻¹. These limited results based on a simulated storm show that the three main mechanisms (runoff, splash and fall down of aggregates) are responsible for the retreat of gully banks and that to mitigate gully erosion, appropriate measures are required to control all three mechanisms. Further research studies are needed to confirm and to scale up, both in time and space, as these data are obtained at one location and from a single artificial storm.     

Clogging mechanical model and its application in gas extraction borehole

A clogging segment mechanical model is established on gas extraction horizontal borehole. Based on the air pressure extremes pmax of the construction site, we solve the corresponding critical clogging length L0 and find clogging will occur when L> L0. With the clogging segment mechanical model, we analyze the calculation method of the retreat drilling rod resistance in borehole. The influence rule of clogging length and air supplying system pressure on retreat drilling rod resistance is analyzed. Analysis results show that the main reason for difficult drilling clogging and retreat drilling rod is the higher pressure in borehole clogging segment. The retreat drilling rod resistance is especially sensitive to the change of air supplying system; therefore, the effective method of reducing the retreat drilling rod resistance is reducing the air supplying system pressure in borehole. The drilling construction status in Jiulishan coal mine is analyzed by using the clogging segment mechanical model, and three technical measures are put forward, including increasing slagging space, reducing slagging resistance and increasing drilling rod strength. When the improving measures are adopted, the pipe-sticking phenomena decreases, the drilling rod broken phenomenon are averted and the drilling efficiency increases by 17%.     

黏性土均质坝“陡坎”移动速度试验研究

"陡坎"式发展是黏性土均质坝漫顶溃决的重要机理。开展了7组黏性土均质坝"陡坎"移动速度室内实体物理模型试验,旨在揭示黏性土均质坝"陡坎"式发展的基本规律。试验结果显示,相同压实度条件下,含水量越大,陡坎移动速度越慢,当含水量达到最优含水量后,陡坎移动速度非常缓慢(本文试验含水量范围为10%~18%)。压实度越小,陡坎移动速度越快。基于土石坝"陡坎"式冲蚀力学机理,建立了坝体土"起动摩阻流速"U*c与坝体材料抗冲能力综合系数C之间的关系,实例验证显示,提出的预报模型能够明显提高"陡坎"移动速度的预测准确度。