土木工程与力学学院知识库

在中国黄土高原黄土灌区中，黑方台灌区为典型的黄土台塬，且是由于农业灌溉导致黄土滑坡形成的典型滑坡案例。自上世纪60年代开始，黑方台修建了提水灌溉工程，由于长时间的采用漫灌的灌溉方式，改变了原有的水文地质条件，使得地下水中盐分急剧上升，土壤盐渍化，导致土体强度降低，在黑方台塬周边诱发了大量的黄土滑坡。研究区内诱发滑坡的主要因素为灌溉加剧了的地下水活动强度，所以了解区内土水的化学性质是研究滑坡的一种重要手段。本文的主要目的是对黑方台灌区内滑坡的土水化学性质进行试验研究，通过大量地、周期性地进行野外观察和取样，通过试验确定黑方台灌区土壤浸提液的最优土水比，从而快速准确地对土中含盐量进行测试；利用4种测试方法对泉水含盐量进行测试，分析各种测试方法的优劣势，再根据试验结果，讨论黑方台灌区泉水中含盐量和阴阳离子的时空分布规律，并利用Piper三线图对泉水水化学类型进行分析。

得到如下结论：(1) 以黑方台灌区所取土样为试验对象时，在土水比为1:10的情况下，浸提液电导率和溶解性固体总量最先达到平衡。在该土水比例下，土壤中绝大部分的可溶性盐都溶于水中，这也便于确定土壤的含盐量，来表征土壤的盐渍化程度。根据本文试验所得结果，建议在黄土灌区或高含盐量土壤制取土壤浸提液时，选取土水比例为1:10。(2) 对于泉水含盐量测试，本文采用烘干法、水质监测仪、离子色谱仪和折射仪对泉水进行测量，烘干法是常规使用方法，具有操作简便、快捷等特点；水质监测仪和离子色谱仪操作繁琐，需要进行预处理或后续地校正；而折射仪在能达到所需精度的情况下，操作更为简单，实用，且精度可达千分位。测试高含盐量水中的含盐浓度时，本文通过试验得出，利用折射仪进行测量也是一种不错的方法。(3) 黑台北缘滑坡出露泉水中的含盐量普遍高于黑台东缘，而黑台东缘，黄土基岩滑坡出露泉水中的含盐量要高于黄土滑坡，且泉水更为清澈。根据所测结果，研究内出露泉水的空间分布规律为：由北向南由东向西逐渐降低；泉水含盐量的时间分布规律与当地农业灌溉活动和地下水季节性冻融存在着联系。(4) 研究区内泉水中，阴离子中以Cl^-和SO₄^2-为主，两种离子共占泉水阴阳离子总量的90%以上，阳离子以Na⁺为主。所有泉水水样中，Cl^-含量最高。时间上，黑台北缘泉水中各阴阳离子在9月份时浓度最高，而黑台东缘泉水中的阴阳离子则在10月份浓度为最高。泉水水化学类型为氯化钠型，其中阳离所占百分比几乎不变，而Cl^-和SO₄^2-所占百分比却有一定变化。

Among the loess irrigation areas on the Loess Plateau in China, Heifangtai Irrigation District is a typical loess tableland, and it is a typical landslide case caused by agricultural irrigation leading to the formation of loess landslides. Since the 1960s, Heilongtai has built a water-pumping irrigation project. Due to the long-term use of flood irrigation, it changed the original hydrogeological conditions, drastically increased the salinity in the groundwater, soil salinization, and led to soil. With reduced body strength, a large number of loess landslides have been induced around the Black Terrace. The main factor inducing landslides in the study area is the intensity of groundwater activity that has been exacerbated by irrigation. Therefore, understanding the chemical properties of soil and water in the area is an important means for studying landslides. The main purpose of this paper is to conduct experimental research on the chemical properties of landslides in the Heifangtai Irrigation District, and to conduct field observation and sampling in large numbers and periodically to determine the optimal soil water for the soil extracts in the Heifangtai Irrigation District. The use of four kinds of test methods to test the salt content of spring water, analyze the advantages and disadvantages of various test methods, and then according to the test results, discuss the temporal and spatial distribution of salt content and anion and cation in spring water in Heifangtai Irrigation District, and use Piper diagram analyzes the type of spring water chemistry.

Get the following conclusions:(1) When the soil sample taken in the Heifangtai Irrigation District is the test object, the conductivity of the extract and the total amount of dissolved solids reach the equilibrium first when the ratio of soil to water is 1:10. Under this proportion of soil and water, most of the soluble salts in the soil are soluble in water, which also facilitates the determination of soil salinity to characterize the degree of soil salinization. According to the results obtained from the experiments in this paper, it is suggested that when the soil extracts are prepared from loess irrigation areas or high salinity soils, the proportion of soil to water is selected to be 1:10.(2) For the salt content test of spring water, this article uses the drying method, water quality monitor, ion chromatograph and refractometer to measure the spring water. The drying method is a routine use method, and has the characteristics of simple and quick operation; water quality monitor And ion chromatograph operation is cumbersome, need to carry on the pretreatment or follow-up correction; And refractometer can reach the required precision, the operation is simpler, practical, and the precision can reach thousand place. When testing the salt concentration in high salinity water, the experiment results show that using a refractometer to measure is also a good method.(3) The salt content in the outcropping springs of the Black-Taipei edge landslide is generally higher than that of the eastern margin of Heitai, while the salt content in the outcrop springs of the Loess basement landslide is higher than that of the Loess landslide and the spring water Clear. According to the measured results, the spatial distribution of dew-springs in the study is: gradually decreasing from north to south from east to west; the time distribution of salt content in springs is related to the local agricultural irrigation activities and seasonal freezing and thawing of groundwater.(4) In the spring water in the study area, Cl^- and SO₄^2- are the main anions in the study area. The two ions together account for more than 90% of the total anion and cation ions in the spring, and the cations are mainly Na+. In all spring water samples, the highest Cl^- content was found. In terms of time, the concentrations of anions and cations in the marginal waters of Black Taipei were highest in September, while the anions and cations in the springs of the eastern margin of Heitai were highest in October. The chemical type of spring water is Sodium-chloride type, in which the percentage of cations is almost unchanged, while the percentage of Cl^- and SO₄^2- has a certain change.