【作者】 向友珍；

【导师】 刘俊民；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2006， 硕士

【摘要】 随着现代灌溉引水工程的发展,黄土台原灌区农业生产用水条件得到了较大改善,其农业生产和经济发展有了迅速的提高,同时其自然生态环境、地质条件与水文地质条件也随着水源的丰富而发生了巨大的变化。这一切缘自于该区土壤——黄土的特殊物质结构特征。黄土的空隙是由孔隙、孔洞和裂隙构成的相互联通的复杂系统,而形成时代和埋深不同的黄土层,空隙系统特征差异很大,从而导致其渗透性和给水性不但具有随埋深减小而增大的特点,且同一时代黄土的渗透性在水平方向上差异很大,具有垂直和水平方向的各向异性。黄土和其它(裂隙岩石和以沙砾石层构成的孔隙岩石等)含水介质的区别在于,黄土含水层的空隙性和水理性质是可变的,这一特点是由黄土的可溶性决定的。在灌溉条件下,入渗水分在包气带下移或在含水层中运移,不断地和黄土介质发生一系列的物理、化学作用,空隙系统不断地被溶蚀改造,表现为黄土的水文地质参数不像其它介质是一个定数,而是随水文地质条件变化而不断演化。因此研究作为表征含水层水理特性的定量指标的水文地质参数具有重大的意义。论文通过一系列渗透试验,揭示了黄土含水层渗透系数k值的演化规律:(1)在相同压力不同水质条件下,黄土含水层的渗透系数k值随水源盐度的增大呈现出减小的趋势。(2)在相同水质不同压力条件下,黄土含水层的渗透系数k值随供水水头的增大呈现出增大趋势。(3)在水头和盐度的综合影响下,黄土的渗透系数k值变化按照水头的递增呈现规律性变化。论文经过分析论证主要得出了3点结论:(1)黄土原灌区新含水层是长期灌溉入渗的必然结果。灌区的灌溉入渗和降雨补给在时间上互补,在强度上互有加强,使得灌溉水入渗效应十分明显。(2)灌溉水的入渗使包气带发生一系列复杂的物理—化学变化。进入含水层中的水质虽与灌溉水原有的化学成分及其组成有所不同,但渗入含水层中的灌溉水的水质较之雨水渗入的水质为差,从而导致地下水的矿化度加大。(3)长期的灌溉,使得具有特殊土壤结构的研究区土壤渗透性能得到很大的改善,其水文地质条件发生了根本性的改变,土层的水理性质(与其在天然条件的值相比较)产生了极大的变化,现在研究区水文地质参数k值已是一个相当可观的值。更多还原

【Abstract】 With the development of irrigation engineering, agricultural water conditions of Wei bei loess tableland has got great improvement. Its agricultural production and economic development had increased promptly. At the same time, its natural ecological environment, geological condition and hydro-geological conditions had changed enormously as the water riching. All these were because of the special structural characteristic of loess.The space system of the loess is a complicated system which connected by small opening, hole and cranny. The loess of different time and dissimilar burying depth had different crevice system characteristics. These not only caused the permeability and water characteristic of loess increasing when its burying depth reduced, but also caused the permeability of identical epoch loess have differences in the horizontal direction, and its characteristics have aeolotropy in the vertical and horizontal direction .The differences of the loess aquifer and the other rocks were the loess aquifer’s interspaces and hydraulic properties were variable, which determined by the solubility of the loess. Under irrigation condition, the filter water should happen a series of physics and chemical action constantly when it filtered in the aerated zone and motioned in the aquifer, the interspace was transformed by the corrosion constantly. It showed that the hydro-geological parameter of the loess is not a fixed number, it evolved with hydro-geological conditions constantly. Therefore, studying the hydro-geological parameter (the quota target of stratum’s water-bearing attribute) had largely significance.The papper made a series of permeated simulated test, approved the permeability coefficient’s evolvement rules of the loess aquifer. The rules were showed as follows:(1)Under a certain fixed water stress, the permeability coefficient of the loess aquifer should be augment with the salinity of supply water’s reducing.(2)Under a certain fixed salinity, the permeability coefficient of the loess aquifer should be augment with the salinity of supply water’s increasing.(3)Under the influences of water stress and salinity, the permeability coefficient of the loess aquifer should be varied regularly with the water stress’s increasing.The paper had drawn the conclusion through the analysis as follows:(1)The new aquifer’s forming was because of Longly irrigating in Wei bei loess tableland. In this area, irrigation and rains supplied groundwater supplementary and their intensify enhanced mutually, thus irrigation water had obvious permeability.(2)The infiltrated water should happen a series of physics and chemical action constantly when it filtered in the aerated zone of aquifer.The irrigation water had less quality than the rain water, thus caused the hardness index of ground water enlarged.(3)After undergoed long-time irrigation, the hydro-geological conditions of Wei bei loess tableland had changed at all. The hydraulic properties of loess had great changed,its hydro-geological parameter should be very considerable(as compared the natural condition).更多还原