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四、黄土喀斯特地貌演化过程 (一)形成条件 黄土结构疏松,胶结程度差,颗粒以粉砂为主,节理发育,含易溶盐,为喀斯特形成创造了基本条件;下渗水带走黄土中的粉砂颗粒,溶解易溶盐,潜蚀节理,从而决定了黄土喀斯特的发生;普遍发育使水产生集中渗流和水平定向径流通道的构造节理,控制了黄土喀斯特的发育,使其具有方向性;地下水的水平定向径流既要有供水区和排水区,又要有水力坡度,地形条件也是不可缺少的。以上四个条件的共同存在与作用,导致了黄土喀斯特的形成。 (二)黄土喀斯特的演化过程
Evolution of loess karst topography (I) Conditions of formation Loess has loose structure and poor degree of cementation. The silt is the main part of the loess. The development of joints and soluble salt are the basic conditions for karst formation. The seepage water takes away the loess Silt particles, soluble salt and latent erosion joint, which determine the occurrence of loess karst. The development of water seepage and horizontal directional runoff channels are generally developed to control the development of loess karst and make it directional. The horizontal directional runoff of groundwater requires not only the water supply area and the drainage area, but also the hydraulic gradient, and the terrain conditions are also indispensable. The common existence and function of the above four conditions led to the formation of loess karst. (B) the evolution of loess karst