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本文通过数值模拟的方法研究了岩溶系统发展演化过程,并对其中分水岭消失现象进行了探讨。岩溶系统发育模拟中,假设裂隙段为光滑平板裂隙,裂隙中的水流处于平流状态,可以应用立方率描述水流在裂隙中的流动规律;碳酸盐岩裂隙的溶蚀过程可以通过溶蚀动力学的经验公式表示,即每个时间步长内,水流都处于稳定流状态。研究结果表明,岩溶系统溶蚀具有差异性,岩溶最为发育的部位位于潜水面附近,而且垂向的裂隙段比水平向的裂隙段发育更为强烈,深部岩溶系统发育缓慢,其裂隙张开度扩展率与潜水面附近的相差8200多倍。差异性溶蚀还造成潜水面附近形成优先水流通道,至分水岭从系统消失时,其强烈的汇水作用使几乎90%的流出量从此优先水流通道排出。分水岭消失时间受河间地块的范围和降雨量的影响,当河间地块的宽度增大至原来的5倍时,分水岭的存在时间几乎延长至原来的10倍,河间地块的范围愈大,分水岭越难以消失;降雨量增加对分水岭消失时间的影响表现出先增加后减小的趋势。
In this paper, the development and evolution of karst system are studied by means of numerical simulation and the disappearance of watershed is discussed. In the karst system developmental simulation, it is assumed that the fracture zone is a smooth plate fracture, and the flow in the fracture is advection. The cubic flow rate can be used to describe the flow of water in the fracture. The dissolution process of carbonate fracture can be explained by the experience of dissolution kinetics The formula states that, for each time step, the water flow is in a steady flow state. The results show that the dissolution of karst system is different, the most developed karst site is located near the surface of the submerged surface, and the vertical fractured zone is more developed than the horizontal fractured zone. The deep karst system develops slowly. Diving near the difference of 8200 times. Differential erosion also causes the formation of a preferential flow path near the surface of the submerged surface. When the watershed disappears from the system, its intensive catchment discharges almost 90% of the outflow from the preferential flow path. The disappearance time of the watershed is affected by the range and rainfall of the Hejian block. When the width of the Hejian block is increased to 5 times of that of the original, the existence time of the watershed extends almost 10 times as long as that of the Hejian block The bigger the watershed, the harder it is for the watersheds to disappear. The effect of increasing rainfall on the disappearance time of the watersheds first increases and then decreases.