降雨对岩溶含水系统演化过程影响的数值模拟
发布时间：2018-08-20 18:33
【摘要】：本文利用有限差分数值模拟技术研究了岩溶含水系统在有降雨入渗的情况下的演化过程,以及不同降雨量对岩溶含水系统发育的影响。在总结前人的研究成果的基础上,构建了岩溶含水系统概念模型,模型假设研究区的范围为2200mⅹ800m的完整碳酸盐岩体,模型左侧、右侧的垂直边界及底部的水平边界为隔水边界,模型顶部为降雨入渗边界,并且假设降雨入渗系数为0.3,模型中间的河谷地段为一地表水体,水头为600m。为了使模型能够更加直实可靠,利用Monte-Carle方法生成两组随机裂隙来代表实际岩体中的微小裂隙及各级结构面,对于发育规模较大的断层则直接输入原始裂隙的坐标及隙宽等参数。在对模型进行数值计算时,假定模型中的裂隙为二维光滑平行板裂隙,裂隙中的水流运动服从立方定律,并根据前人的实验成果,当Re500时对立方定律进行修正,然后利用裂隙网络中的结点流量水均衡原理建立线性代数方程组,并用迭代法求解方程组。当求出岩溶含水系统中裂隙网络的各个结点水头值后,假定在一个时间步长内岩溶含水系统中的裂隙网络结点水头稳定,由此便可依据Palmer的实验得出的碳酸盐岩溶蚀经验公式求解岩溶含水系统的裂隙溶蚀速率,及经过一定时间步长溶蚀后的新的裂隙隙宽。求出新的裂隙隙宽后,便可重新进行上一步的水头计算,并依次计算每一个时间步长内的裂隙溶蚀溶率及裂隙发育情况。此外,还进行了裂隙溶蚀的理论解计算与程序的数值解计算的对比,结果证明了程序的可靠性。本次研究模拟了岩溶含水系统由于裂隙发育的不均匀导致的差异性溶蚀现象,模型的模拟结果再现了岩溶含水系统自我演化过程中不同阶段的演化特点,并定量地给出了岩溶溶蚀过程中两个出露于模型右边界的岩溶泉的泉流量变化及模型中的含水介质场的演变数据。在经过10000年溶蚀后,泉1的流量由初始的0.45ml/s加大到6100年时的9e3ml/s,并在6100年后干涸,泉2的流量由初始的0.33ml/s加大到最后的2.6e5ml/s,裂隙的初始平均隙宽由0.1mm增大到10000年时的0.813mm。在模拟过程中发现,岩溶含水系统的演化成熟度及演化速率与降雨量成正相关,岩溶含水系统的溶蚀主要发生在潜水面附近及岩溶含水系统的源汇处,在深部岩溶并不发育,并且在同一范围内的不同组裂隙在岩溶含水系统的不同部位发育速率是不同的,这主要是由岩溶含水系统的介质场演化是由水力梯度、大气降雨量、岩石岩性等多方面因素共同决定的。
[Abstract]:In this paper, the evolution process of karst water-bearing system under the condition of rainfall infiltration and the influence of different rainfall on the development of karst water-bearing system are studied by using finite difference numerical simulation technique. On the basis of summarizing the previous research results, a conceptual model of karst water-bearing system is constructed. The model assumes that the range of the study area is 2200m x 800m complete carbonate rock mass, the left side of the model. The vertical boundary on the right side and the horizontal boundary at the bottom are water barrier boundaries, and the top of the model is the rainfall infiltration boundary. The rainfall infiltration coefficient is assumed to be 0.3, and the valley section in the middle of the model is a surface water body with a water head of 600 m. In order to make the model more direct and reliable, two groups of random fractures are generated by Monte-Carle method to represent the small fractures and their structural planes in real rock mass, and the parameters such as coordinate and gap width of the original fractures are directly input to the faults with large scale. In the numerical calculation of the model, the fracture in the model is assumed to be a two-dimensional smooth parallel plate fissure, and the flow motion suit in the fissure follows the cubic law. According to the previous experimental results, the opposite square law is modified when Re500 is used. Then the linear algebraic equations are established by using the equilibrium principle of nodal flow and water in the fracture network, and the equations are solved by iterative method. When the water head values of each node in the karst water-bearing system are calculated, it is assumed that the water head of the fissure network in the karst water-bearing system is stable in a time step. According to the empirical formula of carbonate rock dissolution obtained by Palmer's experiment, the dissolution rate of karst water bearing system and the new crack width after a certain time step dissolution can be solved. After the new crack gap width is obtained, the head calculation of the previous step can be carried out again, and the dissolution rate and fracture development of the fracture within each time step can be calculated in turn. In addition, the calculation of the theoretical solution of fracture dissolution is compared with that of the numerical solution of the program. The results show that the program is reliable. In this study, the different dissolution phenomena of karst water-bearing system caused by uneven fissure development are simulated. The simulation results of the model reproduce the evolution characteristics of karst water-bearing system in different stages in the process of self-evolution. The variation of spring discharge of two karst springs exposed to the right boundary of the model and the evolution data of the water-bearing medium field in the model are given quantitatively. After 10, 000 years of dissolution, the flow rate of Quan 1 increased from initial 0.45ml/s to 9e3ml / s at 6100, and dried up after 6100. The flow of Spring 2 increased from initial 0.33ml/s to last 2.6e5ml / s, and the initial average gap width of fissures increased from 0.1mm to 0.813mm. In the process of simulation, it is found that the evolution maturity and evolution rate of karst water-bearing system are positively related to rainfall. The dissolution of karst water-bearing system mainly occurs near the phreatic surface and the source and sink of karst water-bearing system, and does not develop in the deep karst. And the different groups of cracks in the same range have different developing rates in different parts of karst water-bearing system. This is mainly due to the evolution of the medium field of karst water-bearing system from hydraulic gradient and atmospheric rainfall. Rock lithology and other factors together determine.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641.134
本文编号：2194606
[Abstract]:In this paper, the evolution process of karst water-bearing system under the condition of rainfall infiltration and the influence of different rainfall on the development of karst water-bearing system are studied by using finite difference numerical simulation technique. On the basis of summarizing the previous research results, a conceptual model of karst water-bearing system is constructed. The model assumes that the range of the study area is 2200m x 800m complete carbonate rock mass, the left side of the model. The vertical boundary on the right side and the horizontal boundary at the bottom are water barrier boundaries, and the top of the model is the rainfall infiltration boundary. The rainfall infiltration coefficient is assumed to be 0.3, and the valley section in the middle of the model is a surface water body with a water head of 600 m. In order to make the model more direct and reliable, two groups of random fractures are generated by Monte-Carle method to represent the small fractures and their structural planes in real rock mass, and the parameters such as coordinate and gap width of the original fractures are directly input to the faults with large scale. In the numerical calculation of the model, the fracture in the model is assumed to be a two-dimensional smooth parallel plate fissure, and the flow motion suit in the fissure follows the cubic law. According to the previous experimental results, the opposite square law is modified when Re500 is used. Then the linear algebraic equations are established by using the equilibrium principle of nodal flow and water in the fracture network, and the equations are solved by iterative method. When the water head values of each node in the karst water-bearing system are calculated, it is assumed that the water head of the fissure network in the karst water-bearing system is stable in a time step. According to the empirical formula of carbonate rock dissolution obtained by Palmer's experiment, the dissolution rate of karst water bearing system and the new crack width after a certain time step dissolution can be solved. After the new crack gap width is obtained, the head calculation of the previous step can be carried out again, and the dissolution rate and fracture development of the fracture within each time step can be calculated in turn. In addition, the calculation of the theoretical solution of fracture dissolution is compared with that of the numerical solution of the program. The results show that the program is reliable. In this study, the different dissolution phenomena of karst water-bearing system caused by uneven fissure development are simulated. The simulation results of the model reproduce the evolution characteristics of karst water-bearing system in different stages in the process of self-evolution. The variation of spring discharge of two karst springs exposed to the right boundary of the model and the evolution data of the water-bearing medium field in the model are given quantitatively. After 10, 000 years of dissolution, the flow rate of Quan 1 increased from initial 0.45ml/s to 9e3ml / s at 6100, and dried up after 6100. The flow of Spring 2 increased from initial 0.33ml/s to last 2.6e5ml / s, and the initial average gap width of fissures increased from 0.1mm to 0.813mm. In the process of simulation, it is found that the evolution maturity and evolution rate of karst water-bearing system are positively related to rainfall. The dissolution of karst water-bearing system mainly occurs near the phreatic surface and the source and sink of karst water-bearing system, and does not develop in the deep karst. And the different groups of cracks in the same range have different developing rates in different parts of karst water-bearing system. This is mainly due to the evolution of the medium field of karst water-bearing system from hydraulic gradient and atmospheric rainfall. Rock lithology and other factors together determine.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641.134
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