北京房山岩溶水系统渗透系数的条件随机刻画及流场模拟

The karst groundwater system is composed by solution crack, dissolved pore and fissure network, which is characterized by strong heterogeneity. The hydrogeological paramenter is one method to dipict of the heterogeneous attribution of the karst groundwater system. Hydraulic conductivity with larege spatial variability is one of the main paramenters for depicting the heterogeneity of the groundwater aquifer, which is also one of the main control factors for the uncertainty and the complexity of groundwater flow. How to describe the heterogeneity of hydraulic conductivity in the karst aquifer becomes a research challenge in the quantitative study of the regulation of the karst groundwater flow.. Taking one of the typical fracture-karst water systems in Xiayunling-Longmentai synclinorium in Fangshan,Beijing, in Northern China as an example, this study introduces stochastic idea to quantitatively depict the high heterogeneity of hydraulic conductivity in the karst networks. Based on the investigation of fractures and borehole data analysis, spatial variation function of hydraulic conductivity will be analysed and a series of parameter structure will be set up by sequential indicator conditional stochastic simulation and coupled with the groundwater flow simulation model on the platform of Modflow sourse code. A series of water head distribution will be calculated through stochastic models of the flow field. Based on the idea of a probability distribution and variances, the analysis of the head results by stochastic simulation method will reveal the characteristics of the differences and regulations of flow field in the karst aquifer under the circumstances that the heterogeneity was described objectively, which can provide scientific basis for the assessment, exploitation and pollution remediation of the karst groundwater.

岩溶含水系统由不同规模的溶隙，溶孔和裂隙网络组成，含水介质具有非均质性。水文地质参数的描述是表征岩溶含水层结构非均质特征的方法之一，其中渗透系数非均质化程度最大，它也是地下水流动产生不确定性的主控因素。因此，合理刻画渗透系数的空间分布规律，是定量研究岩溶地下水流动与运移的核心问题之一，也是岩溶水文学定量研究的难点。. 本研究将随机思想引入到对介质渗透系数的模型刻画，并应用到北京房山霞云岭-龙门台复向斜裂隙-岩溶含水系统。基于大量的实地裂隙调查数据及钻孔资料，利用渗透系数的空间变异函数关系，通过序贯指示条件随机模拟方法，对渗透系数进行多种模型实现下的分布预测，构建渗透系数的随机结构模型。基于MODFLOW源代码平台，将随机参数模型与地下水流动模型链接，计算地下水头的分布，揭示地下水流场的差异性和规律性。对我国北方裂隙岩溶含水系统的水资源评价、合理开发与污染修复具有重要科学和现实意义。

北京西山张坊地区碳酸盐岩集中分布，地下水赋存于复杂的构造裂隙网络中，形成岩溶裂隙水，由于岩溶区构造裂隙网络空间分布的复杂性，含水介质具有非均质性使得岩溶地下水的定量刻画很难。本项目从构造空间分布的属性和规律出发，分析了在张坊地区褶皱构造格架控制的岩溶水文地质单元内的裂隙发育规律。在裂隙研究的基础上，刻画特有的裂隙发育特征，建立裂隙密度函数，利用地质统计方法刻画随机模拟刻画裂隙空间分布结构，反映介质结构的非均质性；建立裂隙不同控制性水平下的渗透系数的随机模拟结构用于地下水流动模拟.研究表明地下水赋存富集规律与多期构造演化产生的一系列北东-北西向、南北向断裂及裂隙网络有密切的制约关系。裂隙发育的长度宽度及密度等对渗透系数的空间分布有较强的相关。裂隙控制下的渗透系数场存在一定的空间变异性，对区域地下水的赋存与富集有较大的影响。该研究不但对保证北京市的供水安全意义重大，而且从方法上对我国北方类似裂隙岩溶含水系统的水资源评价与合理开发具有重要科学和现实意义。