利用微水试验研究双重介质模型与广义径向流模型的耦合机制

Slug test has a good application prospect in the field of estimating hydrogeology parameters. Due to the complexity of fracture system, with improved slug test, it is a key problem to study the hydraulic characteristics of fractured rock by establishing a mathematical model of groundwater flow, which is more suitable for fractured-rock. The fracture mechanism characteristics in the existing slug test models is not comprehensive enough without taking into account the coupling effect of the differences of fractures and matrix and Irregularity of complex systems. Therefore, coupled double porosity model and generalized radial flow model, this project is to establish a new cross-hole slug test model. Theoretical, indoor and field slug test data analysis are used to reveal the response mechanism of heads in the test and observation well to the change of parameters, such as intensity of water transfer between fracture and matrix, the fractal dimension and so on, and to clarify the influence of intensity of water transfer between fracture and matrix and the fractal dimension on estimating hydraulic conductivity and specific storativity of fractured rock. It will be verified that the coupling model is able to accurately and practically estimate the hydraulic characteristics of fractured rock. The results for this project will provide a reasonable theoretical and technical basis on analyzing hydraulic properties of fractured rock, and can promote the field slug test in engineering application for estimating hydrogeology parameters of fractured rock, which has great significance in theoretical and practical applications.

微水试验在测定岩体水力特性方面具有良好的应用前景。由于裂隙地下水流系统特性复杂，借助改进的微水试验，通过建立更适合于裂隙岩体的地下水流数学模型来研究裂隙岩体水力特性这一关键问题。现有微水试验模型没有综合考虑裂隙-母岩介质特征差异和复杂系统的不规则性等因素的影响，反映出的裂隙结构机制性特征不够全面准确。为此，本项目利用耦合双重介质模型与广义径向流模型，拟建立一种新的跨孔微水试验模型，通过理论分析、室内及野外试验数据分析，揭示测试井和观测井内水位对裂隙-母岩流量交换强度和分形维数等参数变化的响应机理，阐明裂隙-母岩流量交换强度和分形维数对推估裂隙岩体渗透系数和贮水率等特征参数的影响，验证耦合模型定量刻画裂隙岩体水力特性的准确性和实用性。其成果为裂隙岩体水力特性研究提供一种合理的理论基础和技术依据，同时能够推动野外微水试验在探究裂隙岩体水力特性方面的工程应用，具有重要理论研究价值和实际应用意义。

由于裂隙地下水流系统特性复杂，本项目利用耦合双重介质模型与广义径向流模型，建立了一种新的跨孔微水试验模型，通过理论分析及野外试验数据分析，验证耦合模型定量刻画裂隙岩体水力特性的准确性和实用性。研究结果表明：测试井和观测井内非振荡水位的恢复速度或振荡水位的振幅会随裂隙渗透系数、母岩贮水率、裂隙-母岩流量交换强度、承压裂隙含水层厚度小于1米时的径向流维度的增大以及承压裂隙含水层厚度大于1米时的径向流维度的减小而响应性增快或增大，反之亦然。裂隙-母岩流量交换强度对测试井内水位和观测井内水位的影响存在一个失去效力的上限值，还存在一个使母岩贮水率对测试井和观测井内水位失去影响效力的下限值。耦合模型对4个特征参数的敏感程度以大约1个数量级的增幅由高到低依次为：径向流维度>裂隙渗透系数>母岩贮水率>裂隙-母岩流量交换强度。忽略双重介质和分形几何特征会导致渗透系数估值偏高和贮水率估值偏低。