Identification of hydraulic conductivity using the response of groundwater levels to oceanic tide
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摘要: 在地下水扩散方程中，压力传导系数是描述地下水运动的重要参数。传统的方法是通过抽水或注水给地下水系统一个扰动，监测地下水水位的响应，由此计算含水层的压力传导系数。文章提出用潮汐衰减率方法识别含水层压力传导系数，其适用于滨海区承压含水层的参数识别。在推导出解析解的基础上，通过数值拟合、最小二乘法、牛顿迭代法求得含水层的压力传导系数，提出潮汐衰减率的概念，建立余切函数与潮汐衰减率的线性关系，用线性关系中的斜率和截距识别压力传导系数。用潮汐衰减率方法识别出的压力传导系数与其实际值相等，说明该方法是正确有效的。潮汐信号衰减率与海水振荡的余切函数线性相关。数值仿真表明，该方法可以准确地估算出含水层的压力传导系数。潮汐衰减率方法具有少打井,经济高效等优点。潮汐衰减率方法为实际工程应用提供了可靠的理论基础，它可以用于部分实际工程中。该方法的局限性在于需要提供含水层的部分参数，如含水层的长度、海水波动振幅、频率等。Abstract: Hydraulic conductivity is an important parameter describing groundwater movement in the groundwater diffusion equation. The traditional method is to give a disturbance to the groundwater system by pumping or injecting water, monitor the response of groundwater levels to the tide, and calculate the hydraulic conductivity of an aquifer. In this paper, a method of tidal attenuation rate is proposed to identify the hydraulic conductivity. It is suitable for identifying parameters of a confined aquifer in coastal areas. After deriving the analytical solution, the hydraulic conductivity of the aquifer is obtained by numerical fitting, least square method and Newton iteration method. The concept of tidal attenuation rate is proposed. The linear relationship between the cotangent function and the tidal attenuation rate is established. The slope and intercept of the linear relationship are used to identify the hydraulic conductivity. In this paper, the hydraulic conductivity identified by the method of tidal attenuation rate is equal to its actual value, showing that the method is correct and effective. The attenuation rate of tidal signals is linearly correlated with the cotangent function of sea water oscillation. The numerical simulation shows that the method can accurately estimate the hydraulic conductivity of the aquifer. The method of tidal attenuation rate has the advantages of less well-drilling, being economical and efficient. The tidal attenuation rate method provides a reliable theoretical basis for practical engineering applications and can be used in some practical projects. The limitation of this method lies in the need of some parameters of the aquifer, such as the length of the aquifer, the amplitude and frequency of sea water fluctuation, etc.
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