Sensitivity analysis of determining seepage velocity using temperature records
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摘要: 不同深度处的含水介质温度时序资料振幅比或相位滞后能用来计算地下水垂向流速，典型的解析模型是Hatch模型。为了评价Hatch模型的参数灵敏度，采用局部灵敏度分析方法确定该模型的主要影响因子及相关参数与模型响应的依存关系，再由全局灵敏度分析方法评价参数共同作用对模型计算结果的影响。灵敏度分析结果表明：Hatch模型精度的主要影响因子是测点距离（Δz），其次是介质比热容（ρscs）和有效孔隙度（ne），而基准热传导系数（λ0）和热弥散度（β）的影响甚微。基准热传导系数和热弥散度与计算流速呈负相关，其余参数则与之呈正相关。因此在实践中，需保证测点距离的准确性，而对基准热传导系数和热弥散度可取经验值。Abstract: Vertical velocities of groundwater flow can be determined by temperature time series measurements at different groundwater depths. The most typical analytic model is the Hatch model, which uses the characteristic of temperature damping or the phase lag of temperature. A local sensitivity analysis is conducted on the parameter of Hatch model in an effort to identify the most important impact factors of the model, and subsequently, the effect of each parameter on the modeling result. The global sensitivity method is then applied to analyze the interaction among parameters and their effects on model simulations. Results show that the distance between the two measuring points (Δz) is the most influential factor on the model simulation, and followed by the heat capacity of solids (ρscs), the effective porosity (ne). The model simulation is least sensitive to the variations of the heat conduction coefficient (λ0) and the degree of heat dispersion (β), and a negative correlation is found between vertical velocities of groundwater flow and the two parameters λ0 and β. While for other parameters, positive correlations exist. As a result, a special attention should be paid on measurement of the distance between the two measuring points, while empirical values can be assigned to the two parameters λ0 and β.
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Keywords:
- groundwater /
- temperature /
- sensitivity analysis /
- time-series records /
- analytic model
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