Hydrogeological analysis of slug tests in glacier boreholes
Hydrogeological analysis of slug tests in glacier boreholes
复制标题
冰川钻孔段塞试验的水文地质分析
DOI：
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发表时间：
2005
影响因子：
3.4
通讯作者：
Giles H. Brown
中科院分区：
文献类型：
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作者：
B. Kulessa;B. Hubbard;M. Williamson;Giles H. Brown
段塞流测试可以通过评估井眼-冰下流耦合系统对其稳态水头人工位移的响应来估计冰下水力特性。然而，现有的专门用于在冰川钻孔中收集的段塞试验数据的模型在实际应用中具有挑战性。在这里，我们证明了在地下水研究中相对容易适用和广泛使用的传统线性方法也可以用于估计冰下水力特性。在瑞士瓦莱州Haut Glacier d 'Arolla的波动井眼中记录了过阻尼、欠阻尼和临界阻尼段塞测试数据。我们发现数据中的非线性效应可以忽略不计，支持常规水文地质方法的应用。结果表明，受主要冰下排水通道影响的区域内的松散沉积物的水力导电性比受影响区域外的区域（~0.1 × 10-2ms-1，典型的砾石砂）增强（10-2 m - 1，典型的粉砂）。根据段塞试验分析推断出的到冰下含水层内流动边界的距离与冰下河道的实际位置一致。敏感性分析表明，与常规水文地质方法中段塞试验响应的可重复性和曲线拟合程序的不确定性相比，钻孔和过滤器半径以及冰下含水层的储存系数的不确定性更有可能影响水力和距离估计的准确性。
Abstract Slug testing allows estimation of subglacial hydraulic properties by evaluating the response of a coupled borehole–subglacial flow system to an artificial displacement of its steady-state hydraulic head. However, existing models developed specifically for application to slug-test data collected in glacier boreholes are challenging to apply in practice. Here, we demonstrate that conventional linear methods, which are relatively readily applicable and widely used in groundwater studies, can also be used to estimate subglacial hydraulic properties. Overdamped, underdamped and critically damped slug-test data were recorded in fluctuating boreholes drilled to the bed of Haut Glacier d’Arolla, Valais, Switzerland. We find that non-linear effects in the data are negligible, supporting the application of conventional hydrogeological methods. Results suggest that the hydraulic conductivity of the unconsolidated sediments within the area influenced by a major subglacial drainage channel is enhanced (several 10–2 m s–1; typical of gravelly sand) compared to areas outside the zone of influence (~0.1 × 10–2ms–1; typical of silty sand). A distance to a flow boundary within the subglacial aquifer, inferred on the basis of slug-test analysis, was found to coincide with the actual location of the subglacial channel. Sensitivity analyses reveal that uncertainties in borehole and filter radii, as well as the storage coefficient of the subglacial aquifer, are more likely to affect the accuracy of the hydraulic and distance estimates than uncertainties regarding the repeatability of the slug-test responses and curve-fitting procedures involved in the conventional hydrogeological methods.