Dam Seepage Sensing and Modelling

土质堤坝被广泛用于容纳水电站水库、供水和采矿和油砂作业产生的废物。必须避免通过这类大坝的集中渗水，以防止细粒材料的内部侵蚀和管道的发展--管道是大坝坍塌的主要原因。尽管加拿大的大坝标准是世界上最严格的标准之一，但随着时间的推移，最佳实践已经取得了进展，可以应用于老化结构的改进渗漏监测方法的必要性得到了国际上的认可。联合国开发计划署和NB Power将通过实地试验和建模，设计和评估三种早期发现和量化集中渗水的微创地球物理方法。该项目将以NB Power的Mactaquac发电站为基础，该发电站位于北卡罗来纳州弗雷德里克顿附近的圣约翰河上，其中包括一座500米长的分区堤坝，于1968年完工，高出脚趾32米。这些方法将在很大程度上依赖于对大坝内季节性温度变化的监测，直接使用分布式温度传感器(DTS)测量，间接使用电阻率成像(ERI)测量。当大坝水库的水流过时，渗漏较高的地区预计会表现出更大的温度和电阻率的季节性变化。特别感兴趣的区域包括大坝的粘土填充层和左坝肩，在那里大坝毗邻混凝土导流溢洪道结构，由于混凝土中的碱集料活性，溢洪道结构正在经历不同的膨胀。前者将使用沿坝顶的延时2D电阻率监测进行研究，这在瑞典的类似大坝上已经取得了令人鼓舞的结果。将使用钻孔DTS对坝肩区域进行更详细的调查，并辅之以大坝背面电极的时移三维电阻率监测。这项研究将建立在先前使用DTS和自然电位(SP)方法对基牙区域进行监测研究获得的宝贵见解的基础上。它将适用于世界各地，特别是在加拿大等季节性温度变化较大的地区。

Earthen embankment dams are widely used to contain hydroelectric reservoirs, water supplies and wastes such as those produced by mining and oil sands operations. Concentrated water seepage through such dams must be avoided to prevent internal erosion of fine-grained materials and the development of piping - a major cause of dam failure. Although standards for dams in Canada are amongst the strongest in the world, best practices have progressed over time, and the need for improved seepage monitoring methods that can be applied to aging structures is recognized internationally. UNB and NB Power will design and evaluate, through field trials and modelling, three minimally invasive geophysical approaches for the early detection and quantification of concentrated water seepage. The project will be based at NB Power's Mactaquac Generating Station on the Saint John River near Fredericton, NB, which includes a 500 m long zoned embankment dam, completed in 1968, that rises 32 m above its toe. The methods will rely largely on monitoring of seasonal temperature variations within the dam, as measured directly using distributed temperature sensing (DTS), and indirectly by electrical resistivity imaging (ERI). Regions of higher seepage are expected to exhibit greater seasonal variations in temperature and hence resistivity as water from the dam reservoir moves through it. Zones of particular interest include the dam's clay till core and the left abutment where the dam adjoins a concrete diversion spillway structure that is undergoing differential expansion as a consequence of Alkali Aggregate Reactivity in the concrete. The former will be investigated using time-lapse 2D resistivity monitoring along the dam crest which has yielded encouraging results on similar dams in Sweden. The abutment region will be investigated in more detail using borehole DTS complemented by time-lapse 3D resistivity monitoring with electrodes on the back of the dam. The research will build on valuable insights obtained from prior monitoring research in the abutment region using DTS and self-potential (SP) methods. It will be applicable worldwide but particularly in regions such as Canada where seasonal temperature variations are large.