Dam Seepage Sensing and Modelling

土堤坝被广泛用于容纳水力发电水库、供水和废物，例如采矿和油砂作业产生的废物。必须避免集中的水渗透通过这种水坝，以防止细粒材料的内部侵蚀和管涌的发展-这是水坝破坏的主要原因。虽然加拿大的水坝标准是世界上最强的，但随着时间的推移，最佳做法也在不断发展，国际上也认识到需要改进可适用于老化结构的渗漏监测方法。UNB和NB Power将通过现场试验和建模设计和评估三种微创地球物理方法，用于早期检测和量化集中的渗水。该项目将设在NB Power的Mactaquac发电站，该发电站位于NB弗雷德里克顿附近的圣约翰河上，包括一个500米长的分区堤坝，于1968年完工，高出趾部32米。这些方法将在很大程度上依赖于监测大坝内的季节性温度变化，如直接使用分布式温度传感（DNT）和间接通过电阻率成像（ERI）测量的。当大坝蓄水池的水通过时，较高渗透率区域的温度和电阻率的季节性变化预计会更大。特别关注的区域包括大坝的粘土堆芯和大坝与混凝土导流溢洪道结构相邻的左坝肩，由于混凝土中的碱骨料反应性，该结构正在经历不同的膨胀。前者将采用沿大坝顶部沿着的延时二维电阻率监测进行研究，该监测在瑞典的类似大坝上取得了令人鼓舞的结果。坝肩区域将使用钻孔测量进行更详细的调查，并辅以大坝背面电极的延时三维电阻率监测。这项研究将建立在从先前的监测研究中获得的宝贵见解，在桥台区域使用自电位（SP）方法。它将适用于全世界，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.