Experimental study on crack filling by upstream fills in dams

The paper presents the main results of a research study into the crack-filling ability of granular materials located upstream of an erosion path in the core of a zoned dam. Upstream crack fillers are usually considered in dams located in zones of high seismic activity, as a redundant element, should a crack develop in the core and the downstream filter fail to retain the eroded particles. Uniform soils of fine-sand size are highly effective at filling cracks and stopping the progression of erosion; however, they can be significantly expensive. In the interest of reducing the costs of their overuse, an experimental investigation is conducted of the extent to which gap-graded sandy gravels that are naturally present during the construction of dams can safely provide the crack-filling action. It was concluded that the sand content of the upstream material that is susceptible to suffusion, and its relation with D_15F of the filter, is critical for rapid crack filling to occur. Other parameters influencing crack-filling ability are the gravel content, the fines content and the type of the fines in the upstream soil. Practical rules to estimate the likelihood of crack filling by an upstream granular material being effective at stopping the progression of internal erosion along a concentrated leak in zoned dams are also proposed.