Improved design method of gradation band curves for granular filters
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering
Filter structures are extensively employed in various hydraulic and geotechnical structures as a key seepage control measure to prevent leakage and erosion. Based on different filter design criteria, several gradation band curve design methods are introduced, thereby offering apparent evidence for filter design. This paper reviews these design methods specified in Chinese and foreign granular filter design standards, their applications, and previous filtration tests; reveals the problems in the previous methods of gradation band curve type; suggests an improved method. This new method uses a new self-healing index to control the upper half of gradation curves, so that it can efficiently choose appropriate filters to avoid potential internal erosion, and make gradation curves more comprehensive and more straightforward. It is verified against previous filtration tests and engineering examples, and the results show that it efficiently discriminates between valid and invalid filters from the optional grading curves. Thus, our method provides new ideas and would be helpful in revising the relevant existing standards.
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