Chapter 26 Gradation Design of Sand and Gravel Filters
mine the maximum allowable D 15 size for the filter in accordance with the table 26–2. If desired, the maximum D 15 may be adjusted for certain noncritical uses of filters where significant hydraulic gradients are not predicted, such as bedding beneath riprap and concrete slabs. For fine clay base soil that has d. Chapter 26 Gradation Design of Sand and Gravel Filters Part 633 .