For single soil layer, input the D50 in feet/meter.
For two soil layers, input: (top layer thick)*(top layer D50)+(bottom layer D50). For example: 2.5*0.05+0.25
For three soil layers, input: (top layer thick)*(top layer D50)+(2nd layer thick)*(2nd layer D50)+(3rd layer D50). For example: 2.5*0.05+5*0.25+2.5
There shall be no blank space between input data, and the maximum soil layer is limited to three.
Where rock is encountered, use a D50 value of 100 to represent the rock. For example, consider a two layer condition where the top soil layer is 3 feet thick with a D50 value of 0.1 ft.; and the bottom layer is scour resistant rock with an (assumed) D50 value of 100. Enter this information as 3*0.1+100. Please note that the ABSCOUR default minimum abutment scour depth of 6 feet applies to scourable soil and may not be applicable at this site. Further study may be needed to estimate the scour in rock.
For clear water scour conditions the particle size should be representative of the bed material in the bottom of the scour hole. Refer to the geomorphology report and Chapter 14, Appendix B for information on soil samples. Please note if the particle size is smaller than the limit for fine sand (0.0007 ft.), then evaluate the cohesive properties of the soil when estimating its critical velocity.
Note, the measurements of layer thicknesses should be made using the bottom of the ABSCOUR section as the datum.