Cohesionless Soils

The following properties are required for cohesionless soil layers:

• Skin Friction Angle
• End Bearing Angle

FRICTION ANGLE FROM SPT VALUES

There is an option to specify SPT N values with depth in order to calculate the friction angle. RSPile uses the relationship between standard penetration test values and the angle of internal friction as presented by Peck, Hanson, and Thornburn (1974).

Uncorrected N values can be used, or users can correct the N values for the influence of effective overburden pressure

SPT-N Values

The depths used in the SPT 'N' input tables are measured with respect to the top of the ground surface. It is essential to ensure that the SPT depths cover up to the bottom of the soil layer that has SPT 'N' values. The users will be notified before compute or while defining the soil layers in the borehole editor if any layers have SPT depth that is outside the range of the defined layer.

Sample SPT-N values for soil property S1 are shown in the figure:

The maximum depth is 20m.

These depths will be measured from the top of the ground surface.

If the bottom depth of S1 exceeds the maximum depth inputted in the SPT-N table, the user will be prompted to extend their SPT depths so that they fit within the range of the soil property being used in the borehole.

In the figure below, the SPT depth only extends to 15m. Since the bottom depth of the soil layer column is at 20m, the SPT data in this case falls out of range.

Attempts to compute or define boreholes with soils using invalid SPT data will prompt the user with a warning message.