For the soil profile described in Problem 3.5, estimate an average peak soil friction angle. Use Eq. (3.31b).

Problem 3.5

Following is the variation of the field standard penetration number (N₆₀) in a sand deposit:

Depth (m) .............. N₆₀
1.5 ............................. 6
3 ................................ 8
4.5 ............................. 9
6 ................................ 8
7.9 ........................... 13
9 .............................. 14

The groundwater table is located at a depth of 6 m. Given: the dry unit weight of sand from 0 to a depth of 6 m is 18 kN/m³, and the saturated unit weight of sand for depth 6 to 12 m is 20.2 kN/m³. Use the relationship given in Eq. (3.13) to calculate the corrected penetration numbers.

Eq. (3.13)

Eq. (3.31)

1 0.5 CN Pa ||