Select the incorrect statement.
A. Effective cohesion of a soil can never have a negative value.
B. Effective angle of internal friction for coarse grained soils is rarely below 30°
C. Effective angle of internal friction for a soil increases as state of compact-ness increases.
D. Effective angle of internal friction is a complicated function of mineralogy and clay size content.
Answer: Option A
I think if there is negative capillary pressure or capillary tension or capillary suction.. The cohesion value for cohesive soil is negative.
The portion below the water table is hydrostatic pressure. We take +ve value for hydrostatic compression and in that submerged zone cohesion is +ve.
So, above the water table there is suction pressure or capillary tension or capillary potential.. So we would take negative value for it.
How can it be? The cohesion value can be 0 KPa for pure sands but it is never negative.