Horizontal pressure due to saturated soils 2

[DPAJR]

In "Civil Engineering Reference Manual" 6th Ed Michael R. Lindeburg P.E. on page 10-18 there is a section called "Horizontal Pressures From Saturated Sand". It gives an example of increased pressure behind a retaining wall. My question is, does this only apply to cohesionless soils or does being fully saturated cause an increase in lateral pressure in all soils? It seems to me that it should. Would the calculation be the same or do you have to account for other factors like cohesion?

Thanks

 

[DRC1]

For a sand, the drained condition is assumed to exist Instantly. thus you have the lateral pressure due to the bouant weight of sand times the coefficent of lateral pressure, plus the lateral presurre due to the unit weight of water times one.
Clay on the other hand is assumed to be instanly undrained tranitioning over time to drained. Thus inialyy the lateral pressure is a function of cohesion and the unit weight of the saturated soil. Thus the water does not have significant effect at first. As the clay drains, it strength is based on a lateral pressure cofficent that is a function of its friction angle and the lateral load due to the water - similar to sand. In general (although far from always) under consolidated and nomaly consolidated sands gain strength over time and over consolidated clays loose strength over time.

 

[fattdad]

yes, but for phi=zero analysis, the coefficient of active and passive earth pressures is unity, so you can just use the saturated unit weight and apply it horizontally on the wall.

f-d

¡papá gordo ain’t no madre flaca!