Question

Soil Mechanics: lateral pressures and retaining structures

6-11 Neglecting wall friction in computing the active lateral pressure against a retaining wall is conservative if the backfill settles relative to the wall. How- ever, if the wall settles relative to the backfill, neglecting wall friction is unconservative. Show that this is true.

Answer 1

In the first case friction acts at an angle of 'delta' upwards so adds to the stability of the soil.So it will be conservative, if the wall friction is ignored. In the second case, the friction acts downwards and adds to the pressure on the wall, so neglecting wall friction in this case will be unconservative.