When considering lateral pressures, what does 'at rest' pressure mean?

'At rest' pressure refers to the condition where a retaining wall or structure is not experiencing any movement relative to the soil it is retaining. In this state, the lateral earth pressure acting on the wall is balanced and uniform, meaning the wall remains in equilibrium without any net force causing it to move outward or inward.

This condition is particularly important in geotechnical engineering, as it provides a baseline for calculating lateral pressures on structures. It represents the pressures that would be exerted by the soil if the wall were static and no external forces or movements induced changes in these pressures.

In contrast to this concept, options such as movement inward, collapsing, or actively pushing against soil would imply dynamic conditions where the wall interacts differently with the lateral earth pressures, leading to varied and often higher forces acting upon it.