ABSTRACT
Reliable service conditions for structures built on expansive soils may be ensured not only by laying deep or pile foundations, but also by proper preparation of the soil base and adoption of constructional and waterproofing techniques. The material utilised for the soil cushion may consist of loams, sandy loams as well as clays and, in certain cases, sands or sand-gravel mixes. Laboratory and field investigations were conducted on sand cushions to study the effect of their height and width, density of the sand bed, pressure transmitted by the foundation, granulometric composition of the sand etc. on their performance. During preparation of a soil cushion for a foundation the backfill covering the trench forms a load acting on its surface. The experiments confirmed that when the soil is wetted the sand cushion will heave but the foundation will undergo no significant displacement.
