Stiffness of a compacted residual soil

Compacted soils are often used in engineering structures such as pavement, backfills and embankments. The stiffness of the compacted soils is affected by dry density, degree of saturation and applied strain. This paper describes the stiffness-strain relationships of a compacted residual soil from undrained triaxial compression tests. The triaxial apparatus is equipped with load transducer, bender elements, local displacement transducers, linear variable differential transducer and proximity transducers. Therefore, stiffness from very small strain to large strain can be measured. The small strain stiffness is important in pavements where deformations in the subgrade can be small whereas the larger strain stiffness is applicable to retaining walls and foundations. The effects of initial matric suction and confining pressure on the stiffness-strain relationships are examined in the paper. Both initial matric suction and confining pressure affect the very small strain stiffness, G _max. However, only initial matric suction affects the entire stiffness-strain relationship of the compacted residual soil. Copyright ASCE 2006.