Deformation characteristics of two cemented calcareous soils

The effect of cementation on the deformation characteristics of two cemented calcareous soils was investigated through a series of undrained triaxial tests performed under both monotonic and cyclic loading conditions. Increasing the level of cementation significantly increased the initial stiffness, resulting in the stiffness being more independent of the confining pressure. The curves of stiffness degradation with strain obtained from both cemented and uncemented calcareous soils compared with those of other noncalcareous soils revealed that calcareous soil attains a faster rate of modulus reduction with a higher strain threshold. It was also observed that the pattern of stiffness degradation is very similar in both cemented and uncemented samples. The stiffness degradation curves obtained from cyclic tests were found to lie within the range defined by the corresponding monotonic tests. The effect of number of cycles on the stiffness during cyclic loading was also examined and is found to depend on whether the postyield behaviour is controlled by the cohesive or the frictional response. Examination of the variation of damping ratio with strain revealed that the observed difference in the stiffness degradation curves between calcareous and noncalcareous soils was also reflected in the damping ratio, with the damping ratio of calcareous soils being below the range defined for noncalcareous soils.Key words: calcareous soils, triaxial test, shear modulus, damping ratio, repeated loading.