Determination of Coefficient of Secondary Compression in Accelerated Incremental Loading Consolidation Test

Abstract

Coefficient of secondary compression is one of the important consolidation properties of fine-grained soils exhibiting high secondary compression. Generally, soils containing significant amount of organic matter exhibit high secondary compression. It is generally determined by performing laboratory one-dimensional incremental loading (IL) consolidation test, in which each increment is allowed for 24 h or more. Typically, conventional one-dimensional IL consolidation test takes about 10–14 days to complete. Therefore, end-of-primary consolidation (EOP) test and rapid one-dimensional consolidation tests were developed in the literature to reduce the duration of conventional IL tests. The limitation of these methods is that coefficient of secondary compression cannot be determined as the specimen is not allowed to reach the secondary compression phase. This paper describes a method of determining coefficient of secondary compression from accelerated incremental load consolidation testing procedure using $\sqrt{t}$ method. In the proposed method, one of the pressure increments is left for sufficiently long time to obtain the linear secondary compression phase in the log t plots. The suggested procedure is validated by comparing the results obtained from the conventional IL consolidation test on four soil samples with varying range of secondary compressibility and plasticity characteristics.