Constant Rate of Loading Test on Ultra-Soft Soil

The conventional consolidation test on ultra-soft soil takes a long time to complete due to the viscous effect in the early stage of compression. Instead of conducting the test until the end-of-primary (EOP) consolidation at each loading step, the testing time can be shortened if the test is carried out at a constant rate of loading (CRL). In this study the CRL tests were carried out at various loading rates. The settlement and pore pressure behavior were studied, and a suitable rate of loading (1 kPa/800 s) was determined. The proposed rate of loading is slightly slower than the rate of loading for natural clay suggested by others. The transition point between viscous stage and soil stage can be determined from the measured peak pore pressure. The compression indices, the large strain coefficient of consolidation, and the coefficient of permeability can also be determined from the CRL test with the proposed equations. This paper discussed the experimental test on ultra-soft soil at a CRL.