Least-Squares evaluation of DMT dissipation test data – some preliminary results

Abstract

The Flex method does not work if the DMTA total stress dissipation curve is non-monotonic or has no inflexion point. To overcome the problems, various versions of a mathematically precise DMTA total stress dissipation test evaluation method are suggested to be considered. These versions can be classified (i) on the basis of the measured data, as only total stress-based and both total stress and pore water pressure-based methods, (ii) on the basis of the dimension of the model, as oedometer, cylindrical and spherical coupled consolidation models, (iii) as linear models or models with relaxation. In this paper some DMTA dissipation tests made at test sites in Szeged and Ballina test sites are evaluated and the c values identified with various methods are started to be compared. According to the first results, an evaluation method, based on the oedometer relaxation test model and both total stress and pore water pressure data, provided c values about 3 times larger than the Flex method (and could be used to evaluate non-monotonic data). The use of pore water data – generated or measured as C readings – decreased the parameter error.

Keywords

• coupled consolidation
• point-symmetric
• pore water dissipation
• total stress dissipation