Influence of membrane penetration on granitic residual soil in consolidated drained triaxial test

Abstract

Membrane penetration effect can be observed on the cylindrical specimen in the consolidated drained triaxial test when the rubber membrane is deflected into the space among soil particles over its side. It occurs gradually upon the commencement of consolidation stage in which the soil sample experiences the elevation of cell pressure. The volume of the specimen and stress-strain interpretation in consolidation and shearing stages respectively are affected by considering the membrane penetration effect. This study presents a consolidated drained triaxial testing on granitic residual soil grade V under effective confining pressure of 50, 100, 150, 200, 300, 350 and 400 kPa. The testing of effective confining pressure consisted of real specimens and dummy specimens. For real specimens, compacted granitic residual soil in cylindrical with initial diameter of 50 mm and 100 mm height was used. As for dummy specimens, a solid rigid cylindrical core was enclosed with a thin layer of soil material. Dummy specimens were used to observe the behaviour of membrane penetration in triaxial testing. The graphical method was applied in finding the effect of considering membrane penetration in volume changes of the soil sample accurately. The compliancy of the soil material used towards the graphical method has also been determined. The proportion of membrane penetration from this study ranged between 25% and 58%. The obtained angle of friction at failure, φ’ of specimen with and without membrane correction was 27° and 25° respectively, which is insignificantly different. Further investigation is required by considering other factors including specific soil particles size, larger size of soil sample, and variety of thickness and materials of the rubber membrane.