Membrane penetration effects on shear strength and volume change of soil during triaxial test

In a triaxial test of soil, a specimen in the cell is enclosed by a rubber membrane to separate soil particles from the surrounding water that represents the confining pressure. Upon increasing the confining pressure, this membrane penetrates the voids between the particles of the specimen and cause errors in triaxial test results, these errors lead to changes in shear strength and volume change measurements. Therefore, the results need to be corrected for membrane penetration. This paper emphasizes the importance of correcting triaxial test results for membrane penetration by presenting the influence of membrane penetration on shear strength and volume change measurements. It was concluded that the rubber membrane can produce apparent increase in volume change and shear strength either due to membrane penetration (when the test is at drained condition) or due to membrane compliance (when the test is at undrained condition).