Effect on Strength and Other Properties

The unconfined compressive strength as affected by disturbance decreases rapidly with increasing disturbance. The strain at failure, however, is increased as the ductility of the samples is improved by disturbance. Emrich (1971) compared the disturbance effects on 

Pore fluid pressure is sum of the partial pressures of gas (bubble phase) and liquid phases 

Gas bubbles will tend to expand immediately upon release of pore pressure, which tends to destroy fabric 

Summary of pore gas behavior due to microorganisms in marine sediments. (From Rau, G., and Chaney, R.C., Triaxial testing of marine sediments with high gas contents. In Advanced Triaxial Testing of Soil and Rock, ASTM STP 977, Donaghe, R.T., Chaney, R.C., and Silver, M.L., eds., American Society for Testing and Materials, Philadelphia, PA, 338-352,1988. Reprinted with permission from ASTM.) 

The undrained shear strength as measured by unconsolidated (UU) and consolidated undrained (CU) tests behaves in a similar pattern to the compressive strength on disturbance. The maximum undrained strength, still lower than the field strength, is usually obtained in the second quarter from the bottom of a tube sample (De Lory and Salvas, 1969). 

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