Stress path and steady state

Abstract

The effect of stress path on the steady state line of a liquefiable sand is investigated. Results from undrained triaxial compression and extension tests on water-deposited sands show that the steady state line of a given sand, though unique in the effective stress space, is not so in the void ratio – effective stress space. The sand is contractive over a much larger range of void ratios in extension than in compression. While a single steady state line emerges for compression loading, extension loading yields several lines, each characteristic to a given deposition void ratio. All these extension lines lie to the left of the compression line in void ratio – effective stress space. Thus at a given void ratio, steady state strength is smaller in extension than in compression, the difference increasing as the sand becomes looser. The implications of the results are discussed in relation to practical design. Key words: sand, liquefaction, steady state, stress path.