EFFECT OF SPECIMEN SIZE ON NORMALIZED DISSIPATED ENERGY PER UNIT VOLUME

ABSTRACT: The quantity of energy dissipated in a unit volume of soil during cyclic loading can be used as a measure of the soil’s ability to withstand liquefaction. This energy is referred to as the normalized dissipated energy per unit volume (NDEPUV). The greater the NDEPUV required to induce liquefaction, the more seismic energy must be input into the soil during an earthquake for liquefaction to occur. The NDEPUV for a soil subjected to a seismic event or a laboratory test can be calculated from the stress-strain behavior of the soil. In this study, the effect of specimen size on NDEPUV was examined using strain-controlled cyclic triaxial tests performed on specimens of uniform sand prepared to a relative density of 40%. Four specimens were tested at each of four volumes and the NDEPUV required to induce liquefaction was determined. The specimen volumes ranged from 87 to 1525 cubic centimeters. In addition to NDEPUV, the number of cycles of loading required to trigger liquefaction and the pseudo energy capacity (the calibration parameter for the GMP pore pressure model) were examined. The NDEPUV was found to be independent of the specimen volume for three of the four specimen sizes. The largest specimens were found to require less energy per unit volume to liquefy. Conversely, the number of cycles to trigger liquefaction and the pseudo energy capacity were both found to be independent of specimen volume for all four specimen sizes.