LOADING-UNLOADING PV CURVES FOR TUFFS FROM THE NEVADA TEST SITE

摘要

The pressure-volume curves of ten tuffs from the Nevada Test Site were measured to 40 kbar at 22°C. Data for the water-saturated samples showed the phase transitions due to free water at about 10 and 22 kbar. Water freezes at 10 kbar, and transforms from pseudo-orthorhombic to the bcc structure at 22 kbar. However, the presence of "nonliquid" water, which is loosely contained within the lattice of clay or zeolitic minerals or adsorbed on particle surfaces, was also observed. The dry tuffs exhibited behavior typical of weak compressible rock. The bulk modulus is constant from zero to 100 bars, followed by a very compressible region where voids are rapidly removed as a function of pressure. The bulk modulus does not approach its original value until pressures of 2 kbar or more are reached.