True Triaxial Tests on Cross-Anisotropic Deposits of Fine Nevada Sand: Fid-Bau Portal

True Triaxial Tests on Cross-Anisotropic Deposits of Fine Nevada Sand

Rodriguez, Nina M. / Lade, Poul V.

Abstract

An experimental program was designed to study the effects of cross-anisotropy under three-dimensional conditions on fine Nevada sand using tall prismatic specimens. Eighteen drained tests were performed using a true triaxial apparatus. Specimens were created with both horizontal and vertical bedding planes by dry pluviation, then a freezing technique was used to solidify the specimens while they were mounted in the true triaxial apparatus. The specimens were then sheared at various $b$ -values, where $b = (σ_{2} - σ_{3}) / (σ_{1} - σ_{3})$ , in the three sectors of the octahedral plane. The stress-strain behavior and strength under various loading conditions on the octahedral plane are presented. Results show similar strength results in Sectors I and II. Effects of cross-anisotropy are shown when comparing the friction angles in Sectors I and II with those in Sector III. The strength is highest in Sector I, where the friction angle in triaxial compression ( $b = 0.0$ , vertical specimen with horizontal bedding planes) is 5.3° higher than the triaxial-compression friction angle in Sector II/III ( $b = 0$ , horizontal specimen tested with the horizontal bedding planes in the vertical direction). In triaxial extension ( $b = 1.0$ ), the friction angle is 2.5° higher in Sector I/II than that in Sector III. Shear band inclinations in these three sectors were essentially unaffected by the cross-anisotropy.