In soil mechanics, a transparent tri-axial vessel is frequently used, however, in rock mechanics, a metal vessel has been used to withstand higher confining pressure. In this study, a transparent vessel made of an acrylic acid resin with tensile strength of 75 MPa was designed and manufactured for tri-axial compression test under confining pressure up to 10 MPa.
Every component of the vessel was designed with safety factor more than four. Paying special attention to safety, confining pressure was increased over the designed value until its failure. The confining pressure at the failure was more than 55 MPa and daily use at 10 MPa was considered to be safe. It was also revealed that an annular transparent tube made of an acrylic acid resin did not break into pieces, but only a vertical crack was extended.
Preliminary tri-axial tests were conducted for Tage tuff and Dotan that were deformed easily under the confining pressure. Many photographs were taken by a digital camera, and vertical and lateral deformations / strains were read out successfully.