LARGE-SCALE TRIAXIAL TESTING OF GREYWACKE ROCKFILL

This Paper describes the results of a series of large-scale triaxial tests conducted on greywacke rockfill, used in dam construction in Southern Thailand. The tests are conducted at low to moderate confining stresses to relate their findings to the stability of rockfill dams. Considering the current test results in conjunction with previous laboratory data, revised failure criteria for rockfill are proposed in non-dimensional form. For both low and high confining stresses, lower and upper bounds of strength envelopes have been established, based on a wide array of granular materials. The influence of the confining stress on the shear strength of rockfill is studied in depth, and the implications of a non-linear envelope at low normal stress levels on the stability of rockfill dams are discussed. Although two parallel rockfill gradations for specimens compacted to similar porosities are considered, the exact role of particle size effect on shear strength is not examined in detail, as the difference in maximum particle sizes tested in this study is not sufficiently large.