Influence of principal stress direction on the stress-strain-strength behaviour of completely decomposed granite

Abstract

The measurement and study of the stress-strain-strength behavior of soils in general stress states involving principal stress rotation are necessary and valuable. To investigate the strength behavior under principal stress rotation, a series of undrained tests on compacted hollow cylinder specimens of completely decomposed granite (CDG) was carried in hollow cylinder apparatus. Tests were conducted using constant inside and outside pressures and maintained a fixed angle of rotation of principal stress with the vertical (?). Seven different angles of major principal stress orientations were used to cover the entire range of major principal stress directions from vertical to the horizontal. Two different confining stresses were used to find out the variations of the experimental results. It is observed that the deviator stresses as well as excess pore pressures decrease with the angle ?. It is also observed that specimens were getting softer with the increase of ?. The results also show a significant influence of principal stress direction angle on the strength parameters. It is found that the angle ? is related to the occurrence of cross-anisotropy and the localization which resulted in a pronounced influence on the strength parameters of the CDG specimens.Merenja i proucavanja napona-dilatacije cvrstoce tla u opstim stanjima napona ukljucujuci glavni napon rotacije su neophodna i dragocena. Da bi se istrazilo ponasanje cvrstoce pod glavnim naponom rotacije, sproveden je niz opita na uzorcima raspadnutog granita (CDG) sabijenim u supljem cilindru. Opiti su sprovedeni uz stalne unutrasnje i spoljne pritiske uz odrzavanje fiksnog ugla rotacije glavnih napona sa vertikalom (?). Korisceni su sedam razlicitih uglova orjentacije glavnih napona za da se pokrije opseg pravaca glavnih napona od vertikale do horizontale. Dva razlicita ogranicavajuca napona koriscena su za iznalazenje varijanti eksperimentalnih rezultata. Primeceno je da devijator napona kao i prekoracenje pornog pritiska opada sa uglom ?. Takodje je primeceno da su uzorci sve meksi sa povecanjem ugla ?. Rezultati takodje pokazuju znacajan uticaj ugla glavnih napona na parametre cvrstoce. Uoceno je da je ugao ? vezan za pojavu poprecne anizotropije i lokalizaciju koja je rezultirala izrazenim uticajem na parametar cvrstoce CDG uzoraka.