Plane strain and conventional triaxial compression tests are performed on coarse-grained soil by the TSW-40 type true triaxial apparatus in Hohai University. The stress-strain relations and relationships between different strains of coarse-grained soil in plane strain condition are studied

including the relations between principal stress difference ? 1-? 3(or ? 2-? 3) and maximum principal strain ?1

principal stress ratio ? 1 /? 3(or ? 2 /? 3) and maximum principal strain ?1

spherical stress p and volumetric strain ?v

deviator stress q and deviator strain ? s

generalized stress ratio q/p and generalized shear strain ?s

maximum principal strain ?3 and maximum principal strain ?1

volumetric strain ? v and generalized shear strain ? s. The experimental results show that with the same ? 3

the ? 1-? 3 (or ? 1/? 3) curves in plane strain tests lie above those in conventional triaxial tests; the ? 1-? 3(or ? 2-? 3) curves with larger σ3 lie above those with smaller ? 3

while the ? 1/? 3(or ? 2 /? 3) curves with larger ? 3 lie below those with smaller ? 3; at the same σ3 and ? 1

the expansion in the direction of minor principal stress in plane strain condition is larger than that in conventional triaxial condition; at the same ? s

the larger the ? 3 is

the larger the ? v would be

and the volumetric strain ? v in plane strain condition would be larger than that in conventional triaxial compression condition at the same ? 3. There is a uniform hyperbolic stress-strain relationship in both plane strain and conventional triaxial compression conditions. It is proved that it is necessary to consider the anisotropy of elastic modulus E and Poisson’s ratio ? in the calculation of plane strain problems of coarse-grained soil by nonlinear elastic models.