Anisotropic deformation and strength characteristics of gravels in large-scale plane strain and triaxial compression tests

A large plane strain and triaxial apparatus with local strain measurements was developed to study the stress-strain behavior of gravels for a wide strain range from 10(-6) to that at the peak. Specimens were prepared by the air-pluviated or vibration compacted method and by changing the angle delta of bedding plane to or direction between 0 degrees and 90 degrees. Test results from plane strain compression and triaxial compression tests on three types of gravels showed that the strength was clearly a function of delta, with the maximum value at delta = 90 degrees and minimum one at delta = 30 degrees, and it's variation with delta was similar to those of air-pluviated sands. The pre-peak deformation properties including initial elastic modulus obtained at very small strains were also considerably anisotropic with the largest stiffness at delta = 90 degrees.