Mechanical Properties and Water Holding Characteristics of Initially Isotropic Soils and Transversely Isotropic Soils

In order to investigate the difference between the mechanical properties and water quantity variation of unsaturated loess under different initial conditions, a method for preparing isotropic and transversely isotropic specimens was suggested. An improved triaxial apparatus for unsaturated soils was used to carry out 72 consolidated drained triaxial tests on prepared isotropic, transversely isotropic and regular specimens. Isotropic samples with different cutting angles were studied experimentally and found to be approximately isotropic. For three different initial states, the failure stress of the isotropic unsaturated specimen is the largest, followed by that of the transversely isotropic unsaturated specimen; the initial tangent modulus of the transversely isotropic specimen is the largest at the shear stage, while those of the other two groups are smaller and approximately equal. Both the isotropic and transversely isotropic specimens have slight dilatancy at the initial stage of shear, while all ordinary remoulded specimens are in the state of shear contraction. Under different initial conditions, the change of the suction of unsaturated samples has little effect on the drainage, the absolute slope value of the deviator stress-water content curve of the transversely isotropic sample is the lowest, and those of the other two groups are almost the same. The mechanical properties and water holding characteristics of the isotropic, transversely isotropic and ordinary remoulded specimens are different. The research results obtained may provide a useful reference for the establishment of different models of soil under different initial conditions and for various engineering applications.