This study focused on exploring the specificity of mechanical behavior for completely weathered granite, as a special soil, by consolidated drained triaxial tests. The influences of dry density (1.60, 1.70, 1.80 and 1.90 g/cm(3)), confining pressure (100, 200, 400 and 600 kPa), and moisture content (13.0%, that is, natural moisture content) were investigated in the present work. A newly developed Duncan-Chang model was established based on the experimental data and Duncan-Chang model. The influence of each parameter on the type of the proposed model curve was also evaluated. The experimental results revealed that with varying dry density and confining pressure, the deviatoric stress-strain curves have diversified characteristics including strain-softening, strain-stabilization and strain-hardening. Under high confining pressure condition, specimens with different densities all showed strain-hardening characteristic. Whereas at the low confining pressure levels, specimens with higher densities gradually transform into softening characteristics. Except for individual compression shear failure, the deformation modes of the specimens all showed swelling deformation, and all the damaged specimens maintained good integrity. Through comparing the experiment results, the strain-softening or strain-hardening behavior of CWG specimens could be predicted following the proposed model with high accuracy. Additionally, the proposed model can accurately characterize the key mechanical indicators, such as tangent modulus, peak value and residual strength, which is simple to implement and depends on fewer parameters.

Reinforcement of soils with fibers generally increases the mechanical properties of the fiber-reinforced soil (FRS) system. However, published literature is limited to investigating the undrained response of clay and synthetic fibers, with few studies targeting natural clay and natural fibers under drained conditions. There is a need to study the response of fiber-reinforced clay systems under drained conditions to assess long-term stability. This paper investigated the drained shear strength and durability of clays reinforced with natural hemp fibers using isotropically consolidated drained triaxial tests, in which the fiber content, confining pressure, and compaction water content were varied. Results showed that the incorporation of hemp fibers improved the deviatoric stress at failure by up to 60%, which increased the drained cohesion and friction angle of the FRS by 7-10 kPa and 3-7 degrees, respectively. The increase in cohesive intercept was not affected by the compaction water content, while the increase in friction angle was pronounced in specimens compacted at optimum water content (w = 18%). Durability tests showed that the improvement in strength due to hemp fibers diminishes after 3 weeks of curing prior to drained testing, indicating the dramatic negative impact of degradation of natural fibers on the mechanical performance of fiber-reinforced clay and the need for industrial treatment of the fiber.