Abstract:The red mudstone in the Lanzhou area formed in arid and semi-arid environments has different physical and mechanical properties than that in other areas. This study investigates the red mudstone roadbed filling of Lanzhou-Haikou Maintenance Project in G6 Beijing-Tibet Expressway. Through a large number of conventional triaxial tests, the influences of the water content on the mechanical properties and Duncan-Zhang model parameters of the red mudstone were studied. The results show that the stress-strain curve of the red mudstone in the Lanzhou area satisfies the hyperbolic model under different moisture contents. When the moisture content is less than the optimum content, the failure mode is shear failure; when the moisture content is greater than the optimal moisture content, the failure mode is drum failure. With the increase of water content, the internal friction angle gradually decreases more than cohesion because the water content has different effects on the cohesion and internal friction angle. The mathematical model was used for fitting, and it was determined that the relation between the cohesion and water content and the relation between the internal friction angle and water content featured a quadratic parabola and logarithmic curve, respectively. The failure ratio, Rf, of Duncan-Chang model parameters under different moisture contents fluctuates within the interval (0.869, 0.984); the K value decreases linearly with the increase of water content, and the n value increases linearly with the increase of water content.
