Test on triaxial shear properties of saturated undisturbed Q_2 loess in deep-buried tunnel

With a GDS multifunctional triaxial apparatus,the conventional consolidated undrained triaxial shear tests were carried out to study the effects of deformation,changes of pore-water pressure and properties of strength of saturated undisturbed Q_2 loess in the fifteenth tunnel of Yintao water transmission project in Gansu province.Based on scientific interpretation and analysis of test data,the stress-strain curve of saturated undisturbed Q_2 loess under a conventional consolidated undrained triaxial shear test showed a strain softening, while the failure model displayed brittle failure.The softening behavior of the stress-strain curve had a trend of attenuation with the increase of confining pressure,and the strain before the peak was approximately elastic. During the process of shear test,the pore-water pressure was positive.Under lower confining pressure,the porewater pressure curve had peak value and the shape of pore-water pressure curve looked like softening.While the pore-water pressure under a larger confining pressure increased with an increasing axial strain.It was also shown that the strength of undisturbed Q_2 loess would increase with the confining pressure and the breaking stress of loess would augment with it.The curve of the effective stress path had a similar linear shape.