Abstract: Unconsolidated-undrained triaxial shear test was conducted on weathered sand from the Three Gorges Reservoir area stabilized by lime-fly ash. The ratio of lime to fly ash was 1∶2, 1∶3, 1∶4, and the corresponding lime dosage was 4%, 5%, and 6%. The shear strength indexes of weathered sand stabilized by different dosages of lime-fly ash were obtained, and then the results of triaxial test were compared with those obtained by direct shear test. Conclusions are as follows: 1) the stress-strain curve of weathered sand stabilized by lime-fly ash displays strain softening feature under different confining pressures; 2) the change of lime-fly ash content in specimens exerts little impact on the internal friction angle, but dramatic impact on cohesion; 3) at a stable lime content, cohesion increases with the rise of fly ash content, while internal friction angle increases but then declines with the rise of fly ash content. Comparison between triaxial test and direct shear test results reveals that the cohesion obtained by triaxial test is greater than that by direct shear test, but the value of internal frictional angle shows little difference.

Key words: lime-fly ash, weathered sand, triaxial test, internal friction angle, cohesion, Three Gorges Reservoir area