Abstract: Leaching tests under 12 kinds of stress combination were carried out to explore the weakening effect of soluble salt on the strength of compacted loess (Q2) during leaching. The ion concentration, soluble salt content and ultimate normal stress with different times of infiltration were determined. The results showed that the ion concentrations, the soluble salt amount and shear strength decreased in a step-like manner during leaching. With regard to the stress combination, the leaching stress (s) affected the form and hysteresis of the curves of ion and soluble salt; the confining pressure ( ) changed the smoothness of the curve; the soluble salt residue was positively correlated with s and . To measure the difference of soluble salt content under different , the average difference index ( ) was defined, and the index was positively proportional to s. To evaluate the process of leaching, the relative change amount of soluble salt content ( ) was defined as the dissolved salt ratio. When the value was less than 1%, the leaching process was determined to be stable. In terms of shear strength, the ultimate normal stress ( ) decreased with the decrease of relative soluble salt; s determined the intensity of the initial weakening; the difference of between different confining pressures weakened with the increase of s. The three characteristics of indicate that the occurrences of weakened strength and deformation in the leaching process are the result of the combined action of stress and changes in the soluble salt. Finally, the strength weakening formula considering the combined effect of soluble salt and stress was established.

Key words: compacted loess Q2, leaching, soluble salt, stress combination, strength weakening