Undrained shear behavior of loess saturated with different concentrations of sodium chloride solution

A series of ring-shear tests was conducted on saturated loess to investigate the effects of NaCl concentration in pore water and desalinization on the shear behavior under undrained conditions. The loess samples were taken from the ground surface of a frequently active landslide in China, were saturated by de-aired, distilled water with different concentrations of NaCl, and then were sheared undrained. After that, the samples were retrieved, remolded, re-set into the shear box, and re-saturated by passing through de-aired, distilled water such that the samples were desalinized, and then were sheared undrained again. Through comparing the undrained shear behavior, the effects of NaCl in the pore-water and desalinization on the undrained shear behavior of loess were examined. The results showed that the variation of NaCl concentration in pore water can strongly affect the shear behavior of saturated loess. Both the peak shear strength and steady-state strength increased with increase of NaCl concentration until a certain value, after which they decreased with further increase of NaCl concentration. Meanwhile, the peak shear strength and steady-state strength of the desalinized samples recovered to those of the original sample; hence, the effects of salinization are reversible. These findings may be of practical importance to better understand the repeated occurrence of some irrigation-induced loess landslides in China.