The pre-soaking method is widely used to address loess collapsibility. However, this method requires a long construction time and has a limited application range. To foster the strengths and avoid the weaknesses of the pre-soaking method regarding ease of use, acid-addition collapsibility tests and acid-addition shear tests were performed to investigate the effect of combining the pre-soaking method with the use of an acetic acid solution. This approach is based on the principle that acid can dissolve cemented connections, which is the main factor of loess collapsibility, in a short period of time. Moreover, a Scanning Electron Microscope (SEM) was used to observe the features of loess samples before and after these tests. The SEM images also confirm our inferred conclusions. The experimental results showed that, compared with the conventional pre-soaking method, the addition of acetic acid sharply decreases the loess collapsibility under low pressure condition and reduces the construction time. In addition, the proposed approach simultaneously increases the strength of modified soil under low pressure conditions. Further, the addition of acetic acid allows the pre-soaking method to be applied to a non-self-weight collapsible loess, to which the conventional pre-soaking method cannot be applied.
