Method for calculating coefficient of collapsibility of loess under unloading

The concomitant process of unloading and collapse exists in the loess between piles of self-weight collapse loess site subjected to inundation. It is difficult to calculate the collapse deformation of loess under unloading. The difference between unloading collapse and traditional collapse is discussed firstly, and the effects of collapse completion ratio and unloading ratio on unloading collapse deformation of loess are analyzed. Then, the unloading collapse tests are carried out considering the above-mentioned factors. The unloading collapse process is described by the collapse completion ratio, unloading collapse ratio and unloading ratio. Because they are more in accordance with the continuous unloading conditions in engineering practice, the multiple-unloading tests are mainly carried out. Based on the results of single- and multiple-unloading tests, the method for calculating the coefficient of collapsibility considering unloading effect is established. Further, the method for calculating the self-weight loess between piles is obtained by using the coefficient of collapsibility under unloading. The rationality of the proposed method for unloading collapse is demonstrated through laboratory verification tests and project cases.