Abstract: Traditional pre-immersion method requires long immersion time with the scope of immersion treatment difficult to determine. In view of this, a borehole pre-immersion method to eliminate the collapsibility of loess is proposed in line with the law of water movement in soil based on the reliability theory, the limit state design method and the compound Poisson process principle. The deterministic model of the horizontal and vertical immersion influence range is given. On this basis, the method of determining the parameters of water immersion holes such as hole depth, hole spacing and the number of holes is given in association with Darcy’s law. Combined with a project in Tongchuan, the rationality of the proposed method is verified by borehole pre-immersion test on site at Tongchuan, and the treatment effect of the method is further evaluated through on-site drilling, on-site exploration, and indoor collapsibility test. The proposed immersion method is proved to be of short immersion time, controllable range of immersion influence via the layout of immersion holes, and sound treatment effect, which fully meets construction requirements.

Key words: collapsible loess, borehole pre-immersion method, effective immersion radius, depth of immersion influence, reliability theory, limit state design method