Deep soaking test study of collapsible loess foundation controlling remnant collapse

A site of self-weight collapse loess with heavy section is treated by four treating depths of lime soil(pure soil) compaction pile; and beneath the compaction reign, deep soaking test on the untreated loess is carried out in order to research the law of collapse deformation, treating depth and reasonable limit of remnant collapse of the self- weight collapse loess with heavy section in this soaking condition. The results show that, when the foundation of self-weight collapse loess with heavy section is treated with lime soil and pure soil, the compaction effects of lime soil and pure soil have little difference. In case of deep soaking, the deformation in treated region with 6-15 m depths cannot meet loess code's demands about upper load and presents a triple-section law: stable in the first test stage, slowly decreasing in middle stage, and suddenly dropping in later stage. According to the correlated researches of field soaking tests and neutral point of pile foundation, the concept of critical collapsibility depth of self-weight collapse loess with heavy section has been proposed firstly; and the critical depth is set as 20-25 m temporarily. In this way, the remnant collapse of deep loess layer can be decreased to certain degree; and the aim to limit treating depth of loess foundation is achieved. It is suggested that 15-20 and 10-15 m can be set respectively as the maximum treating depth of class B and C building in self-weight collapse loess area with heavy section.