In order to study the influence of collapsibility of large thickness collapsible loess stratum on the underground structure of urban rail transit, aiming at the shortcomings of inaccuracy of traditional indoor test evaluation results, selects typical large thickness collapsible loess construction site based on DOUDAOGOU station of the first phase project of Lanzhou Metro Line 3, and tests the different depths of the ground infiltration process through the ground water immersion test. In this paper, the collapsible deformation characteristics of the existing loess stratum are studied and verified by the results of laboratory tests. The results show that: ① the collapsibility of loess in the site is sudden, and the collapsibility deformation of surface soil layer and deep soil layer generally presents three stages: steep increase, sudden drop and stable; ② the collapsibility coefficient of loess in the site decreases with the increase of loess depth, and the relation curve between the selfweight collapsibility coefficient and depth conforms to the power function, with the correlation of 0.983; ③ The correction coefficient of selfweight collapsible deformation of collapsible loess stratum is suggested to be 1.675 in Lanzhou area. The research results can be used for reference in the design and construction of Metro in Lanzhou area.
