Loess collapsibility characteristics of railway engineering sites using large-scale trial immersion pit experiments

Estimating and preventing loess collapsibility are important for the design and construction of the Xi’an North–Airport Intercity Railway. Laboratory tests and large-scale in situ immersion experiments were carried out to assess the collapsibility characteristics, seepage field, and deformation properties of loess at sites located on the third terrace of the Wei River (Bai Qi Zhai village) and the Xianyang loess tableland (Bu Li village). The calculated and measured in situ self-weight collapsibility are 363.0 mm and 3.0 mm for the Bai Qi Zhai village experimental site (the third terrace with loess covering permeable alluvium) and 306.0 mm and 318.5 mm for the Bu Li village experimental site (loess tableland), respectively. The presence of underlying highly permeable strata inhibits the in situ collapsibility characteristics of the loess at the third terrace site. Along the project route, the third terrace of the Wei River and the loess tableland can be assessed as non-self-weight and self-weight collapsible sites, respectively, for which relevant foundation treatment methods can be suggested to alleviate the collapse settlement of the foundation of the project.