Large deformation of rich water loess tunnels has been a serious problem for a long time. To analyze the causes of large deformation and give countermeasures, a model is established based on the Yulinzi tunnel in Gansu by the load-structure method. This model considers support forces including the friction force and bearing capacity. Calculation results show that the main causes for the large deformation are lack of systematic bolts, insufficient strength of foot steel pipe and foundation softening caused by the accumulation of groundwater. To solve these problems, four kinds of countermeasures are proposed. Through the model calculation, increasing the diameter of the foot steel pipe is more efficient to control the deformation. The study shows that the model can provide the influence degree of each factor on the deformation of the tunnel. Moreover, the model helps find a way to control deformation and provides a practical guide for the construction of similar projects.

loess tunnel;foot steel pipe;large deformation