Suffusion, one of the modes of internal erosion, occurs when fine particles are detached under hydraulic force. More fine particles are washed out with the void growth, which subsequently causes the failure of earthworks. At present, constitutive models considering suffusion are mostly established through DEM simulations and constitutive models that can capture the main features of eroded soils are quite limited. This study aims to establish constitutive equations to model the mechanical behaviour of soils subjected to suffusion by using drained triaxial experimental data. The modified subloading Cam-clay model incorporated with the normal yield surface for the eroded soil is proposed, which can express the variation of the normal yield surface with the loss of fine particles. The determination method of the erosion-related model parameters is also proposed. The erosion-related model parameters are estimated through empirical equations with curve-fitted parameters. Finally, the capability of this modified model is demonstrated through the comparisons with experimental results.

During the construction stage of the small radius TBM (tunnel boring machine) interval, the improper control of the boring parameters and the boring posture can cause the horizontal axis deviation of the shield tunnel. In order to address this issue, the TBM segments lining structure of the small radius interval is simplified as the continuous circular curved beam based on the longitudinal equivalent continuous model and Winkler elastic foundation beam theory. The theoretical model is solved through the transfer matrix method, and its applicability is verified by comparing it with the field monitoring data. It is found that the horizontal axis deviation of the completed tunnel increases with the total jack thrust, and the lateral displacement tends to be stable when the distance between the ring and the tail is far. The horizontal axis deviation has a negative relationship with the thrust difference or path difference when the jack thrust in the outside of the shield curve is larger than that of inside the shield curve. The horizontal axis deviation has a positive relationship with the thrust difference or path difference when the jack thrust in the outside of the shield curve is smaller than that of inside the shield curve.