Ability of three different soil constitutive models to predict a tunnel’s response to basement excavation

Abstract

Many constitutive models are available nowadays to predict soil-structure interaction problems. It is sometimes not very easier for engineers to select a suitable soil model to carry out their design analyses in terms of complexity versus accuracy. This paper describes the application of three constitutive models to back-analyse a well-instrumented centrifuge model test, in which the effect of basement excavation on an existing tunnel was simulated. These three models include a linear elastic-perfectly plastic model with the Mohr-Coulomb failure criterion (called MC model), a nonlinear elastic Duncan-Chang model (DC) and a hypoplastic model (HP), the last of which can capture path-dependent and strain-dependent soil stiffness even at small strains. By comparing with measured data from the centrifuge model test, it is found that the HP model yielded the best predictions of tunnel heave among the three models. Not only the gradient but also the magnitude of tunnel heave is predicted well by this HP model. This can be explained by the fact that the HP model can capture the path-dependent and strain-dependent soil stiffness even at small strains but not the MC and DC models. However, all three models underestimated the change in tunnel diameter and the maximum tensile bending strain in the transverse direction.

Effect of Soil Reinforcement on Tunnel Deformation as a Result of Stress Relief

“…The concentrated stress may increase largely beneath the diaphragm wall and then dissipate behind the wall. Thus, it is possible that there will be an increase in stress, which has also been observed in the literature [14]. The vertical stress in the soil increased by more than 100 kPa.…”

“…The Young's modulus and Poisson's ratio of the aluminum alloy were 70 GPa and 0.2, respectively. The sand was simulated using the Mohr-Coulomb model as a first-order model based on the comparison reported by Ng et al [14]. To describe the mechanical behavior of the soil in this model, five parameters are needed: Young's modulus E, Poisson's ratio ν, friction angle ϕ, cohesion c, and dilatancy angle ψ.…”

“…The chosen parameters are listed in Table 1. The parameter selection process and parameter values have been reported by Ng et al [14].…”

“…If the induced tunnel deformation and internal forces exceed the capacity of the tunnel structures, segment cracking, leakage, and even longitudinal distortion of the railway track may occur and seriously threaten the smooth travel and safety of the trains in operation. Many studies have investigated the effects of adjacent excavation on existing shield tunnels using various methods, including in situ monitoring [1][2][3], centrifuge model tests [4][5][6], numerical analysis [7][8][9][10][11][12][13][14][15], and semi-analytical methods [16][17][18][19]. For example, the main objects of investigation have been the excavation dimension [13,15], relative distance between the tunnel and excavation [4,8,9,11,13], construction and reinforcement methods [10,12], tunnel dimension and physical parameters [9,13], soil density and wall stiffness [6], different constitutive models [14], and influence zone [20].…”

“…However, its influence law and deformation mechanism are not clear yet. On the basis of the centrifuge model test without ground reinforcement and the calibrated constitutive models reported by Ng et al [14], a finite element analysis was conducted to investigate the effect of ground reinforcement on tunnel deformation, both in the longitudinal and in the transverse directions. The effect of the reinforced soil's Young's modulus and the effect of the reinforcement depth under the basement bottom were investigated.…”