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.

Basement excavation inevitably causes stress changes in the ground leading to 38 soil movements which may affect the serviceability and safety of adjacent tunnels. Despite 39 paying much attention to the basement-tunnel interaction, previous research has mainly 40 focused on the influence of tunnel location in relation to the basement, tunnel stiffness and 41 excavation geometry. The effects of sand density and basement wall stiffness on nearby 42 tunnels due to excavation, however, have so far been neglected. A series of three-dimensional 43 centrifuge tests were thus carried out in this study to investigate these effects on the complex 44 basement-tunnel interaction. Moreover, three-dimensional numerical analyses and a 45 parametric study by adopting hypoplastic sand model were conducted to improve the 46 fundamental understanding of this complex problem and calculation charts were developed as 47 a design tool. When the basement was constructed directly above the existing tunnel, 48 excavation-induced heave and strain were more sensitive to a change in soil density in the 49 transverse direction than that in the longitudinal direction of the tunnel. Because a looser sand 50 possesses smaller soil stiffness around the tunnel, the maximum tunnel elongation and 51 transverse tensile strain increased by more than 20% as the relative sand density decreased by 52 25%. Moreover, the tensile strain induced along the longitudinal direction was insensitive to 53 the stiffness of the retaining wall, but that induced along the transverse direction was 54 significantly reduced by a stiff wall. When the basement was constructed at the side of the 55 existing tunnel, the use of a diaphragm wall reduced the maximum settlements and tensile 56 strains induced in the tunnel by up to 22% and 58%, respectively, compared with the use of a 57 sheet pile wall. Under the same soil density and wall stiffness, excavation induced maximum 58 movement and tensile strains in the tunnel located at a side of basement were about 30% of 59 the measured values in the tunnel located directly beneath basement centre. 60

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In comparison with tetragonal retaining structures, circular retaining structures have an advantage in terms of controlling the deformation caused by foundation excavation, and are a reasonable choice in engineering practice. Many results have been obtained regarding the effect of tetragonal excavation on the deformation of an adjacent tunnel. Nevertheless, a sufficient understanding of the circular excavation’s effect on the deformation of an adjacent tunnel is currently lacking. Therefore, this study focused on the problem of precise predicting tunnel deformation below a circular excavation. A numerical model was established to calculate the tunnel deformation caused by the circular excavation. An advanced nonlinear constitutive model, known as a hypoplasticity model, which can capture path-dependent and strain-dependent soil stiffness even at small strains, was adopted. The models and their associated parameters were calibrated by centrifuge test results reported in the literature. The deformation mechanism was revealed, and the calculated results were compared with those obtained with a square excavation and the same excavation amount. The differences between the deformations caused by these two types of excavation shapes were analyzed. It was found that under equal excavation area conditions, the excavation-induced deformations of the metro tunnel below a circular excavation were approximately 1.18–1.22 times greater than those below a square excavation. The maximum tunnel tensile bending strain caused by the circular excavation was 32% smaller than that caused by the square excavation. By comparing with the measured results, it is proved that the proposed numerical method can provide effective reference for engineers to analyze soil-structure problems.

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To solve the control problem of the surrounding rock of gob-side entry retaining under typical roof conditions in deep mines, we conduct theoretical analysis, numerical simulation, and actual measurements. Starting from the plastic zone of the surrounding rock, the serious damage area, the degree and scope of damage, and the dynamic evolution process of the surrounding rock of the gob-side entry retaining are systematically analyzed under four typical roof conditions in deep mines; the expansion and evolution laws of the plastic zone of the surrounding rock are expounded; and a key control technology is proposed. The results indicate that (1) the plastic failure of surrounding rock was concentrated mainly on the coal side and on the floor, especially in the filling body. The plastic zone of the surrounding rock of the gob-side entry retaining with the thick immediate roof was widely distributed and deep, but the plastic failure of the filling body was not obvious. The plastic failure of the surrounding rock of the gob-side entry retaining with the compound roof was mainly concentrated on the roof, filling body, and floor of the filling area. (2) According to the typical roof conditions of the deep gob-side entry retaining, the order of the degree of damage to the surrounding rock was as follows: thick immediate roof, compound roof, thin immediate roof, and thick-hard roof. (3) A “multisupport structure” control system is proposed for the gob-side entry retaining in a deep mine, including measures for enhancing the bearing performance of the anchorage system, increasing the strength of the cataclastic coal-rock mass, enhancing the bearing capacity of the filling body, and increasing the bearing capacity on the tunnel side. The proposed technology was applied to the deep gob-side entry retaining project in the east area of Panyi Mine, and it effectively fulfilled the reuse requirements of gob-side entry retaining in deep mines.