Time-dependent behavior of tunnel lining in weak rock mass based on displacement back analysis method

Analysis of time-dependent deformation in tunnels using the Convergence-Confinement Method

An exact closed form solution is derived for the mechanical behaviour of a linear viscoelastic Burgers rock around an axisymmetric tunnel, supported by a linear elastic ring. Analytical formulae are provided for the displacement of the rock/lining interface and for the pressure exerted by the rock on the lining, taking into account the stiffness and its installation time. Results calculated from these formulae do validate the corresponding numerical results of a 2D finite differences code. Further, comparison to previous existing solutions for the same viscoelastic model indicates similarities and differences. A parametric study is performed to investigate the effect of the viscoelastic constants, the stiffness and installation time of the support. The derived closed form solution is used to construct the time-dependent Supported Ground Reaction Curves of the viscoelastic rock, i.e. the time contour plots on the convergence confinement diagram. The importance of the effect of the support on the restrained rock creep and the exerted pressure on the lining, during the design life of a structure, is examined.

Supported Axisymmetric Tunnels Within Linear Viscoelastic Burgers Rocks

Coupled analytical solutions for deep-buried circular lined tunnels considering tunnel face advancement and soft rock rheology effects

Due to the time dependency of the crack propagation, columnar jointed rock masses exhibit marked time-dependent behaviour In this study, in situ measurements, scanning electron microscope (SEM), back-analysis method and numerical simulations are presented to study the time-dependent development of the excavation damaged zone (EDZ) around underground diversion tunnels in a columnar jointed rock mass Through in situ measurements of crack propagation and EDZ development, their extent is seen to have increased over time, despite the fact that the advancing face has passed Similar to creep behaviour, the time-dependent EDZ development curve also consists of three stages: a deceleration stage, a stabilization stage, and an acceleration stage A corresponding constitutive model of columnar jointed rock mass considering time-dependent behaviour is proposed The time-dependent degradation coefficient of the roughness coefficient and residual friction angle in the Barton–Bandis strength criterion are taken into account An intelligent back-analysis method is adopted to obtain the unknown time-dependent degradation coefficients for the proposed constitutive model The numerical modelling results are in good agreement with the measured EDZ Not only that, the failure pattern simulated by this time-dependent constitutive model is consistent with that observed in the scanning electron microscope (SEM) and in situ observation, indicating that this model could accurately simulate the failure pattern and time-dependent EDZ development of columnar joints Moreover, the effects of the support system provided and the in situ stress on the time-dependent coefficients are studied Finally, the long-term stability analysis of diversion tunnels excavated in columnar jointed rock masses is performed

Analysis of EDZ Development of Columnar Jointed Rock Mass in the Baihetan Diversion Tunnel

Analytical solution for the excavation of circular tunnels in a visco-elastic Burger’s material under hydrostatic stress field

Ovaling deformations develop when waves propagate perpendicular to the tunnel axis. Two analytical solutions are used for estimating the ovaling deformations and forces in circular tunnels due to soil-structure interaction under seismic loading. In this paper, these two closed form solutions will be described briefly, and then a comparison between these methods will be made by changing the ground parameters. Differences between the results of these two methods in calculating the magnitudes of thrust on tunnel lining are significant. For verifying the results of these two closed form solutions, numerical analyses were performed using finite element code (ABAQUS program). These analyses show that the two closed form solutions provide the same results only for full- slip condition.

Arash Vakilzadeh

Papers

Analytical solution for the excavation of circular tunnels in a visco-elastic Burger’s material under hydrostatic stress field

Numerical and Analytical Solutions for Ovaling Deformation in Circular Tunnels Under Seismic