The Mechanical Behaviour of Clay Shales and Implications on the Design of Tunnels

Bonini, Mariacristina; Debernardi, Daniele; Barla, Marco; Barla, Giovanni Battista

doi:10.1007/s00603-007-0147-6

Cited by 96 publications

(25 citation statements)

References 12 publications

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“…However, engineering rock mass is usually located in a triaxial compressive stress state. Therefore, we will deduce further the creep equation of rock under three-dimensional stress state based on the above mentioned creep equation under one-dimension stress state (Bonini et al 2009). …”

Section: Triaxial Creep Test Results Of Coalmentioning

confidence: 99%

Nonlinear visco-elastic and accelerating creep model for coal under conventional triaxial compression

Yang

2015

Geomech. Geophys. Geo-energ. Geo-resour.

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On basis of triaxial creep experimental results of coal with various deviatoric stress levels, a new nonlinear visco-elastic and accelerating creep model is put forward. First, Burgers visco-elastic triaxial creep model is deduced and used to identify the creep parameters by the discrimination criterion of the square of correlation coefficient (R 2 ) and sum of least error square (Q). In Burgers visco-elastic triaxial creep model, the visco-elastic modulus G 2 of coal decreases but the visco coefficient g 1 and g 2 all increase with increasing time, which has distinct time scale effect. The Burgers visco-elastic triaxial creep model fails in predicting long-term deformation characteristics. Then by introducing a time index, a nonlinear visco-elastic triaxial creep model is put forward, which can predict better for long-term deformation behavior of coal. R 2 identified by nonlinear visco-elastic triaxial creep model is higher, but Q identified by nonlinear visco-elastic triaxial creep model is smaller 1 order than that by Burgers triaxial creep model. However, Burgers and nonlinear viscoelastic triaxial creep model is very difficult to describe the accelerating creep stage of coal. Therefore in the end, a new nonlinear accelerating creep model is put forward in order to describe the complete creep curve of coal. The nonlinear accelerating creep model has a better agreement with the experimental data.

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Section: Triaxial Creep Test Results Of Coalmentioning

confidence: 99%

Nonlinear visco-elastic and accelerating creep model for coal under conventional triaxial compression

Yang

2015

Geomech. Geophys. Geo-energ. Geo-resour.

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“…In this model, the visco-elastic strains are deviatoric and depend only on the deviatoric stress S i,j ; instead, the plastic strains are both deviatoric and volumetric and depend on r ij in accordance with the chosen flow rule (Bonini et al 2009). …”

Section: Creep Behaviormentioning

confidence: 98%

“…In this study, the contact between the cutterhead and the rock mass, as well as the contact between the shields and (Bonini et al 2009) Impact of Advance Rate on Entrapment Risk the rock mass, has been modeled by using interface elements on both the tunnel and shield boundaries, and by considering the gap between these components according to a non-uniform overcut in the shielded TBM. Crosssections of the front shield and the rear shield are illustrated in Fig.…”

Section: Numerical Modelmentioning

confidence: 99%

Impact of Advance Rate on Entrapment Risk of a Double-Shielded TBM in Squeezing Ground

2014

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Shielded tunnel boring machines (TBMs) can get stuck in squeezing ground due to excessive tunnel convergence under high in situ stress. This typically coincides with extended machine stoppages, when the ground has sufficient time to undergo substantial displacements. Excessive convergence of the ground beyond the designated overboring means ground pressure against the shield and high shield frictional resistance that, in some cases, cannot be overcome by the TBM thrust system. This leads to machine entrapment in the ground, which causes significant delays and requires labor-intensive and risky operations of manual excavation to release the machine. To evaluate the impact of the time factor on the possibility of machine entrapment, a comprehensive 3D finite difference simulation of a double-shielded TBM in squeezing ground was performed. The modeling allowed for observation of the impact of the tunnel advance rate on the possibility of machine entrapment in squeezing ground. For this purpose, the model included rock mass properties related to creep in severe squeezing conditions. This paper offers an overview of the modeling results for a given set of rock mass and TBM parameters, as well as lining characteristics, including the magnitude of displacement and contact forces on shields and ground pressure on segmental lining versus time for different advance rates.

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“…The prediction and modeling of the behavior of squeezing ground around tunnels has been the subject of many studies, and the reader is referred to the papers by Aydan et al (1996), Hoek and Marinos (2000), Hoek (2001), Barla et al (2004), Bonini et al (2009), Debernardi and Barla (2009), Sterpi and Gioda (2009), Cantieni and Anagnostou (2009aand 2009b as well as the papers by Ramoni and Anagnostou cited above for modern approaches and for further references. As indicated in Figure 1, the tunneling approaches may be divided into two large groups: those that proceed by sequential excavation (Figure 1a and b), and those that proceed by full face (Figure 1c).…”

Section: Tunneling In Squeezing Conditionsmentioning

confidence: 98%

Tunneling in Difficult Conditions - The Squeezing Case

Tonon

2012

Geotechnical Engineering State of the Art and Practice

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The Mechanical Behaviour of Clay Shales and Implications on the Design of Tunnels

Cited by 96 publications

References 12 publications

Nonlinear visco-elastic and accelerating creep model for coal under conventional triaxial compression

Nonlinear visco-elastic and accelerating creep model for coal under conventional triaxial compression

Impact of Advance Rate on Entrapment Risk of a Double-Shielded TBM in Squeezing Ground

Tunneling in Difficult Conditions - The Squeezing Case

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