Effect of relative orientation of anisotropy planes to tunnel axis on the magnitude of tunnelling displacements

Klopčič, Jure; Logar, Janko

doi:10.1016/j.ijrmms.2014.02.024

Cited by 12 publications

(5 citation statements)

References 6 publications

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“…">IntroductionUnder natural conditions, the soil commonly exists in a normally consolidated state. However, with construction activities, such as excavation of foundation pits [13,41, 56], tunnel excavation [25, 48,51], embankment slope lling [9,20,24], the soil undergoes loading and unloading, changes in horizontal and vertical stresses, which cause the consolidation state to transition from the original isotropic consolidation to anisotropic consolidation. Many studies have emphasized the necessity of considering the anisotropy of the soil when designing and analyzing geological structures [9,20,24].…”

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confidence: 99%

WITHDRAWN: Effect of matric suction on stress-induced anisotropy behavior of unsaturated clay

Su,

Cai,

et al. 2024

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Lots of geotechnical engineering problems are closely related to the anisotropic behavior of unsaturated soils. In this paper, suction-controlled, consolidated, drained triaxial shear tests were conducted on clay under unsaturated conditions. For unsaturated clay, the effects of matrix suction (suctions of 30 kPa, 100 kPa, and 200 kPa), initial stress ratio (R1 = 0.5 and 1) and subsequent stress ratio (R2 = 1, 2 and 3) on the hydro-mechanical behavior were studied, and the evolution of water retention, stress-induced anisotropy characteristics and critical state parameters under different stress paths were obtained. The stress path exerted a substantial influence on the water retention capacity of the clay, and the initial stress ratio was found to be the determining factor for the air entry value of the clay. Under identical initial stress ratio conditions, the water retention capacity of the clay was observed to diminish commensurately with an increase in the subsequent stress ratio. As suction increases and subsequent stress ratios escalate, the specimen transitions from a state of shear shrinkage to dilatancy, the peak shear strength (qf) and initial stress ratio change from negatively to positively correlated, while the critical state volumetric strain (\(\varepsilon _{{\text{v}}}^{{\text{c}}}\)) and initial stress ratio are positively to negatively correlated, and the anisotropy of unsaturated clay undergoes a transformation from negative correlation to positive correlation with the subsequent stress ratio. The critical state saturation (\(S_{r}^{{\text{c}}}\)) exhibits a negative correlation with the initial stress ratio and subsequent stress ratio. Under the same stress path and different matrix suctions, there exists a unique critical state line in the p'-q plane passing through the origin, with its slope is critical state effective stress ratio (M'). The initial stress ratio determines the range of variation for the M' value, which is positively correlated with the subsequent stress ratio.

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confidence: 99%

WITHDRAWN: Effect of matric suction on stress-induced anisotropy behavior of unsaturated clay

Su,

Cai,

et al. 2024

Preprint

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“…12.4b). Klopčič and Logar (2014) obtained similar results and therefore concluded that tunnel advance with the dip is advantageous because in this case the major part of the displacements occurs ahead of the face and, consequently, the convergences are smaller. This conclusion is correct concerning the crown displacement, but disregards that the convergence at the invert, which under squeezing conditions is equally important, will be considerably bigger.…”

Section: Influence Of the Dip Angle On The Pre-deformationsmentioning

confidence: 57%

“…They found out that the existing expressions (valid for isotropic rock masses under a uniform state of stress) are applicable only if the plane of transverse isotropy strikes parallel to the tunnel axis; otherwise three-dimensional analyses are necessary. Klopčič and Logar (2014) and Madkour (2012) showed that a large portion of displacements occurs ahead of the tunnel face especially when tunnelling with the dip, but did not consider failure of the rock matrix. Schubert and Mendez (2017) also investigated the influence of the orientation of the schistosity on the tunnel behaviour using the example of the Galgenberg Tunnel.…”

Section: Introductionmentioning

confidence: 99%

On the variability of squeezing behaviour in tunnelling

Mezger¹

2020

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The magnitude of squeezing deformations in tunnelling often varies over short distances, even if there is no obvious change in the construction method, in the depth of cover, in the lithology or rock structure. As long as the reasons for the variability are not known, the tunnelling-induced convergences cannot be predicted with sufficient reliability. Reliable predictions, however, are important for determining the temporary support or the excavation diameter. Otherwise, large-scale tunnel repairs may be necessary, which can cause delay and additional costs due to remedial actions as well as due to the enforced interruption of other operations in progress at the same time. The analysis of different case studies concerning the AlpTransit project shows that the squeezing variability can be traced back to the heterogeneities in the rock mass at different scales as well as the variation of the orientation of the planes of anisotropy (bedding or schistosity) to the tunnel axis. In order to improve safety and economy of tunnel construction in squeezing ground, the influence of these factors on the convergences was determined quantitatively (by means of analytical solutions or numerical modelling), so that they can be used as indicators during construction for the timely identification and prediction of the squeezing behaviour. Particular attention was paid on factors, whose variation, even if small, may affect the convergences sensitively . Based on these quantitative investigations, design aids were developed, which should help the project engineer to estimate and better understand the variability of the squeezing intensity. The squeezing variability also concerns TBM tunnelling: In contrast to conventional tunnelling, shielded TBMs are particularly vulnerable to squeezing due to the very limited space available. Therefore, in order to better deal with the squeezing variability in TBM tunnelling, different (stiff as well as deformable) lining options were discussed.

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“…Simona (2014) analyzed the influence factors regarding the opening stability, including the support stiffness, rock damage and tunnel depth, and proposed an analytical approach based on the determination and integration of the rock-lining interface differential equation. Jure and Janko (2014) simulated the effect of overburden and the orientation of anisotropy plane on tunnel deformation and compared their results to the measurements at the Trojane tunnel (Slovenia). Zhao et al (2018) discussed the strengthening and isolation strategies to reduce seismic damage to tunnels and thought that the isolation layer is better to collaborate with the strengthening layer and a relatively large modulus and small thickness should be chosen for the isolation layer.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear deformation and failure characteristics of horseshoe-shaped tunnel under varying principal stress direction

2022

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To reveal the nonlinear deformation characteristics and failure mechanisms of surrounding rocks of horseshoe-shaped tunnel affected by varying principal stress directions, the physical experiments are carried out based on the similarity theory and control variable method. Simultaneously, on the basis of the statistical strength theory and meso-damage mechanics, a series of 2D numerical models which are able to consider the rock heterogeneity are established to further investigate the mechanical mechanism of damage evolution of surrounding rocks. Seven different kinds of horseshoe-shaped tunnel models are tested and the typical failure modes are analyzed according to the experimental data and numerical simulations. The results show that when the lateral pressure coefficient is small, fractures mainly develop towards the remote maximum principal stress direction; when the pressure difference between the vertical and horizontal directions is small, tunnel surrounding rocks damage seriously; initial damage of surrounding rocks basically occurs at the bottom floor corners and arch shoulders; the process of stress buildup, shadow and transfer is the fundamental mechanical process for the formation of mesoscopic damage and macroscopic failure.Overall, these achievements can provide valuable insights into the nonlinear failure mechanisms of horseshoe-shaped tunnel and will contribute to tunnel support design and stability evaluation in geotechnical engineering.

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Effect of relative orientation of anisotropy planes to tunnel axis on the magnitude of tunnelling displacements

Cited by 12 publications

References 6 publications

WITHDRAWN: Effect of matric suction on stress-induced anisotropy behavior of unsaturated clay

WITHDRAWN: Effect of matric suction on stress-induced anisotropy behavior of unsaturated clay

On the variability of squeezing behaviour in tunnelling

Nonlinear deformation and failure characteristics of horseshoe-shaped tunnel under varying principal stress direction

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