Three-dimensional undrained tunnel face stability in clay with a linearly increasing shear strength with depth

Ukritchon, Boonchai; Yingchaloenkitkhajorn, Kongkit; Keawsawasvong, Suraparb

doi:10.1016/j.compgeo.2017.03.013

Cited by 114 publications

(20 citation statements)

References 11 publications

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“…At present, two methods are used to analyze the stability of the tunneling surface. One is the limit analysis method [1][2][3][4][5], which is divided into the upper limit analysis method and lower limit analysis method. Due to the complexity of calculation, the limit analysis method is seldom used in engineering.…”

Section: Introductionmentioning

confidence: 99%

Wedge Instability Model Improvement of Shield Tunnel Excavation Face under Inclined Surface

Wang

Feng

et al. 2021

Advances in Civil Engineering

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In the process of the underground tunnel excavation, a kind of geological condition Necking Region is often encountered. The ground surface inclines very fast, which also leads to the increase of Earth pressure on the excavation face. The determination of the excavation face support pressure is essential to solve the active Earth pressure when the shield passes through the Necking Region. In this paper, based on Horn’s wedge model, considering the influence of surface dip angle on excavation face support pressure, the traditional wedge model was improved. The analytical solution of the ultimate support pressure for the active failure of shield excavation face was derived. To evaluate the quality of the model, the theoretical model was compared with the ultimate bearing pressure of the horizontal surface test. The influence of the ultimate support pressure on the parameters of Nc, Nγ, and Nq was consistent with the results of finite element simulation and existing theories, which verified the rationality of the model. The stability of the excavation face of the Heyan road river crossing tunnel was analyzed by using the improved wedge model. The results show that the mud support pressure considering the slope angle was 36 kPa higher than that without considering the slope angle.

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Section: Introductionmentioning

confidence: 99%

Wedge Instability Model Improvement of Shield Tunnel Excavation Face under Inclined Surface

Wang

Feng

et al. 2021

Advances in Civil Engineering

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“…Many studies have investigated the undrained stability of shallow tunnels and sinkholes by model tests [5,6], the limit analysis method [1,[7][8][9][10][11][12][13][14][15], and the displacement finite element/difference method [16,17]. To investigate the influence of embedment ratio and tunnel heading geometry on tunnel stability, Mair [5] conducted two series of 2D/3D centrifuge model tests in clays, and found that the tunnel heading stability was strongly affected by the tunnel heading geometry.…”

Section: Introductionmentioning

confidence: 99%

Undrained Stability Analysis of Shallow Tunnel and Sinkhole in Soft Clay: The Cavity Contraction Method

Li³

et al. 2021

Applied Sciences

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This paper presents theoretical methods for the undrained stability analysis of shallow tunnels/sinkholes in clay based on the cavity contraction theory, with some assumptions and simplifications. To examine the accuracy and reliability of the new methods, a database was assembled, which consists of stability numbers of tunnel/sinkholes in clays from 22 centrifuge model tests, 10 field tests, and 62 FELA results. It is shown that the proposed methods give an average of 2.5% overestimation for the stability numbers from model tests and is in a good agreement with the FELA results. The cavity contraction theory-based methods are then discussed, which could provide useful guidance for designers to roughly assess shallow tunnel/sinkhole stability in clays.

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“…In fact, there exists an easy-to-use indicator called the stable number, N = (σ s + γH − σ T )/c u , which can be used to estimate the stability of a tunnel face. In this equation, σ s denotes the surcharge acting on the ground surface, γ is the unit weight of the soil, H is the depth to tunnel axis, σ T is the support pressure applied at the tunnel face, c u is the undrained cohesive strength of the ground prior to excavation [26][27][28]. Observations suggested that the tunnel face is deemed to be stable if the stable number N is less than or equal to 3 and deemed unstable if the stable number N is larger than 6.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Tunnel Face Stability Using a Naive Bayes Classifier

2019

Applied Sciences

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This paper develops a convenient approach for facilitating the prediction of tunnel face stability in the framework of Bayesian theorem. First, a number of values of the features influencing the face-stability of tunnels are chosen according to the full factorial design. Secondly, the software OptumG2 is utilized to performed strength reduction analyses to obtain safety factors regarding tunnel face stability. Based on the simulated safety factors, the chosen samples are labeled as stable (Fs≥1) or unstable samples (Fs<1). Thirdly, the model parameters that characterize the distribution of the random variables are then estimated by maximizing the well-known likelihood function. After that, the probability density functions (PDF) of the features are identified, and a naive Bayes classifier is constructed with the prior probabilities of the stable and the unstable state. The so-called type І and type І І errors are estimated with stable and unstable samples, respectively. The model parameters are then calibrated with additional stable samples to obtain the second classifier. Finally, the two classifiers are evaluated using independent samples that have not been seen in the training dataset. The proposed method allows geotechnical engineers to predict the stability of tunnel faces with great efficiency. It is applicable for general cases of tunnels where the parameters are within the ranges bounded by the specified values.

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Three-dimensional undrained tunnel face stability in clay with a linearly increasing shear strength with depth

Cited by 114 publications

References 11 publications

Wedge Instability Model Improvement of Shield Tunnel Excavation Face under Inclined Surface

Wedge Instability Model Improvement of Shield Tunnel Excavation Face under Inclined Surface

Undrained Stability Analysis of Shallow Tunnel and Sinkhole in Soft Clay: The Cavity Contraction Method

Prediction of Tunnel Face Stability Using a Naive Bayes Classifier

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