Shallow tunnel face stability analysis using finite elements

Purpose. This work aims to study the tunnel face stability (Algiers subway Tunnel) and evaluate common numerical procedures that are used for analyzing the tunnel face stability. Two-dimensional (2D) and three-dimensional (3D) Finite Element (FE) modeling using PLAXIS programs. Methodology. Tunneling is executed by the NATM method; two types of calculations are used. The first one is done by reducing the applied face pressure until the face is collapsed. The second calculation method involves the Phi-c (the angle of internal friction and bonding) reduction method, which is based on calculating the safety factor of the shear strength of the soil. Both methods are applied for 2D and 3D FE-modelling. Findings. It is found that determining the applied face pressure is an important consideration to avoid face failure or excessive deformations with numerical methods resulting in more precise findings than analytical methods. Originality. The originality of this work is the use of both 2D and 3D modelling, combined with two approaches: structural analysis of plastic state and Phi-c reduction method based on calculating the safety factor of the shear strength of the soil. Practical value. This study illustrates that the reducing shear strength method is much better than the reducing applied face pressure method. Moreover, the result of 3D FE-modelling gives a better prediction comparing with the 2D FE-modelling results.

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

Computers and Geotechnics ◽

10.1016/j.compgeo.2017.03.013 ◽

2017 ◽

Vol 88 ◽

pp. 146-151 ◽

Cited By ~ 41

Author(s):

Boonchai Ukritchon ◽

Kongkit Yingchaloenkitkhajorn ◽

Suraparb Keawsawasvong

Keyword(s):

Shear Strength ◽

Three Dimensional ◽

Tunnel Face ◽

Face Stability ◽

Tunnel Face Stability

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Probabilistic analysis of tunnel face stability considering spatially variable undrained shear strength with linearly increasing mean trend

Proceedings of the Institution of Mechanical Engineers Part O Journal of Risk and Reliability ◽

10.1177/1748006x20927152 ◽

2020 ◽

pp. 1748006X2092715

Author(s):

Hongzhan Cheng

Keyword(s):

Shear Strength ◽

Finite Difference ◽

Finite Difference Method ◽

Difference Method ◽

Undrained Shear Strength ◽

Tunnel Face ◽

Face Stability ◽

Tunnel Face Stability ◽

The Stability ◽

Undrained Shear

The inherent spatial variability of soil properties has been considered as one of the main sources of uncertainties in geotechnical problems. The need for probabilistic analysis of the tunnel face stability that takes into account the variability of soil properties has been acknowledged. This article employed a probabilistic-based method, called random finite difference method, for evaluating the stability of tunnel face under the influence of the variability of undrained shear strength in clays. The two-dimensional spatial variation in soil undrained shear strength is modeled by random fields, which are discretized by the Covariance Matrix Decomposition method. The procedure for random finite difference method is presented. An illustrative example is employed to investigate the effect of soil variability. Particular attention has been paid to the situation that undrained shear strength increases with depth. The results demonstrate that ignoring the variability of undrained shear strength will result in overestimates of the tunnel face stability if the support pressure of the tunnel face exceeds the deterministic value, especially for higher coefficient of variation of soil undrained shear strength. Minor differences in the failure mechanism are observed in comparison to the deterministic case, considering only the global failure of the tunnel face is observed. In addition, ignoring the increase of undrained shear strength with depth will lead to conservative designs. The random finite difference method can provide a practical tool for evaluating the stability of a tunnel face in variable soils.

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Analisis Stabilitas dan Deformasi Terowongan Kereta Cepat Indonesia dengan Pendekatan Numerik Tiga Dimensi

RekaRacana: Jurnal Teknil Sipil ◽

10.26760/rekaracana.v6i2.111 ◽

2021 ◽

Vol 6 (2) ◽

pp. 111

Author(s):

Rinaldi Alamsyah ◽

Indra Noer Hamdhan

Keyword(s):

Static Analysis ◽

Safety Factor ◽

Tunnel Face ◽

Face Stability ◽

Level Of Activity ◽

Tunnel Face Stability ◽

The Stability ◽

High Level ◽

Double Track ◽

Plaxis 3D

ABSTRAKWilayah perkotaan yang didalamnya terdapat perkantoran dan tempat yang memiliki tingkat kegiatan yang sangat tinggi, menjadikan struktur terowongan bawah tanah sebagai salah satu solusi untuk meningkatkan infrastruktur transportasi secara optimal. Terowongan kereta cepat Indonesia merupakan salah satu terowongan yang dibangun dan berlokasi di Halim, DKI Jakarta. Terowongan dengan panjang 1.885 m ini memiliki jalur ganda (Double Track Railway). Untuk mengetahui stabilitas dan deformasi terowongan pada saat konstuksi, dilakukan analisis geoteknik. Analisis yang dilakukan yaitu analisis statik dan kondisi longterm dengan analisis dinamik. Tunneling Bore Machine (TBM) dengan sistem perkuatan linning precast dan grouting dipilih sebagai metode konstruksi untuk membangun terowongan. Pemodelan analisis statik menghasilkan deformasi terbesar 0,03056 m dan nilai faktor keamanan 1,869.Kata kunci: terowongan kereta cepat Indonesia, stabilitas, deformasi, faktor keamanan, TBM, PLAXIS 3D, linning, grouting ABSTRACTUrban areas with offices and places that have a very high level of activity make underground tunnel structures one of the solutions to optimally improve transportation infrastructure. The Indonesian fast train tunnel is one of the tunnels built and located at Halim, DKI Jakarta. The tunnel with a length of 1,885 m has a double track (Double Track Railway). To determine the stability and deformation of the tunnel during construction, a geotechnical analysis was performed. The analysis performed is static analysis and longterm conditions with dynamic analysis. Tunneling Bore Machine (TBM) with precast linning reinforcement and grouting system was chosen as the construction method for tunneling. Static analysis modeling produces the largest deformation 0.03056 m and a safety factor value of 1.869.Keywords: tunnel, face stability, deformation, safety factor, TBM, numerical method, PLAXIS 3D, linning, grouting

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Tunnel Face Stability Study in Soft Shallow Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1079-1080.170 ◽

2014 ◽

Vol 1079-1080 ◽

pp. 170-176

Author(s):

Jun Du ◽

Zhi Rong Mei ◽

Yong Zhao Chen

Keyword(s):

Three Dimensional ◽

Horizontal Displacement ◽

Stability Study ◽

Plastic State ◽

Shallow Tunnel ◽

Tunnel Face ◽

Maximum Displacement ◽

Face Stability ◽

Tunnel Face Stability ◽

The Impact

With Xiamen Jiaheyuan underground access as the project background, tunnel face stability of soft shallow tunnel was analyzed under the condition of no pre-reinforcement by means of three-dimensional finite element method. The results indicated that the ground was relaxed because the tensile stress appeared in front and top of tunnel face after excavation, at the same time, the ground into the plastic state around the tunnel face. From the point of view of deformation, the displacement of tunnel face were such as the longitudinal horizontal displacement reached the maximum, the vertical deposition following by, and the lateral horizontal displacement being the least. Further analysis showed that the longitudinal horizontal displacement in front of tunnel face mostly produced at 1.0D (one excavation width) distance before tunnel face, the maximum displacement was located at the center of tunnel face. The conclusions remind that engineers also pay attention to the tunnel face reinforcement in front and top of tunnel face to minimize the impact of surface environment during tunnel construction in soft shallow tunnels.

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