The stability of tunnel face accounting for the effects of groundwater

2004 ◽  
pp. 433-438
Author(s):  
R Al Hallak ◽  
J Magnan ◽  
N Droniuc
Keyword(s):  
Tunnel Face ◽  
The Stability

Stability Analysis of the Nanjung Water Diversion Twin Tunnels based on Convergence Measurement

2019 ◽  
Vol 1 (1) ◽  
pp. 49-60
Author(s):  
Simon Heru Prassetyo ◽  
Ganda Marihot Simangunsong ◽  
Ridho Kresna Wattimena ◽  
Made Astawa Rai ◽  
Irwandy Arif ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Convergence Rate ◽  
Critical Strain ◽  
Convergence Rates ◽  
Strain Analysis ◽  
Water Diversion ◽  
Tunnel Face ◽  
Tunnel Stability ◽  
The Stability ◽  
Twin Tunnels

This paper focuses on the stability analysis of the Nanjung Water Diversion Twin Tunnels using convergence measurement. The Nanjung Tunnel is horseshoe-shaped in cross-section, 10.2 m x 9.2 m in dimension, and 230 m in length. The location of the tunnel is in Curug Jompong, Margaasih Subdistrict, Bandung. Convergence monitoring was done for 144 days between February 18 and July 11, 2019. The results of the convergence measurement were recorded and plotted into the curves of convergence vs. day and convergence vs. distance from tunnel face. From these plots, the continuity of the convergence and the convergence rate in the tunnel roof and wall were then analyzed. The convergence rates from each tunnel were also compared to empirical values to determine the level of tunnel stability. In general, the trend of convergence rate shows that the Nanjung Tunnel is stable without any indication of instability. Although there was a spike in the convergence rate at several STA in the measured span, that spike was not replicated by the convergence rate in the other measured spans and it was not continuous. The stability of the Nanjung Tunnel is also confirmed from the critical strain analysis, in which most of the STA measured have strain magnitudes located below the critical strain line and are less than 1%.

scholarly journals Stability Analysis of Shallow and Bias Loess Tunnel Based on Finite Difference Method

2019 ◽  
Vol 131 ◽  
pp. 01027
Author(s):  
Li Yongbing ◽  
Binglei Li ◽  
Guanyu Hua ◽  
Xinran Jia ◽  
Yanqiao Chen ◽  
...  
Keyword(s):  
Finite Difference ◽  
Shear Failure ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Failure Zone ◽  
Tunnel Face ◽  
Whole Process ◽  
The Earth ◽  
Practical Engineering ◽  
The Stability

Based on the Mohr-Coulomb elastic-plastic model and the practical engineering background of Mopanshan tunnel, this paper applies the finite-difference software FLAC3D to simulate and analyse the whole process of loess tunnel construction. Then, it analyses the stability of the surrounding rock and sup-port structure after partial excavation of the loess tunnel under the shallow burying and unsymmetrical load-ing condition. The study showed that in the absence of support, the shear failure occurred to the top/upper pilot tunnel of the tunnel face, the failure zone under tensile stress happened to the shallow soil of the earth surface, and the soil of tunnel face appeared to be damaged. Finally, according to the analysis results, a rea-sonable construction method suitable for the shallow and bias loess tunnel is determined.

scholarly journals Upper-Bound Finite Element Adaptive Analysis of Plane Strain Heading in Soil with a Soft Upper Layer and Hard Lower Layer

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jian Zhang ◽  
Li Ding ◽  
Yu Liang ◽  
Jingyao Zong ◽  
Zhenya Li
Keyword(s):  
Finite Element ◽  
Failure Mechanism ◽  
Upper Bound ◽  
Lower Layer ◽  
Adaptive Strategy ◽  
Tunnel Face ◽  
Slip Lines ◽  
The Stability ◽  
Tunnel Depth ◽  
Soil Interface

This paper investigates the stability of a rectangular tunnel face affected by surcharge loading in soil with a soft upper layer and hard lower layer using upper-bound finite element methods with a plastic-dissipation-based mesh adaptive strategy (UBFEM-PDMA). Seven different positions for the soil interface are selected to study this problem. The upper bounds on the ultimate surcharge loads σs are presented in terms of dimensionless stability charts. The σs increases with tunnel depth, and it increases when the position of the soil interface moves up along the tunnel face. The failure mechanism primarily involves a wedge-shaped zone around the tunnel face and two slip lines originating from the top and bottom of the tunnel face, and it is mainly influenced by three factors, i.e., the position of the soil interface, the soil properties, and the tunnel depth. In contrast to the failure mechanism for uniform soil, multiple slip lines exist in the tunnel face in soil with a soft upper layer and hard lower layer. The results compare reasonably well with those in the literature and those from the numerical method.

scholarly journals A Theoretical Calculation Method of the Unsupported Span for the Shallow Tunnel in the Soft Stratum

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiaoxu Tian ◽  
Zhanping Song ◽  
Guannan Zhou ◽  
Xiaowei Zhang
Keyword(s):  
Soft Rock ◽  
Friction Angle ◽  
Soil Mass ◽  
Calculation Model ◽  
Support Pressure ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Rock Stratum ◽  
The Stability ◽  
Shallow Buried Tunnel

During the construction of the tunnel in soft stratum, it is often found that the unsupported span is too large, resulting in instability of the tunnel face and collapse of the vault. However, the unsupported span was often selected according to the experience of engineers in the actual construction process, which was lack of the theoretical basis. Therefore, based on the calculation model of the surrounding rock pressure of shallow buried tunnel, this paper analyzed the stability of the tunnel face and the vault and then obtained the calculation formula of the unsupported span of the shallow buried tunnel in soft rock stratum. It was pointed out that the unsupported span is not determined by the arch crown stability or the tunnel face stability alone, but by both. The rationality of the formula was verified by a centrifugal test and an engineering case. The analysis and discussion showed that the unsupported span is sensitive to the cohesion and internal friction angle of the rock-soil mass, especially the cohesion. The unsupported span of the shallow buried tunnel in the soft rock stratum is a linear function of the support pressure. The support pressure has a more significant contribution to the increase of the unsupported span by the centre cross diaphragm (CRD) method, and the unsupported span increases linearly with the increase of the support pressure. The research results provide a theoretical reference for the determination of the unsupported span for the shallow tunnel in the soft stratum.

The stability of a tunnel face with a free span and a non-uniform support

geotechnik ◽  
2013 ◽  
Vol 36 (1) ◽  
pp. 40-50 ◽  
Author(s):  
Georgios Anagnostou ◽  
Paolo Perazzelli
Keyword(s):  
Tunnel Face ◽  
The Stability

Three-Dimensional Analysis of Excavating Face Stability Supported by Pipe Roof

2013 ◽  
Vol 275-277 ◽  
pp. 1257-1263 ◽  
Author(s):  
Xiang Yuan ◽  
Shun Hua Zhou ◽  
Quan Mei Gong
Keyword(s):  
Analytical Solution ◽  
Dimensional Analysis ◽  
Load Transfer ◽  
Three Dimensional ◽  
Subgrade Reaction ◽  
Large Section ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Stability

This paper analyzes the load transfer characteristics of pipe roof over the excavating face, and the analytical solution of tunnel face stability is established by the method of three-dimensional analysis. Through the calculation of the load transfer of the pipe roof, it indicates that the released load of excavation is passed to the supporting structure and soil which is not excavated by the effect of the pipe roof, and the magnitude of load and coverage of impact are in connection with excavating footage as well as subgrade reaction. The three-dimensional analytical solution of tunnel face stability is used to analyze a project case of Airport Road underpass in Hangzhou. The results show that the tunnel face stability is not guaranteed when excavated on a large section while the stability is enhanced when excavated on separated pilot headings.

scholarly journals Upper Bound Solution of Safety Factor for Shallow Tunnels Face Using a Nonlinear Failure Criterion and Shear Strength Reduction Technique

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Fu Huang ◽  
Zai-lan Li ◽  
Tong-hua Ling
Keyword(s):  
Safety Factor ◽  
Upper Bound ◽  
Reduction Technique ◽  
Nonlinear Failure Criterion ◽  
Upper Bound Theorem ◽  
Tunnel Face ◽  
Bound Solution ◽  
Strength Reduction Technique ◽  
Bound Theorem ◽  
The Stability

A method to evaluate the stability of tunnel face is proposed in the framework of upper bound theorem. The safety factor which is widely applied in slope stability analysis is introduced to estimate the stability of tunnel face using the upper bound theorem of limit analysis in conjunction with a strength reduction technique. Considering almost all geomaterials following a nonlinear failure criterion, a generalized tangential technique is used to calculate the external work and internal energy dissipation in the kinematically admissible velocity field. The upper bound solution of safety factor is obtained by optimization calculation. To evaluate the validity of the method proposed in this paper, the safety factor is compared with those calculated by limit equilibrium method. The comparison shows the solutions derived from these two methods match each other well, which shows the method proposed in this paper can be considered as effective.

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