Prediction of Ground Conditions Ahead of an Advancing Tunnel Face by Quantification of Vector Orientation

2014 ◽  
Author(s):  
N. Goswami ◽  
K. G. Sharma
Keyword(s):  
Tunnel Face ◽  
Ground Conditions ◽  
Vector Orientation

scholarly journals 3D Numerical Investigation of Face Stability in Tunnels with Unsupported Face

2021 ◽  
Author(s):  
DIMITRIOS GEORGIOU ◽  
ALEXANDROS KALOS ◽  
MICHAEL KAVVADAS
Keyword(s):  
Stability Parameter ◽  
Volume Loss ◽  
Tunnel Wall ◽  
Tunnel Face ◽  
Face Stability ◽  
Ground Conditions ◽  
The Face ◽  
Suitable Combination ◽  
Average Face ◽  
The Stability

Abstract The paper studies the stability of unsupported tunnel faces by analyzing the results of a large number of 3D numerical analyses of tunnel faces, in various ground conditions and overburden depths. The analyses calculate the average face extrusion (Uh) by averaging the axial displacement over the tunnel face. Limiting face stability occurs when the average face extrusion becomes very large and algorithmic convergence becomes problematic. Using the results of the analyses, a dimensionless “face stability parameter” is defined, which depends on a suitable combination of ground strength, overburden depth and tunnel width. The face stability parameter correlates very well with many critical tunnel face parameters, like the safety factor of the tunnel against face instability, the average face extrusion, the radial convergence of the tunnel wall at the excavation face, the volume loss and the deconfinement ratio at the tunnel face. Thus, semi-empirical formulae are proposed for the calculation of these parameters in terms of the face stability parameter. Since the face stability parameter can be easily calculated from basic tunnel and ground parameters, the above critical tunnel parameters can be calculated, and conclusions can be drawn about tunnel face stability, volume loss and the deconfinement ratio at the excavation face which can be useful in preliminary tunnel designs.

scholarly journals 3D Modelling of a Tunnel Re-excavation in Soft Ground

10.14311/1378 ◽  
2011 ◽  
Vol 51 (3) ◽  
Author(s):  
M. Hilar
Keyword(s):  
Ground Improvement ◽  
3D Modelling ◽  
Concrete Lining ◽  
Soft Ground ◽  
Tunnel Face ◽  
Technical Problems ◽  
Support Measures ◽  
Geological Conditions ◽  
Ground Conditions ◽  
Additional Support

The construction of the shallow tunnel at Brezno started using the Pre-Vault Method. The tunnel excavation, in complicated geological conditions, led to many difficulties which finally resulted in a collapse, when a significant part of the temporary tunnel lining collapsed. Various options for re-excavating the tunnel were evaluated prior to further construction. Finally a decision was made to separate the collapsed area into sections 9 m in length using 16 m-wide, transversally oriented pile walls, to improve the stability of the collapsed ground. The walls were constructed from the surface prior to excavation. It was also decided to re-excavate a collapsed area using the Sprayed Concrete Lining (SCL) method. Due to problematic soft ground conditions, which had been made even worse by the collapse, some additional support measures had to be considered prior to re-excavation (ground improvement, micropile umbrellas embedded into the pile walls, etc.)This paper describes numerical modelling of the tunnel re-excavation through the collapsed area. Initial calculations of the tunnel re-excavation were made using a 2D finite element method. Subsequently, further calculations to evaluate the rock mass behaviour in the collapsed area were provided in 3D. The 2D calculations were used to provide sensitivity studies, while 3D modelling was mainly used for evaluating the tunnel face stability (impact of the pile walls, impact of ground improvement) together with other factors (length of advances, moment of the temporary invert closure, etc.) The results of the modelling were compared with the monitoring results.The paper also briefly describes the construction experience (technical problems, performance of various support measures, etc.) The excavation and the primary lining construction were completed in 2006, and the tunnel was opened for traffic in April 2007.

scholarly journals Predicting Slurry Pressure Balance with a Long Short-Term Memory Recurrent Neural Network in Difficult Ground Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Qiang Wang ◽  
Xiongyao Xie ◽  
Hongjie Yu ◽  
Michael A Mooney
Keyword(s):  
Neural Network ◽  
Recurrent Neural Network ◽  
Short Term Memory ◽  
Shield Tunnel ◽  
Geological Data ◽  
Short Term ◽  
Tunnel Face ◽  
Term Memory ◽  
Ground Conditions ◽  
Long Short Term Memory

The safety of tunneling with shield tunnel boring machines largely depends on the tunnel face pressure, which is currently decided by human operators empirically. Face pressure control is vulnerable to human misjudgment and human errors can cause severe consequences, especially in difficult ground conditions. From a practical perspective, it is therefore beneficial to have a model capable of predicting the tunnel face pressure given operation and the changing geology. In this paper, we propose such a model based on deep learning. More specifically, a long short-term memory (LSTM) recurrent neural network is employed for tunnel face pressure prediction. To correlate with PLC data, linear interpolation is employed to transform the borehole geological data into sequential geological data according to the shield machine position. The slurry pressure in the excavation chamber (SPE) is taken as the output in the case study of Nanning Metro, which is confronted with the clogging problem due to the mixed ground of mudstone and round gravel. The LSTM-based SPE prediction model achieved an overall MAPE and RMSE of 3.83% and 10.3 kPa, respectively, in mudstone rich ground conditions. Factors that influence the model, including different kinds and length of input data and comparison with the traditional machine learning-based model, are also discussed.

Radiation-Induced Precipitation in Ti-6A1-4V

1980 ◽  
Vol 38 ◽  
pp. 154-155
Author(s):  
J. E. O'Neal ◽  
S. M. L. Sastry ◽  
J. W. Davis
Keyword(s):  
Dark Field ◽  
Dislocation Loops ◽  
Beta Titanium Alloy ◽  
Defect Clusters ◽  
Weak Beam ◽  
Beta Titanium ◽  
Small Defect ◽  
Radiation Induced ◽  
Vector Orientation ◽  
Defect Microstructures

The radiation-induced defect structure and nonequilibrium phase precipitation were studied in T1-6A1-4V (an alpha-beta titanium alloy), irradiated at 450 ± 30°C in row VII of the EBR-II to a fluence of 3.0 × 1021 neutrons/cm2 (En > 0.1 MeV). The Irradiation-induced defect microstructures were examined using bright-field, conventional dark-field, and weak-beam dark-field techniques. The nature of dislocations and dislocation loops was determined by standard-contrast experiments under two-beam conditions, and the small defect clusters were identified using the line-of-contrast criterion and black-white vector orientation criterion.

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