Classification of Weak Rock Masses in Dam Foundation and Tunnel Excavation

1996 AEG Student Professional Paper: Graduate Division A Graphical Method for the Classification of Rock and Weak Rock Masses Based on Field Observations

Environmental and Engineering Geoscience ◽

10.2113/gseegeosci.iii.1.7 ◽

1997 ◽

Vol III (1) ◽

pp. 7-12 ◽

Cited By ~ 3

Author(s):

K. PALICKI

Keyword(s):

Graphical Method ◽

Weak Rock ◽

Field Observations ◽

Rock Masses ◽

Weak Rock Masses

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Tunnel behaviour associated with the weak Alpine rock masses of the Driskos Twin Tunnel system, Egnatia Odos Highway

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0025 ◽

2013 ◽

Vol 50 (1) ◽

pp. 91-120 ◽

Cited By ~ 12

Author(s):

N. Vlachopoulos ◽

M.S. Diederichs ◽

V. Marinos ◽

P. Marinos

Keyword(s):

Numerical Models ◽

Three Dimensional ◽

Monitoring Data ◽

Tunnel Construction ◽

Weak Rock ◽

Rock Masses ◽

Tunnel Excavation ◽

Twin Tunnel ◽

Geological Conditions ◽

Weak Rock Masses

Based on the excessive deformations and support failure encountered during tunnel construction at the Driskos Twin Tunnel site in Northern Greece, this paper provides insight on how tunnels designed in such weak rock environments can be realistically analyzed with a view of determining better analytical tools to predict deformations and improving current design methods. Specific factors that were assessed include rock strength based on the geological strength index (GSI), tunnel deformation, numerical analysis techniques employed, three-dimensional model type, support considerations, dilation, sequencing of tunnel excavation, influence of single bore construction on twin bore, and homogenization of tunnel faces. This work involves the use of nominally identical two- and three-dimensional numerical models of tunnel sequencing for analytical simulation of weak material behaviour and sequential tunnel deformation response with the goal of investigating the strength and deformation of such weak rock masses. These have been used in combination with monitoring data that were obtained in the field during the Driskos Twin Tunnel construction. A discussion of the geological conditions, material property determination, monitoring data, and model calibration strategy is given. This paper provides insight into these issues and poses many more fundamental questions regarding the analysis of tunnel excavation within weak rock masses requiring further investigation.

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Investigation into the influence of excavation of twin-bored tunnels within weak rock masses adjacent to slopes

Canadian Geotechnical Journal ◽

10.1139/cgj-2017-0392 ◽

2018 ◽

Vol 55 (11) ◽

pp. 1533-1551 ◽

Cited By ~ 3

Author(s):

N. Vlachopoulos ◽

I. Vazaios ◽

B.M. Madjdabadi

Keyword(s):

Numerical Models ◽

Three Dimensional ◽

Weak Rock ◽

The Novel ◽

Pillar Width ◽

Rock Masses ◽

Tunnel Excavation ◽

Twin Tunnel ◽

Overall Stability ◽

Weak Rock Masses

The focus of this investigation is twin tunnelling projects designed and constructed adjacent to slopes. To this end, several state-of-the-art two-dimensional (2-D) and three-dimensional (3-D) numerical models for multiple scenarios were utilized. The novelty of this research (further highlighted by two case studies) explicitly demonstrates that for 2-D and 3-D elastic and plastic analyses for weak rock masses, the interaction between the two tunnel branches for various conditions show how the pillar width minimally influences such interaction past two diameter widths of separation. As well, the 3-D sequential longitudinal tunnel excavation of the twin tunnel does not significantly influence the crown displacements of the two tunnels prior to construction of the mid-span of the twin tunnel. Slope stability analysis was conducted by employing the novel shear strength reduction (SSR) method. These findings confirm that changes in the location of the twin tunnels with respect to the slope and one another in combination with the natural angle of the slope can improve the overall stability without any other special measures taken. As well, by having the twin tunnel pillar width constant, the vertical translation of the tunnels (i.e., increase in the overburden) is more beneficial than that of a horizontal translation, resulting in a higher factor of safety.

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