Performance of Forepole Support Elements Used in Tunnelling Within 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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Identification of Geotechnical Properties of Weak Rock Masses and Stockpiles at Tunçbilek Open Pit Mining and the Related Slope Stability Analyses

Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards - Advances in Science, Technology & Innovation ◽

10.1007/978-3-030-01665-4_30 ◽

2018 ◽

pp. 129-131

Author(s):

Zeynal Abiddin Erguler ◽

Huseyin Karakus ◽

I. Goktay Ediz ◽

Cem Sensogut

Keyword(s):

Slope Stability ◽

Geotechnical Properties ◽

Open Pit ◽

Open Pit Mining ◽

Weak Rock ◽

Rock Masses ◽

Stability Analyses ◽

Weak Rock Masses

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Empirical approaches for opening design in weak rock masses

Mining Technology ◽

10.1179/037178405x44494 ◽

2005 ◽

Vol 114 (1) ◽

pp. 13-20 ◽

Cited By ~ 3

Author(s):

Tom Brady ◽

Lewis Martin ◽

Rimas Pakalnis

Keyword(s):

Weak Rock ◽

Rock Masses ◽

Weak Rock Masses ◽

Empirical Approaches

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Application of rock mass classification techniques to weak rock masses: A case study from the Ruahine Range, North Island, New Zealand

Canadian Geotechnical Journal ◽

10.1139/t08-019 ◽

2008 ◽

Vol 45 (6) ◽

pp. 800-811 ◽

Cited By ~ 6

Author(s):

Martin S. Brook ◽

Erin Hutchinson

Keyword(s):

Rock Mass ◽

New Zealand ◽

Rock Mass Classification ◽

Early Pleistocene ◽

Weak Rock ◽

Rock Masses ◽

Classification Techniques ◽

Classification Schemes ◽

Mass Classification ◽

Weak Rock Masses

Rock mass classification systems were first generated for use in engineering applications, but their potential for utilization in geomorphic studies has since been recognized. These techniques were mostly developed for hard rock environments, and questions remain about their applicability to weak rocks. Here, the applicability of three rock mass classification techniques (rock mass strength (RMS), rock mass rating (RMR), and slope mass rating (SMR)) to weak rock masses was analyzed. Techniques incorporated parameters such as uniaxial compressive rock strength, discontinuity condition and orientation, and groundwater ratings. Rock mass classification values were determined from 14 profiles sited on recently excavated road cuttings on the Saddle Road, in the Ruahine Range, North Island, New Zealand. This is an important transport route across the North Island’s axial ranges, with the road excavated into weak late Pliocene – Early Pleistocene mudstone. Mean slope and minimum slope angle were measured at each profile in concert with the rock mass classification schemes. The three classification techniques all appear to have limited usefulness given the subaerial conditions prevalent at the study site. It would appear that the relative weightings of the different parameters within the RMR, RMS, and SMR classification schemes would need modifying for weak rock masses, but the precise details of this are difficult to determine.

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