A case history of tunnelling through difficult ground

Goel, Ramesh; Swarup, Anil

doi:10.1016/j.tust.2005.12.179

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…The tunnel aligned E-W, earlier was constructed by conventional method in D-shape (cf. Goel and Swarup, 2006). This was not able to withstand the developing stress and abnormal ground behavior with subsequent invert heaving, lateral displacement and deformation (convergence up to 300-1000 mm), partial and total collapse at different locations (Table 1) (Fig.…”

Section: Introductionmentioning

confidence: 95%

“…The density and the specific gravity of the rock mass vary from 2.5-2.7 kg/cm 3 and 2.62-2.92 respectively. XRD of the rock masses shows the occurrence of fair amount of mica, montmorillonite, kaolinite and illite (Goel and Swarup 2006;RITES, 2008) (Table 3). Therefore, the earlier tunnel experienced excessive swelling and squeezing (3-5%) ground conditions around tunnel meter (TM) 1320-1490, consequently invert heaving occurred and steel rib supports have buckled.…”

Section: Geotechnical Informationmentioning

confidence: 99%

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Tunneling in lesser Himalaya, Jammu and Kashmir, India with special emphasis on tectonic mélange

Dhang¹

2016

J Geol Soc India

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Himalayan fold belt has full of geological surprises, 'mélange' is one of them which create difficulties during tunneling. Such mélange completely went unnoticed during surface mapping and geotechnical investigation preceding the construction of the Udhampur railway tunnel (URT). During the construction, the mélange zone has encountered across the tunnel, which occurs along the Tanhal thrust (equivalent to MBT) that separates the Murree Group and the Shiwalik Group. The mélange was characterized by a chaotic, heterogeneous geological mixture of stronger blocks (scale independence) and weaker sheared fine-grained matrix, often termed as "block-in-matrix rocks" or bimrocks, which enforced mixed face tunneling. The heterogeneity in a tectonic mélange led to stress concentrations in the rock blocks, and there were relatively high deformations within the matrix also. Release of stress from the blocks due to excavation, with unfavorable joint and thrust orientations enforced brittle failure of the blocks (face and crown collapses) while matrix deformation (time dependent) caused convergence of primary support later. Additionally, the clay minerals with high swelling potential within the matrix swelled and created pressure on the primary support. Due to the geomechanical heterogeneity in mélange, homogenizing the rock-mass by the commonly used quantitative systems might have lead to an inappropriate design and construction. The adopted New Austrian Tunneling Method (NATM) proved to be an useful tool for tunneling.

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Section: Introductionmentioning

confidence: 95%

Section: Geotechnical Informationmentioning

confidence: 99%

Tunneling in lesser Himalaya, Jammu and Kashmir, India with special emphasis on tectonic mélange

Dhang¹

2016

J Geol Soc India

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Dynamic and Probabilistic Multi-class Prediction of Tunnel Squeezing Intensity

Chen

Zeng

et al. 2020

Rock Mech Rock Eng

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Tunnel squeezing is a time dependent process that typically occurs in weak or over-stressed rock masses， 2 significantly influencing the budget and time of tunnel construction. This paper presents a new framework to 3 probabilistically predict the potential squeezing intensity, and to dynamically update the prediction during 4 construction based on the sequentially revealed ground information. An extensively well documented database, 5 which contains quantitative data from 154 squeezing sections with 95 unpublished inventories is established. A 6 Decision Tree method is employed to train a probabilistic multi-classification model to predict the tunnel 7 squeezing intensity. The trained classifier is then integrated with a Markovian geologic model, which features 8 embedded Bayesian updating procedures, to achieve a dynamic prediction on the state probabilities of the 9 geologic parameter within the Markovian geologic model and the resulting squeezing intensity during 10 excavation. An under-construction tunnel case -Miyaluo #3 tunnel-is used to illustrate the proposed 11 framework. Results show that the Decision Tree classifier, as opposed to other black-box models, is easily to be 12 interpreted. It provides reliable predictive accuracy while leading to insights into the understanding of squeezing 13 problem. The strength-stress ratio (SSR) is suggested to be the most important factor. Moreover, the 14 implementation of the updating procedures is efficient since only simple field test (eg. Point Load index or 15 Schmidt rebound index) is required. Multiple rounds of predictions within the updating process allow different 16 levels of prediction, for example long-range, short-term, or immediate, to be extracted as useful information 17 towards the decision-making of construction operations. Therefore, this framework can serve as a pragmatic tool 18 to assist the selection of optimal primary-support and other construction strategies based on the potential 19 squeezing risk.

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