Observations of brittle failure around a circular test tunnel

Martini, Chiara; Read, Rodney S.; Martino, J.B.

doi:10.1016/s1365-1609(97)90200-8

Cited by 308 publications

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“…We investigated the evolving stresses in the elastic models during various loading conditions and compared the final stresses against fracture criteria to identify where extensional-type fracturing may occur (stress path analysis; see, e.g., [32,33]). We applied fracture criteria, based on intact rock strength properties of CAGr, similar to criteria used for predicting spalling around underground openings [3,34] in order to select numerical models where the stress path indicates that fractures nucleate and/or propagate (the fracture criteria are explained in Section 4.1). This allows for later comparison with fractographic data.…”

Section: Constitutive Behaviour Intact Rock and Rock Mass Propertiesmentioning

confidence: 99%

“…During the last three to four decades the techniques to estimate rock mass stress have substantially been improved and 'stress measurements' have become a standard practice [1,2]. Virgin stresses, i.e., stresses acting in a rock mass prior to man-made disturbances, of high-magnitude can cause brittle fracturing, e.g., around underground openings in massive rock (often referred to as spalling fractures [3]) and close to the landscape surface (e.g., exfoliation fractures [4][5][6][7][8]), and squeezing ground conditions in weak rock and/or heavily fractured rock masses with visco-plastic behaviour [9]. Within the uppermost parts of the crust rock mass stress magnitudes are mostly anisotropic, i.e., they are not lithostatic and at least two principal stress components are of unequal magnitude [10].…”

Section: Introductionmentioning

confidence: 99%

“…Within the uppermost parts of the crust rock mass stress magnitudes are mostly anisotropic, i.e., they are not lithostatic and at least two principal stress components are of unequal magnitude [10]. The maximum, intermediate, and minimum principal stresses are denoted σ 1 , σ 2 , and σ 3 (σ 1 > σ 2 > σ 3 ; compressive stresses are positive).…”

Section: Introductionmentioning

confidence: 99%

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Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Ziegler

Loew

Amann

2016

International Journal of Rock Mechanics and Mining Sciences

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The fractographic analysis of plumose axis of exfoliation fracture surfaces from a preceding study in the Grimsel region of the Swiss Alps suggested complex directional trends of near-surface (i.e., within ~100 m below ground surface) maximum principal stress (σ 1 ) trajectories within the investigated inner-trough valleys (i.e., U-shaped valleys). The stress trajectories describe a pattern governed by local topographic variations. In situ stress measurements from the region are scarce, locally scattered, based on different methods, and, thus, difficult to interpret at regional scale. In this study, we inferred that plumose structure axes form parallel to compressive σ 1 , and improve our knowledge of the near-surface three-dimensional stress field in alpine settings with complex topography. We investigated near-surface stress tensors utilising three-dimensional, elastic numerical models. Our models account for morphological details of the Grimsel area at the decametre scale. We used two models with vertical boundaries aligned N-S/W-E (0°-model) and NW-SE/SW-NE (45°-model). These models allowed investigating gravitational stresses and superimposed isotropic and anisotropic compressive stresses arising from (active) tectonic shortening and/or stresses induced by exhumation (remnant stresses). Our model results illustrate that the superposition of gravitational stresses and realistic horizontal strains reveals complex near-surface stress trajectories that widely

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Section: Constitutive Behaviour Intact Rock and Rock Mass Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Ziegler

Loew

Amann

2016

International Journal of Rock Mechanics and Mining Sciences

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“…Martin [23] stated that the grain size of LDB granite taken from the 240 Level of the URL (Underground Research Laboratory) ranges from 3 to 7 mm, with an average of 5 mm. Martin et al [24] reported the grain size of LDB granite from the 420 Level of the URL ranging from 1 to 3.5 mm. As for the aspect ratio of the grains of LDB granite, no direct study can be found from the published literature, but some studies on the aspect ratio of granite grains can be used for a reference.…”

Section: Numerical Simulation Of Ldb Granitementioning

confidence: 99%

Studying the effect of non‐spherical micro‐particles on Hoek–Brown strength parameter m_i using numerical true triaxial compressive tests

Zhang

Zhu

Zhang

2014

Num Anal Meth Geomechanics

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SUMMARYThe strength parameter m i in the Hoek-Brown strength criterion is empirical and was developed by trial and error. To better understand the fundamental relationship between m i and the physical characteristics of intact rock, this paper presents a systematic study of m i by representing intact rock as a densely packed cemented particle material and simulating its mechanical behavior using particle flow modeling. Specifically, the three-dimensional particle flow code (PFC3D) was used to conduct numerical true triaxial compression tests on intact rock and to investigate the effect of non-spherical micro-particle parameters on m i . To generate numerical intact rock specimens containing non-spherical micro-particles, a new genesis process was proposed, and a specific loop algorithm was used based on the efficiency of the process and the acceptability of generated specimens. Four main parameters-number, aspect ratio, size, and shape-of non-spherical micro-particles were studied, and the results indicated that they all have great effect on m i . The strength parameter m i increases when the number, aspect ratio, or size is larger or the shape becomes more irregular, mainly as a result of the higher level of interlocking between particles. This confirms the observations from engineering experience and laboratory experiments. To simulate the right strength parameter m i , it is important to use appropriate non-spherical micro-particles by controlling these four parameters. This is further demonstrated by the simulation of two widely studied rocks, Lac du Bonnet granite and Carrara marble.

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“…However, considering the practical stress-strain behavior of real rocks, especially soft rock and broken rock, is not ideal elastoplastic, the Fenner and Kastner formulae are not appropriate for most cases. To solve this problem, some numerical methods that consider the strain-softening behavior and materialsoftening behavior of surrounding rock were proposed by different researchers (Vesic 1972;Wilson 1980;Yuan and Chen 1986;Ogawa and Lo 1987;Fu 1995;Ma and Zhang 1996;Jiang and Shen 1997;Martini et al 1997;Martin et al 1999;Carranza-Torres and Fairhurst 2000;Jiang et al 2001).…”

Section: Introductionmentioning

confidence: 99%

New strength formulae for rock surrounding a circular opening

et al. 2013

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In this paper, the unified strength theory proposed by Yu Mao-hong in 1991 is used to develop new strength formulae for rock surrounding a tunnel. The new formulae can be applied to an elastic-plastic material. The formulae have a series of expressions with the unified parameter, especially variations such as the well-known Kastner and Airy formulae, which are widely used in rock mechanics and engineering. These formulae are derived on the basis of the Mohr-Coulomb strength criterion. For the strength-weakening (plastic-softening) of geomaterials, the analytical solutions for the radius of the plastic residual zones, radius of the plastic-softening zones, and displacement around the opening are presented according to the elastoplastic-softening -residual plastic, tri-linear stress-strain model. In addition, the derivation for the stress state in the surrounding rock is given. The Kastner formula, Airy formula, and available solutions can be considered as special cases in the new strength formula. The influence of softening, shear dilatancy, and different strength models on the results is analyzed. The results presented in this paper are useful for analyzing surrounding rock with various stress conditions and reinforcement of caves.Résumé : Dans cet article, la théorie unifiée de résistance proposée par Yu Mao-hong en 1991 est utilisée pour développer des nouvelles formules de résistance pour la roche entourant un tunnel. Les nouvelles formules peuvent être appliquées pour un matériau élastique-plastique. Les formules comportent une série d'expressions avec le paramètre unifié, particulièrement les variations qui incluent la formule bien connue de Kastner et celle d'Airy, qui sont couramment utilisées en mécanique des roches et en ingénierie. Ces formules sont dérivées sur la base du critère de résistance de Mohr-Coulomb. Pour la réduction de la résistance (adoucissement plastique) de géomatériaux, les solutions analytiques pour le rayon des zones plastiques résiduelles, pour le rayon des zones d'adoucissement plastique et pour le déplacement tout autour de l'ouverture, sont présentées selon le modèle plastique de contrainte-déformation tri-linéaire élasto-plastique-adoucissement-résiduel. De plus, la dérivation de l'état des contraintes de la roche environnante est donnée. La formule connue de Kastner, la formule d'Airy et les solutions disponibles peuvent être considérées comme des cas spéciaux de la nouvelle formule de résistance. L'influence de l'adoucissement, de la dilatance en cisaillement et des différents modèles de résistance sur les résultats est analysée. Les résultats présentés dans cet article sont utiles pour l'analyse de la roche environnante sous différentes conditions de contraintes et renforcements de cavités. [Traduit par la Rédaction]Mots-clés : roche environnante, théorie unifiée de résistance, dilatance en cisaillement, modèle de contrainte-déformation.

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Observations of brittle failure around a circular test tunnel

Cited by 308 publications

References 3 publications

Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Studying the effect of non‐spherical micro‐particles on Hoek–Brown strength parameter m_i using numerical true triaxial compressive tests

New strength formulae for rock surrounding a circular opening

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Observations of brittle failure around a circular test tunnel

Cited by 308 publications

References 3 publications

Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling

Studying the effect of non‐spherical micro‐particles on Hoek–Brown strength parameter mi using numerical true triaxial compressive tests

New strength formulae for rock surrounding a circular opening

Contact Info

Product

Resources

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Studying the effect of non‐spherical micro‐particles on Hoek–Brown strength parameter m_i using numerical true triaxial compressive tests