Determining rock mass deformability: experience from case histories

Bieniawski, Z.T.

doi:10.1016/0148-9062(78)90956-7

Cited by 532 publications

(174 citation statements)

References 2 publications

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“…(1) is the same as the relation of Coon and Merritt [7], while for RQD < 57 % the Eq. (1) gives E m /E r = 0.15. Note that, this method is adopted by the American Association of State Highway and Transportation Officials in the Standard Specification for Highway Bridges [9].…”

Section: Rqd Based Methodsmentioning

confidence: 97%

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Empirical methods of calculating the mechanical parameters of the rock mass

Vásárhelyi

Kovács²

2016

Period. Polytech. Civil Eng.

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The knowledge of the main mechanical constants of a rock mass (such as strength, deformability and the Poisson's ratio) is one of the most important for rock engineering design on or in rock mass. Until now, several empirical relationships were determined for calculating these material constants based on both the quality of the studied rock mass (ie. RMR or GSI values) IntroductionLarge scale rock mass characterization introduces material parameters related to mechanical properties. The most important properties are the deformation modulus; the unconfined strength and the Poisson's ratio value of the rock mass in interest. These material parameters are frequently related to laboratory data characteristics of intact rock samples and to the classical rock mass classification systems (e.g. RQD, Q, RMR or GSI). These rock mass quality measures quantify the relation between the rock mass and the intact rock.The established empirical relations between the mechanical parameters of rock masses (unconfined compressive strength, deformation modulus) and the rock mass classification systems (RMR or GSI values) show exponential increasing deformation modulus and compressive strength with the increasing quality of the rock mass.The paper summarizes the observed correlations published between the mechanical properties of rock masses and one of the rock mass classification systems. It was found, that the deformation modulus and the strength of a rock mass data may reflect a simple exponential relationship of the observed quantities. According to analysis of different proposed equations a new formula is suggested and the modification ratio (i.e. ratio of the deformation modulus and the strength of rock mass) is also determined.However, it is important to note, that there are huge differences between the published date and the empirical formulas. The reason for this variance is the difference in situ testing methods, that may give different values of mechanical parameters even for the same rock mass. According to Bieniawski [1], even a single testing method, such as flat jack test, can lead to a widely scattering results even where the rock mass is very uniform. The other reason for the discrepancy in the different calculation methods is the directional effect. Most rock masses are anisotropic and do not have single deformation modulus [2].There is no mechanical (physical) interpretation of the above empirical equations but these were analysed by e.g. [3]. Recently, Ván and Vásárhelyi [4] suggested a damage mechanical approach to analyse them. In this paper their method will be also presented.

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Section: Rqd Based Methodsmentioning

confidence: 97%

“…Firstly Bianiawski [13] suggested a linear relationship between deformation modulus of the rock mass and the RMR value. He studied seven projects and assumed the deformation modulus of the rock mass is independent of the deformation modulus of intact rock:…”

Section: Independent Equationsmentioning

confidence: 99%

Empirical methods of calculating the mechanical parameters of the rock mass

Vásárhelyi

Kovács²

2016

Period. Polytech. Civil Eng.

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“…The modulus of elasticity of rock is a widely variable quantity. Bieniawski (1978) Assume the load to be uniformly distributed over the area of contact between the load-frame and the roof. For a stress of a, the vertical displacement at the center of the loaded area is given as (Groth and Chapman, 1969 …”

Section: Stiffness Of Rock Specimenmentioning

confidence: 99%

Underground large scale test facility for rocks

Sundaram¹

1983

International Journal of Rock Mechanics and Mining Sciences &am

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“…The strength, stiffness and deformation resistance of the jointed rock is often more than one order of magnitude than that of the non-jointed rock material. The comprehensive characteristic value, which was proposed by the Z. T. Bieniawski [5] aiming at the classification of rock and widely used in Europe and America, contains the joint spacing, joint state and other joint related factors. S. Jade et al [6] carried out the statistical analysis of uniaxial compressive strength and of elastic modulus of jointed rock masses under different confining pressures.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis on Rock Breaking by Disc Cutters with Different Joint Characteristics

Tan¹,

Yi²,

Xia³

et al. 2017

Open Civil Eng. J.

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Background:With the development of tunnel engineering, shield tunneling machines (shield machines, for short) have been widely used. Tunnel projects encountered complex geological conditions. Objective:To study the effects of joint characteristics on rock fragment by disc cutters of tunnel boring machine. Method:Firstly, the 3D (three-dimensional) rock breaking process of disc cutters (cutters, for short) was simplified as a 2D (two-dimensional) problem, and the rock-breaking model with different joint characteristics by disc cutters was established by using the particle discrete element method (PFC2D). By carrying out statistical analysis on the value of cutting forces, number of cracks, rock breaking area, specific energy, the length of main cracks and changing law of their crack angles in the process of breaking rock, the effects of joint characteristics on breaking rock by disc cutters are studied. Results:The relationship between the joint characteristics and the cutting performance of cutters is obtained. Conclusion:The study shows that the weaker strength of jointed rock mass lead to the greater influence of joint dip angle on cracks and rock breaking efficiency. The stronger strength of jointed rock mass leads to the bigger main crack depth, as well as, higher specific energy. Generally, the existence of joints helps to improve the speed of excavation. However, the speed of the cutter is decreased with some certain joint characteristics. When the strength of the joint surface is 5kPa and α=135º, the specific energy reaches its minimum.

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Determining rock mass deformability: experience from case histories

Cited by 532 publications

References 2 publications

Empirical methods of calculating the mechanical parameters of the rock mass

Empirical methods of calculating the mechanical parameters of the rock mass

Underground large scale test facility for rocks

Numerical Analysis on Rock Breaking by Disc Cutters with Different Joint Characteristics

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