Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions

doi:10.1016/J.JRMGE.2013.05.008

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Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions

Journal Article•DOI•

Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions

01 Aug 2013-Journal of rock mechanics and geotechnical engineering (Elsevier)-Vol. 5, Iss: 4, pp 249-261

TL;DR: Although many intact rock types can be very strong, a critical confining pressure can eventually be reached in triaxial testing, such that the Mohr shear strength envelope becomes horizontal as discussed by the authors.

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Abstract: Although many intact rock types can be very strong, a critical confining pressure can eventually be reached in triaxial testing, such that the Mohr shear strength envelope becomes horizontal This critical state has recently been better defined, and correct curvature or correct deviation from linear Mohr–Coulomb (M-C) has finally been found Standard shear testing procedures for rock joints, using multiple testing of the same sample, in case of insufficient samples, can be shown to exaggerate apparent cohesion Even rough joints do not have any cohesion, but instead have very high friction angles at low stress, due to strong dilation Rock masses, implying problems of large-scale interaction with engineering structures, may have both cohesive and frictional strength components However, it is not correct to add these, following linear M-C or nonlinear Hoek–Brown (H-B) standard routines Cohesion is broken at small strain, while friction is mobilized at larger strain and remains to the end of the shear deformation The criterion ‘c then σn tan φ’ should replace ‘c plus σntan φ’ for improved fit to reality Transformation of principal stresses to a shear plane seems to ignore mobilized dilation, and caused great experimental difficulties until understood There seems to be plenty of room for continued research, so that errors of judgement of the last 50 years can be corrected

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Journal Article•DOI•

Mechanical behaviour of Australian Strathbogie granite under in-situ stress and temperature conditions: An application to geothermal energy extraction

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W.G.P. Kumari¹, Pathegama Gamage Ranjith¹, Mandadige Samintha Anne Perera², Shi Shi Shao¹, Bernard Chen¹, Aref Lashin³, N. Al Arifi⁴, Tharaka Dilanka Rathnaweera¹ - Show less +4 more•Institutions (4)

Monash University¹, University of Melbourne², University College of Engineering³, King Saud University⁴

01 Jan 2017-Geothermics

TL;DR: In this paper, the authors investigated the stress-strain behavior under in-situ stress and temperature conditions by conducting a series of high-pressure, high-temperature triaxial experiments on Australian Strathbogie granite under four different confining pressures (10, 30, 60, 90 MPa) and four different temperatures (RT, 100, 200, 300 °C).

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148 citations

Journal Article•DOI•

Random Forests and Cubist Algorithms for Predicting Shear Strengths of Rockfill Materials

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Jian Zhou, Enming Li, Haixia Wei, Chuanqi Li, Qiuqiu Qiao, Danial Jahed Armaghani - Show less +2 more

18 Apr 2019-Applied Sciences

TL;DR: The predictive reliability and feasibility of random forests and Cubist models were analyzed by estimating the shear strength of rockfill materials from the relative density, particle size, distribution, material hardness, gradation and fineness modulus, and confining (normal) stress.

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Abstract: The shear strength of rockfill materials (RFM) is an important engineering parameter in the design and audit of geotechnical structures. In this paper, the predictive reliability and feasibility of random forests and Cubist models were analyzed by estimating the shear strength from the relative density, particle size, distribution (gradation), material hardness, gradation and fineness modulus, and confining (normal) stress. For this purpose, case studies of 165 rockfill samples have been applied to generate training and testing datasets to construct and validate the models. Thirteen key material properties for rockfill characterization were selected to develop the proposed models. Validation and comparison of the models have been performed using the root mean square error (RMSE), coefficient of determination (R2), and mean estimation error (MAE) between the measured and estimated values. A sensitivity analysis was also conducted to ascertain the importance of various inputs in the prediction of the output. The results demonstrated that the Cubist model has the highest prediction performance with (RMSE = 0.0959, R2 = 0.9697 and MAE = 0.0671), followed by the random forests model with (RMSE = 0.1133, R2 = 0.9548 and MAE= 0.0665), the artificial neural network (ANN) model with (RMSE = 0.1320, R2 = 0.9386 and MAE = 0.0841), and the conventional multiple linear regression technique with (RMSE = 0.1361, R2 = 0.9345 and MAE = 0.0888). The results indicated that the Cubist and random forests models are able to generate better predictive results of the shear strength of RFM than ANN and conventional regression models. The Cubist model was considered to be more promising for interpreting the complex relationships between the influential properties of RFM and the shear strengths of RFM to some extent, which can be extremely helpful in estimating the shear strength of rockfill materials.

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143 citations

Journal Article•DOI•

Influence of surface roughness and hydrophilicity on bonding strength of concrete-rock interface

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Yanjun Shen¹, Yongzhi Wang¹, Yang Yang¹, Qiang Sun¹, Tao Luo, Huan Zhang¹ - Show less +2 more•Institutions (1)

Xi'an University of Science and Technology¹

20 Jul 2019-Construction and Building Materials

TL;DR: In this article, the effects of surface roughness and hydrophilicity on the bonding performances of concrete-granite interfaces were investigated, and a two-element interfacial shear model for concrete-rock composite was proposed based on the experimental tests and theoretical derivation.

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132 citations

Journal Article•DOI•

An approach to predicting the overall strengths of unwelded bimrocks and bimsoils

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Aycan Kalender¹, Harun Sonmez¹, Edmund Medley, C. Tunusluoglu², K.E. Kasapoglu¹ - Show less +1 more•Institutions (2)

Hacettepe University¹, General Directorate of Mineral Research and Exploration²

09 Dec 2014-Engineering Geology

TL;DR: In this article, the authors developed a preliminary Bim strength criterion, a generalized conceptual empirical approach for predicting the overall strength of unwelded bimrocks and bimsoils.

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119 citations

Cites background from "Shear strength criteria for rock, r..."

..., 2010; Barton, 2013 etc.). But the evaluation of strength and deformation properties of complex and mixed geological masses such as mélanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentines is still wide open to innovative research, in order to improve generalized predictive approaches similar to those extant for jointed rock masses. Mélanges were defined as “block-in-matrix rocks” by Raymond (1984). (“Mélange” is French for “mixture”; the acute accent “é” in mélange, can be neglected). To focus engineers' attentions on the fundamental engineering properties of complex geological mixtures for the purpose of design and construction, Medley (1994) suggested the non-geological term of “bimrock”, coined by compressing the geological term “block-in-matrix rocks” as mixtures of rocks composed of geotechnically significant blocks, within a bondedmatrix of finer texture. The term “bimsoil”may be preferred for complex mixtures which include rock blocks surrounded by soil-like matrix material, such as colluvium and glacial tills. Some examples of bimrocks are presented in Fig. 1. Medley and Zekkos (2011) provided a comprehensive review of geopractice with mélanges and similar bimrocks....
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..., 2010; Barton, 2013 etc.). But the evaluation of strength and deformation properties of complex and mixed geological masses such as mélanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentines is still wide open to innovative research, in order to improve generalized predictive approaches similar to those extant for jointed rock masses. Mélanges were defined as “block-in-matrix rocks” by Raymond (1984). (“Mélange” is French for “mixture”; the acute accent “é” in mélange, can be neglected)....
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...Ulusay, 2002; Dinç et al., 2010; Barton, 2013 etc.)....
[...]
..., 2010; Barton, 2013 etc.). But the evaluation of strength and deformation properties of complex and mixed geological masses such as mélanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentines is still wide open to innovative research, in order to improve generalized predictive approaches similar to those extant for jointed rock masses. Mélanges were defined as “block-in-matrix rocks” by Raymond (1984). (“Mélange” is French for “mixture”; the acute accent “é” in mélange, can be neglected). To focus engineers' attentions on the fundamental engineering properties of complex geological mixtures for the purpose of design and construction, Medley (1994) suggested the non-geological term of “bimrock”, coined by compressing the geological term “block-in-matrix rocks” as mixtures of rocks composed of geotechnically significant blocks, within a bondedmatrix of finer texture....
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Journal Article•DOI•

Indirect measure of shale shear strength parameters by means of rock index tests through an optimized artificial neural network

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Danial Jahed Armaghani¹, Mohsen Hajihassani¹, Behnam Yazdani Bejarbaneh¹, Aminaton Marto¹, Edy Tonnizam Mohamad¹ - Show less +1 more•Institutions (1)

Universiti Teknologi Malaysia¹

01 Sep 2014-Measurement

TL;DR: In this article, a particle swarm optimization-artificial neural network (PSO-ANN) integrated model was developed by setting the results of rock index tests as inputs and shear strength parameters as outputs of the model.

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111 citations

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References

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Open Access

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Journal Article•DOI•

Engineering classification of rock masses for the design of tunnel support

[...]

Nick Barton¹, R. Lien, J. Lunde•Institutions (1)

Norwegian Geotechnical Institute¹

01 Dec 1974

TL;DR: In this article, an analysis of some 200 tunnel case records has revealed a useful correlation between the amount and type of permanent support and the rock mass quality, with respect to tunnel stability.

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Abstract: An analysis of some 200 tunnel case records has revealed a useful correlation between the amount and type of permanent support and the rock mass qualityQ, with respect to tunnel stability. The numerical value ofQ ranges from 0.001 (for exceptionally poor quality squeezing-ground) up to 1000 (for exceptionally good quality rock which is practically unjointed). The rock mass qualityQ is a function of six parameters, each of which has a rating of importance, which can be estimated from surface mapping and can be updated during subsequent excavation. The six parameters are as follows; theRQD index, the number of joint sets, the roughness of the weakest joints, the degree of alteration or filling along the weakest joints, and two further parameters which account for the rock load and water inflow. In combination these parameters represent the rock block-size, the interblock shear strength, and the active stress. The proposed classification is illustrated by means of field examples and selected case records. Detailed analysis of the rock mass quality and corresponding support practice has shown that suitable permanent support can be estimated for the whole spectrum of rock qualities. This estimate is based on the rock mass quality Q, the support pressure, and the dimensions and purpose of the excavation. The support pressure appears to be a function ofQ, the joint roughness, and the number of joint sets. The latter two determine the dilatency and the degree of freedom of the rock mass. Detailed recommendations for support measures include various combinations of shotcrete, bolting, and cast concrete arches together with the appropriate bolt spacings and lengths, and the requisite thickness of shotcrete or concrete. The boundary between self supporting tunnels and those requiring some form of permanent support can be determined from the rock mass qualityQ.

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2,474 citations

Journal Article•DOI•

The shear strength of rock joints in theory and practice

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Nick Barton¹, V. Choubey•Institutions (1)

Norwegian Geotechnical Institute¹

01 Dec 1977

TL;DR: In this paper, the authors describe an empirical law of friction for rock joints, which can be used both for extrapolating and predicting shear strength data, and demonstrate that it can be estimated to within ± 1° for any one of the eight rock types investigated.

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Abstract: The paper describes an empirical law of friction for rock joints which can be used both for extrapolating and predicting shear strength data. The equation is based on three index parameters; the joint roughness coefficientJRC, the joint wall compressive strengthJCS, and the residual friction angleφ r . All these index values can be measured in the laboratory. They can also be measured in the field. Index tests and subsequent shear box tests on more than 100 joint samples have demonstrated thatφ r can be estimated to within ± 1° for any one of the eight rock types investigated. The mean value of the peak shear strength angle (arctanτ/σ n ) for the same 100 joints was estimated to within 1/2°. The exceptionally close prediction of peak strength is made possible by performing self-weight (low stress) sliding tests on blocks with throughgoing joints. The total friction angle (arctanτ/σ n ) at which sliding occurs provides an estimate of the joint roughness coefficientJRC. The latter is constant over a range of effective normal stress of at least four orders of magnitude. However, it is found that bothJRC andJCS reduce with increasing joint length. Increasing the length of joint therefore reduces not only the peak shear strength, but also the peak dilation angle and the peak shear stiffness. These important scale effects can be predicted at a fraction of the cost of performing large scale in situ direct shear tests.

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2,139 citations

Journal Article•DOI•

Review of a new shear-strength criterion for rock joints

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Nick Barton¹•Institutions (1)

Norwegian Geotechnical Institute¹

01 Jan 1973-Engineering Geology

TL;DR: In this paper, a sliding scale of roughness is proposed for estimating the shear strength of rough joints, and the curvature of the proposed strength envelopes reduces as the roughness coefficient reduces, and also varies with the strength of the weathered joint wall or unweathered rock.

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1,168 citations

Journal Article•DOI•

Some new Q-value correlations to assist in site characterisation and tunnel design

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Nick Barton

01 Feb 2002-International Journal of Rock Mechanics and Mining Sciences

TL;DR: In this article, the authors explored the application of Q and its six component parameters, for prediction, correlation and extrapolation of site investigation data, and for obtaining first estimates of some input data for both jointed distinct element and continuum-approximation modelling.

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706 citations

Journal Article•DOI•

The shear strength of rock and rock joints

[...]

Nick Barton¹•Institutions (1)

Norwegian Geotechnical Institute¹

01 Sep 1976-International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts

TL;DR: In this article, empirical non-linear laws of friction and fracture are derived which explain this paradoxical behaviour and which can be used to predict or extrapolate shear strength data over the whole brittle range of behaviour.

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640 citations