ISRM SUGGESTED METHOD Lade and Modified Lade 3D Rock Strength Criteria (original) (raw)
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International Journal of Rock Mechanics and Mining Sciences, 2002
In this study we examine seven different failure criteria by comparing them to published polyaxial test data (s 1 > s 2 > s 3) for five different rock types at a variety of stress states. We employed a grid search algorithm to find the best set of parameters that describe failure for each criterion and the associated misfits. Overall, we found that the polyaxial criteria Modified Wiebols and Cook and Modified Lade achieved a good fit to most of the test data. This is especially true for rocks with a highly s 2-dependent failure behavior (e.g. Dunham dolomite, Solenhofen limestone). However, for some rock types (e.g. Shirahama Sandstone, Yuubari shale), the intermediate stress hardly affects failure and the Mohr-Coulomb and Hoek and Brown criteria fit these test data equally well, or even better, than the more complicated polyaxial criteria. The values of C 0 yielded by the Inscribed and the Circumscribed Drucker-Prager criteria bounded the C 0 value obtained using the Mohr-Coulomb criterion as expected. In general, the Drucker-Prager failure criterion did not accurately indicate the value of s 1 at failure. The value of the misfits achieved with the empirical 1967 and 1971 Mogi criteria were generally in between those obtained using the triaxial and the polyaxial criteria. The disadvantage of these failure criteria is that they cannot be related to strength parameters such as C 0 : We also found that if only data from triaxial tests are available, it is possible to incorporate the influence of s 2 on failure by using a polyaxial failure criterion. The results for two out of three rocks that could be analyzed in this way were encouraging.
A Simplified Failure Criterion for Intact Rocks Based on Rock Type and Uniaxial Compressive Strength
The uniaxial compressive strength (UCS) of intact rock, which can be estimated using relatively straightforward and cost-effective techniques, is one of the most practical rock properties used in rock engineering. Thus, constitutive laws to represent the strength and behavior of (intact) rock frequently use it, along with additional intrinsic rock properties. Although triaxial tests can be employed to obtain best-fit failure criterion parameters that provide best strength predictions, they are more expensive and require time-consuming procedures; as a consequence, they are often not readily available at early stages of a project. Based on the analysis of an extensive triaxial test database for intact rocks, we propose a simplified empirical failure criterion in which rock strength at failure is expressed in terms of confining stress and UCS, with a new parameter which can be directly estimated from the UCS for a specified rock type in the absence of triaxial test data. Performance of the proposed failure criterion is then tested for validation against experimental data for eight rock types. The results show that strengths of intact rock estimated by the proposed failure criterion are in good agreement with experimental test data, with small discrepancies between estimated and measurements strengths. Therefore, the proposed criterion can be useful for preliminary (triaxial) strength estimation of intact rocks when triaxial tests data are not available.
REVIEW OF ROCK STRENGTH CRITERIA
It is not clear exactly how a rock fails, either in terms of the precise details of each micro crack initiation and Propagation or in terms of the total structural breakdown as many micro cracks propagate and coalesce. In both cases, the process is extremely complex and not subject to convenient characterization through simplified models. Nevertheless, as engineers, we should like some measure of the failure properties and the ability to predict when failure will occur. The strength criteria of rock materials can be divided into three major groups: theoretical failure criteria, experimental and curve fitting based criteria. And the last set of them is composed of two mentioned sets of failure criteria. The Mohr-Coulomb criterion expresses the relation between the shear stress and the normal stress at failure. The plane Griffith criterion which locates in theoretical group, express the uniaxial tensile strength in terms of the strain energy required to propagate micro cracks. One of the most widely used empirical strength criterion for intact rock and rock masses is Hoek-Brown Criterion. In this paper we present outlines of these criteria and focus on the Hoek-Brown criterion. The method of research is based on books and articles published in authoritative publications and journals. As a result, various types of rock failure criteria are classified and some useful suggestions regarding presented criteria have been presented. Empirical criteria, Specially Hoek and Brown Criterion, Which are in good correlations with real conditions, can be significantly much more efficient in the rock mechanics problems.
2013
In recent decades several empirical criteria have been presented, in order to simulate the triaxial behavior of rock samples. These factors have mostly been associated with some limitations, because of the natural complexity in rock sample's behavior in deformation and physical form. Some of these parameters are appropriate for a specific type of rock or special condition in laboratory. By comparison with other parameters, although Bieniawski, Ramamurthy and Hoek criteria show minimal limitations, but according to this paper, they are not accurate enough in correlation with the results of the tests. In this paper a new empirical criteria is introduced and compared to the three mentioned criteria and as a result, the advantages of this newly introduced parameter in correlation with the test results are interpreted.
Quantitative comparison of fifteen rock failure criteria constrained by polyaxial test data
Journal of Petroleum Science and Engineering, 2017
Failure criterion is a mathematical relationship with respect to applied stresses on rocks which shows the ultimate strength of rocks. Up until now, different investigations have been devoted for preparation of failure criteria. In this study, grid search and axis changing methods are used to compare various failure criteria for different types of rock with the experimental polyaxial test data. These criteria include; Mohr-Coulomb, Hoek-Brown, Bieniawski-Yudbir, linear, second order and power law form of Mogi 1967, linear, second order and power law form of Mogi 1971, Modified lade, Drucker-Prager, 3D Hoek-Brown, Modified Wiebols and Cook, HBMN and Modified Mohr-Coulomb. Polyaxial data were determined experimentally. The results show that, Mohr-Coulomb, Hoek-Brown and Bieniawski-Yudbir criteria in which intermediate stress is not included on rock failure, have the least accuracy and approximately have the same absolute relative error. Among all the criteria, the Modified Lade results have the best agreement with the experimental data. In particular, the Modified Lade criterion is the best choice for assessing wellbore stability in oil and gas wells drilling industry and mine tunneling.
2014
Abstract- In recent decades several empirical criteria have been presented, in order to simulate the triaxial behavior of rock samples. These factors have mostly been associated with some limitations, because of the natural complexity in rock sample’s behavior in deformation and physical form. Some of these parameters are appropriate for a specific type of rock or special condition in laboratory. By comparison with other parameters, although Bieniawski, Ramamurthy and Hoek criteria show minimal limitations, but according to this paper, they are not accurate enough in correlation with the results of the tests. In this paper a new empirical criteria is introduced and compared to the three mentioned criteria and as a result, the advantages of this newly introduced parameter in correlation with the test results are interpreted.
Accounting for Lode Angle in the Failure Criterion of Rocks
Archives of Mining Sciences
Paper presents general hypothesis of the relationship between the strength of rocks and the third invariant of the stress tensor deviator at failure. It has been assumed that the normal and tangential stresses acting on the strictly determined planes defined by the directional cosines depending on the three invariants of the stress state should be taken into account in the calculation of the rock strength. The hypothesis is the extension of the former Burzynski's work. Geometrical interpretation of the hypothesis has been given and its verification for Sandstone and Dunham Dolomite, on the basis of experimental data known from the relevant literature, has been presented.
A Unified Strength criterion for rock material
A non-linear Unified Strength criterion for rock material is presented. It is the development of the Unified Strength Theory (in: M. Jono, T. Inoue (Eds.), Mechanical Behaviour of Materials-VI (ICM-6), Pergamon, Oxford, 1991, pp. 841-846) and the modification of the Hoek-Brown strength criterion (Underground Excavations in Rock, The Institution of Mining and Metallurgy, London, 1980). The effect of intermediate principal stress on rock strength is considered in the non-linear Unified Strength criterion. The
Strength Criterion for Intact Rock
Indian Geotechnical Journal, 2016
Based on studies of the peak strength for soil by the authors, a simple strength criterion for intact rock is obtained in the general principal stress space. There are two material parameters in the equation. One is the uniaxial compression strength of the rock; the other describes the influence of stress level, and similar parameters are well studied in soil mechanics. It is seen that the proposed general strength criterion represents well the strength of various rocks and can provide a useful tool for geotechnical engineering practice.