scholarly journals Calculating the cohesion and internal friction angle of volcanic rocks and rock masses

Volcanica ◽  
2021 ◽  
pp. 279-293
Author(s):  
Marlène Villeneuve ◽  
Michael Heap
Keyword(s):  
Failure Criterion ◽  
Large Scale ◽  
Volcanic Rocks ◽  
Friction Angle ◽  
Failure Criteria ◽  
Rock Masses ◽  
Rock Failure Criteria ◽  
Input Parameters ◽  
Coulomb Failure Criterion ◽  
The Stability

Rock failure criteria are key input parameters for models designed to better understand the stability of volcanic rock masses. Cohesion and friction angle are the two defining material variables for the Mohr-Coulomb failure criterion. Although these can be determined from laboratory deformation experiments, they are rarely reported. Tabulated data for volcanic rocks, calculated using published triaxial results, show that cohesion and friction angle decrease with increasing porosity. If porosity is known, these empirical fits can provide laboratory-scale cohesion and friction angle estimations. We present a method to upscale these parameters using the generalised Hoek-Brown failure criterion, discuss the considerations and assumptions associated with the upscaling, and provide recommendations for potential end-users. A spreadsheet is provided so that modellers can (1) estimate cohesion and friction angle and (2) upscale these values for use in large-scale volcano modelling. Better constrained input parameters will increase the accuracy of large-scale volcano stability models.

scholarly journals A Simple Three-Dimensional Failure Criterion for Jointed Rock Masses under True Triaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yaohui Gao ◽  
Chunsheng Zhang ◽  
Zhaofeng Wang ◽  
Jun Chen
Keyword(s):  
Failure Criterion ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Friction Angle ◽  
Failure Criteria ◽  
Jointed Rock ◽  
Rock Masses ◽  
True Triaxial ◽  
Jointed Rock Masses ◽  
Triaxial Strength

The joint configuration and the intermediate principal stress have a significant influence on the strength of rock masses in underground engineering. A simple three-dimensional failure criterion is developed in this study to predict the true triaxial strength of jointed rock masses. The proposed failure criterion in the deviatoric and meridian planes adopts the elliptic and hyperbolic forms to approximate the Willam–Warnke and Mohr–Coulomb failure criterion, respectively. The four parameters in the proposed failure criterion have close relationships with the cohesion and the internal friction angle and can be linked with the joint inclination angle using a cosine function. Two suits of true triaxial strength data are collected to validate the correctness of the proposed failure criterion. Compared with other failure criteria, the proposed failure criterion is more reasonable and acceptable to describe the strength of jointed rock masses.

scholarly journals The ARMR Classification System and the Modified Hoek-Brown Failure Criterion Compared to Directional Shear Strength Models for Anisotropic Rock Masses

2019 ◽  
Author(s):  
Neil Bar ◽  
Charalampos Saroglou
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Failure Criterion ◽  
Classification System ◽  
Failure Criteria ◽  
Rock Masses ◽  
Anisotropic Rock ◽  
Anisotropic Rock Mass ◽  
Degree Of Anisotropy ◽  
Strength Models

The anisotropic rock mass rating classification system, ARMR, has been developed in conjunction with the Modified Hoek-Brown failure to deal with varying shear strength with respect to the orientation and degree of anisotropy within an anisotropic rock mass. Conventionally, ubiquitous-joint or directional shear strength models have assumed a general rock mass strength, typically estimated using the Hoek-Brown failure criterion, and applied a directional weakness in a given orientation depending on the anisotropic nature of the rock mass. Shear strength of the directional weakness is typically estimated using the Barton-Bandis failure criterion, or on occasion, the Mohr-Coulomb failure criteria. Directional shear strength models such as these often formed the basis of continuum models for slopes and underground excavations in anisotropic rock masses. This paper compares ARMR and the Modified Hoek-Brown failure criterion to the conventional directional shear strength models using a case study from Western Australia.

Experimental Study on Dynamic Strength Regional Characteristics of Undisturbed Loess Based on the Mohr-Coulomb Failure Criterion

2013 ◽  
Vol 700 ◽  
pp. 111-118 ◽  
Author(s):  
Ping Wang ◽  
Jun Wang ◽  
Shao Feng Chai ◽  
Nai Wang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Failure Criterion ◽  
Void Ratio ◽  
Dynamic Strength ◽  
Friction Angle ◽  
Dynamic Shear ◽  
Coulomb Failure ◽  
Coulomb Failure Criterion ◽  
Dynamic Shear Strength

Based on Mohr - Coulomb failure criterion, dynamic strength characteristic of undisturbed loess in Xining, Lanzhou, Xiji and Xian was studied through dynamic triaxial test. And the regional characteristics of void ratio, natural moisture content, plasticity index and dynamic shear strength with different vibration frequency and natural conditions were analyzed. The research shows that dynamic shear strength of loess increases when consolidation stress rises under the same water content condition. However the increase trend is not proportional relationship. Initial void ratio and water content of loess under natural state rises from northwest to southeast, and dynamic cohesive force enhances. On the contrary, internal friction angle decreases with the change of characteristic. With the increasing trend of disturbed loesss clay content from northwest to southeast, dynamic cohesive force increases and internal friction angle decreases in the different amplitude. The conclusion enriches and develops the evaluation theory of loess regional dynamic characteristic and it is a universal method to reduce cost of different loess regional classification.

scholarly journals VARIATION OF THE INTRINSIC ROCK PROPERTIES ON HOEK-BROWN FAILURE CRITERION PARAMETERS

2021 ◽  
Vol 36 (4) ◽  
pp. 73-84
Author(s):  
Sina Salajegheh ◽  
Kourosh Shahriar ◽  
Hossein Jalalifar ◽  
Kaveh Ahangari
Keyword(s):  
Inverse Relationship ◽  
Rock Strength ◽  
Contact Stiffness ◽  
Friction Angle ◽  
Failure Criteria ◽  
Rock Properties ◽  
Fundamental Parameter ◽  
Constant Parameter ◽  
Rock Failure Criteria ◽  
Triaxial Compressive Strength

The Hoek-Brown (H-B) criterion is one of the most commonly used rock failure criteria in recent years. This criterion includes a constant parameter called mi which is a fundamental parameter for estimating rock strength. Due to the importance of the mi parameter in the H-B criterion, it is necessary to conduct comprehensive studies on various aspects of the effect of this parameter on the behavior of rocks. Therefore, in this study, using numerical simulation of the Triaxial Compressive Strength (TCS) tests in PFC-2D code, the effects of microscopic properties of different rocks on the H-B parameter mi have been studied. Based on the results of this study, it was found that the effects of micro-parameters on the H-B parameter mi can be different depending on the type of rock, however this parameter has an inverse relationship to the micro-parameters of bond tensile strength and bond fraction of the rocks. Also, the mi parameter increases with an increase in the micro-parameters of the friction coefficient, the friction angle, the particle contact modulus, and the contact stiffness ratio of rocks.

Evaluation of Aseismic Stability of Gangue Slope Based on Nonlinear Mohr-Coulomb Failure Criterion

2011 ◽  
Vol 243-249 ◽  
pp. 2771-2774
Author(s):  
Gang Fei Zhao ◽  
Hui Zhi Guo ◽  
Yong Liang Lin ◽  
Wei Duan
Keyword(s):  
Failure Criterion ◽  
Hazard Maps ◽  
Permanent Displacement ◽  
Wide Range ◽  
Coulomb Failure ◽  
Coulomb Failure Criterion ◽  
Real Earthquake ◽  
Displacement Based ◽  
The Stability ◽  
Almost All

It is extremely important to establish hazard maps showing earthquake-induced displacements, safety factors and probabilities of failure. The combination of pseudo-static method and displacement-based method is commonly used to evaluate the stability of gangue slope. Conventional calculations are formulated in terms of a linear Mohr–Coulomb (MC) failure criterion. However, experimental data shows that the strength envelops of almost all types of rocks are nonlinear over the wide range of normal stresses. In this paper, the nonlinear failure criterion is introduced. The resulting safety factor and permanent displacement are discussed and demonstrated using several real earthquake records.

scholarly journals NUMERICAL AND EXPERIMENTAL RESEARCH OF ROCK FAILURE MECHANISM AND ITS DEPENDENCE ON mi HOEK-BROWN FAILURE CRITERION

2021 ◽  
Vol 36 (3) ◽  
pp. 157-165
Author(s):  
Sina Salajegheh ◽  
Kourosh Shahriar ◽  
Hossein Jalalifar ◽  
Kaveh Ahangari
Keyword(s):  
Compressive Strength ◽  
Stability Analysis ◽  
Failure Mechanism ◽  
Failure Criteria ◽  
Strength Test ◽  
Rock Failure ◽  
Rock Failure Criteria ◽  
Triaxial Compressive Strength ◽  
Compressive Strength Test ◽  
The Stability

Rock failure mechanism is one of the most important issues in rock mechanics engineering which plays a key role in the stability analysis of various structures. Therefore, different failure criteria have been proposed to understand the failure mechanism of rocks. One of the most commonly used rock failure criteria is the Hoek-Brown criterion, in which there is a parameter called mi, which is very important to the response provided by this criterion. Due to the importance of conducting extensive studies on this parameter, in this current research, by performing a series of experimental triaxial compressive strength test and numerical simulating in PFC-2D code, the effect of the Hoek-Brown constant mi on the failure mechanism and crack growth of different rocks has been studied. Based on the results of this study, it was found that the effect of parameter mi on the failure mechanism of different rocks varied according to the type of rocks, and the greatest effect of this parameter was on the peak strength of rocks. In addition, it was found that under higher lateral pressures, there are less destructive cracks in rocks, and as a result, they show more ductile behaviour.

scholarly journals Study on Deflection of Surrounding Rock Force Chain and Disaster Mechanism of Instability in Deep Stope

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Guang-Xiang Xie ◽  
Anying Yuan ◽  
Lei Wang
Keyword(s):  
Large Scale ◽  
Vertical Direction ◽  
Surrounding Rock ◽  
Horizontal Direction ◽  
Force Chain ◽  
Force Chains ◽  
Rock Masses ◽  
Working Face ◽  
The Stability ◽  
Overburden Strata

The mechanism of force chain deflection and instability-caused disaster in the deep surrounding rock of large-scale stopes was examined in this study using theoretical analyses, laboratory experiments, PFC3D numerical simulations, and other comprehensive research methods based on a discrete element theory that included force chain research as the main line. The results indicated that the overburden strata of the stope presented an arched force chain in both the strike and the inclined direction of the working face. In addition, a force chain shell composed of strong chains similar to “ellipsoid” in shape had been formed in the overburden strata space of the entire stope. The main mechanical characteristics of the force chain shell were as follows: the strength levels of the force chains within the shell were the largest; the strength levels of the force chains inside and outside the shell were relatively low and had evolved with the advancement of the working face; the directions of the force chains in different areas of the surrounding rock masses of the stope were deflected, forming an anisotropic characteristic with a certain deflection angle which was distributed in the vertical direction at the shell base; the force chains at the shell shoulder were angled in the horizontal direction, and the force chain at the shell top had an obvious horizontal direction; finally, the strong chain clusters of the surrounding rock masses of the stope formed a force chain shell in the stope space, and the stress shell was the macroscopic embodiment of the force transference in the force chain shell formed by the force chain clusters, which revealed not only the mechanical mechanism of the force chain shell formed by the surrounding rock but also the relationship between the macro stress shell and the stress chain shell. The stability of the shell determines the stability of the surrounding rock, and the instability of the shell will lead to dynamic disasters such as strong dynamic pressure or rock burst.

scholarly journals EVALUATING ELASTIC-PLASTIC BEHAVIOUR OF ROCK MATERIALS USING HOEK–BROWN FAILURE CRITERION

2012 ◽  
Vol 18 (3) ◽  
pp. 402-407 ◽  
Author(s):  
Hadi Hasanzadehshooiili ◽  
Ali Lakirouhani ◽  
Jurgis Medzvieckas
Keyword(s):  
Failure Criterion ◽  
Yield Criterion ◽  
Failure Criteria ◽  
Flow Rule ◽  
Rock Masses ◽  
Rock Materials ◽  
Failure Initiation ◽  
Plastic Behaviour ◽  
Yield Behaviour ◽  
Stress States

As a matter of fact, the failure criteria only predict failure's initiation in materials. And, in order to predict post-yield behaviour of materials, a much complicated formulation for stress-strain relationship is required, which we know as plasticity theory. For instance, these formulations are developed based on Mohr-Coulomb criterion for soils and Drucker-Prager criterion for concrete. According to a majority of rock mechanics researchers, the empirical and experimental Hoek-Brown failure criterion is one of the well-progressed and suitable criteria, which can efficiently predict the rock failure initiation under different stress states for various types of intact rocks and rock masses. In this article, according to the suggestion by Heok explained in his paper of 1997, this rugged mentioned criterion is considered as a yield criterion and the elastic-perfect plastic behaviour of rock masses is determined using calculating material constitutive matrix's arrays in terms of Hoek-Brown's material constants and mechanical characteristics of rock materials in the general stress space, considering associated flow rule.

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