The Berea sandstone used in this study is transversely isotropic with respect to elastic response, with P -wave velocities of 2,160 m∕s normal to bedding and 2,290 m∕s parallel to bedding, a variation of only 6%. Triaxial compression and extension tests involving failure by loading and unloading were performed along the two directions of symmetry. With axial stress applied parallel to bedding, the internal friction angle was approximately 55° for compression and extension, indicating no intermed...

#2P Marinos(NTUA: National Technical University of Athens)H-Index: 1

The Hoek-Brown failure criterion was developed in the late 1970s to provide input for the design of underground excavations. Bieniawski’s RMR was originally used to link the criterion to engineering geology input from the field but a more specific classification system called the Geological Strength Index (GSI) was introduced in 1995. Both the Hoek Brown criterion and the GSI classification have evolved and continue to evolve to meet new applications and to deal with unusual conditions encounter...

We investigate the performance of a numerical algorithm for the integration of isotropically hardening three-invariant elastoplastic constitutive models with convex yield surfaces. The algorithm is based on a spectral representation of stresses and strains for infinitesimal and finite deformation plasticity, and a return mapping in principal stress directions. Smooth three-invariant representations of the Mohr–Coulombmodel, such as the Lade–Duncan and Matsuoka–Nakai models, are implemented withi...

Preface 1. Stress and strain 2. Elastic and inelastic material behaviour 3. Yield 4. Plastic flow 5. Collapse load theorems 6. Slip line analysis 7. Work hardening behaviour A. Non-Cartesian coordinate systems B. Mohr's circles C. Principles of virtual work D. Extremum principles E. Drucker's stability postulate F. The associated flow rule G. A uniqueness theorem for elastic-plastic deformation H. Theorems of limit analysis I. Limit analysis and limiting equilibrium.

Abstract Using test data for three rock types from a published ASTM interlaboratory study of the precision of rock-property test methods, closed-form solutions for rock-strength failure envelopes are presented for pairs of Mohr stress circles in a loading series. Linear, parabolic, and hyperbolic envelopes are used to evaluate the coordinates of the envelopes’ points of tangency with the stress circles. Four types of least-squares and three types of cubic-spline curves are then fit to the points...

#2C. Fairhurst(UMN: University of Minnesota)H-Index: 5

Abstract This paper is intended to illustrate the relationship between the Hoek–Brown parameters describing the strength of rock masses and the mechanical response of underground openings. A formulation of the elasto-plastic behavior of rock in terms of the Hoek–Brown criterion is presented. The analysis assumes that the joint system present in the rock mass has no preferred orientation so that the medium can be considered to behave as an isotropic continuum. It is shown that appropriate scaling...

Two new and related true-triaxial apparatus are described that make use of conventional triaxial pressure vessels in combination with specially configured, high-pressure hydraulic jacks inside these vessels. The development combines advantages not found in existing facilities, including a compact design, pore-pressure and flow-through capabilities, the ability to attain high principal stresses and principal stress differences, direct access to parts of the sample, and provisions to go to relativ...

A new apparatus for determining the constitutive response of rock and concrete, named the University of Minnesota Plane-Strain Apparatus, was designed and built on a passive stiff-frame concept. The biaxial device, with U.S. Patent number 5,063,785, is unique, because it allows the failure plane to develop and propagate in an unrestricted manner, as opposed to conventional systems where the material is constrained by the testing apparatus. By placing the upper platen on a low friction linear bea...

#1Kun Du(CSU: Central South University)H-Index: 16

#2Xuefeng Li(CSU: Central South University)H-Index: 1

Last. Shaofeng Wang(CSU: Central South University)H-Index: 22

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Abstract null null The surrounding rocks of underground engineering are usually subjected to the coupling of compressive and shear stresses. The variable angle shear tests (VASTs) and direct shear tests (DSTs) are two types of lab tests that can easily achieve different compression-shear stress states. The VASTs and DSTs on cubic rock specimens were conducted to analyze the shear strength parameters and acoustic emission (AE) characteristics during rock failure process. The test results show tha...

Soil and stone mixture is widely distributed in China, and its physical and mechanical properties are complex, which has a significant impact on geotechnical engineering. Usually soil and stone mixture shows anisotropic features along or perpendicular to the direction of settled layers, and the strength will be significantly affected by intermediate principal stress. True triaxial tests were carried on, Paul–Mohr–Coulomb (PMC) failure criterion was used for the strength analysis in soil-stone mi...

The headcut migration describes the physical process of breach side slope retreat that governs the widening of the breach. Modeling the growth of a breach due to embankment failure is the first step in mapping the resulting inundation in a floodplain. As removal of soil from the toe of the headcut effectively removes physical support for the upper part, the headcut fails on the plane normal to the direction of tensile stress. This process is a typical mode of tensile failure. A numerical model o...

#1Kun Du(CSU: Central South University)H-Index: 16

#2Chengzhi Yang(CSU: Central South University)H-Index: 2

Last. Shaofeng Wang(CSU: Central South University)H-Index: 22

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Abstract Cubic specimens of granite, marble, and sandstone, with side lengths of 50 mm, were prepared in the laboratory. True triaxial compression tests were conducted on each rock type with minor principal stress (σ3) magnitudes of 10, 20, 30, 50, and 100 MPa and the intermediate principal stress (σ2) varying from σ2 = σ3 to σ2 = σ1 (where σ1 represents the major principal stress). The experimental results demonstrated that the failure strength, fracture dip angle, non-linear behavior and failu...

Abstract The strength properties of frozen saline soils under cyclic loading are more complex than those of unfrozen soils and frozen salt-free soils due to the existence of salt crystals in soil matrix. In this paper, a serious of tri-axial cyclic loading tests are conducted for frozen sulfate saline silty clay (FSSSC) with different Na2SO4 contents under different confining pressures and loading dynamic stress ratios at the temperature of −6 °C, respectively. The experimental results illustrat...

Last. Joseph F. Labuz(UMN: University of Minnesota)H-Index: 32

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A true triaxial apparatus was designed and fabricated to achieve multi-axial stress states with prismatic specimens. The device, which is a modification of the University of Minnesota plane-strain apparatus, is equipped with piston assemblies that generate the intermediate principal stress. A closed-loop, servo-hydraulic load frame is used to control the major principal stress, while the minor principal stress is developed by fluid pressure. A stress path was developed to perform experiments und...