scholarly journals Stress Drop as a Result of Splitting, Brittle and Transitional Faulting of Rock Samples in Uniaxial and Triaxial Compression Tests

2015 ◽  
Vol 37 (1) ◽  
pp. 17-23 ◽  
Author(s):  
Jerzy Cieślik
Keyword(s):  
Stress Drop ◽  
Rock Sample ◽  
Triaxial Compression ◽  
Failure Process ◽  
Strength Loss ◽  
Axial Stiffness ◽  
Compression Tests ◽  
Rock Samples ◽  
Test Pressure ◽  
Triaxial Compression Tests

Abstract Rock samples can behave brittle, transitional or ductile depending on test pressure, rate of loading and temperature. Axial stiffness and its changes, relative and absolute dilatancy, yield, and fracture thresholds, residual strength are strongly pressure dependent. In this paper the stress drop as an effect of rock sample strength loss due to failure was analyzed. Uniaxial and triaxial experiments on three types of rock were performed to investigate the stress drop phenomenon. The paper first introduces short background on rock behavior and parameters defining a failure process under uniaxial and triaxial loading conditions. Stress drop data collected with experiments are analyzed and its pressure dependence phenomenon is described. Two methods for evaluation of stress drop value are presented.

Constitutive model to simulate full deformation and failure process for rocks considering initial compression and residual strength behaviors

2019 ◽  
Vol 56 (5) ◽  
pp. 649-661 ◽  
Author(s):  
Wengui Cao ◽  
Xin Tan ◽  
Chao Zhang ◽  
Min He
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Failure Process ◽  
Deformation Model ◽  
Good Prediction ◽  
Compression Tests ◽  
Deformation And Failure ◽  
Macroscopic Deformation ◽  
Triaxial Compression Tests

A constitutive model with capacity to simulate the full deformation and failure process for rocks considering initial compression and residual strength behaviors is discussed in this paper. The rock was assumed to consist of the initial voids portion and the solid skeleton portion. The full deformation model of rocks can be established by the consideration of the macroscopic deformation of rocks and the microscopic deformations of the two different portions based on the statistical damage theory. Comparisons between the experimental data from triaxial compression tests and calculated results show that the proposed constitutive model provided a good prediction of the full deformation and failure process, including the effects of initial void compression, stiffness degradation, strain hardening–softening, and residual strength.

The Application of Coreless Inductors for Displacement Measurements in Laboratory Investigations of Rock Properties

2014 ◽  
Vol 59 (4) ◽  
pp. 1033-1050
Author(s):  
Janusz Nurkowski
Keyword(s):  
Temperature Compensation ◽  
Measurement Accuracy ◽  
Triaxial Compression ◽  
Rock Properties ◽  
Variable Pressure ◽  
Compression Tests ◽  
Rock Samples ◽  
Laboratory Investigations ◽  
The Impact ◽  
Triaxial Compression Tests

Abstract The paper presented the coreless inductive sensor, its construction and principle of operation. The impact of temperature on the outcome of a measurement performed with the inductor was discusses, together with the possibility of temperature compensation of the inductor’s performance. Subsequently, the reasons for limited measurement accuracy and resolution were discussed, particularly under the variable pressure in the order of some hundreds MPa. Two types of such sensor were presented: a sensor for measuring linear strains, e.g. during compressibility measurements, and an sensor for measuring circumferential strains during triaxial compression tests. Additionally, the manners of fixing the sensor on rock samples were presented. Finally, some examples of the sensor application were shown, together with the results of measurements of deformations of rock samples - especially in cases when resistance gauges cannot be used, and the samples are subjected to a load in the uniaxial and triaxial system, under the hydrostatic pressure of up to 400 MPa and the normal one.

EMPIRICAL STRENGTH ENVELOPE FOR SHALE

2016 ◽  
Vol 78 (7-3) ◽  
Author(s):  
Mohd For Mohd Amin ◽  
Nur‘Ain Mat Yusof ◽  
Rini Asnida Abdullah
Keyword(s):  
Failure Criterion ◽  
Sedimentary Rock ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Failure Envelope ◽  
Rock Samples ◽  
Failure Envelopes ◽  
Project Site ◽  
Coulomb Criterion ◽  
Triaxial Compression Tests

Effectively, strength envelope describes behavior of rock when subjected to common stresses in construction, i.e. compressive, triaxial and tensile stresses. This study is aimed at investigating the strength envelope for shale, a sedimentary rock obtained from dam project site in Baram, Sarawak. Series of triaxial compression tests were carried out to obtain the strength envelope for the rock samples. For verification of failure criterion, uniaxial compression and Brazilian tests were also conducted on the rock samples. Results from the relevant tests were analysed using RocData software to obtain the strength envelope. Subsequently, Mohr-Coulomb and Hoek-Brown failure criterion are used to determine failure envelop for the rock samples. Based on the failure envelopes and the related strengths (i.e. compressive and tensile strength), suitability of both approach, in defining strength envelope for shale, is verified. The study shows that for highly laminated sedimentary rock like shale, Hoek-Brown criterion gave a more representative failure behaviour. The failure envelope clearly shown all the strength limits when the rock is subjected to triaxial, uniaxial and tensile stress, which is not clearly shown in the Mohr-Coulomb criterion. Therefore, Hoek-Brown criterion is a more appropriate method for describing strength envelope, as it able to show the limiting stresses when rock samples are subjected to common stresses in construction.

scholarly journals An Analysis of the Mechanical Characteristics and Constitutive Relation of Cemented Mercury Slag

2017 ◽  
Vol 2017 ◽  
pp. 1-14
Author(s):  
Xinwei Li ◽  
Sui Zhang ◽  
E-chuan Yan ◽  
Duoyou Shu ◽  
Yangbing Cao ◽  
...  
Keyword(s):  
Triaxial Compression ◽  
Failure Process ◽  
Guizhou Province ◽  
Coarse Grained ◽  
Uniaxial Compression Test ◽  
Compression Tests ◽  
Slag Structure ◽  
Triaxial Compression Tests ◽  
Chang Model ◽  
Coarse Grained Soil

This study focuses on mercury slag in the Tongren area of Guizhou Province, China. Computed tomography (CT) is used with uniaxial and triaxial compression tests to examine the mechanical changes in cemented mercury slag and its formation. The CT results for the uniaxial compression test reveal the overall failure process of the mercury slag structure. Based on the coarse-grained soil triaxial test, a modified Duncan-Chang model is compared with the actual monitoring results and is found to be suitable for the analysis of the slag constitutive model.

Swelling and softening behaviour of La Biche shale

1998 ◽  
Vol 35 (2) ◽  
pp. 206-221 ◽  
Author(s):  
RCK Wong
Keyword(s):  
Electrolyte Concentration ◽  
Triaxial Compression ◽  
Strength Loss ◽  
Test Results ◽  
Compression Tests ◽  
Swelling Behaviour ◽  
One Dimensional ◽  
Failure Theory ◽  
Free Swell ◽  
Triaxial Compression Tests

Free swell, semiconfined swell, and one-dimensional oedometer swell tests were performed on La Biche shale specimens in solutions of different salinities. The swelling behaviour of La Biche shale was found to be highly anisotropic and dependent on electrolyte concentration, stress, and swelling history. Drained triaxial compression tests were conducted on La Biche shale specimens subjected to different degrees of swelling. The test results indicate that the Young's modulus decreases with increasing swelling. The strength loss due to swelling can be explained by the Hvorslev failure theory. A descending power law is proposed to describe the cohesion reduction with the swelling.Key words: shale, salinity, swelling, strength weakening, modulus softening.

scholarly journals SCALAR DAMAGE VARIABLE DETERMINED IN THE UNIAXIAL AND TRIAXIAL COMPRESSION CONDITIONS OF SANDSTONE SAMPLES

2013 ◽  
Vol 35 (1) ◽  
pp. 73-84
Author(s):  
Jerzy Cieślik
Keyword(s):  
Main Part ◽  
Triaxial Compression ◽  
Damage Variable ◽  
Triaxial Tests ◽  
Axial Stiffness ◽  
Compression Tests ◽  
Damage Development ◽  
Laboratory Investigations ◽  
Definition Of ◽  
Triaxial Compression Tests

Abstract The article is based on the results of uniaxial and triaxial compression tests, performed on Wustenzeller sandstone. An overview of the possible definitions of damage variable describing the process of damage development on the basis of various hypotheses has been presented in the first part of the article. In the main part of the article the author has presented the results of laboratory investigations, where the state of damage and its changes in rock samples under uniaxial and triaxial compression conditions were being observed. Using a modified procedure of triaxial tests, a definition of damage variable, determined on the basis of changes of volumetric stiffness of an examined rock, has been developed. Damage variable defined this way, in relation to a variable determined on the basis of axial stiffness changes, points to some anisotropy effects of damage phenomenon. The results obtained from both methods have been compared whereas the relations determining the evolution of damage variable in the loading process have been established.

scholarly journals Evaluation of Failure Behavior and Strength of Fractured Rock Sample Using In Situ Triaxial Compression Tests and Expanded Distinct Element Method

2010 ◽  
Vol 452-453 ◽  
pp. 225-228
Author(s):  
B. Li ◽  
Y. Jiang
Keyword(s):  
Rock Sample ◽  
Fractured Rock ◽  
Distinct Element ◽  
Triaxial Compression ◽  
Peak Stress ◽  
Failure Behavior ◽  
Compression Tests ◽  
In Situ Tests ◽  
Triaxial Compression Tests

The in-situ tests have been widely used to directly assess the strength and deformability of rock mass, along with which, various numerical approaches were proposed to give rational interpretations to the mechanical phenomenon happening during these tests. In this study, the so-called potential cracks are introduced into DEM model, leading to expanded DEM (EDEM) approach which is capable of simulating the cracking in intact rocks. The EDEM is applied to an in-situ triaixal compression test on a fractured rock sample. The simulation has well represented the failure mode, peak stress and elastic modulus obtained from tests as well as the cracking phenomenon and the slips on fracture planes during the loading process.

A Simple Unconsolidated Undrained Triaxial Compression Test Emulator

2015 ◽  
Vol 771 ◽  
pp. 104-107
Author(s):  
Riska Ekawita ◽  
Hasbullah Nawir ◽  
Suprijadi ◽  
Khairurrijal
Keyword(s):  
Triaxial Compression ◽  
Measurement Data ◽  
Radial Strain ◽  
Compression Tests ◽  
Viscous Effects ◽  
Axial Pressure ◽  
Strain Stress ◽  
The University ◽  
And Storage ◽  
Triaxial Compression Tests

An unconsolidated undrained (UU) test is one type of triaxial compression tests based on the nature of loading and drainage conditions. In order to imitate the UU triaxial compression tests, a UU triaxial emulator with a graphical user interface (GUI) was developed. It has 5 deformation sensors (4 radial deformations and one vertical deformation) and one axial pressure sensor. In addition, other inputs of the emulator are the cell pressure, the height of sample, and the diameter of sample, which are provided by the user. The emulator also facilitates the analysis and storage of measurement data. Deformation data fed to the emulator were obtained from real measurements [H. Nawir, Viscous effects on yielding characteristics of sand in triaxial compression, Dissertation, Civil Eng. Dept., The University of Tokyo, 2002]. Using the measurement data, the stress vs radial strain, stress vs vertical strain, and Mohr-Coulomb circle curves were obtained and displayed by the emulator.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

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