scholarly journals Classification and Fractal Characteristics of Limestone Fragments Obtained in Conventional Compression and Cyclic Loading Tests under Uniaxial and Triaxial Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Rui Yang ◽  
Xiaodi Wang ◽  
Hao Zha ◽  
Xiuzhang Yang ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Small Difference ◽  
Confining Pressure ◽  
Test System ◽  
Theoretical Research ◽  
Loading Conditions ◽  
Loading Test ◽  
Loading Tests ◽  
Fractal Characteristics ◽  
Cyclic Loading Tests

The mechanical response characteristics of rocks under cyclic loading conditions are crucial factors for evaluating and analyzing the stability of rock mass during underground excavation. In this study, based on fractal theory and a series of tests using the MTS815.02 rock mechanics test system, the classification and fractal characteristics of limestone specimen fragments are investigated. The results show that limestone specimens subjected to cyclic loading can generate more small-sized fragments than conventional compression, but the large-fragment-producing abilities of the two tests exhibit small difference. The mass fraction of the fragments in the cyclic loading test is obviously greater than that in the conventional test when the fragment size is less than 4.75 mm; however, only a small difference is observed between the cyclic loading tests with frequencies of 0.25 and 0.5 Hz. In the same type of test, a confining pressure is helpful in reducing the fragmentation of limestone specimen. As the size interval decreases, the shapes of limestone fragment transition from rectangular to long slice and then to square. The results also indicate that the confining pressure has a significant influence on the size-quantity and size-mass fractal dimensions of limestone fragments. The former has a positive correlation with the confining pressure, whereas the latter decreases with confining pressure. The conclusions obtained in this investigation can enrich the theoretical research on the failure response and mechanism of rock under cyclic loading conditions.

scholarly journals AN EVALUATION OF CYCLIC LOADING CONDITIONS AND COMPUTED TOMOGRAPHY FOR THE STRENGTH AND PETROPHYSICAL PROPERTIES OF ANHYDRITE CAPROCK

2021 ◽  
Vol 36 (4) ◽  
pp. 139-149
Author(s):  
Mostafa Farrokhi ◽  
Hossein Jalalifar ◽  
Saeed Karimi Nasab
Keyword(s):  
Computed Tomography ◽  
Cyclic Loading ◽  
Ct Imaging ◽  
Petrophysical Properties ◽  
Loading Conditions ◽  
X Ray Diffraction ◽  
Imaging Results ◽  
Porosity And Permeability ◽  
Loading Tests ◽  
Cyclic Loading Tests

Underground gas storage (UGS) in depleted reservoirs affects caprock properties. The resemblance of Qom anhydrite outcrop with cutting obtained from a 2629 m depth was confirmed using X-ray diffraction (XRD) results and scanning electron microscope (SEM) tests. The anhydrite specimens unconfined compressive strength (UCS) changed under static cyclic loading conditions, and also petrophysical properties, such as porosity and permeability altered under 10, 20, and 30 cycles of loading. The magnitude of loading ranged from 30 to 43% of intact anhydrite UCS. The loading rate used for cyclic loading tests was 0.004 mm/s. The samples’ UCS decreased between 3.5 to 23.9% under cyclic loading conditions. The study of specimens computed tomography (CT) imaging with porosity and permeability indicated the growth of cracks, the cracks did not initiate in all lengths of specimens, hence the incremental increase in porosity did not increase the permeability of specimens. Even being under cyclic loads, the permeability of specimens stayed lower than 10-15 m2 (0.001 mD) but the trend of pressure versus time for measuring permeability shows a higher drop in pressure due to changes in permeability. The study indicated that the CT imaging results are in good accordance with petrophysical findings.

scholarly journals Experimental Study on Initial Damage Point of Deep Granite under Step Cyclic Loading Method

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Lu Chen ◽  
Shan Wu ◽  
Lijie Guo
Keyword(s):  
Cyclic Loading ◽  
Turning Point ◽  
Confining Pressure ◽  
Peak Strength ◽  
Deep Mining ◽  
Loading Method ◽  
Initial Damage ◽  
Important Concern ◽  
Loading Tests ◽  
Cyclic Loading Tests

In deep engineering, the initial damage point of host rock has become an important concern. Nowadays, there are many methods which can work out the initial damage point. However, each existing method introduces some significant subjective or parametric errors. In this paper, a new determination method of initial damage point employing step cyclic loading tests was designed and a series of tests were conducted on deep granite. After analyzing the peak strength and effect of cyclic loading, the turning point of initial damage was confirmed. The testing results show that the turning stress of initial damage was about 45% peak strength and will present a little decrease with the confining pressure increasing. These calculated damage points are much more scientific, accurate, and intuitive, which provides a new method for the study on rock mechanics in deep mining.

scholarly journals Payne Effect in Filled Nitrile Rubber Submitted to Cyclic Loadings

2012 ◽  
Author(s):  
Pierre P. Garnier ◽  
Jean-Benoît J. B. Le Cam ◽  
Michel M. Grédiac
Keyword(s):  
Cyclic Loading ◽  
Strain Amplitude ◽  
Viscoelastic Properties ◽  
Nitrile Rubber ◽  
Loading Conditions ◽  
Payne Effect ◽  
Two Temperatures ◽  
Loading Tests ◽  
Number Of Cycles ◽  
Cyclic Loading Tests

This study deals with the viscoelastic properties of filled nitrile rubber submitted to cyclic loading conditions. Classic strain amplitude sweeps were first carried out on both a filled and an unfilled nitrile rubber. Tests were performed at two temperatures ambient and 80 °C. Some specimens were then subjected to a high number of cycles to study the variations in the viscoelastic properties and the sensitivity of the Payne effect to cyclic loading tests at several given strain amplitudes.

scholarly journals Investigating the Fatigue Characteristics of Large Stone Asphalt Mixtures Based on the Disturbed State Concept

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jianhui Wei ◽  
Tao Fu ◽  
Yongjun Meng ◽  
Chengming Xiao
Keyword(s):  
Cyclic Loading ◽  
Asphalt Mixtures ◽  
Theoretical Research ◽  
External Work ◽  
Large Stone ◽  
Disturbed State Concept ◽  
Loading Tests ◽  
Fatigue Characteristics ◽  
Cyclic Loading Tests ◽  
Disturbance Function

The mechanical response characteristics of large stone asphalt mixtures (LSAMs) are key factors in studying its fatigue characteristics during cyclic loading tests. Based on disturbed state concept (DSC) and viscoelastic continuum damage model (VECD), a series of tests using an overlay test (OT) were carried out to investigate the fatigue characteristics of LSAM. The results showed that disturbance and damage increased with decreasing frequency and increasing loading displacement and aging degree, while the asphalt content had no obvious adverse effect on the increase in damage. In addition, the disturbance and damage grew rapidly in the early stage of loading and reduced in the later stage of loading. On the contrary, based on DSC, the constitutive model modified with disturbance function (D) defined by external work could describe the mechanical properties, and the evolution process of disturbance function (D) could reflect the damage change in cyclic loading tests. The research conclusion can enrich the theoretical research on the fatigue failure response and mechanism of LSAM under cyclic loading and expand the application scope of DSC in the field of pavement.

Stress-Strain Relationship for Steel under Uniaxial Cyclic Loadings

2002 ◽  
Vol 5 (3) ◽  
pp. 143-151 ◽  
Author(s):  
Luís Calado ◽  
António Brito
Keyword(s):  
Complex Loading ◽  
Steel Structures ◽  
General Purpose ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Relationship ◽  
Complete Failure ◽  
Loading Tests ◽  
Cyclic Loading Tests ◽  
Mathematical Relationships

The mechanical properties of steel in the inelastic range can generally be described by mathematical relationships. Many such constitutive relationships have been validated by static or uniaxial cyclic loading tests. Very few models have been substantiated by test results under complex loading conditions. For that reason, the implementation of such models in general purpose structural analysis programs for steel structures under seismic actions, is in some cases complex and in others impossible. This paper is concerned with a uniaxial non-linear model for structural steel under complex loading condition and with damage accumulation. The Giuffré, Menegoto and Pinto model was taken as a basis for the development of this model. The accuracy of the proposed numerical model was drawn with uniaxial cyclic experiments. Some numerical simulations are presented in order to illustrate the capabilities of the model for use as a stress-strain relationship for steel under uniaxial complex loading conditions up to the complete failure of the material.

scholarly journals TENSILE AND CYCLIC LOADING TESTS OF HORIZONTAL BRACE USING GLUED LAMINATED TIMBER WITH STEEL INSERTED PLATE

2019 ◽  
Vol 25 (60) ◽  
pp. 655-659
Author(s):  
Shuzo HIROISHI ◽  
Akira OKADA ◽  
Naoya MIYASATO ◽  
Noburu NAKAMURA ◽  
Kenichi MAMURO ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Glued Laminated Timber ◽  
Loading Tests ◽  
Cyclic Loading Tests
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