Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths

In order to understand the influence of unloading path on the mechanical properties of coal, triaxial unloading confining pressure tests with different initial confining pressure and different unloading rate were carried out. The test results show that the triaxial unloading strength of coal samples...

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Main Authors: Yang Zhang, Yongjie Yang, Depeng Ma
Format: Article
Language:English
Published: Wiley 2020-01-01
Series:Shock and Vibration
Online Access:http://dx.doi.org/10.1155/2020/8870821
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author Yang Zhang
Yongjie Yang
Depeng Ma
author_facet Yang Zhang
Yongjie Yang
Depeng Ma
author_sort Yang Zhang
collection DOAJ
description In order to understand the influence of unloading path on the mechanical properties of coal, triaxial unloading confining pressure tests with different initial confining pressure and different unloading rate were carried out. The test results show that the triaxial unloading strength of coal samples under different test conditions is lower than conventional triaxial tests, but the brittleness characteristics are more obvious. This result indicates that the coal samples are easily damaged under unloading conditions. In the axial loading stage of the confinement unloading tests, the axial strain plays a leading role. However, during the confining pressure unloading stage, the circumferential deformation is large, which is the main deformation in this stage. Higher unloading rates of confining pressure are associated with shorter times between the peak stress position and sample complete failure. This shows that samples are more easily destroyed under higher unloading rates and the samples are more difficultly destroyed under lower unloading rates. In addition, with increasing unloading rate, the peak principal stress difference and confining pressure at failure decrease gradually, whereas the confining pressure difference at failure increases gradually. Compared with conventional triaxial compression tests, the cohesion of coal is reduced and the internal friction angle is increased under the condition of triaxial unloading test.
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institution Kabale University
issn 1070-9622
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publishDate 2020-01-01
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series Shock and Vibration
spelling doaj-art-e198b3084d8a4c4ea602c586044aa5b42025-02-03T01:04:59ZengWileyShock and Vibration1070-96221875-92032020-01-01202010.1155/2020/88708218870821Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test PathsYang Zhang0Yongjie Yang1Depeng Ma2State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, ChinaState Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Water Conservancy and Civil Engineering, Shandong Agricultural University, Tai’an 271018, ChinaIn order to understand the influence of unloading path on the mechanical properties of coal, triaxial unloading confining pressure tests with different initial confining pressure and different unloading rate were carried out. The test results show that the triaxial unloading strength of coal samples under different test conditions is lower than conventional triaxial tests, but the brittleness characteristics are more obvious. This result indicates that the coal samples are easily damaged under unloading conditions. In the axial loading stage of the confinement unloading tests, the axial strain plays a leading role. However, during the confining pressure unloading stage, the circumferential deformation is large, which is the main deformation in this stage. Higher unloading rates of confining pressure are associated with shorter times between the peak stress position and sample complete failure. This shows that samples are more easily destroyed under higher unloading rates and the samples are more difficultly destroyed under lower unloading rates. In addition, with increasing unloading rate, the peak principal stress difference and confining pressure at failure decrease gradually, whereas the confining pressure difference at failure increases gradually. Compared with conventional triaxial compression tests, the cohesion of coal is reduced and the internal friction angle is increased under the condition of triaxial unloading test.http://dx.doi.org/10.1155/2020/8870821
spellingShingle Yang Zhang
Yongjie Yang
Depeng Ma
Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
Shock and Vibration
title Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
title_full Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
title_fullStr Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
title_full_unstemmed Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
title_short Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths
title_sort mechanical characteristics of coal samples under triaxial unloading pressure with different test paths
url http://dx.doi.org/10.1155/2020/8870821
work_keys_str_mv AT yangzhang mechanicalcharacteristicsofcoalsamplesundertriaxialunloadingpressurewithdifferenttestpaths
AT yongjieyang mechanicalcharacteristicsofcoalsamplesundertriaxialunloadingpressurewithdifferenttestpaths
AT depengma mechanicalcharacteristicsofcoalsamplesundertriaxialunloadingpressurewithdifferenttestpaths