Dynamic Tensile Test of Coal, Shale and Sandstone Using Split Hopkinson Pressure Bar: A Tool for Blast and Impact Assessment

Dynamic Tensile Test of Coal, Shale and Sandstone Using Split Hopkinson Pressure Bar: A Tool for Blast and Impact Assessment

Kaiwen Xia (University of Toronto, Canada), Sheng Huang (University of Toronto, Canada) and Ajay Kumar Jha (Indian Institute of Technology, India)
Copyright: © 2010 |Pages: 14
DOI: 10.4018/jgee.2010070103
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Abstract

The dynamic tensile strength plays a pivotal role in rock fragmentation affecting the overall economics under the present ‘Mine to Mill Concept’. In this paper, a modified SHPB technique and Brazilian test method is presented to test the dynamic tensile strength of coal, shale and sandstone rock samples collected from three opencast mines of Coal India Limited and is compared with the static strength value. The dynamic tensile strength of coal and rock is much higher than static strength and tensile strength of coal and rock samples increase with loading rate. The result shows that the dynamic strength of the coal sample is 1.5 times higher than static strength and the dynamic strength of the sandstone sample is 3 times higher than the static strength.
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2. Review Of Dynamic Tests Carried On Coal, Sandstone And Shale Samples

Recently, Okubo et al. developed an alternative test method for anthracite coal samples by subjecting the samples to alternating slow and fast strain rates within the quasi-static loading range (Okubo et al., 2006). Shan et al. (2006) extended the alternative test method procedure to the dynamic loading range. Wang et al. (2007) carried out the compression mechanical properties of coal with the confinement of 8.06MPa, and their experiments can also be done with a Hopkinson bar to investigate the dynamic properties with confinement. The test results from the above referred literature are summarized in Table 1.

Table 1.
Strength of various coals
StudycoalsTesting methodStrength
(MPa)		Strain rate
(s-1)
Okubo et al.(2006) Beijing CoalUniaxial Compression50 (X)*10-6~10-5
25(Y)
22(Z)
Uniaxial tension0.42(X)
1.04(Y)
0.57(Z)
Indirect tension2.1(Y/Z)**
1.9(Z/Y)
3.7(X/Z)
2.8(Z/X)
3.2(Y/Z)
3.0(Z/Y)
Wang et al. (2007) Jingyuan coalCompression
With 8.06MPa confinement		23.6-
Shan et al.(2006) Yunjialing coalHopkinson bar
(Compression)		9.2/6.1**24
13.5/7.144
12.0/8.466
21.0/16.7118

*Loading direction

**Boring direction/ Loading direction

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