Energy Evolution Principles of Shock-Wave in Sandstone under Unloading Stress
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-1691-9
Geotechnical Engineering
Energy Evolution Principles of Shock-Wave in Sandstone under Unloading Stress Yun Chenga,b, Zhanping Songa,b, Xiaoxu Changc,d, and Tong Wanga School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi'an 710055, China c Henan Zhidi Group Co. Ltd., Zhumadian 463000, China d School of Architectural and Surveying Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China a
b
ARTICLE HISTORY
ABSTRACT
Received 18 September 2019 Revised 12 March 2020 Accepted 2 June 2020 Published Online 20 August 2020
Excavation process often induces the unloading rock mass to be in different damage stages, thus changing the propagation and attenuation characteristics of shock-wave energy in rock mass. This paper involved an investigation on the energy dissipation principles during unloading stress process. First, the paper presented small disturbance impact tests to acquire shock-wave data using the modified split Hopkinson pressure bar device. Then we discussed the shock-wave characteristics under different unloading stresses, attenuation characteristics of shock-wave energy at distance and its effects on unloading stress on the attenuation characteristics of shock-wave energy. Results showed that the presence or absence of unloading stress in sandstone had significant effect on shock-waveform. The shock-wave energy showed a spatial exponential attenuation characteristic, and the decay coefficient indicated that the variation degree in low unloading stress region was significantly greater than that in high unloading stress region. The unloading stress cut-off point was /c = 23.88%. The shock-wave energy at different locations declined with a trend of slight decrease and rapid attenuation, illustrated that the closer the incident end of the sandstone was, the greater the attenuation degree of the shock-wave energy would be. This paper also analyzed the attenuation rate of shock-wave energy and corresponding different sensitivity to unloading stress, showed that the relationship between attenuation rate and unloading stress could be exposed by a composite linear exponential equation. Therefore, the conclusions can provide reference for the attenuation evolution analysis of shock-wave energy in the excavated rock mass.
KEYWORDS Unloading stress Shock-wave energy Modified split-Hopkinson pressure bar Decay coefficient Response intensity Attenuation rate
1. Introduction With the constant development and utilization of underground space such as mine excavation, deep coal mining and tunnel blasting excavation (Shin et al., 2011; Song et al., 2019a; Tian et al., 2019; Fabro et al., 2019; Song et al., 2020), natural or human activities can trigger instability of surrounding rock mass such as buckling failure and tunnel collapse (Wu and Shao, 2019), bringing severe challenges to the
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