Energy Dissipation and Particle Size Distribution of Granite under Different Incident Energies in SHPB Compression Tests

Jian Hu,Fengqiang Gong,Zongxian Zhang,Song Luo,Xuesheng Liu,Hangyu Jia

doi:10.1155/2020/8899355

Jian Hu, Fengqiang Gong + Show 4 more

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https://doi.org/10.1155/2020/8899355

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Abstract

To investigate energy dissipation and particle size distribution of rock under dynamic loads, a series of dynamic compression tests of granite specimens were conducted using a conventional split-Hopkinson pressure bar (SHPB) device with a high-speed camera. The experimental results show that the dissipated energy increases linearly with an increasing incident energy, following two different inclined paths connected by a critical incident energy, and the linear energy dissipation law in the dynamic compression test has been confirmed. This critical incident energy was found to be 0.29–0.33 MJ/m3. As the incident energy was smaller than the critical incident energy, the rock specimens remained unruptured after the impact. When the incident energy was greater than the critical incident energy, the rock specimens were ruptured or fragmented after the impact. In addition, the experimental results indicate that the dissipated energy and energy consumption ratio of a rock specimen, either unruptured or fragmented, increase with an increasing strain rate. Furthermore, it was found that fragment sizes at each mesh decrease with an increasing incident energy; that is, fragmentation becomes finer as incident energy increases.

Highlights

Rock structures are frequently subjected to dynamic loads from rock drilling, rock blasting, rock bursts, and seismic events or earthquakes [1,2,3,4]
As the split-Hopkinson pressure bar (SHPB) system is used in measuring rock strengths and fracture toughness, two conditions should be satisfied: one-dimensional loading condition and stress equilibrium condition at the two ends of the rock specimen. e first condition means that a stress wave on each cross section of elastic bars always is kept as a planar wave. e second condition states that the stresses on both ends of the specimen are approximately equal before or when the specimen is failed
Based on the dynamic compression tests of granite specimens under different incident energies by using an SHPB testing system, the following conclusions can be drawn: (1) Under the impact of different incident energy, three states appear in the dynamic compression tests of the granite specimens, unruptured state, ruptured state, and fragmented state. ese three states correspond to three different types of stress-strain curves

Summary

Introduction

Rock structures are frequently subjected to dynamic loads from rock drilling, rock blasting, rock bursts, and seismic events or earthquakes [1,2,3,4]. Rock damage or fracture may occur and energy consumption happens [5,6,7]. Experimental studies have confirmed that the deformation and failure of rock is a process of energy input, dissipation, and release. Li et al [25] carried out dynamic compression tests on Bukit Timah granite and concluded that fractured specimens absorb more energy than unbroken ones and energy absorption per unit volume of rock increases linearly with increasing strain rates. Hong et al [26] conducted dynamic compression tests on granite, sandstone, and limestone and found that the average size of rock specimens decreases with the increase of the energy consumption per unit volume. Deng et al [27] conducted dynamic uniaxial compressive tests on granite and

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