Experimental Study on the Dynamic Mechanical Properties of Large-Diameter Mortar and Concrete Subjected to Cyclic Impact

Bi Sun,Yang Ping,Nan Wu,Zhende Zhu,Zhijian Jiang,Qing Ma

doi:10.1155/2020/8861197

Abstract

Rock bursts are typically accompanied by multiple shocks. In order to explore the dynamic characteristics of filling materials in rock burst roadways, we employ the split Hopkinson pressure bar (SHPB) test to analyze the dynamic mechanical response of mortar and concrete under cyclical impact. The SHPB test results of the large-size specimen indicate the improvement in the waveform shape and the reduction in the wave dispersion via the application of the rubber sheet as the pulse shaper. Under cyclic impact, the peak stress and energy utilization ratio of mortar and concrete specimens were reduced, demonstrating obvious fatigue characteristics. The mortar peak stress and energy utilization ratio were observed to be sensitive to the impact times, while those of concrete were sensitive to impact pressure. The damage evolution of mortar and concrete exhibited very similar trends under the cyclic impact load, whereby the impact pressure had minimal effect on the damage evolution.

Highlights

In order to explore the dynamic characteristics of filling materials in rock burst roadways, we employ the split Hopkinson pressure bar (SHPB) test to analyze the dynamic mechanical response of mortar and concrete under cyclical impact. e SHPB test results of the large-size specimen indicate the improvement in the waveform shape and the reduction in the wave dispersion via the application of the rubber sheet as the pulse shaper
Experimental Principle. e split Hopkinson pressure bar (SHPB) is considered as the most reliable experimental method when investigating the mechanical properties of materials at medium and high strain rates. e SHPB system used in this paper is located at the structural laboratory of Hohai University and operates at the strain rate range 102–104 s−1. e basic working principle of the SHPB testing device is described as follows. e bullet is pushed by air pressure to impact the incident pressure bar, such that an incident wave εI is formed in the bar
(4) Trends in the damage evolution of mortar and concrete were in strong agreement under the cyclic impact load

Summary

Research Article

Experimental Study on the Dynamic Mechanical Properties of Large-Diameter Mortar and Concrete Subjected to Cyclic Impact. In order to explore the dynamic characteristics of filling materials in rock burst roadways, we employ the split Hopkinson pressure bar (SHPB) test to analyze the dynamic mechanical response of mortar and concrete under cyclical impact. E SHPB test results of the large-size specimen indicate the improvement in the waveform shape and the reduction in the wave dispersion via the application of the rubber sheet as the pulse shaper. E SHPB test device is based on the application of a thin copper sheet on the impact surface of the incident bar to improve the SHPB waveform, producing an almost constant strain rate in the specimen. E split Hopkinson pressure bar (SHPB) is considered as the most reliable experimental method when investigating the mechanical properties of materials at medium and high strain rates. Multiple impact tests must be performed on the same specimen, and the critical impact stress should be determined to ensure that the specimen can withstand multiple impacts. e impact stress at different amplitudes was obtained by controlling the air pressure for cyclic

Brass sheet Rubber sheet

Experimental Results and Analysis

Number of cycles