Behaviour of Foam Concrete under Impact Loading Based on SHPB Experiments

This paper presents an innovative method for using foam concrete as a typical building material for soft structures in underground coal mines subjected to dynamic loading. To understand the behaviour of foam concrete under impact loading, a total of 30 specimens with a diameter of 50 mm and a height of 50 mm were experimentally tested using a 75 mm diameter split Hopkinson pressure bar (SHPB) device. The key parameters investigated in the present study included the type of foam concrete (fly ash and sand), the density of foam concrete (1000, 1200 and 1400 kg/m3), and the impact velocity (3.0, 4.0, 5.0, 6.0, and 7.0 m/s). Six specimens were also tested under static loading for comparison. The stress-strain curve of foam concrete under impact loading showed three stages, started with a linear elastic stage, followed by a yield stage and ended with a pore wall destruction stage. The test results also indicated that the dynamic increase factor, ultimate compressive strength, tenacity, and specific energy absorption increase with the strain rate under the same density. In particular, both the failure model and the behaviour of foam concrete were affected by the impact velocity. The findings of this research provide a reference for further research on the application of foam concrete in underground coal mines.