Two types of coal samples’ dynamic mechanical properties under impact loading

Abstract

This study presents a kinetic experiment process of briquette and raw coal samples in detail by means of Φ 75mm split Hopkinson pressure bar test system and dynamic stress-strain relations and mechanical properties of this two different coal samples. According to the experimental results, this two coal samples both have strain rate effect. The DIF (dynamic stress increasing factor) and DEIF (dynamic strain increasing factor) of the two coal samples have different trends. There is a turning phenomenon of DIF as the strain rate is around 100s-1, and the DIF of the hard coal increases rapidly over 100s-1, but the DIF increasing rate of soft coal has little change before or after the turning point. The DEIF of the two types of coal all increases with the increase of strain rate, but the turning strain rate of ordinary coal is 120s-1, while a platform of turning strain rate exists for outburst coal with strain rate ranging from 100s-1 to 210s-1. It represents the discrepancy in their strain rate hardening effect and dynamic toughening effect.