Mechanical and Failure Characteristics of Rock-coal-rock Combined Body under Different Strain Rates: A Numerical Study from Micro Perspective

Strain rate has critical influence on rock and coal strength. Understanding and controlling rock failure is critical in many geological projects, such as mining, tunneling and other underground engineering project. The mechanical and failure characteristics of rock-coal-rock sandwich structures under different strain rates of uniaxial compression were numerically investigated. And detailed analysis of uniaxial compressive strength (UCS), elastic modulus, full scale stress-strain curves and acoustic emission (AE) characteristics of roof rock-coal-floor rock combined body is presented. The results show that with the increase of strain rate, the peak strain, peak strength and crack number all show an increasing trend. However, elastic modulus decreases with increasing strain rate. And with the increase of strain rate, the AE event count of rock-coal-rock combined body increases accordingly. The failure of rock-coal-rock combined body extends from the rock on both sides of coal to the whole rock on both sides, and the failure is more serious. This study provides an explanation for the strength and deformation of the rock-coal-rock combined sample in engineering from a micro perspective.