Study on Impact Penetration Test of Rock

Abstract

Impact penetration test is important to observe the behaviour of rock undergoing very rapid loading which can not be realized by a testing machine. A force-penetration relationship is considered to be closely related to performance of percussive rock fragmentation process.
A lot of experimental studies have been carried out and it was found that the slope of force-penetration curve in impact penetration test is steeper than that in static penetration test. However, qualitatively much difference exists from author to author.
A system of impact penetration test developed in this study comprises a hammer and a cylindrical bar with a bit at one end. Stress wave is measured by a pair of semi-conductor strain gauges, and penetration is calculated by the measured stress wave.
Nine rocks were tested and force-penetration curves in impact and static tests were obtained together with uniaxial compressive strength, indirect tensile strength, Young's modulus, Poison's ratio, rebound hardness by Schmidt hammer and Shore hardness. Good correlation was found between force-penetration curves in impact and static tests, and slope by impact test, Kd can be expressed by slope in static test, Ks as Kd=1.2Ks
The difference between Kd and Ks is not so much as expected, just 20%.