Characteristic Impedance and Its Applications to Rock and Mining Engineering

Abstract

The characteristic impedance of a rock is defined as the product of the sonic velocity and the density of the rock. Based on previous studies, this article finds that: (1) For an intact rock, its characteristic impedance is a comprehensive physical property, since it is closely related with strengths, fracture toughness, Young’s modulus, and Poisson’s ratio. (2) For rock masses, their characteristic impedances either increase markedly or slightly with increasing depth. (3) The bursts of intact rocks in laboratory are dependent on their characteristic impedances to a great extent, and strong rock bursts happen mostly in the rocks with large characteristic impedance. (4) Rock burst occurrence in tunnel and mines has a close relation with the characteristic impedances of the rocks. (5) Laboratory experiments on different rock samples show that seismic velocity increases as applied stress rises, and field monitored results from coal mines indicate that in the areas where rock bursts happened, the seismic velocity was increasing markedly before or during the bursts. (7) Drillability of rock depends on the characteristic impedance of the rock and the rock with larger impedance has lower drillability or lower penetration rate. (8) The potential applications of characteristic impedance include evaluation and classification of rock masses, and prediction of rock burst proneness and drillability.

Research of borehole drilling parameters for determining the optimum size of granite stone blocks

“…It is based on the optimal choice of the type of drilling equipment according to the current condition of massif and determination of the sufficient force for penetration into the rock [6]. Assessing drilling efficiency considering rocks' properties is also an important part of research [7].…”

Experiment Study of Stemming Length and Stemming Material Impact on Rock Fragmentation and Dynamic Strain

“…In that case, the amplitude of the final wave in the blast hole will be greater than that of the original detonation wave. On the other hand, if the characteristic impedance of the stemming material is smaller than that of the explosive, the amplitude of the final wave in the blast hole will be smaller than that of the original wave [5,22,55]. The characteristic impedance of explosives in digital electronic detonators is calculated as Z e = 1130 × 6800 = 7.648 × 10 6 kg/m 2 s, while the characteristic impedance of the clay material (Z clay ) is calculated as Z clay = 2600 × 3480 = 9.048 × 10 6 kg/m 2 s. It can be observed that the characteristic impedance of the clay is greater than that of the explosive, resulting in an increase in detonation wave pressure within the blast hole.…”