Experimental Study on Shock Wave Propagation of the Explosion in a Pipe with Holes by High-Speed Schlieren Method

Gang Zhang

doi:10.1155/2020/8850443

Abstract

The shock wave propagation of the explosion in a pipe with holes was studied by a high-speed schlieren experimental system. In the experiments, schlieren images in the explosion were recorded by a high-speed camera from parallel and perpendicular orientations, respectively, and the pressure in the air was measured by an overpressure test system. In parallel orientation, it is observed that the steel pipe blocks the propagation of blast gases, but it allows the propagation of shock waves with a symmetrical shape. In perpendicular orientation, oblique shock wave fronts were observed, indicating the propagation of explosion detonation along the charge. Shock wave velocity in the hole direction is larger than that in the nonhole direction, indicating the function of holes in controlling blast energy, that is, leading blast energy to hole direction. Furthermore, the function of holes is verified by overpressure measurements in which peak overpressure in the hole direction is 0.87 KPa, 2.8 times larger than that in the nonhole direction. Finally, the variation of pressure around the explosion in a pipe with holes was analyzed by numerical simulation, qualitatively agreeing with high-speed schlieren experiments.

Highlights

Blast has been widely applied in geotechnical engineering, such as rock roadway excavation, open-pit mining, and slope engineering [1]
By using the slit charge holder and highspeed photography, Qiu Peng et al [4, 5] studied the mechanism of the interaction between blast stress waves and controlled blast fractures
Laser light direction is perpendicular to the page

Summary

Introduction

Blast has been widely applied in geotechnical engineering, such as rock roadway excavation, open-pit mining, and slope engineering [1]. Gao [21] studied the propagation process of shock waves and blast-induced products from a slit charge holder. Ese blast experiments using schlieren method verify that this optical method is a useful approach to study shock waves and blast products near the borehole. A charge holder with holes is practically useful in cutting roadway roof in coal mines, but its mechanism of shock wave propagation is not specific, partly because shock wave propagation cannot be visualized in the rock mass, partly due to limitations in high-speed measurements. The mechanism of shock wave propagation of the charge in a pipe with holes was studied by high-speed schlieren method, overpressure test, and numerical simulation. Numerical simulation was conducted for a better understanding of shock wave propagation of the charge in a pipe with holes

Experimental Preparations

Experimental Results and Discussion

Unit: mm

Numerical Verification