Dynamic tensile experiment of rock using underwater shock wave

In order to promote blasting efficiency and to establish effective blasting demolition techniques, it is important to know the mechanism of the dynamic fracture process on rock or construction materials. We proposed a new technique to estimate the dynamic fracture process of the cylindrical rock specimen. In this technique the explosive is used as the explosion source, and a pipe filled with water is arranged between the explosive and the cylindrical rock specimen. The strength of incident underwater shock wave is adjusted by changing the length of the water pipe. The main purpose of this test is to collect the experimental data on the behaviors of dynamic fracture of the rock. We would like to provide these experimental data, which can confirm the validities of the related numerical simulations or fracture models for the rock materials. In addition, one of the aims of this test is to estimate the dynamic tensile strength of the rock for a wide range of the strain rate utilizing Hopkinson's effect. The free surface velocity at the end of rock specimen and the position of cracks on the rock surface are observed by using a laser vibration meter and high-speed camera, respectively. The behavior of the underwater shock wave that is generated by underwater explosion of explosive is also estimated by numerical simulation. We will discuss the validity of this test based on the experimental and numerical results.