On development of urgent repair techniques for steel pipe destroyed by natural disaster (II) - the numerical simulations on contribution of explosion energy to pipe damage and on flyer motion

This paper presents the numerical analysis on the application of the explosive welding technique to the field of the urgent repair of gas and water pipe networks. By carrying out numerical calculation of 1-dimensional impact problem, we examined how the difference in the stand off distance affect the contributions of the explosion energy of explosive to the pipe damage. As a result, in the case of short stand off distance it is demonstrated that the rise of gas pressure at the contact surface between gas and flyer plate caused by impact is one of the factors which increase the pipe damages. The behaviors of the flyer motion were also examined by use of 2-dimensional hydrodynamic code. Regardless of the weight of explosive, the flyer plate is accelerated instantly over 200 m/s within 0.5 mm flying distance and more than 400 m/s at about 2 mm flying distance. The gas pressure at the contact surface is abruptly attenuates approximately 5 mm flying distance.