Numerical Study of the Impact of Explosive Material Specifications on Tunnel Boring

Tunnels are one of the access elements to underground structures playing a vital role in passive defense. In regard to the high cost of constructing tunnels, many methods have been presented to improve and make such projects more cost effective. One of the common methods in our country to construct tunnels is the ditching and firing. In tunnel construction using ditching and firing, the explosive features are determined, taking the stone material of the tunnel site into consideration. The number and diameter of blast holes, type and the amount of explosive material to be used and the explosion pattern, as well, are among the items to be determined. One way to reduce the costs is to use the appropriate type and amount of the explosive material which is in turn, dependent on knowing the specifications of the explosive material and tunnel site stone. The explosive material is especially important due to properties such as density, blast velocity, impedance, energy in mass unit and pressure. Therefore, the type and explosive material for every stone should be exactly identified. Predicting the destruction intensity is dependent on long experience, repeating several explosions and observing the results. In general, after several explosions and observing the results,the optimum amount of explosive material will be determined with trial and error. The explosion simulation before performing the main operation can be one of the appropriate methods to reduce time, costs and predicting better explosion-induced results. In this essay, the equations governing blast wave propagation are solved using limited numerical elements and the behavioral model of RHT has been used as the criteria of separation and submission of stone material. The results of this research indicate that in order to choose reliable explosive material to destroy stones, the most effective variable is the amount of energy on the mass unit of that explosive material. The analytical results of the project sensitivity can be used to reduce the costs of underground passive defense projects.