Abstract <p>The initial boundary value problem of the evolution of a wave pulse in a shock tube initiated by the decay of a rupture is solved numerically. Cases of the reflection of a shock-wave pulse from a layer of granular bulk medium are considered. The influence of the parameters of the bulk layer on the initiation of a stress wave in the skeleton of a porous medium is investigated. A comparison of the obtained results with experimental data is given. It is established that over time in any section of the bulk layer the contribution of pore pressure to the total stress becomes predominant compared to the reduced stress.</p>