An Explicit Nonlinear Numerical Model of Explosive Air Blast on Snow and Implications for Avalanche Control

Recent post explosive control avalanches and the lack of analytical methods for evaluating explosive control have motivated this study to better quantify the effects explosives on snow. Currently, there are insufficient tools for predicting the effects that explosives will have on snow avalanche release. While there is significant practitioner experience, that experience has (on occasion) not adequately anticipated control response. This research seeks to develop analytic tools describing phenomenology and that can examine the “internal” snow response during explosive events. A state-of-the-art explicit nonlinear dynamic model (using ANSYS/AUTODYN) is presented where the explosion, shock propagation through air and snow response is simulated in a single analysis. This versatile approach handles the complex interactions from explosive events and solids, gases and liquids. Nonlinear interactions and responses are modeled over the very short blast/propagation time. The axisymmetric model predicts internal structural response during explosive events, including important parameters such as stress, strain, density changes velocity and acceleration. Various snowpack configurations and explosive charges with variable locations can be examined. The results point to a rolling shear stress wave in the snow that lags behind the explosive shock wave traveling over the surface. The intensity, effective depth and lateral extent of the stress wave may determine the control effectiveness. The analytic approach provides a tool for future detailed examination of critical avalanche control parameters.