Experimental Evaluation and Finite-Element Simulations of Explosive Airblast Tests on Clay Soils

Abstract

This study examined the effects of small-scale airblast experiments on clay soils and compared experimental results with numerical solutions obtained through finite-element simulations. Thirty-three suspended explosive blasts were conducted above clay soils with explosive masses ranging from 0.9 to 100.9 g and suspended heights ranging from 2.5 to 7.6 cm. The experiments were instrumented with airblast sensors and subsurface triaxial geophones to measure vibration energy and air overpressure from the blast events. Laboratory tests were conducted on the experimental soils to obtain geotechnical and shear strength soil properties. Two-dimensional (2D), arbitrary Lagrangian Eulerian (ALE) finite-element simulations were performed using a finite-element software program and compared with the experimental results. Soils were modeled using the Federal Highway Administration (FHWA) soil material model. Air overpressure, ground vibration, and crater geometry data obtained from the experimental blasts were compared with the numerical simulation results. The first-order simulated results compared fairly well with the experimental results, with the exception of simulated crater diameters, which were 1.5 times larger than experimental results. However, stress-response instabilities were observed in the model after the initial stress pulse had propagated through the soil, and the model did not appear to capture postpeak behavior. Therefore, the soil model used in the study is recommended for use only as a first estimate for capturing the response of airblast loading of clay soils in a 2D ALE analysis. More recent models, such as a cap plasticity model or the disturbed state concept (DSC) model, are more applicable if stress path and postpeak behaviors are to be adequately captured. In addition, a three-dimensional analysis of ALE coupled with Lagrange elements should be considered for capturing a more accurate strength response.