Abstract
Detonations in soil can occur due to several reasons: e.g. land mines or bombs from the Second World War. Soil is also often used as a protective barrier. In all cases the behaviour of soil loaded by shock waves is important. The simulation of shock wave loaded soil using hydro-codes like AUTODYN needs a failure model as well as an equation of state (EOS). The parameters for these models are often not known. The popular material law for sand from Laine and Sandvik [1], e.g., is a first approximation, but it can only be used for dry sand with a certain grain grading. The parameters porosity, grain grading, and humidity have a big influence on the material behaviour of cohesive soils. Micro-mechanic models can be used to develop the material behaviour of granular materials. EOS data can be obtained by numerically loading micro-mechanically modelled grains and measuring the density under a certain pressure in the finite element model. The influence of porosity, grain grading, and humidity can be easily investigated. EOS data are determined in this work for cohesive soils depending on these parameters.
Highlights
The simulation of shock wave loaded soil is complex
Cohesive and noncohesive soils are often mixed; the diameters of the particles are varying and other parameters like humidity have a significant influence on the behaviour of the soil
The description of high strain rate loaded materials is done by splitting the stresses in a hydrostatic and a deviatoric part
Summary
The simulation of shock wave loaded soil is complex. Soil is often not a homogeneous material. The pressure-density curve for concrete is, more complex and is similar to the one of granular materials (Figure 1). For granular materials (Figure 1) the EOS starts at the unloaded density ρ0. This density corresponds to the density under low pressure compaction (e.g. gravity). The pressure-density curve of granular material like sand or gravel is often not known in detail. In the hydrocode AUTODYN mainly the ‘sand’ model from Laine and Sandvik [1] is used for all kind of granular soils This model is based on some experiments of sand from Sjobo, Norway and represents a quite coarse gravel when humidity most probably has no influence.
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