Finite element method simulation of explosive compaction in saturated loose sandy soils

Abstract

Explosive Compaction (EC) is a deep soil treatment method for saturated sands with low density. Beside soil characteristics, its efficiency remarkably depends on charges weight, placement pattern and placement depth. Various empirical equations have been proposed by many researchers for selecting of such parameters, but their lack of accuracy makes adopting of a more precise tool for design and evaluation of engaging parameters in EC method essential. Therefore, the present study was devoted to the application of an advanced finite element simulation scheme called arbitrary Lagrangian-Eulerian (ALE) formulation in LS-DYNA as an alternative approach to enhance EC design procedure. SOIL_AND_FOAM material model in LS-DYNA was used for soil and explosives were defined with HIGH_EXPLOSIVE_BURN material model and JWL equation of state. The developed model was validated by using the existing single borehole blast test result. Subsequently, the effectiveness of EC was evaluated by assessing the maximum soil settlement and pore water pressure (PWP) dissipation for different cases where soil permeability, charge weight, depth and detonation delay were varied. Consequently, results suggested that multiple small charges with detonation delays increases EC effectiveness regarding the final settlement and reaching liquefaction during the explosion. Moreover, when charges are placed on lower half of soil layer, more compaction and less heave are achieved. The findings also show that an increase in permeability value of the soil increases the resulting settlement, however, this difference is negligible. Furthermore, based on the obtained results, using more charge weight increases both surface heave and compaction of lower layers. Thus, an optimum weight of explosives should be chosen in this case.