Testing and modeling clay behavior subjected to high strain rate loading in a tunneling problem

Abstract

Complex numerical simulations of tunnels are often used to model effects of high strain rate surface loads. Most of this modeling ignores soil's strength dependency on strain rate to lessen the complexity. A series of Split Hopkinson Pressure Bar (SHPB) tests emulates the high strain rate compression occurring in blast events, for Nile Silty Clay (NSC) samples. The Cowper Symonds parameters are calibrated to SHPB test results and are used in advanced three-dimensional finite element analysis of a benchmark tunnel problem using Abaqus/Explicit software. The shallow tunnel in NSC formation is subjected to a blast event at the ground surface simulated by the CONWEP algorithm. The Smoothed Particle Hydrodynamic (SPH) mesh-free technique captures the crater formed due to the explosion. Results from the benchmark problem show that including the strain rate dependency in the analysis leads to a significant reduction in the calculated tunnel liner straining actions and deformations.

Keywords

• Blast loads
• CONWEP
• High strain rate
• Tunneling
• Cowper symonds
• Split Hopkinson Pressure Bar test