Study on Tamped Spherical Detonation-Induced Dynamic Responses of Rock and PMMA Through Mini-chemical Explosion Tests and a Four-Dimensional Lattice Spring Model.

The dynamic responses of both underground structures and their surrounding geoformations induced by tamped spherical detonation have been recognised as one of the key topics in both defence engineering and civil engineering. Proper understanding and evaluation of tamped detonation-induced particle movement, spherical stress wave propagation/attenuation, and dynamic crack propagation in geoformations require effective experimental methods and numerical tools. To capture the main characteristics of the spherical shock waves, including the wave propagation and attenuation, a systematic tamped spherical detonation test technique on PMMA has been designed in this study. A mini-explosive sphere with a diameter of 4 mm is generated to produce a small-scale explosion within the PMMA specimen. To monitor the movement of particles during explosion, an electronic measurement system consisting of embedded particle velocity sensors and high-intensity magnetic field generators, has been developed. For the modelling of tamped spherical detonation, a modified multibody failure criterion, equation of state (EOS), and Johnson–Holmquist–Beissel (JHB) model have been implemented in a four-dimensional lattice spring model, thus forming an improved JHB-4DLSM model (M-JHB-4DLSM). It is capable of reproducing the effects of large Poisson's ratios, the strain rate and the high ratio of uniaxial compressive strength to the uniaxial tensile strength values (UCS/T). The developed M-JHB-4DLSM model has been validated through modelling the dynamic responses of both granite and PMMA. Results indicate that the dynamic process and fracturing patterns reproduced by M-JHB-4DLSM are consistent with experimental observations. M-JHB-4DLSM model is then applied to investigate the impact effects of tunnels subjected to close-in buried blasting. Highlights: A systematic experimental technique has been developed for the tamped spherical denotation test. A M-JHB-4DLSM model has been proposed for more realistic modelling of brittle materials subjected to blasting load. The proposed model has been validated through modelling the dynamic responses of both PMMA and granite. [ABSTRACT FROM AUTHOR]