Performance testing and preparation methods of similitude materials for explosion model tests in gravelly soil

Centrifuge modeling provides an effective means for simulating prototype explosion effects, with the preparation of analogous soil materials that exhibit dynamic responses equivalent to undisturbed soil serving as a prerequisite for the applicationof this technology. To establish a scientific preparation methodology, theoretical analysis was first employed to identify key soil parameters governing explosion-induced ground shock, focusing on density and wave velocity (wave impedance), which are fundamentally controlled by soil gradation characteristics. Based on this, four scaling methods—elimination, equivalent substitution, parallel gradation, and hybrid—were systematically applied to prepare 12 types of analogous soil samples with varying maximum particle sizes. Through systematic void ratio tests and bender element tests under effective confining pressure, quantitative relationships between the extreme void ratio of gravelly soil and its fine content and median particle size were revealed, and an empirical predictive model for the small-strain elastic modulus was developed. By comparing model-predicted wave velocities with in-situ measured data, the study confirmed that the coefficient of uniformity, fine content, and median particle size are the key controlling parameters for achieving dynamic similitude in explosion effects in gravelly soils. Comparative analysis demonstrated that analogous soil samples with a maximum particle size of 10 mm, prepared by the equivalent substitution method, exhibited the closest equivalence to the undisturbed soil in terms of these key parameters. Hypergravity centrifuge explosion tests conducted on this analogous soil showed that the attenuation law of normalized peak acceleration on the blast plane agreed well with in-situ test results, thereby validating—from the perspective of explosion-induced dynamic response—the dynamic equivalence between the prepared analogous soil and the undisturbed soil, as well as the reliability and applicability of the proposed soil preparation method.