Successive boulder impacts on the soil-embedded baffle: an experimental study

Baffles have been used to resist boulder impacts during debris flow. Soil-embedded baffles offer flexibility to prolong the system’s service life across multiple impacts. However, the behaviour of this design is unclear due to limited investigation. This study aimed to experimentally investigate the load and energy transfer mechanisms within a soil-embedded baffle system through heavily instrumented pendular impact tests. Tactile sensors were attached to the baffle foundation to measure contact pressures at the soil–foundation interface during impacts. New scaling laws specific to the soil-embedded baffle system was tailored-derived to ensure model tests data can be scaled up to the prototype. Two tests were conducted on the model baffles in dense and loose soils, with ten successive impacts applied in each to evaluate the system capacity evolution. Significantly less contact force and baffle deflection were observed in looser soil because of greater kinetic energy absorption during impacts. However, the trade-off was larger permanent rotation post-impact. Dynamic compaction due to successive impacts progressively densified the soil, gradually reduces system flexibility and simultaneously increases the contact force. Ignoring the dynamic effects and soil densification led to an underestimation of the peak contact pressure at the soil–foundation interface by over 400% after 10 successive impacts.