Impact mechanisms of granular and viscous flows on rigid and flexible barriers

TLDR

Structural countermeasures such as rigid and flexible barriers are commonly installed in mountainous regions to intercept mass‑wasting processes, yet the study of their impact mechanisms remains difficult due to a lack of sufficient and reliable comparable physical data. The study aims to evaluate the impact mechanisms of dry granular and viscous flows on rigid and flexible barriers using a geotechnical centrifuge. The flexible barrier consists of four instrumented cables with spring mechanisms to replicate a bilinear prototype loading response, and both barriers were tested under simulated dry granular and viscous liquid impacts in a centrifuge. Tests showed that both barrier types exhibited similar frontal dynamic impact coefficients near unity, yet the flexible barrier mobilized only 249 kJ of its 10 MJ kinetic energy capacity, indicating that debris‑resisting barriers mainly need to intercept the dynamic flow front while the remaining energy is dissipated internally; additionally, the flexible barrier’s large deformation reduced its granular static load by 39 % compared to the rigid barrier, leading to an active failure mode and lower earth pressure.

Abstract

Structural countermeasures such as rigid and flexible barriers are commonly installed in mountainous regions to intercept mass-wasting processes. Without sufficient and reliable comparable physical data, the study of impact mechanisms remains difficult and not well understood. In this study, a newly developed flexible model barrier together with a rigid barrier are used to simulate either dry granular or viscous liquid impacts on these model barriers in a geotechnical centrifuge. The novel flexible barrier is made of four instrumented cables controlled by spring mechanisms to replicate a bilinear prototype loading response. Tests revealed that regardless of barrier type, both dry granular and viscous flows could have similar frontal dynamic impact coefficients around unity. Compared with the kinetic energy of flow mass (∼10 MJ), only 249 kJ of flexible barrier energy capacity was mobilized. This implies that debris-resisting barriers may only be required to intercept the dynamic flow front as the subsequent flow energy may mainly be dissipated through internal shearing. Attributing to the large deformation of the flexible barrier, the granular static load acting on the flexible barrier could be 39% lower than that on the rigid barrier, resulting in an active failure mode and a lower earth pressure.