Large-scale successive boulder impacts on a rigid barrier shielded by gabions

Abstract

Debris flows occur in multiple surges. Boulders entrained within the flow have been reported to incapacitate structures within its flow path. Single-layer cushions, such as gabions, are often installed to shield debris-resisting barriers from boulder impact. However, most relevant works only focus on single impact and the performance of gabions subjected to successive loading is still not well understood. A new large-scale pendulum facility was established to induce impact energy of up to 70 kJ on an instrumented rigid barrier shielded by 1 m thick gabions. The response of the gabions under six successive impacts was investigated. Results show that the peak boulder impact force given by the Hertz equation is at least four times the measured values. The recommended load-reduction factor (Kc) used in practice can be reduced by a factor of two. After six successive impacts at an energy level of 70 kJ, the transmitted force increases by up to 40%. Based on the Swiss guidelines, a 13% increase of gabion thickness is required when successive impacts are concerned. The results presented in this paper will be useful for practitioners designing rigid barriers.

Coarse granular flow interaction with slit structures

“…Such fronts are highly inertial, potentially incapacitating structures along their flow path and claiming lives (Hungr & Evans, 1988;Ng et al, 2016). Zhang et al (1996) reported a boulder-rich debris flow front impacting a reinforced concrete bridge pier on the Chengdu-Kunming Railroad in China, destroying the pier and causing 220 fatalities.…”

Research on the Obstruction Process of Rigid Netting Barriers toward Granular Flow

“…en, the dynamic behavior of dry granular flows toward barriers has been further studied [9,13,[22][23][24]. In the studies, some more critical influence mechanisms were revealed, such as the formation of dead zones [21,25] and run-ups [26,27]. e dead zones allow momentum to run-up vertically along the barrier [28], and the run-ups reduce the load on the top of the barrier and increase the impact pressure.…”

Eco-friendly recycled crushed glass for cushioning boulder impacts

“…However, the change in the bulk stiffness of the cushion layer due to compaction under successive impacts (ASTRA 2008) is often ignored in current design. Ng et al (2016) demonstrated that the reduction of impact loads rely predominantly on the irreversible rearrangement of rock fragments. The mechanism of crushing in gabion cushioning layers strongly depends on the mechanical properties of the rock and their size (Lambert et al 2009).…”

“…Generally, the particle sizes of the rock fragments used to construct gabion cushion layers range from 160 to 300 mm (GEO 1993;Ng et al 2016). Zhang et al D r a f t (2016) and Su et al (2018) both showed that the transmitted load on a rigid barrier which is shielded by a cushion layer comprising rock fragments (rock-filled gabions) decreases with the particle size, although particle crushing was not considered in these studies.…”

“…As will be shown in this study, when subjected to impacts RCG shows both grain rearrangements and crushing, which are the cushioning mechanisms exhibited by rock fragments and cellular glass aggregates as shown in previous investigations. In this study, the cushioning performance of RCG under successive boulder impacts is investigated using a large-scale pendulum impact setup described by Ng et al (2016) and .…”