This study aims to investigate behavior of guardrail supporting piles subjected to horizontal impact and static load using centrifuge model tests. A centrifuge testing system capable of impact and static loading was developed. A series of centrifuge model tests was carried out at 11.3g of a centrifugal acceleration. The parameters of the centrifuge tests include ground type (flat ground and slope) and loading type (static and impact). From the results, load-displacement curves were constructed and the ultimate load was determined from the load- displacement curve. The corresponding soil reaction pressure distributions at the ultimate state were calculated and discussed in terms of load types and ground conditions.
Guardrail barriers are a typical safety system, protecting vehicles from falling into roadside slope. The guardrail generally consists of a protection cross-beam and supporting in-line piles (Wu and Thomson, 2007; Sassi, 2011; Pajourh et al., 2017). These guardrail piles are installed almost at the slope edge of the road embankment because the roadside area is too narrow. Korean design practices of these piles solely relies on engineers' experience. The final design of the piles is determined by engineers' judgement and afterward its capacity is validated with a full-scale car-crash test carried out in a certified testing site. Then, the final design of the pile as well as the barrier system are constructed and inspected by a field static test to check whether the piles would meet a criterion, which is that the static bearing capacity of the pile should meet 90% of the dynamic bearing capacity measured by the car-crash test. This static load test at the construction site is performed for every sample pile selected from in-lined piles at every 1 km (MOLITK, 2016). Throughout these design procedures, any geotechnical consideration is not involved. Moreover, the behavior of piles supporting guardrail barriers has not been well understood.
In general, the lateral capacity of piles is estimated by semi-theoretical methods. These methods assume a form of lateral soil pressure distribution along the length of the pile. This lateral soil pressure distribution has been updated by analytical and/or experimental studies (Brinch Hansen, 1961; Broms, 1964; Petrasovits and Award, 1972; Chari and Meyerhof, 1983; Prasad and Chari, 1999). However, the above studies focused on conventional piles much larger and deeper than guardrail supporting piles and the dynamic behavior of piles subjected to impact load was not considered.