The influence of geosynthetics design on the behavior of reinforced soil embankments subjected to rockfall impacts: Fid-Bau Portal

The influence of geosynthetics design on the behavior of reinforced soil embankments subjected to rockfall impacts

Korini, Oltion / Bost, Marion / Rajot, Jean-Pierre / Bennani, Yassine / Freitag, Nicolas

Abstract Rockfall hazard in mountainous areas requires the construction of protective structures for the buildings or transport facilities. Reinforced soil embankments can be effective protections against rockfalls due to the combination of the damping characteristics of the soil and the tensile resistance of the reinforcements. Following the advances in soil reinforcements, the research is ongoing for this type of structures aiming to optimize their shape and reinforcement design. In order to study the influence of the different geosynthetics design, two reinforced soil embankments are tested experimentally. The embankments had vertical facings and a slenderness ratio of two with the purpose to reduce the footprint of the conventional trapezoidal shape. Embankment 1 had two vertical layers of geogrids that divided its cross section in three equal parts, while Embankment 2 had multiple geogrid strips installed horizontally close to the front facing. Horizontal impact tests are performed on the two embankments using reinforced concrete blocks as impactors with the aid of a pendulum device. Several instruments and sensors are used to monitor the behavior of the embankments, namely accelerometers, pressure sensors, strain gauges, rapid cameras and a laser scanner. During the tests, the two embankments experienced local shearing at the impact position and overall backward leaning. Moreover, a waves' propagation effect is observed during the first moments of the impact at the sensors installed in the embankments. The speed of the propagation of these waves appears to be influenced by the reinforcement design of the embankments. After the tests, Embankment 2 was less deformed than Embankment 1, which is attributed to their different reinforcement design. According to the strain gauges measurements, the geogrids of Embankment 2 were more mobilized in the vicinity of the impact compared to the ones of Embankment 1. These tests showed that the geogrids installed in horizontal position close to the front facing are more efficient compared to the ones installed vertically and deeper in the embankment.

Highlights • The tested reinforced soil embankments have vertical facings for foundation optimization. • The reinforced soil embankments have a slenderness ratio of two. • The geosynthetics design plays an important role in the impact response of embankments. • The tested embankments are vulnerable with regard to structural stability. • The impact waves propagation is demonstrated by accelerometers, pressure sensors and strain gauges.