Model Test Investigation of Eccentric Load Effect on a Gully Installed Circular Culvert

Some mountainous areas have a relative height difference of up to 2 km and an average slope of more than 13°, and most high-fill culverts are laid asymmetrically, resulting in uneven distribution of earth pressure on top of the culvert and subjecting the culvert to eccentric loading. Current research often neglects the influence of topographic conditions and eccentric loading effect on culvert earth pressure. This paper addresses the load-reducing culvert under high-fill embankment in a gully area as the research object. The influence of eccentric loads on circular culvert installations in a gully was investigated through 24 comprehensive load tests, addressing the neglect of this aspect in current studies. The analysis focused on the impact of eccentricity and gully slope inclination on the mechanical behavior of culverts, comparing those with and without expanded polystyrene (EPS) plates. The results revealed that culverts located closer to the slope experienced higher rates of eccentric loading, while an inverse relationship between the eccentric load rate of vertical earth pressure and gully slope inclination angle was observed. Adjusting the eccentricity allowed for a 2.8% to 21% enhancement in the load reduction rate. For gully slope inclination angles between 60° and 90°, maintaining an eccentricity of 1/3 to 1/4 was recommended to minimize vertical earth pressure. Under eccentric loading conditions, two different earth arches are generated in the backfill on both sides of the culvert, resulting in an asymmetric distribution of earth pressures in the soil on both sides of the culvert, especially at locations corresponding to 135°, 225°, and 270°. The horizontal earth pressure on the left side of the culvert (close to the slope) is inversely proportional to the slope inclination, while the horizontal earth pressure on the right side of the culvert (away from the slope) remains essentially constant. This study provides valuable insights for designing culverts in mountainous terrains.