Mitigating Thermally Induced Cyclic Displacements in Geosynthetic Reinforced Soil Abutments Using Triaxial Geogrid Reinforcement

Integral bridge systems eliminate the need for bearings and expansion joints by integrating the bridge deck with the facing, resulting in a more durable and efficient design. However, this configuration subjects the abutments to repeated lateral movements due to seasonal and diurnal thermal fluctuations, leading to significant challenges in serviceability and long-term performance. Conventional uniaxial and biaxial geogrids have been widely employed in geosynthetic reinforced soil (GRS) abutments but often fall short in controlling deformations under such cyclic loading conditions. Triaxial geogrids, owing to their multi-directional stiffness and superior interlocking capacity, offer a promising alternative, although their use remains underexplored in this context. This study presents a detailed experimental investigation using scaled 1 g physical model tests to evaluate the performance of uniaxial, biaxial, and triaxial geogrids in reinforced integral abutments. The abutments were subjected to 100 cycles of cyclic facing displacements under three modes—cyclic active (CA), cyclic passive (CP) and cyclic active–passive (CAP), with varying displacement amplitudes (d/H) and loading rates (r). Surface settlement (s/H) and lateral earth pressure coefficient (K) were monitored to assess performance against serviceability thresholds. The results revealed that triaxial geogrids consistently outperformed others, particularly in CAP and CP modes, by maintaining lower settlements and higher resistance to failure against large lateral pressures. However, in CA mode, none of the configurations met the serviceability criterion. The findings highlight the influence of loading characteristics on GRS abutment behavior and underscore the potential of triaxial geogrids for climate-adaptive and resilient bridge infrastructure.