Reinforcement Effect Investigation of Geogrids in the Junction between New and Existing Subgrades in Highway Widening

ABSTRACT To investigate the reinforcement effect of geogrids with different laying schemes in subgrade widening, one tested road was selected in northern China, and the subgrade deformation and the geogrid strains were analyzed by field testing, the centrifuge model test, and numerical calculation. It was revealed that the geogrid strain of the construction period was mainly derived from the roller’s compaction. The addition of the geogrid is helpful to prevent shear sliding of the new subgrade. In the centrifugal model test and numerical calculation, the geogrid reinforcement was proved to be effective in reducing the settlement of the new subgrade, but little effect to the existing one. Strain of the lower geogrid layer was generally larger, and the connection line of maximum strain points in each layer is close to the shear-sliding location of the new subgrade. The reinforcement effect of different geogrid layers changed noticeably, and the bottom one played a major role in withstanding the tensile stress.