Full Text Book of Minar Congress9

Abstract

Using geogrid in road pavements can enhance pavement performance by enhancing bearing capacity, lateral confinement, and overall stiffness, in addition to lowering lateral and vertical pavement deformations. A Number of large-scale direct shear experiments were applied in this paper to assess the influence of compaction degree on the mechanical interaction among a clay subgrade soil and a subbase layer in both cases of using and not using reinforcement at the interface. Clay subgrade soil, Subbase granular materials as Type B, and Biaxial Geogrid BX1100 were employed as reinforcing materials in this investigation. In the current investigation, direct shear test was employed by fabricating a large-scale direct shear apparatus consisting of a square upper box with dimensions of (200 mm × 200 mm × 100 mm), and a rectangular lower box with dimensions of (200 mm × 250 mm × 100 mm). On specimens with and without reinforcement, 40 interface tests were performed for five degrees of compaction (100, 98, 93, 90, and 84%), which corresponded to (60, 55, 50, 45, and 40 blows/layer) for the shear box, with the regular loads applied for each combination being (25 -50 -75 -100) kPa. The results demonstrate that the interface shear stress curves grew and trailed a similar pattern for the four normal stress (25 -50 -75 -100) kPa. At their optimal moisture levels, the effect of dry density on the interface properties of these combinations (geogrid-soil) was also examined. The interface shear failure envelopes grew with increasing molding dry densities (i.e. degree of compaction), reaching a maximum value at 97% degree of compaction.