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The term Reinforced Earth is referred to as strengthening the soil by inclusion of artificial reinforcement elements, in the form of strips, bars, grids, or sheets fabricated or manufactured from metals or geosynthetics. The reinforcement restrains the tensile deformations of the soil and thus increases the overall performance of the composite soil through interfacial bond resistance, but limited by its own tensile strength. Some of the numerous applications of reinforced earth or soil structures include retaining walls, embankments, subgrades beneath the pavements, etc. Owing to the flexibility of reinforced structures, they can withstand large displacements and are found to perform better under seismic conditions.

he in situ density of compacted layers obtained from sand-cone test is commonly used to assess the quality of compaction of pavement layers. This test is tedious, time consuming, and sometimes not feasible to perform in accordance with specifications. In this study, a lightweight deflectometer (LWD) is used to measure the modulus of deformation, ELWD, of pavement layers and to perform the quality control (QC) of pavement layers. An extensive LWD field testing program was undertaken on 95 test locations of an expressway along the outer ring road located in Hyderabad, India, and the ELWD values of the compacted base and surface layers were commonly found to range from 45 to 60 MPa and 105 to 120 MPa, respectively. The coefficient of variation of the ELWD of base and surface layers was found to range from 4 to 12%. Finite-element analysis was also carried out to study the effect of bottom pavement layers on measured ELWD values from LWD testing. The results showed that the top stiff layer absorbs a significant portion of the load applied on the surface of the layered pavement system, indicating that the ELWD obtained from LWD testing is affected predominantly by the top stiff layer. Finally, a case study on a low-volume road is presented to demonstrate the relationship between the LWD modulus of deformation and in situ density obtained from a sand-cone test. The LWD device was found to provide quick test results and simple to operate on any pavement layer, and hence the frequency of QC tests can be increased, leading to an improvement in the overall quality of compacted pavement layers and, thus, pavement performance.

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Reinforced earth or soil structures are becoming increasingly popular in the present day. For proper design of any reinforced structure, it is important to study the soil-reinforcement interface properties. The interaction mechanism can broadly be classified into two types: direct shear mechanism and pullout mechanism. In this study, tests were performed as per ASTM D5321 to study the interface characteristics of two types of reinforcements commonly used in practice (geogrid and metal grid) with Indian standard sand. A large-size direct shear test apparatus of dimensions equal to 300 mm x 300 mm x 200 mm (in length, width, and depth) is used in the study. Pluviation method is adopted to prepare uniform sand samples with a relative density of 90%. This paper provides details on sample preparation and interface properties of two types of reinforcements with sand material. Based on the test results, the average interface shear strength coefficients of geogrid-sand and metal grid-sand are found to be equal to 0.88 and 1.02 for the normal stresses considered in the study. These coefficients are in good agreement with the results reported in the literature.