The Light Weight Deflectometer (LWD) is a portable device that measures the onsite dynamic or resilient modulus (Evd) of subgrade soils and pavements. The LWD, which has been used extensively in Europe and the United States, has become popular for assessing the stiffness of embankments, structural fills and other earth structures. It assesses the bearing capacity, the stiffness and the compaction degree of soils that have a maximum grain size of 63mm. The LWD assessment considers the stiffness (or compressibility) characteristics of the materials under testing to a depth of 600mm below plate level. The paper presents available correlations between Evd with the static soil modulus Ev obtained from static plate load tests. It also presents how Evd can be linked with CBR and thus be useful for pavement design, but also with the subgrade reaction modulus K of the assessed soils. It also discusses the fundamental principles behind the testing along with the benefits that may arise from its use on specific applications. Such applications include the design and construction monitoring of gravel rafts, the design of pavements, engineered and non-engineered fills, landfills, MSE walls, pipelines and services, evaluation of ground improvement effectiveness and soil stiffness mapping.

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