One of the unsung heroes of our motorways and highways are the pavements that stretch on either side of the road. This is the domain of the pedestrian and constructing and maintaining it properly is the job of municipalities and town councils, since it is as important as the highway. It is usually difficult to assess whether the contractor constructing the pavement is doing a proper job of road testing, unless you have someone alongside them all the time.
One of the instruments used by consultants of road and transport ministries and other governing bodies is the light weight deflectometer or LWD and falling weight deflectometer or FWD. A highway is usually built for heavy uninterrupted traffic for a very long time, with the minimum of scheduled repair expectations. For a highway to perform well over a long period of time, its basic structure underneath the road also needs to meet certain standards. The light weight deflectometer primarily tests insitu base and sub-grade module before the road is constructed. And the falling weight deflectometer can provide a quick study of the elasticity of the strata which is essential for a uninterrupted road measures the approximate remaining life of the pavement before repair and rehabilitation is required.
A light weight deflectometer is used in many other fields besides road construction and road testing, during construction of airport runways and taxiways, dams, embankments, pipeline laying, installing railway track beds, and other similar earthworks. This device is easy to use and quick assessment is possible with test results in 3 minutes maximum. Suitable for coarse grain and mixed grain soilshaving a maximum grain size of 63mm, for determining the dynamic modulus of deformation of soil (resilience) in the range Evd = 15 to 70MN/m.
Another road testing device is the falling weight deflectometer or FWD that is specifically used to evaluate the structural capacity of the pavement. It works by imparting a load pulse to the pavement surface which is supposed to simulate the weight and load produced by moving vehicles. This is done by dropping a large weight on the road or pavement being tested and the waves transmitted to the pavement through a circular load plate. The deflection sensors or geophones installed then measure the deformation of the pavement in response to the load, providing an estimate of the pavement structural capacity for overlay design and to determine if a pavement is being overloaded.
