A new high cadency apparatus: the Portancemetre, has been implemented to give a continuous measurement of the load bearing capacity of the platforms. It judges the stiffness of the structure, and thus gives useful information for monitoring the homogeneity and the conformity of subgrades. The principle is a low width vibrating wheel equipped with sensors giving at every time of the periodic movement: the vertical dynamic force, and the vertical displacement at the contact wheel-soil, when rolling. This information is exploited in term of stiffness, or modulus using a straight correlation with plate tests. The result is plotted versus the longitudinal profile of the embankment, and many possibilities are offered by the program: determination of average and minimal values in the total section or sub-sections, homogeneous zones, percentage in the distance in conformity with the specifications. The apparatus is rolling at 3.5 km/h and is capable to measure modulus in the range 30 MPa to at least 300 MPa. About 15 km of distance per day is able to be controlled in operational conditions, with continuous information. The control may be made in one, two or more parallel lines, depending of the width of the platform. Due to the good mobility of the apparatus which is towed by a 4 WD vehicle, and the measurement capacities, it is also expected to use it on unbound roadbase layers of economic roads, to assess their quality. For the covering abstract see ITRD E135448.
Samenvatting