Multi-Depth Deflectometers (MDD) are pavement
sensors used to measure in-situ elastic deformation and/or permanent
deformations in the various pavement layers of a test section. The BDI MDD
system is a series of parallel rods in a 50 or 75 mm diameter hole in the test
section. The parallel rods are anchored at various depths inside the MDD tube
wall. Each rod, starting from the bottom hydraulic anchor, passes up to the
reference head where linear potentiometers measure rod (depth anchor) movements
relative to the road surface.
SPECIFICATIONS