TRENDING Design Professionals are taking a closer look at pavers as drainage and traffic calming problem solvers. Distance Learning Platforms are rapidly replacing traditional seminar forums for professionals.
TECH SPOTLIGHT Another Look at Interlock ICPI Foundation Lands PICP at Civil Engineering’s Front Door
HARDSCAPE SOURCEBOOK Paver Manufacturers Paver Installers Industry Suppliers
Another Look at Interlock David R. Smith ICPI Technical Director
John Knapton, Ph.D. a structural engineer, prolific researcher, writer, and one of the pioneers in the segmental paving world defined interlock as the “inability of a paver to move independently of its neighbors.” In other words, interlock spreads wheel loads across interlocking concrete pavement. This surface reduces stress and rutting on the base and soil subgrade making walking, bicycling, and driving faster and easier.
There are many technical papers measuring interlock by American, UK, European, Australian, South African and Japanese researchers. They all agree that interlock happens in the joint sand via shear transfer. A vertically applied load gets transferred or spread horizontally thanks to the shear capacity of the joint sand against the vertical paver sides. Obviously, the sand characteristics, paver thickness and joint widths all contribute to interlock. The bottom line is pavers, joint and bedding sand spread wheel loads in a manner similar to an equivalent thickness of asphalt but without its inferior material performance. Since its start, ICPI literature— especially concrete paver installer education courses—defined interlocking concrete paving units by their aspect and plan ratios. Aspect ratio is paver length divided by thickness. Plan ratio is length divided by width. The rule of thumb