Ring Compression

The principal stress in a confined thin circular ring subjected to external pressure.

Rip Rap

Rough stone of various sizes placed compactly or irregularly to prevent scour by water or debris.

Riser

A thin ring located between the frame and cone of a manhole. Used to bring the frame and cover final grade. Commonly, several riser are present in a manhole.

Robot

Remote control device with closed circuit television (CCTVClosed circuit television used to carry out internal inspection and survey of pipelines.) monitoring, used mainly in localized repair work, such as cutting away obstructions, re-opening lateral connections, grinding and re-filling defective areas and injecting resin into cracks and cavities.

Rock

Per ASTMAmerican Society of Testing and Materials; technical organization formed for the development of standards on characteristics and performance of materials, products, systems and services, and the promotion of related knowledge. D653 and ISRM, any naturally formed aggregate of mineral matter occurring in large masses or fragments.