Interactive engineering model
Riprap stone stability
Compare provided stone size against the unfactored dumped-stable Isbash requirement as design velocity, specific gravity, and flow depth change.
Preparing the 3D model...
A trapezoidal channel is cut into a soil block and lined with a riprap blanket on a bedding band, with stone scattered across the invert and both banks to the design water surface. Two reference stones beside the channel are drawn at true relative size for the required and the provided D50, so the stability factor is read as a diameter ratio. When that factor falls below one, individual stones work loose and travel downstream, opening bare patches in the blanket.
Focus the 3D view and use the arrow keys to orbit, plus or minus to zoom, and Home to reset the view.
Text explanation and non-WebGL fallback
A trapezoidal channel is cut into a soil block and lined with a riprap blanket on a bedding band, with stone scattered across the invert and both banks to the design water surface. Two reference stones beside the channel are drawn at true relative size for the required and the provided D50, so the stability factor is read as a diameter ratio. When that factor falls below one, individual stones work loose and travel downstream, opening bare patches in the blanket.
Important: This is the unfactored Isbash screening equation. The calculator applies rock-shape and stability factors, so its required D50 is larger; use the calculator for design.
The numeric controls and readouts remain usable if WebGL is unavailable. Drag or swipe the 3D view to orbit and use a wheel or pinch gesture to zoom. With the 3D view focused, use the arrow keys to orbit, plus or minus to zoom, and Home to reset. The complete numeric lesson is also keyboard-accessible in the adjacent controls and readouts. This model is an educational aid and does not replace applicable design standards or professional review.