Internal Friction angle for riprap 2

[nderinoz]

hi, I am trying to find a manual or any article referring to the internal friction angle or slope angle for a riprap covering made with rocks greater than 80 cm for protecting the natural river alluvium hill from the flooed of the river. I think a slope of 1.5H:1V is appropriate, but I have to confirm this.

 

[ishvaaag]

Were it for dry use this would be no doubt safe. I have made a search in Google

From

http://huron.lre.usace.army.mil/coastal/LMPDS/documents.htm

document pdf

http://huron.lre.usace.army.mil/coastal/LMPDS/Downloads/shorepimpacts.pdf

gives for lake coast use 2 examples 3:1V and 4:1V less steeper then than your proposal. Obviously duration may be very relevant to the choice.

In the more general search

http://www.google.com/search?q=rip-rap+%22friction+angle%22&hl=es&btnG=B%FAsqueda+en+Google&lr=

you should find better assessment.

 

[cvg]

the requirement in my area is 1.5H:1V for angular rock (quarry stone) and 2H:1V for rounded river rock.

Chuck
cgopperton@stantec.com

http://www.stantec.com/

 

[georam]

My observation usually revealed a slope of about 1.3H:1V. This is usually for angular riprap particles. Riprap perhaps can stand at 1H:1V slope, but the Factor of safety may be close to 1. If you are looking for higher minimum factor of safety, such as 1.5, etc and some of the slope under water, you will need flatter slope than 1H:1V.

 

[Sandman]

As you can tell by some of the responses that have been posted already, there is no simple answer to your question they are willing to give since they don´t know your problem exactly. If you are evaluating the effects of river currents, wave runup, etc. then many other factors com into play.

However, if you are simply trying to perform a static stability analyses of a 1.5:1 (H:V) rock slope that has good interlocking using rough quarry stone, then you can easily use values of 40 to 45 degrees. Hence, the factor of safety for your slope would be about 1.25 to 1.5 depending the overall design and quality of construction. Nevertheless, riprap is often placed at 1.5:1 without any problems if nothing else happens. The thickness, toe burial, crest width, underlayer design, water conditions, etc. will control the design.

Good luck.

Moi Arzamendi, PE
LKS Ingeniería, S. Coop.
Arrasate 20550, España