gudday everyone...would like to ask for any guidelines in designing riprap at 45 degree slope of banks?also, velocity of river ranges from 13 to 16 fps..
There are several methods that can be used to desing riprap. In addition to the information you provided, you also need the unit weight of the rock being used, depth of flow, and amount of turbulance.
No one on these forms is going to design the riprap for you. You could look up one of the methods on-line and do the calculations yourself or have the project civil or geotechnical engineer do them.
45 degree slope with 16 feet/sec velocity is probably too extreme for normal size riprap. Riprap is generally limited to 1.5H:1V slopes or flatter. Concrete or other materials may be a better choice
Check the USACE design manual for a good procedure
EM1110-2-1601, Hydraulic Design of Flood Control Channels
If the rock is large enough the slope can be that of talos. It's all relative. There are at least 7 different methods to calculate sediment stability, which this basically is. One important facet of the design is the stability of the subgrade - a fabric is important for that to keep the expense of a filter down.
I agree with above. Stand alone rip-rap is completely out of the question. You're going to need to create a rock-lined and concrete grouted spillway with walls.
Be carefull with this one, I recently did a detention pond with 45 degree slopes.
First off, at 45% you are now in the realm of a structural retention, and should be analyzed as such. I think anything steeper than 3:1 will need at least some soils analysis and probably some structural provisions. I would be sure a geotech or structural guy gives you an opinion. (If you are general civil like I am)
Second, an alternative you might consider are wire mesh gabions. They are very popular in this part of the country (Texas). Basically it is a wire cube which is filled with rip rap. They work very well, easy to assemble and can tie together.
They can be stacked atop eachother with a varying degree of offset, or laid end to end along a slope. Because they are porous, they remove the water surcharge element.
First, don't use rip-rap - then read through the following...
NRCS Stream Restoration Design Handbook
Part 654 (Chapter 14) Stream Restoration Design of the National Engineering Handbook
Over 200 practitioners from government, private, and academic fields participated in the development of Part 654 (Chapter 14) Stream Restoration Design of the National Engineering Handbook (NEH). National Engineering Handbook Part 654 focuses on design tools for stream restoration projects.
Copies are available free of charge on CD from LANDCARE or by calling 1-888-LANDCARE (e-mail: landcare@usda.gov). The handbook can also be downloaded from the NRCS Directives Website.
this depends on the case. fill areas, not advisable. dense to very dense, admissible. Very stiff to hard plastic materials, admissible. The case depends on the flow type and shear stress.
it has no single absolute solution. 45 degrees... stable should stability concerns are questioned.
scour on the other hand should be addressed. shear stress is high, can be addressed by grout type. i.e. i approximate the range of shear stress at 250-300KPa (this is high and theoretically dangerous at a state of supercritical flow). however, 3000psi grout may be utilized. 3000psi has a tensile strength of 8-15% of compressive strength. making it a basis for the shear strength assuming a tresca model, the material has around 2.5-5 times the shear stress, therefore admissible.
Detailing is another matter, structural aspect may provide a minimum reinforcement to maintain the geometry and may utilize a gabion mattress.
im sure, as the case may be that the flow is intermittent. furthermore, not all areas are dry. so use a mixed approach when necessary. gabions when applicable, gabion mattress when applicable, grouted riprap when applicable.
in the end, its easier to design utilizing sheet piles and reinforced concrete for protection. however, it may also be easier to widen the river if the value of the land is low.
