45 ft High Berm for Gun Range

Question

45 ft High Berm for Gun Range

jmcc3265 (Geotechnical)

(OP)

19 Feb 17 16:04

Anyone have experience with designing the berms for a gun range?

Our client is requesting 1.5:1 slopes for the 45 ft high berm, and the front face will be nearly vertical. The supporting soils are medium dense sands down to 50+ ft deep; therefore a deep seated slope stability fsilure is not a concern.

Is a reinforcement such as geogrid commonly used in addition to seedeing the slope faces? Maybe a clay face for the nearly vertical side you shoot at? The client understands contined maintenance will be needed.

oldestguy (Geotechnical) · Answer 1 · 2017-02-19 17:01:28

I'd be concerned about any slope steeper than 1.5 to 1 and even that may be to steep for some soil. Using geogrid to retain a steeper slope will work, but how do you anchor the front face where impact of shots are likely to damage it, in time? Most geogrids also can deteriorate in sunlight. Repairs later will be darn difficult. Why 45 feet? If this is merely to protect against stray high shots, why a steep front face? I'd opt for slope front and back at the angle of repose for loose material, more like 30 degrees for long term protection against severe erosion problems. Run a test fill pile to check on what works. Better to kw ahead of time rather than fighting the slope later.

EireChch (Geotechnical) · Answer 2 · 2017-02-20 13:05:36

I would say a geogrid MSE wall would be an ideal solution for this slope. However i dont think you will be able to achieve a near vertical face (depends what you call near vertical i suppose). Tensar do geogrid walls which require a steel facing at the front that connects to the geogrid layers( see attached pic). Approximately 300mm of topsoil is placed behind the cage and then the face can be hydro seeded and grass should grow.
They steepest they do in the UK is 78 degrees i think. The only issue would be bullets ricocheting off the steel cage. I imagine this wouldn't be ideal.

I know they also do a face where the geogrid is extneded up the face and lapped back into the slope. From memory i think they only do this to 50ish degrees. Again the issue would be bullets hitting the face and piercing the geogrids.

Sunlight damaging the grid should not be an issue as most geogrids are UV protected, hence painted black.

As OG said a slope at 30 odd degrees would be better if possible.

I would contact Tensar or Mcaferri directly, they are the experts.

http://files.engineering.com/getfile.aspx?folder=2b96d7d1-5bca-41d9-97b5-b5

Doctormo (Geotechnical) · Answer 3 · 2017-02-20 23:12:53

welded wire face, steep reinforced slope would probably be best, 2V:1H They can be built quite steep if need be.

doctormo

PEinc (Geotechnical) · Answer 4 · 2017-02-21 16:19:50

Consider damage to the facing and steel or plastic grids due to gunfire.

www.PeirceEngineering.com

RocEngineer (Civil/Environmental) · Answer 5 · 2017-02-21 17:51:45

The NRA publishes the Range Source Book, which has construction guidelines.

jmcc3265 (Geotechnical) · Answer 6 · 2017-02-21 18:03:57

RocEngineer,

Thanks for the recommendation!

OldBldgGuy (Structural) · Answer 7 · 2017-02-25 01:28:16

I gotta say, we don't get these requests north of the 49th. Interesting from a distance, though.

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45 ft High Berm for Gun Range