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    Northwest Geology Field Trips, by Dave Tucker, is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 United States License. You can use what you find here, repost it with attribution to the author, "remix" it for your own purposes, but may not use it with the intent of making money off of it.

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Urbanite examples sent by readers- 1

Reader submissions to my initial ‘Urbanite’ posts are rolling in. Here’s one from Dan Burwell. (I have another in the works to follow this one already. Send yours!) Dan shows us a really cool ‘soil nail wall’, so I follow up with a basic explanation about ‘soil nail walls’ using photos from the internet . The wall on W. College Way in Bellingham, featured in my preceding post, is a nicely disguised soil nail wall.

We’ll start out with Dan’s note and photos.


Dan’s ‘soil nail wall’. Can you spot the fault? Answer at the end of this post. NO PEEKING!!!!

Here is a wall I designed, installed in Manson, WA near Chelan in 2008. It’s a soil nail wall where “nails” are drilled behind the wall as the face of the wall is excavated from the top, working down. The nails are set in grout and then attached to the wall face. The nails use friction to resist soil pressure pushing the wall outward. Once the nails are installed, the wall face is then sprayed with shotcrete to form a short term construction wall face (usually done in stages to keep sloughing to a minimum). A final wall face can then look like a rock outcrop or whatever else you want to dream up which combines with the construction face and is designed for seismic forces.

The sculptors are a specialized group that work all over the world. I asked them to sculpt a fault and they did a reasonable job of it. Can you spot it?

D. Burwell wall 2

Dan Burwell | RH2 Engineering, Inc.,  Bellingham

Now, here is my photo essay on construction of a soil nail wall.


A soil nail schematic, so you can see where we’re headed here. This example has no cast concrete or rock work on the outer surface, so differs form the fancy wall Dan showed us.


Here’s a ‘soil nail’. Not really a nail, but a grouted steel rod or pin.









There are variations on the method, but here’s a generic one. Start out with an unstable soil or rock face. Work progresses from the top down if the finished cut is tall. dywidag-systems-soil-nails-wall-construction-08

Drill holes into the exposed face.

3. Drilling

This is one hell of a noisy job. Hopefully with a strong union so workers can enforce safety. Note protruding soil nails and mesh higher on the wall.

4. drilling detail

Insert the ‘nail’ structure into the drilled holes. Layer with steel mesh. Remember work is from the top down so the rock or soil face above these drilled holes is already stabilized with shotcrete.

6. shotcreting a low wall. drains

Applying shotcrete, blown under pressure through a feeder hose. The kickback can be strong so watch it! This wall has drainage installed at the base, usually required. The drain pipe collects water to reduce pore pressure in the soil behind the wall.

Blow shotcrete over the mesh. Add outer bearing plates on the ends of the exposed nails, to bind the shotcrete/mesh structure to the nails in the soil wall beneath. Another coat of shotcrete could be added to cover the ends of the nails as in the case above.

Now for the urbanite. Install poured concrete or concrete blocks or even cemented real rocks over the shotcrete. Sculpt as desired. 4fbac1ae9814b22f440e824a6b165325_XL

Finished product. Plus a couple decades.W. College Way 1 mark

If you didn’t spot the fault in the first photo, here it is. The ‘faux fractures’ are offset at the top of the face. The lower fracture cuts across the fault, and is an added touch of disguise. Well done, Dan and crew who built the wall.OLYMPUS DIGITAL CAMERA

3 Responses

  1. Good post! And yes, I did spot the fault (thank goodness; can’t be that out of touch).

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