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bench cut cribbing

Dec. 9, 2012, 10:35 p.m.
Posts: 690
Joined: Aug. 14, 2007

I built an XC trail/loop a few years back that can be ridden both ways, AmbideXCrous. The terrain is pretty steep. It was challenging to make it a fun trail when it points down but not too hard when you are riding up the opposite direction. I've gotten pretty good at incorperating bench cut and switchbacks into my build style. The Muddbunnies used AmbideXCrous as their backdrop for November in their 2013 Calander.

Last month, I attended the Arcteryx Builder Academy workshop put on by FVMBA. Mark Wood had talked about different technics with bench cuts and cribbing. One of the technics he covered was the Deadman Anchor. This essentially is perpendicular beams that are tied into the outside cribbing, then barried into the benchcut. Its meant to help prevent the outside crib from falling away when you are unable to stake it in.

There are a few ravine crossings on AmbideXCrous. For the most part of the year, these ravines are dry. But in the winter and early spring melt, they can really see some heavy flow. And after a few years of heavy rain filling a ravine and the stream digging away at its banks, one of my ravine crossings needed some attention.

Heres my recent rework on one of the ravine, using the Deadman Anchor. http://www.facebook.com/media/set/?set=a.459074447461018.92270.185261884842277[HTML_REMOVED]type=1

http://ca.youtube.com/watch?v=pH51rAX-G3o

Dec. 10, 2012, 12:57 p.m.
Posts: 5731
Joined: June 24, 2003

I built an XC trail/loop a few years back that can be ridden both ways, AmbideXCrous. The terrain is pretty steep. It was challenging to make it a fun trail when it points down but not too hard when you are riding up the opposite direction. I've gotten pretty good at incorperating bench cut and switchbacks into my build style. The Muddbunnies used AmbideXCrous as their backdrop for November in their 2013 Calander.

Last month, I attended the Arcteryx Builder Academy workshop put on by FVMBA. Mark Wood had talked about different technics with bench cuts and cribbing. One of the technics he covered was the Deadman Anchor. This essentially is perpendicular beams that are tied into the outside cribbing, then barried into the benchcut. Its meant to help prevent the outside crib from falling away when you are unable to stake it in.

There are a few ravine crossings on AmbideXCrous. For the most part of the year, these ravines are dry. But in the winter and early spring melt, they can really see some heavy flow. And after a few years of heavy rain filling a ravine and the stream digging away at its banks, one of my ravine crossings needed some attention.

Heres my recent rework on one of the ravine, using the Deadman Anchor. http://www.facebook.com/media/set/?set=a.459074447461018.92270.185261884842277[HTML_REMOVED]type=1

Nice work. Very nice.

Debate? Bikes are made for riding not pushing.

Dec. 10, 2012, 1:56 p.m.
Posts: 4300
Joined: June 24, 2010

Great work Matt; I'm so glad to see techniques from Builders Academy being put to use!

flickr

Dec. 10, 2012, 7:23 p.m.
Posts: 3518
Joined: May 27, 2008

That's awesome. I'm somewhat familiar with the Ledgeview/McKee trails, but I haven't done AmbideXCrous yet. Is it accessible from the radio tower or from Flintstones/Autobahn? I'll be in Abby for Christmas so weather permitting I want to do a little riding (and escaping of the inlaws).

Being cheap is OK. Being a clueless sanctimonious condescending douchebag is just Vlad's MO.

Dec. 10, 2012, 8:06 p.m.
Posts: 0
Joined: June 26, 2011

Looks great! Haven't run across sections where I've needed to do something like this before but will definitely be using it when I get the chance.

Dec. 10, 2012, 8:23 p.m.
Posts: 479
Joined: May 28, 2009

I have used this technique and it works great, very nice work my friend!

Dec. 10, 2012, 10:02 p.m.
Posts: 690
Joined: Aug. 14, 2007

That's awesome. I'm somewhat familiar with the Ledgeview/McKee trails, but I haven't done AmbideXCrous yet. Is it accessible from the radio tower or from Flintstones/Autobahn? I'll be in Abby for Christmas so weather permitting I want to do a little riding (and escaping of the inlaws).

It's on the southside. There are several ways to access it. Flintstones/Autobahn would be the most straight forward way if your not 100% familiar with the area.

Parking at Sandringham off of Whatcom and ridding up Autobahn is another. This way is best if you have time constraints. 1hr to ride both clockwise and counterclockwise directions.

Don't bring a big bike, unless you really like the hurt.

http://ca.youtube.com/watch?v=pH51rAX-G3o

Dec. 11, 2012, 1:08 p.m.
Posts: 1065
Joined: Oct. 23, 2003

Nice work. That section looks challenging to work on, and that's a good looking solution.

I recently attended a builder's academy, and I had some comments on the dead man technique, but did not think the academy was the proper place to bring up the debate. I meant to talk to Mark about it after, but we got sidetracked talking about cool trails. :) Not sure that your thread is really the right place either, hope you are not offended.

My concern with doing it this way, (as recommended by the builder's academy), is that the deadman, or header log, relys on the pull out strength of the spike to hold it to the sill log. In general, you want to avoid using the fastener as the sole means of holding the structure together. Fastener under shear is sometimes acceptable, but under pull is no bueno, so was suprised to see NSMBA endosing it. USFS suggests notching the sills and deadmen, so there is interference fit, and then big rebar spikes thru that attach minimum three layers of logs together.

USFS Trail Construction and Maintenance Notebook - Retaining walls:
http://www.fs.fed.us/t-d/pubs/htmlpubs/htm07232806/page12.htm#reta

Dec. 11, 2012, 1:42 p.m.
Posts: 4300
Joined: June 24, 2010

…was suprised to see NSMBA endosing it…

Keep in mind that Builders Academy uses the IMBA Trail Solutions book as a guideline and reference, and the deadman log is cited as a possible solution for unstable trail beds where other techniques may not be successful. The book's suggestions are not always the best application in our local terrain, and the curriculum is constantly being updated. Your comments are much appreciated, Thad!

flickr

Dec. 11, 2012, 2:15 p.m.
Posts: 11685
Joined: Aug. 11, 2003

My concern with doing it this way, (as recommended by the builder's academy), is that the deadman, or header log, relys on the pull out strength of the spike to hold it to the sill log. In general, you want to avoid using the fastener as the sole means of holding the structure together. Fastener under shear is sometimes acceptable, but under pull is no bueno, so was suprised to see NSMBA endosing it. USFS suggests notching the sills and deadmen, so there is interference fit, and then big rebar spikes thru that attach minimum three layers of logs together.

The bigger concern that I have is with the longevity of buried lumber in BC.The wood will only last a few years if you are lucky, and then you are back to the original problem. I much prefer rock for that situation, or if possible (and rarely is) a re-route.

Dec. 11, 2012, 3:11 p.m.
Posts: 690
Joined: Aug. 14, 2007

Nice work. That section looks challenging to work on, and that's a good looking solution.

I recently attended a builder's academy, and I had some comments on the dead man technique, but did not think the academy was the proper place to bring up the debate. I meant to talk to Mark about it after, but we got sidetracked talking about cool trails. :) Not sure that your thread is really the right place either, hope you are not offended.

My concern with doing it this way, (as recommended by the builder's academy), is that the deadman, or header log, relys on the pull out strength of the spike to hold it to the sill log. In general, you want to avoid using the fastener as the sole means of holding the structure together. Fastener under shear is sometimes acceptable, but under pull is no bueno, so was suprised to see NSMBA endosing it. USFS suggests notching the sills and deadmen, so there is interference fit, and then big rebar spikes thru that attach minimum three layers of logs together.

USFS Trail Construction and Maintenance Notebook - Retaining walls:
http://www.fs.fed.us/t-d/pubs/htmlpubs/htm07232806/page12.htm#reta

Thad and Biggles, I agree with you both. I am aware that this is a fix to a problem area that I will most likely have to revisit in two to three years from now. And Thad, this is the right thread to constructively discuss build technic.

The Builder Academy preaches about working with cedar and nothing else for sustainability. I would have liked to have used cedar to barry and tie into the cribbing. But my area has next to no cedar. The rungs for that bridge were packed almost 1km into that spot.

The crib logs that I used was a recent fir blowdown. I did notch the perpendicular logs into the top and bottom outside cribbing. It is also step into the slope. The soil is a sand stone/rock/dirt/clay mixture. It compacts pretty good. So the hope is that when the logs do rot, the ground will firm enough o support itself.

http://ca.youtube.com/watch?v=pH51rAX-G3o

Dec. 11, 2012, 3:29 p.m.
Posts: 11685
Joined: Aug. 11, 2003

Thad and Biggles, I agree with you both. I am aware that this is a fix to a problem area that I will most likely have to revisit in two to three years from now. And Thad, this is the right thread to constructively discuss build technic.

The Builder Academy preaches about working with cedar and nothing else for sustainability. I would have liked to have used cedar to barry and tie into the cribbing. But my area has next to no cedar. The rungs for that bridge were packed almost 1km into that spot.

The crib logs that I used was a recent fir blowdown. I did notch the perpendicular logs into the top and bottom outside cribbing. It is also step into the slope. The soil is a sand stone/rock/dirt/clay mixture. It compacts pretty good. So the hope is that when the logs do rot, the ground will firm enough o support itself.

It's awesome work given what you had. Sometimes maintenance can be so much harder than new construction. One thing I have learned from building new trail is that there are three golden rules: 1: Line selection 2: Line selection 3: Line selection.
When you don't have that luxury, it's a compromise.
You may get lucky and the soil could pack in really hard and set before the wood fails, meaning it will last a lot longer.

Dec. 11, 2012, 5:04 p.m.
Posts: 10077
Joined: Nov. 19, 2002

Decades ago when working for Parks Canada I built some huge retaining walls using that type of construction using old CPR mainline railroad ties (12"x12"x12') oak that weighed somewhere in the 300lb range, spiked together with rebar.

Last time I was through the area (5 years ago), the walls were still standing so the construction method is good, it just comes down to the life of the materials.

Dec. 11, 2012, 5:14 p.m.
Posts: 8242
Joined: Dec. 23, 2003

if you use a decent sized dead man you will get 5+ yrs of life span..

Dec. 11, 2012, 5:59 p.m.
Posts: 263
Joined: Nov. 23, 2002

nice work matt and good execution of this building technique.

having built a number of retaining walls at work out of 6x6 timbers i'll add my two cents worth in here.

the deadmans or tie backs rely on a few key point to be effective. as thad has pointed out one of the important things is the way the tie back is fastened together. ideally the portion of the tieback that is parallel to the retaining wall should be placed underneath the perpendicular portion. the two sections of the tie back should be spiked together (typically using re-bar in pre-drilled holes) using spikes that allow for nearly full penetration of both pieces of wood - i would say at minimum use a 12" spike. as well, notching the two pieces to create a lap joint will greatly increase the strength of the tie back.

the other factor that's important is making sure the tie back is buried deep enough as it relies on the pressure of the dirt above it to keep it anchored and the wall from pulling away.

one other point to consider is of course burying the tie back within gold dirt only. gold dirt has no organic content and it is the organic content in brown and black soil that causes and speeds up the rotting process.

as uncle duke mentioned, using a decent sized timber will greatly increase the lifespan of the tie back. personally i would used a timber that is a minimum of 6" in diameter (preferably 8") and of course make sure it's cedar. one final note is to pack a few large boulders into the dirt in front of the tie back as this will also help resist the wall from pulling away from the bank.

I'm not a human in real life, I just play one on the internet. 

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