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bench cut cribbing

Dec. 11, 2012, 6:11 p.m.
Posts: 0
Joined: Dec. 7, 2008

I will second Synchro's method.

Having used this technique to build on the Grouse Grind and other steep alpine trails I think that the key is to make the deadman part of a box structure that ties everything together.

To further cantilever the structure inwards we have used large boulders placed on top of the deadman to prevent the structure from sloughing off the steep slope. Without something to hold it in place the slope forces are often too great for the crib to stay in place.

Dec. 12, 2012, 9:38 a.m.
Posts: 690
Joined: Aug. 14, 2007

Love the illistrations. AmbideXCrous actually crosses this ravine again just above. Im going to be doing a little rework on the that area too. Seeing both Thad and Syncro's drawings and hear everyones feed back, I'm inspired to execute this technic a little better.

The tread is a much larger working area up above so I have room to sort things out. I will also be pack in some rebar and a cordless drill to auger proper holes in the beams to tie everything in. The spot is right where the lower rider in white is. I'll document the work and post picture in the next week or so.

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

Dec. 12, 2012, 12:12 p.m.
Posts: 464
Joined: Nov. 23, 2002

Hey Matt, one other thing I forgot to add is if the slope above the trail bed sheds a lot of water then pack small rocks behind the wall to act as drainage and punch a few holes into the wall with your drill to allow water to escape. It's the buildup of water behind the wall that will put pressure on it and cause it to be pushed away from the bank.

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

Dec. 12, 2012, 8:50 p.m.
Posts: 5697
Joined: April 10, 2005

When you drill the holes for the rebar, should the drill bit be a little smaller diameter than the rebar, or the same size? If it's the same size it might loosen up after awhile. Drill it smaller [HTML_REMOVED] once the wood gets wet [HTML_REMOVED] swells, it'll all tighten up.

Dec. 12, 2012, 10:17 p.m.
Posts: 10077
Joined: Nov. 19, 2002

When you drill the holes for the rebar, should the drill bit be a little smaller diameter than the rebar, or the same size? If it's the same size it might loosen up after awhile. Drill it smaller [HTML_REMOVED] once the wood gets wet [HTML_REMOVED] swells, it'll all tighten up.

Don't go to small as once you drive the rebar through a stack of timbers it get progressively harder to do. A lot to small and the rebar will bend. We used to make 3 foot long spikes from rebar.

Dec. 12, 2012, 10:22 p.m.
Posts: 464
Joined: Nov. 23, 2002

you can also leave the rebar a few inches long and bend it over on the top with a sledge.

that way there's never any worry of your rod slipping out if the hole is too big

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

Dec. 12, 2012, 10:23 p.m.
Posts: 464
Joined: Nov. 23, 2002

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

Dec. 13, 2012, 9:21 a.m.
Posts: 1065
Joined: Oct. 23, 2003

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!

IMBA trail solutions book is based on the USFS trail guidelines. It covers the same info, but with an emphasis on solutions that work well for bikes, ex. knicks and rolling grade dips instead of waterbars. The most recent revision of the USFS trail guide added "Trail Solutions" to their bibliography.
http://www.fs.fed.us/t-d/pubs/htmlpubs/htm07232806/page16.htm
There is a wealth of good information in there on bridge design, strength and rot resistance of native trees, geotextiles, etc, etc.

"Why write another trail construction and maintenance guide? Good question. Since publication of the first edition of the "Trail Construction and Maintenance Notebook" in 1996, several excellent books about trail construction and maintenance have been published by the International Mountain Bicycling Association (IMBA), the Student Conservation Association (SCA), and the Appalachian Mountain Club, among others. At the same time, this notebook has remained popular, especially because of its pocket size and its wide availability through a partnership between the Forest Service, U.S. Department of Agriculture, and the Federal Highway Administration's Recreational Trails Program.

Based on helpful critiques of our earlier edition, we made numerous changes to reflect the latest thinking about constructing and maintaining trails. Much remains from the original edition."

I like the USFS manual, because it is available FOR FREE on the web, and FOR FREE from the parks in handy back pocket booklet.
http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf07232806/pdf07232806dpi72.pdf
The IMBA book is $40…. I also like that it is short and sweet, under 150 pages, while the IMBA book is almost 300… I think USFS did a good job of boiling it down to the essentials.

USFS Wetland Trail Design [HTML_REMOVED] Construction; gets into more detail.
http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf07232804/pdf07232804dpi72.pdf

I think there is room for improvement. For instance, the "how to build DH trails" chapter of the IMBA book is about 3 pages, and essentially says "get someone who knows how to build good DH trails help you."

Stoked that the NSMBA is working on Builder's Academy and making solid trail building knowledge more accessible.

Dec. 13, 2012, 6:19 p.m.
Posts: 494
Joined: Dec. 29, 2006

lapping, pre-drilling and spiking with re-bar is very sturdy but with smaller walls, 3 or 4 stacks high, i find it unnecessary and time consuming. i usually only have a few 8" spikes and if im to lazy to hike in the re-bar and drill i would just leave the logs round, 6-8" cedar, and square lash them together. it goes up very fast and the cedar sap wood rots slow so the knot stays tight for a long time.

Dec. 23, 2012, 5:10 p.m.
Posts: 416
Joined: June 19, 2011

In construction retaining walls made with rail road ties and secured with dead mans are held together with 10 mil rebar cut to about one foot lengths. The rebar secures many logs together.
You can purchase rebar and have it cut for you at many construction supply stores. You pound the rebar into the wood with a five pound sledge. The wood stacked to create the retaining wall should be stacked at angle. The best angle is 45 degrees which is not always possible.
The builing code in N.V. dictates a 45 degree slope for retaining walls. This has been established by engineers as the only way to keep the retaining wall from pushing out.
The base that the logs sit on is what needs to be the most stable. I would suggest that the first course of logs be dead maned.
If the retaining wall can not drain the water behind the wall then hydrostatic pressure becomes a serious problem. The solution. Weep holes at the base of the retaining wall.
I use 4 inch pipe for weep holes any smaller and the holes will get plugged with dirt.
The pics of the construction of the trail look solid. nice work. I hope my suggestions come in handy.

common sense…..Whats common about sense?!

Jan. 16, 2013, 3:16 p.m.
Posts: 690
Joined: Aug. 14, 2007

I took some of the input everyone offered up and tried to incorporate it into the fix of the upper ravine crossing of AmbideXCrous.

You can see more photos from the fix here http://www.facebook.com/media/set/?set=a.474096052625524.94761.185261884842277[HTML_REMOVED]type=1

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

Jan. 16, 2013, 4:44 p.m.
Posts: 17868
Joined: Oct. 28, 2003

Looks good! Is it outsloped so the rainwater doesn't run down the trail? You'd hate to have it all washed away in a good storm.

Jan. 17, 2013, 4:45 p.m.
Posts: 1065
Joined: Oct. 23, 2003

Looks good. It looks like he has a rolling grade dip right before the corner, which gets the water off the trail. From the crown of the roller to the bride, it does look kinda insloped… looks like water will run to the edge of the backslope and run past the corner…

My suggestion is the backslope. The backslope is cut near vertical. That dirt is going to slough off onto the tread over time. Also water sheeting down the hillside will fall off that steep cut like l'il waterfall and pound puddles into the tread. 45% backslope is as steep as you are supposed to go.

I would set those two ferns aside safely, rake the duff up by that tree temporarily, and scalp that dirt mound down til it's about 45% and smoothly transitions into the tread. I'd start digging maybe 6-8 feet up from the tread, but not dig more that 12" deep, and 6" most places. It looks like people take that corner real wide to get lined up for the bridge, so I'd use some of the extra dirt to extend that bank, so you can carve on it. Use the rest to get the last bit of tread outsloped before the bridge. Tamp it down, including the backslope. Pull the duff back, replant the ferns.

Jan. 17, 2013, 7:15 p.m.
Posts: 1111
Joined: Jan. 9, 2007

that way there's never any worry of your rod slipping out if the hole is too big

hehehehe

diggin

Jan. 17, 2013, 9:20 p.m.
Posts: 0
Joined: Oct. 5, 2006

Looks good. It looks like he has a rolling grade dip right before the corner, which gets the water off the trail. From the crown of the roller to the bride, it does look kinda insloped… looks like water will run to the edge of the backslope and run past the corner…

My suggestion is the backslope. The backslope is cut near vertical. That dirt is going to slough off onto the tread over time. Also water sheeting down the hillside will fall off that steep cut like l'il waterfall and pound puddles into the tread. 45% backslope is as steep as you are supposed to go.

I would set those two ferns aside safely, rake the duff up by that tree temporarily, and scalp that dirt mound down til it's about 45% and smoothly transitions into the tread. I'd start digging maybe 6-8 feet up from the tread, but not dig more that 12" deep, and 6" most places. It looks like people take that corner real wide to get lined up for the bridge, so I'd use some of the extra dirt to extend that bank, so you can carve on it. Use the rest to get the last bit of tread outsloped before the bridge. Tamp it down, including the backslope. Pull the duff back, replant the ferns.

A 3/4 to 1 slope will stand up just fine. Most slopes along hwys are built that way.

Fraser Valley Mountain Bikers Assoc.

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