Wednesday, June 3, 2009

Trail Timberworking Techniques

We were working above the Stoney Fork Overlook on the Blue Ridge Parkway last weekend. Along this stretch we have used a variety of timber techniques to provide stabilization to the trail bed and to provide safety from rockfall occurrences. All the timber was cut from downed locust or standing dead locust within the vicinity of the trail needs. Good trail timbering utilizes all available resources, tree trunks, limbs, and even debris laps as you will see in the following photos. One of the more complex uses of cut locust is visible in this photo. Whenever possible it is preferred to use standing trees for support posts. But in long spans if becomes necessary to construct a support post and sink it 24+ inches.
In this example we are using bark stripped locust logs for the trail edge, for rockfall prevention, for rock retention, and as an upright sunken post for support. All of the timbers are cut to measure from the adjacent forest.
I found this to be an interesting example of log cabin cribbing. One log rests against the tree, a second log against the first log and then onto a third log to bridge the gap between the next secure prop.
Sometimes stone fillers are used to lock the cribbing logs in place against a standing tree.
On occasion we built safety barriers when there was sufficient dirt for trail tread. The purpose of these barriers is to stop any rockfall before it drops onto the parkway.
This is a good example of a below the trail roll barrier.

A good long straight stretch of sturdy locust timber creates an excellent and long lasting trail edge cribbing.
Flat stones lay on the down side to aid in stabilizing the soil as seen through this fallen oak timber.
Sometimes we built timber cribs to hold rocks that were excavated from the trail. The crib is for safety purposes and will hold the stones until they settle into the earth.
On less severe slopes, simply laying stones with cut brush debris is used below the trail cut.
I love the engineering of this solution. There was no upright tree to prop against and we needed a safety crib. So the span was connected to an standing tree on both ends at a diagonal. A stone placed below the angles to lock it in place and then the diagonal bridged with hypotenuse. This provided a continuous and stable safety crib.
In the next post enjoy seeing the process of gathering trail timbers!

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