A post-hole digger for the Power Curber 5700-Super-B digs pier holes up to 34 in. (86 cm) deep for slipforming concrete foundations for steel cable, strung in highway medians.
A pier hole can be dug in a matter of minutes by machine, as opposed to the much more time-consuming manual digging methods, according to the manufacturer.
Using a concrete foundation in the steel cable application prevents grass from growing around the posts. Grass-cutting crews can run mowers over the edge of the concrete, which is flush with the ground, reducing maintenance costs.
The post-hole digger attachment mounts on the left rear of the machine and is powered with the machine’s auger conveyor circuit.
The auger for the post-hole digger operates inside a cylinder. It moves the dirt upward into a hinged chute, catching the material before it hits the ground. The hinged chute allows the material to be dumped out of the way of the slipform application and eliminates the need for a crew member to move the dirt manually. The excavated material does not fall back into the hole, leaving it clean for the slipform application.
Steel cable is proving extremely effective in saving lives in highway accidents, according to a July 20, 2006, article in USA Today. While concrete barrier and steel beams also cut down on accidents where cars cross over into oncoming traffic, low-cost steel cable has proven to cut down on the number of rebound accidents, in which a vehicle hits a barrier and bounces back into traffic.
When a vehicle hits a concrete barrier, it usually bounces back into traffic, according to Brian Chandler, a traffic-safety engineer of the Missouri Department of Transportation (MoDOT), as quoted in USA Today. “But when you hit the guard cable, it gives 10 to 12 feet and helps absorb the force. The posts that hold the cable up are designed to break away. The cable stretches and wraps up the car in it.”
North Carolina, Missouri, Texas, Washington, California and Utah are leaders in installing the cable, according to the Texas Transportation Institute, a research body at Texas A&M University. Twenty-seven other states also are installing cable.
Using a Power Curber machine for installing the concrete foundation and posts requires a quick-connect mold mount option for the post hole digger.
After the holes are dug, the 5700-Super-B then slipforms the foundation, filling the holes with concrete as it passes over them. The machine’s vibrators consolidate and strengthen the concrete so that no voids are left in the concrete inside the pier holes.
After the mold passes over a hole, a crew member inserts a tube into the pier. A steel post is then inserted into each tube and the wire rope is strung between the posts.
A stop rod is available for the attachment for consistency of hole depth.