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Date: January 30, 1996
Author: Thomas Bird, Senior Engineer Foresight Products LLC Commerce
City, Colorado (USA)
Subject: MANTA RAY® anchoring project with Nicolon "Armorform"
mattress to protect bridge piers in an intermittent riverbed from erosion.
Description of Problem: Ground anchoring was required to hold the
upstream edge of the mattress against oncoming heavy rainfall flows in the riverbed. The mattress was selected
to provide erosion control of the embankment surrounding the bridgeís piers.
Proposed Solution: The Manta Ray anchor model MR-1 was selected over
other anchoring options by the contractor, Young & Sons, Inc., from Tucson, Arizona, because of the ease of
installation of the Manta Ray anchor system. The MR-1 anchors were driven to 20' depths using a Case backhoe equipped
with a mounted breaker. All anchors were locked to 18,000 lbs. Other anchoring alternatives required specialized
machinery and undesirable traffic divergence measures from the bridge deck.
Anchor Assembly:
(1) MR-1 anchor
(2) SAR-10A 1"x7' solid galvanized anchor rod
(1) AT-32-G72 1"x6' galvanized all-thread anchor rod
(2) C-1 coupling nuts 1" UNC
(1) EN-32G galvanized eyenut for attachment to ABM
Installation Equipment:
Drive steel to reach 20':
(1) SG-18 hex shank
(2) SG-2-96 8' extensions
(1) SG-3-72 6' drive tip
(3) SG-4 drive steel couplers
(1) Case backhoe with 500 ft* lb. breaker and 3" diameter modified driving shank, see attached.
(1) LL-1 load locker
*Note the backhoe hydraulics were used to power the LL-1 load locker. Special care must be taken to limit the flow
to the LL-1 to 8 GPM or less. A selector switch on the backhoe was placed into the appropriate position to accomplish
this. See picture attached.
Additional Notes: Manta Ray anchors are used extensively to secure
erosion control concrete mattresses. The Manta Ray "MR-88" anchor can, in most cases, be driven through
the open cell of the mattress. See attached sketch.
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