Description
Cuttable Crib is a two component system consisting of a 48 inch diameter cement pillar topped by a yielding bag. The cement pillar is a super strong breaker post designed to stop any falls caused by geologic anomalies in advance of the longwall face. The topper bag is designed to yield at 900 psi to the expected yield of the adjacent pillars, under abutment load. This designed yield preserves the structural integrity of the immediate roof by minimizing roof shear.
Installation
The cement required for the lower is pumped down a borehole thousands of feet. The topper bag is filled with Tekset, a specially designed cement that facilitates yield under abutment load. The Tekset is mixed and pumped from an underground location, within 1,500 ft of the crib. Wright Concrete supplies all the necessary forms for the pillar, topper bags, underground pipe, borehole pipe, and surface mixing and pumping equipment. The underground equipment can generally be shipped to the job site on only a few flat cars.
Cuttable crib has been extremely successful in both the Pittsburgh and Eagle coalbeds, in entries as wide as 20 feet and as high as 11 feet. Cuttable crib are generally placed in a single row on an average of 10 foot centers. For example, 4,000 feet of open entry would require 400 cuttable cribs. This includes closer spacing in and around cross-cuts. Cuttable cribs are located on wider 12-14 feet centers in entries parallel to the direction of panel extraction.
We have built cuttable cribs in Pennsylvania, West Virginia and Utah and have a couple versions to choose from depending on your particular condition. To save tremendous time on your longwall section when it comes to making that move call for our technical assistance.
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