Engineered metal crib for use as a support structure
Inactive Publication Date: 2011-10-13
SOUTHERN ILLINOIS UNIVERSITY
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AI Technical Summary
Benefits of technology
[0019]This invention provides an improved cribbing support in mines and tunnels through a lightweight, engineered steel crib element to provide support between two surfaces. It is easy to carry manually and offers very low resistance to airflow depending upon the selected embodiment. The elements can be used in multiple ways to construct cribs. The element provides high stiffness support to develop a crib with literally any desired load carrying capacity. However, it is anticipated that initially cribbing with load carrying capacity of 100-tons to 300-tons will be commonly used to minimize rock mass movement in mines and tunnels.
[0021]The novel crib element offers the following advantages: it has much higher stiffness (10-20 times or more) than the wooden cribs (about 40,000 psi) commonly used today; it can be designed to have variable stiffness; it can be designed to support any loads but typically varying from 100 tons to 300 tons for a 6-ft high cribs; it has the ability to sustain almost peak load even after the steel starts to yield; it is lightweight; it may offer very low resistance to airflow in underground mine roadways; and, it does not shrink like the wooden cribs that are almost exclusively used today in mining and tunneling industries.
Problems solved by technology
A 2-by-2 crib configuration is most common, although 3-by-3, 3-by-2, 3-by-3, and 4-by-4 configurations have been considered and have found limited application.
A typical solid wood cribbing for support has several disadvantages, including: low rigidity, a limited load carrying capacity, a high resistance to airflow, heavy weight per crib element, limited pre-load capacity, insufficient post-failure characteristics, flammability, and shrinkage.
Because of large deformations, the column has limited load carrying capacity; a typical crib column fails due to buckling before achieving its full load carrying capacity.
Installing typical solid wood crib element is difficult in locations where the surfaces are not parallel to each other or irregular.
Each wooden crib element typically weighs about 35 pounds, making carrying them by hand and assembling a crib column an arduous process, especially when one must lift an element above one's head.
Since low-rigidity wedges, cut parallel to the wood grain, are typically used to preload the crib, the amount of preload force that can be introduced to a column is limited and it tends to decay with time.
The wedges typically deform under low loads, which means that the column does not support significant loads until the upper and lower surfaces have deformed toward each other, through compression of the column.
Moreover, wood shrinks as it loses moisture.
In addition to the above, the post-failure characteristics of wood do not provide a relatively flat load-deformation curve and wood is flammable.
However, despite the advantages of using steel, it has only found limited use as a material in cribbing elements because solid steel is heavy and expensive.
Understandably, steel would not be a suitable material to construct prior art cribbing elements; a conventional solid cribbing element made of steel would be very heavy.
Method used
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[0038]A conceived steel crib may consist of two or more pieces of metal load carrying members of any geometrical cross-section connected to each other through one or more elongate structural elements. The elongate structural elements may be rod of any shape or plate metal or any other material that provides appropriate load-deformation characteristics prior to and after yielding, has appropriate flexural rigidity in different orientations, and is reasonable in cost. The material used may also have any geometry that satisfies the above requirements. Mechanistically, the size of the load carrying member, its wall thickness, its geometry (square, rectangle, circular), and its loading orientation control its stiffness and load-deformation characteristics. The elongate structural elements may be metal rod or bar, non-metal, or polymers. The elongate structural elements may be interconnected at suitable intervals to provide appropriate strength and stiffness in different spatial planes. S...
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This invention provides improvements through an engineered metal crib element for construction of cribs in mines to provide support between two surfaces and use of crib elements to construct cribs. The engineered metal crib element consists of a center elongate structural element and at least two outer load carrying steel members. The outer load carrying members may be composed of solid or hollow metal with one or more reinforcements within each load carrying member. Each outer load carrying member is attached to the center elongate element at the distal ends of the elongate structural element. The crib structure may be constructed by superimposing only these steel crib elements in 2×2 layers, 2×3 layers, 3×3 layers or in any other suitable layering system. The engineered metal crib elements are lightweight, have controllable higher stiffness and load carrying capacity than current wooden cribs, have engineered plastic yielding characteristics and allow much lower resistance to air flow in underground mine roadways.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to and benefit of an earlier filed co-pending Provisional Patent application Ser. No. 61 / 323,537 filed Apr. 13, 2010 entitled Engineered Steel Crib for Use as Mine and Tunnel Support.FIELD OF INVENTION[0002]This invention relates primarily to the mining, tunneling, and construction industries and, more specifically, to an engineered steel crib for the support of hanging wall and foot wall, roof and floor, or upper and lower surfaces in underground mining, or providing temporary support for heavy structures such as ships, cars, houses or buildings being relocated or receiving foundation work.BACKGROUND OF INVENTION[0003]Wooden posts and wooden cribs, or chocks, are probably the oldest support systems used in the mining and construction industries. A wooden post, typically 4 inches to 10 inches in diameter or square cross-section, loaded axially provides support between two points. A wooden crib or chock pro...
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Login to View More IPC IPC(8): E02D17/00E02D29/00
CPCE21D17/01E21D17/006
InventorCHUGH, YOGINDER P.
OwnerSOUTHERN ILLINOIS UNIVERSITY