Roof support timbers

Crib A roof support of prop timbers or ties, laid in alternate cross-layers, log-cabin style it may or may not be filled with debris and is also maybe called a chock or cog. 

Cribbing The construction of cribs or timbers laid at right angles to each other, sometimes filled with earth, as a roof support or as a support for machinery. 

Prop Coal mining term for any single post used as roof support. Props may be timber or steel if steel, screwed, yieldable, or hydraulic. 

Traditional roof control plans require that numerous timber posts be set during each stage of pillar recovery (Figure 23.6). Recently, mobile roof supports (MRS) have become available that replace many of the timbers (Figure 23.7). MRS resemble longwaU shields mounted on bulldozer tracks. They can have many safety advantages over timbers. In particular, they are more effective as roof supports, they do not require workers to approach the mined-out gob area to set them, and they reduce the potential for materials handling injuries (Chase et al. 1997). 

Provide supplemental roof support such as timbering and cribbing where excessive widths exist... 

Many U.S. and British miners distrust roof bolts because they cannot see whether the bolts have been installed properly. Some miners point to examples of chandeliers —rough outcroppings of roof bolts with little roof material in between—as evidence that roof bolts provide little effective support in the event of a large roof fall. They trust timbers as a means of roof support because timbers prtxluce sensory information that can save their lives. Although timbers cannot support a roof in the event of a fall, their yielding and cracking can warn miners to escape. Miners depend upon this constant flow of sensory information to save their lives. 

The type of strata in the first few feet above the coal also has a very important effect on mining. The material must be strong enough to remain stable for a required time when it is supported by either timbering or roof bolts. Shale and siltstone are the most common roof types, and probably the most varied in composition and character. Some of the shales and siltstones are relatively hard and... 

Crossbar The horizontal member of a roof timber set supported by props located either on roadways or at the face. 

Open end pillaring A method of mining pillars in which no stump is left the pockets driven are open on the gob side and the roof is supported by timber. 

Support The all-important function of keeping the mine workings open. As a verb, it refers to this function as a noun it refers to all the equipment and materials—timber, roof bolts, concrete, steel, etc.—that are used to carry out this function. 

Timbering The setting of timber supports in mine workings or shafts for protection against falls from roof, face, or rib. 

Timber set A timber frame to support the roof, sides, and sometimes the floor of mine roadways or shafts. 

In old buildings timber often fails where it enters a masonry wall or in roofs at the junction of rafter and tie beam where the truss is supported on the wall plate. In both cases leaking water over a long period has resulted in wet rot. The repair process consists of replacing the decayed timber with reinforced epoxy mortar. The reinforcement may consist of steel plate or bars which are drilled or set deep into the sound portion of the timber to ensure a good bond and load transfer. Fig. 6.23 shows bonded dowel bars used to repair the end section of a column or beam while Fig. 6.24 illustrates a typical repair to a roof truss. 

Falls of road in unsupported roadways is actually a major cause of accidents in Britain too—whatever method of support you use. But it s a matter of fact that whether you re using roof bolting or traditional arch supports, you must break down the loose ground in front of before you can set them. .. and what we need to do is to make sure that they—that you—find a method of support in advance of setting the permanent support—through temporary means of timber and try to do everything from this side of the support. .. urn. .. [viewpoint of trainer]... 

Unlike arch supports and timbers, roof bolts act internally within the physical environment of the mine roof in order to control and prevent roof... 

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