A typical production layout consists of a sequence that advances re the limits of the ore body or property bounda1y and is then retreated. The advancing sequence (Figure 12.2) has an extraction ratio of about 40%. After these rooms are completed, the belt tailpiece and rigid frame structure is advanced 49 m (160 ft), and the sequence is repeated. Belt storage units are sec in•line near the head of the panel belt to expedite moves. The retreat sequence (Figure 12.3) is characterized by a chevron pattern. The firsr belt move is a 24•m (80-ft) retreat. After the first rerre,n pattern is mined, subsequent moves of the retreating
belt are on 49-m (160•fr) centers. The extraction ratio of r.he l'errear pattern shown is also about 4()