By Bob Moore
| Friday, April 06, 2018 | 815 Views
A Reclaim Tunnel refers to a buried conduit that encloses a material conveyor. The conduit is used to transport aggregate, sand, coal or other minerals from a central stock pile to an off loading location. These material stock piles can be as tall as 80’ high. Reclaim Tunnels will normally have hopper openings to allow flow of the material from the stockpile to the conveyor inside the conduit.
The conduit is normally between 8’ to 14’ in span, and are made primarily from pre-cast concrete, cast-in-place concrete, reinforced steel, and galvanized corrugated steel. In rare cases, reclaim tunnels can have spans in excess of 20’. High stock piles exert a large dead load over the Reclaim Tunnel. Because the dead load is large, the most efficient shape structurally of a Reclaim Tunnel is round or half circle arch on footings.
|HEL-COR Reclaim Tunnel
|MULTI-PLATE Arch with hopper/feeder
supported from the floor
CORRUGATED STEEL STRUCTURES
Of the four types of conduits available for reclaim tunnels, corrugated steel structures are the most cost effective because corrugated steel structures have the most efficient design for high fill applications.
Corrugated steel reclaim tunnels are designed to meet American Iron and Steel Institute (AISI) design criteria. Hopper openings on the reclaim tunnel are designed per ASTM 998 specification. The best design for the hoppers, chutes, and the conveyor are when these loads are supported from the floor of the tunnel and not directly on the tunnel.
Corrugated Steel Structures are available in corrugated steel pipe (HEL-COR®) and steel structural plate (MULTI-PLATE®). HEL-COR is shipped to the project site in pipe diameters up to 12’ and standard lengths from 10’ to 40’. The pipe is connected with steel bands. Flat gaskets are recommended to be placed between the steel band and pipe during assembly to decrease any leakage into the tunnel.
MULTI-PLATE is shipped in individual plates that are assembled at the project site into a round or arch shape. MULTI-PLATE reclaim tunnels have been manufactured in spans in excess of 20’.
When do you design with HEL-COR compared to MULTI-PLATE?
HEL-COR is more cost-effective in both material and assembly compared to MULTI-PLATE, however the maximum span available is 12’ diameter. MUTLI-PLATE is manufactured with a deeper corrugation and in heavier steel gages than HEL-COR providing larger diameter availability as well as arch shapes.