Mining machines include tunnel boring machines (TBM) and boring rigs, roof bolting rigs, rock crushing vehicles, and other heavy equipment used for tunneling and mine excavation. This product area also includes drilling rigs, stripping shovels, dragline excavators, dredging equipment, blast-hole drills, mining crushers, and surface feeder-breakers. Loaders, cutters, lifters, dump trucks, drills, bulldozers, charging vehicles, bulk handling equipment, mineral processing equipment, nodulizers, pelletizers, trams, and other types of mining machines are also available. Selecting mining machines requires an analysis of product capabilities and application requirements. Tunnel boring machines (TBM) or moles are used to excavate tunnels. They produce a circular cross-section and differ in terms of diameter. An alternative to traditional drilling and blasting methods, tunnel boring machines are used mainly with longer tunnels because of upfront costs. Typically, trenchless construction or horizontal directional drilling are used to dig shorter tunnels. Other mining machines for drilling through hard rock, soil and sand are also available. Roof bolting machines and wall bolting machines are used to prevent the collapse of underground mines. Roof bolts are either point-anchored (tensioned) or full-length anchored (non-tensioned), depending upon the application. In the United States, coal mines must be roof-bolted. In addition to roof bolting rigs, mining machines include a variety of rock crushing vehicles. Examples include jaw, cone, and gyratory crushers. Vertical and horizontal impactors are also available. Mining machines such as drilling rigs include blasthole drillers (blasthole drills) and rotary table drilling equipment. Striping shovels, loading or quarry-mine shovels, and hydraulic shovels are used in coal mining operations and to load rocks. Dragline excavators are mining machines that consist of a large bucket suspended from a boom with wire ropes. They are used mainly in open pit mining or strip mining operations for coal and tar-sand. Mining dredges are used to remove sand and gravel from rivers, lakes, and other bodies of water. Typically, they feature a submersible pump and suction dredger. Mining feeder-breakers may be designed to work with battery-powered haulers, ram cars, scoops, shovels, front-end loaders, and dump trucks. These mining machines feature a rotary pick breaker that reduces the mined material to a consistent size.