Hopper barge is a kind of non-mechanical ship or vessel that cannot move around by itself, unlike some other types of barge

Barge

A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Some barges are not self-propelled and need to be towed by tugboats or pushed by towboats...

s. Designed to carry materials, like rocks

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

, sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

, soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 and rubbish, for dumping into the ocean, a river or lake for land reclamation

Land reclamation

Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

.

Hopper barges are seen in two distinctive types; raked hopper or box hopper barges. The raked hopper barges move faster than the box hoppers; they are both designed for movement of dry bulky commodities

There are several "hoppers" or compartments

Chute

A chute is a vertical or inclined plane, channel, or passage through which objects are moved by means of gravity.-Landform:A chute, also known as a race, flume, or river canyon, is a steep-sided passage through which water flows rapidly....

 between the fore

Bow (ship)

The bow is a nautical term that refers to the forward part of the hull of a ship or boat, the point that is most forward when the vessel is underway. Both of the adjectives fore and forward mean towards the bow...

 and aft

Aft

Aft, in naval terminology, is an adjective or adverb meaning, towards the stern of the ship, when the frame of reference is within the ship. Example: "Able Seaman Smith; lay aft!". Or; "What's happening aft?"...

 bulkhead

Bulkhead (partition)

A bulkhead is an upright wall within the hull of a ship or within the fuselage of an airplane. Other kinds of partition elements within a ship are decks and deckheads.-Etymology:...

 of the barge. On the bottom of the barge hull

Hull (watercraft)

A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

 there is (are) also a large "hopper door(s)", opening downwards. The doors are closed while the vessel is moving, so she can carry the materials that are to be dumped. The door(s) open when the ship has arrived at the spot where the materials are to be dumped.

Split barges serve the same purpose, but instead of a door in the hull's bottom, the hull of the whole barge splits longitudinally between the end bulkheads. The vessel consists of two major parts (port and starboard halves), both are mostly symmetrical

Symmetry

Symmetry generally conveys two primary meanings. The first is an imprecise sense of harmonious or aesthetically pleasing proportionality and balance; such that it reflects beauty or perfection...

 in design. Both parts of the vessel are hinged

Hinge

A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation. Hinges may be made of flexible material or of moving components...

 at the deck

Deck (ship)

A deck is a permanent covering over a compartment or a hull of a ship. On a boat or ship, the primary deck is the horizontal structure which forms the 'roof' for the hull, which both strengthens the hull and serves as the primary working surface...

 and operated by hydraulic

Hydraulics

Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

 cylinders

Hydraulic cylinder

A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...

. When the vessel splits the load is dumped rapidly, which means the barge has to be very stable in order not to capsize or otherwise get damaged.