Valves used underground are mainly used in pipeline systems to control the flow, pressure, and direction of fluids. Different types of valves have different functions and uses in underground applications. The following are some common types of valves used underground:

Gate Valve: Gate valve is a common type of valve, typically used for fully open or fully closed applications, rather than for regulating flow. They have flat blades that can be moved up and down to open or close channels.

Butterfly Valve: The butterfly valve uses a round butterfly plate to regulate the flow in the pipeline by rotating. They are relatively lightweight, easy to operate, and suitable for applications that require frequent opening and closing.

Ball Valve: A ball valve uses a sphere to control the flow of fluid through rotation. Ball valves are usually used to quickly cut off fluid flow, but are not very suitable for regulating flow.

Check Valve: Check valves are used to prevent fluid backflow. They are usually designed to be unidirectional, allowing fluid to flow only in one direction to prevent backflow.

Control Valve: Control valves are used to precisely control the flow rate, pressure, or temperature of fluids. They usually include adjustment mechanisms that can be adjusted as needed.

Blowdown Valve: The blowdown valve is used to discharge wastewater or exhaust gas from the system to maintain its normal operation.

Safety Valve: A safety valve is used to release excessive pressure in the event of system overload to prevent damage to equipment or pipelines.

Fire Hydrant: A fire hydrant is a part of an underground water supply system, usually located on streets, used to provide a water source for firefighting purposes.

These are just some common types of underground valves, and there may be other specially designed valves in practical applications to meet specific needs and environmental conditions.