The pipeline stability during laying for a curved route has been investigated with various offshore pipeline projects which were successfully performed recently. During a curved laying operation, it is very difficult to keep pipeline m the designed route if pipeline being in contact with seabed doesn't create enough resistant force against the external force. To maintain the designed configuration in a curved route, a sufficient lateral force created by the pipeline/soil interaction should be provided. The lateral force is a function of submerged pipcweight, contact length, soil property, embedment, size of pipe, etc. For a decided pipe for the project, the laterral resistance required to maintain the route is dependent on the external force, contact length, soil property and embeded depth. This paper introduces how to control the laybarge to keep the curved route and shows how to estimate the allowable stable radius for various pipelines during laying in a curved route.
The main pipe properties (diameter, wall thickness, grade, type, etc.) are decided during a basic design stage considering internal/external pressures, buckle propegation, flow rate, corrosion, pipe staility, hydrotests, etc. in design life. The weight coating is usually applied to make pipes heavier which increases dry and submerged weights. Heavier pipes have more resistance force against external force created by mainly wave and current. The thickness of concrete coating effects greatly on lay conditions. The stress during installation should not be exceeded the allowable stress as defined in the international codes and standards. The weight coating also affects on the allowable pipeline radius for curved route. Even with the bare pipes satisfying the stress limit, the concrete coating to them limits the radius of pipeline during installation. This paper illustrates the laybarge path to maintain the designed pipeline route in a curved area.
