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Geotechnical and Environmental Research Group


Dynamic modellingSAM ACTUATOR

The geotechnical group at CUED has been active for many years in the field of centrifuge modelling of earthquakes. The first earthquake actuator was designed by Morris in 1979 and since then many experiments have been carried out into the dynamic behaviour of soils. Much of this work was carried out using the "Bumpy-Road" Earthquake actuator, designed by Bruce Kutter in 1981, which saw continued use until 1995 when a new Stored Angular Momentum or SAM actuator was developed by Dr Gopal Madabhushi. All of the experimental work currently being carried out at Cambridge on soil dynamics now uses this system.

The SAM actuator stores energy in a pair of spinning flywheels driving a reciprocating rod. This energy can be released to a model by means of a fast-acting hydraulic clutch. This actuator imparts an approximately sinusoidal input motion to the model, with control over amplitude, frequency and duration being available.

At present, all dynamic centrifuge models are tested within the confines of an Equivalent Shear Beam, (ESB) model container. This container has a stiffness equal to that of the soil column enclosed within it in order to minimise the generation and reflection of waves from the box's boundaries. the box also has glass sides in the direction of shaking to minimise side friction and to maintain a plane-strain condition.

Associate Professor in Geotechnical Engineering, Tianjin University, China
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PhD Student
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