Geoscience Reference
In-Depth Information
Fig. 5.29. ESB model container mounted onthe shaking table on the SAM actuator,
and theSAM actuator showing the3-phase motor and flywheels
TheCambridgePhilosophyhasbeentousesinglefrequencytoneburstsasinputmotions
and investigate the soil response. For liquefaction problems, where the sole purpose of
input motion is to generate excess pore water pressures that cause soil liquefaction, this
type of input motion is considered satisfactory. On the other hand if the purpose of the
dynamic centrifuge test is to investigate dynamic soil-structure interaction say in dry
soils, then more realistic input motions may be required. Recently Madabhushi et al.
(2006)haveinvestigatedtheinfluenceoftypeofinputmotionontheexcessporepressure
generation insaturated sand beds.
5.3. PNEUMATIC SHAKER ATCEA-CESTA, FRANCE
Twodecadesago,theCEA-CESTAusedsmallexplosionsattheendofanairblastmod-
ification chamber. The resulting air blast would then be modified by resonating cavities
andfinallyappliedtothemodelthroughamembranerubber(ZeliksonandLeguay,1985).
A new pneumatic system (Figure 5.30) to generate vertical or horizontal shocks has also
been designed (Sabourault et al.,1999).
5.4. EARTHQUAKE SIMULATION AT LCPC, FRANCE
An innovative shaker has recently been put in operation in the LCPC centrifuge. It was
manufactured by Actidyn Systems and includes a dynamic balancing feature, both with
respecttothemechanicsandatthecommand-controllevel.Thisfeaturemakesitpossible
to generate amplitude excitations, with direction and frequency being chosen in advance
and controlled. The second advantage of this dynamic balancing feature is the reduction
or elimination of vibrations currentlybeing transmittedtothe machine.
Figure 5.31 shows the LCPC shaker and the laminar box developed by LCPC. In
Figure 5.31, an example of results of the commissioning tests recently carried out is
