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Behaviour of deep immersed tunnel under combined normal fault rupture deformation and subsequent seismic shaking 总被引：1，自引：0，他引：1
Ioannis Anastasopoulos Nikos Gerolymos Vasileios Drosos Takis Georgarakos Rallis Kourkoulis George Gazetas 《Bulletin of Earthquake Engineering》2008,6(2):213-239
Immersed tunnels are particularly sensitive to tensile and compressive deformations such as those imposed by a normal seismogenic
fault rupturing underneath, and those generated by the dynamic response due to seismic waves. The paper investigates the response
of a future 70 m deep immersed tunnel to the consecutive action of a major normal fault rupturing in an earthquake occurring
in the basement rock underneath the tunnel, and a subsequent strong excitation from a different large-magnitude seismic event
that may occur years later. Non-linear finite elements model the quasi-static fault rupture propagation through the thick
soil deposit overlying the bedrock and the ensuing interaction of the rupture with the immersed tunnel. It is shown that despite
imposed bedrock offset of 2 m, net tension or excessive compression between tunnel segments could be avoided with a suitable
design of the joint gaskets. Then, the already deformed (“injured”) structure is subjected to strong asynchronous seismic
shaking. The thick-walled tunnel is modelled as a 3-D massive flexural beam connected to the soil through properly-calibrated
nonlinear interaction springs and dashpots, the supports of which are subjected to the free-field acceleration time histories.
The latter, obtained with 1-D wave propagation analysis, are then modified to account for wave passage effects. The joints between tunnel segments are modeled with special non-linear hyper-elastic elements, properly accounting
for their 7-bar longitudinal hydrostatic pre-stressing. Sliding is captured with special gap elements. The effect of segment
length and joint properties is explored parametrically. A fascinating conclusion emerges in all analysed cases for the joints
between segments that were differentially deformed after the quasi-static fault rupture: upon subsequent very strong seismic
shaking, overstressed joints de-compress and understressed joints re-compress—a “healing” process that leads to a more uniform
deformation profile along the tunnel. This is particularly beneficial for the precariously de-compressed joint gaskets. Hence,
the safety of the immersed tunnel improves with “subsequent” strong seismic shaking! 相似文献
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S. Michaelides V. Levizzani E. Anagnostou P. Bauer T. Kasparis J.E. Lane 《Atmospheric Research》2009,94(4):512-533
This review paper deals with four aspects of precipitation: measurement, remote sensing, climatology and modeling. The measurement of precipitation is summarized in terms of the instruments that count and measure drop sizes (defined as disdrometers) and the instruments that measure an average quantity proportional to the integrated volume of an ensemble of raindrops (these instruments are normally called rain gauges). Remote sensing of precipitation is accomplished with ground based radar and from satellite retrievals and these two approaches are separately discussed. The climatology of precipitation has evolved through the years from the traditional rain gauge data analyses to the more sophisticated data bases that result from a coalescence of data and information on precipitation that is available from several sources into amalgamated products. Recently, rain observations from both ground and space have been assimilated into regional and global numerical weather prediction models aiming at improved moisture analysis and better forecasts of extreme weather events. The current status and the main outstanding issues related to precipitation forecasting are discussed, providing a basic structure for research coordination aimed at the improvement of modeling, observation and data assimilation applicable to global and regional scales. 相似文献
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John E. Lane Takis Kasparis Philip T. Metzger W. Linwood Jones 《Acta Geophysica》2014,62(6):1450-1477
In situ calibration is a proposed strategy for continuous as well as initial calibration of an impact disdrometer. In previous work, a collocated tipping bucket had been utilized to provide a rainfall rate based ～11/3 moment reference to an impact disdrometer’s signal processing system for implementation of adaptive calibration. Using rainfall rate only, transformation of impulse amplitude to a drop volume based on a simple power law was used to define an error surface in the model’s parameter space. By incorporating optical extinction second moment measurements with rainfall rate data, an improved in situ disdrometer calibration algorithm results due to utilization of multiple (two or more) independent moments of the drop size distribution in the error function definition. The resulting improvement in calibration performance can be quantified by detailed examination of the parameter space error surface using simulation as well as real data. 相似文献
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