| With the advancement of my country's maritime power strategy,the Maritime Silk Road,and the development and construction of the South China Sea islands and reefs,marine engineering construction has become more frequent.At the same time,due to the frequent occurrence of medium and strong earthquakes in my country's offshore waters,the degree of basic research on marine earthquakes is relatively low.The marine ground motion observation record is not rich enough to provide basic information and data support for theoretical research on sea ground motion.Therefore,researches on the characteristics of marine engineering ground motions and the field effects of sea ground motions have received extensive attention from the scientific and engineering communities.In view of several scientific problems in the soil dynamics and ground motion site effects exposed in the current marine engineering seismic research,the dynamic characteristics and site effects of sea ground motions are analyzed based on the centrifugal model test.The main work and research results obtained are as follows:(1)Design and construct two weak free-field centrifugal models with overlying water and overlying without water to restore saturated soft soil sites in sea and land areas.Through acceleration record analysis,it is found that the two sets of models have the ground and underground layers.The peak acceleration is in the shape of "C" as a whole,and the amplification factor gradually decreases with the increase of the input ground motion amplitude;the response spectrum amplitude of the land area gradually shifts to the long-period direction,but the response spectrum amplitude of the sea area has a direction The tendency to move in a short period of time.It can be seen from the displacement record that the horizontal displacement of the land site is greater than that of the sea site,and the horizontal displacement near the surface is the largest,but due to the influence of the seawater's own weight,the vertical displacement of the sea site is greater than that of the land site.(2)According to Code for seismic design of buildings,the US NEHRP and the Bo Jingshan team's engineering method,the response spectrum was calibrated,and it was found that the platform value and characteristic period of the “Code Design Spectrum” were far from the test response spectrum.The characteristic period of the "NEHRP design spectrum" is basically the same as the test response spectrum,but the platform value is too small,which is unsafe in engineering.The design spectrum of the Bo Jingshan team's engineering method is basically consistent with the test response spectrum,and has good engineering applicability.(3)The acceleration and displacement records are further analyzed for dynamic characteristics,and the changes of shear stress-shear strain,dynamic shear modulus and damping ratio are obtained.It is found that the shear modulus of the land site is larger than that of the sea site,and the greater the buried depth,the greater the shear wave velocity.(4)Peak acceleration,spectral acceleration,etc.can only represent a specific ground motion characteristic.In order to describe ground motion characteristics more comprehensively,the Arias intensity,cumulative absolute velocity.The root mean square acceleration is used for comparative analysis to describe the difference between the two models more comprehensively and reveal the influence of the overlying water weight on ground motion.The dynamic centrifugal model test was used to simulate and restore ground motion observation stations in land and sea areas.The ground motion characteristics of sea areas and land saturated soft soil sites were compared and analyzed,which provided a new idea for the study of ground motion site effects in marine engineering.The seismic resistance of marine engineering has certain reference value and engineering significance. |
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