| Summary: | 博士 === 國立中興大學 === 土木工程學系 === 90 === A Study of the Dynamic Properties of
Taichung Gravelly Formation
Abstract
With the reference to the geological conditions in Taichung areas, its topography is classified as the alluvial gravelly formation and main gravelly deposit is over 100 m in thickness. The frequent earthquake shock cannot be avoided. Therefore, a further study on the dynamic properties of gravelly formation and the provision of application to the seismic response analysis during earthquake would be needed.
It aims to investigate the relationships between the maximum grain size (Dmax), gravel content (GC), confining pressure ( ) and anisotropic behavior through the large scale triaxial tests and cyclic simple shear tests with specimens of 15 cm and 30 cm in diameters respectively. It is found that the shear modulus ( G ) increases as the increase of maximum grain size, gravel content and confining pressure. The above trend can be simplified to a linear relationship with all parameters under the shear strain equal to 0.1%, i.e. G ( ) = 7.70GC (%) + 81.03Dmax (cm) + 147.18 ( )－136.82. And it is established two normalized curve of dynamic properties in the adoption of above trend through the triaxial tests and cyclic simple shear tests. A linear relationship between shear wave velocity ( ) and depth (Z), where 5m < Z < 20m, is obtained by means of regression ( (m/s) = 6.50Z (m) + 379.69) taken from the tests of down-hole method, seismic reflection method and seismic refraction method.
In the comparison of shear waves velocity predicted in the forms of dynamic test results and in situ measurement, it is required to develop the investigation method of field dynamic characteristics curve. Moreover, a preliminary seismic response analysis is conducted by SHAKE program. It is suggested that a conservative seismic response result from the developed dynamic characteristics curve generated by the cyclic simple shear tests can be obtained and applied practically.
Key words: gravelly formation, cyclic triaxial tests, cyclic simple shear tests, down-hole method, seismic refraction method, seismic reflection method
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