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Xu P.,Zhengzhou University | Zhou X.,Seismological Bureau of Zhejiang Province | Xia T.,Zhejiang University
Disaster Advances | Year: 2012

The amended Biot model of wave motion and the expansion method of wave functions are adopted, the scattering problem of a circular lining deeply buried in saturated soils by incident shear waves is studied, dynamic stress concentration factor (SCDF) at inner side of the lining and pore pressure concentration factor (pf*) at the boundary between the lining and saturated soils are analyzed and some important conclusions are obtained. The curves of SCDF and pf* are smooth and nearly not influenced by the lining's thickness when the incident frequencies of shear waves are lower, while the curves of SCDF and pf* have concave and convex parts and SCDF and pf* decrease when the lining's thickness increase and the incident frequencies of shear waves are higher. Source


Huang B.,Zhejiang University | Xia T.,Zhejiang University | Zhou X.,Seismological Bureau of Zhejiang Province | Liu Z.,Zhejiang University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2016

Based on the macroscopic equivalent model and microscopic contact theories, the shear wave velocity was studied. Considered as a kind of homogeneous, continuous and isotropic media macroscopically, the sand was assumed microscopically as an aggregate of randomly packed uniform equivalent spheres with the same material properties. Then, the formulas of the equivalent shear modulus and shear wave velocity in sand were derived by using particle contact theory and by introducing the correcting coefficient of the granule shape. The main influencing factors were analyzed through quantitative calculations. The results indicate that the shear wave velocity is mainly influenced by void ratio, elastic modulus of sand granule, burial depth and the correcting coefficient of the granule shape, while it is hardly influenced by inner friction angle, Poisson's ratio of sand granule, density of the sand and the constant connected with the coordination number. Through comparison, the calculation results using the present formulas agree well with measured data so as to verify the validity of the proposed method. © 2016, Central South University Press. All right reserved. Source


Chen W.-Y.,Zhejiang University | Xia T.-D.,Zhejiang University | Liu Z.-J.,Zhejiang University | Zhou X.-M.,Seismological Bureau of Zhejiang Province
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2013

The unsaturated poroelasticity theory was used to describe the propagation characteristics of elastic waves in unsaturated soil, and the reflection problem of plane-S-waves at the free boundary of unsaturated soil was analyzed. According to the boundary conditions, the theoretical expressions of amplitude reflection ratios and energy reflection ratios for the four reflected waves including reflected P1 wave, reflected P2 one, reflected P3 one and reflected S one at the boundary were respectively derived and the numerical calculations were then performed. The effects of incident angle of plane-S-waves and saturation level of soil layer on the amplitude reflection ratios and energy reflection ratios of the four reflected waves were discussed in numerical examples. It was shown that amplitude reflection ratios and energy reflection ratios of various reflected waves are influenced by not only incident angle but also saturation level. The results were useful for the theoretical study on soil dynamics and the related seismic exploration projects. Source


Xia T.-D.,Zhejiang University | Liu Y.,Zhejiang University | Wu M.,Zhejiang University | Zhou X.-M.,Seismological Bureau of Zhejiang Province
Harbin Gongye Daxue Xuebao/Journal of Harbin Institute of Technology | Year: 2011

Assuming deep buried sand is an aggregate of randomly packed uniform spheres, the equivalent shear modulus and the formula of shear wave velocity (Vs) in sand media were derived based on the the spheres-contact theory and the research results of microscopic particles elasticity. Seven influencing factors were analyzed, including porosity, saturation, internal friction angle, soil grain density, magnitude of stress, elastic modulus of sand grain and Poisson ratio of sand grain. The results were compared with the measured data, and the calculated value of Vs were generally in good agreement with the measured values. This study indicates that the value of Vs is mainly influenced by porosity, magnitude of stress and the elastic modulus of sand grain, and the shear wave velocity increases with the increasing of stress in high stress state, especially after the degree of density achieves 100%. Source


Chen W.-Y.,Nanjing University of Technology | Chen W.-Y.,Zhejiang University | Xia T.-D.,Zhejiang University | Huang R.,Zhejiang University | Zhou X.-M.,Seismological Bureau of Zhejiang Province
Gongcheng Lixue/Engineering Mechanics | Year: 2013

The unsaturated soil is the most common nature soil form on the earth's surface, unlike the fully saturated soil, four bulk waves exist in this soil: one shear wave (i.e., S wave) and three compressional waves (i.e., P1 wave, P2 wave, P3 wave). Among these four type waves, P1 wave is the wave with fastest wave velocity and lowest attenuation coefficient, which is similar to the fast compressional wave in fully saturated soil. Hence the unsaturated poroelasticity theory is used to describe the propagation characteristics of elastic waves in unsaturated fluid-saturated soils, and the reflection problem of plane-P1-waves at the free boundary of unsaturated soils is analyzed. Based on the boundary conditions, the theoretical expressions of the amplitude reflection coefficients and energy reflection coefficients for the four reflected waves at the boundary, i.e., reflected P1 wave, reflected P2 wave, reflected P3 wave and reflected S wave, are respectively derived and the numerical calculations are then carried out. The effects of the incident angle and saturation degree of the soils on the amplitude reflection coefficients and energy reflection coefficients of the four reflected waves are discussed in the numerical example. It is shown that the amplitude reflection coefficients and energy reflection coefficients of the waves is effected by not only the incident but also the saturation degree. These conclusions are useful for the theoretical research and seismic exploration projects. Source

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