Reduction of dynamic shear modulus of saturated marine sandy silt under complex stress conditions

• Published in: Marine georesources & geotechnology 2023-11, Vol.41 (11), p.1288-1298
• Main Authors: Wu, Qi, Tianzhu, Hang, Zhao, Kai, Guoxing, Chen
• Format: Article
• Language: English
• Subjects: Consolidation; Cyclic loading; cyclic loading pattern; Cyclic loads; Dynamic characteristics; Dynamic response; dynamic shear modulus; Dynamic stability; Earthquakes; G evaluation method; initial consolidation condition; Marine sandy silt; Mathematical models; Nonlinear systems; Nonlinearity; Ocean floor; Parameter modification; Parameters; Seismic activity; Shear modulus; Shear strain; Silt; Stability analysis; Stress ratio; Vibrations
• ISSN: 1064-119X; 1521-0618
• DOI: 10.1080/1064119X.2022.2137714

Investigating the dynamic characteristics of seabed soil under complex vibrations or cyclic loads such as waves and earthquakes is important for analyzing the dynamic response and stability of the foundations of marine geotechnical structures. This paper presents an experimental investigation on the dynamic shear modulus (G) of saturated marine sandy silt subjected to various initial consolidation conditions and cyclic loading patterns. The initial consolidation condition is characterized by the initial effective mean principal stress P 0 ' and the stress ratio of anisotropic consolidation R 0 (= σ 1 /σ 3 ), and the cyclic loading pattern is described quantitatively by the ellipse ratio of elliptical stress path (δ) and the orientation angle of major principal stress of linear stress path (α 0 ). A remarkable finding is that the maximum dynamic shear modulus G max and G/G max -γ z θ curve is affected significantly by the initial consolidation condition (P 0 ′ or R 0 ) but is insensitive to changes in the cyclic loading pattern (δ and α 0 ). G max increases with increasing P 0 ′ or R 0 , and the nonlinearity of the G/G max -γ z θ curve decreases with increasing P 0 ′ or R 0 . The control parameters G max and reference torsional shear strain γ r of the modified hyperbolic model usually known as the KZS model are related linearly to the synthesizing initial consolidation state parameters (P 0 ′/P a )(R 0 ) 0.5 and (P 0 ′/P a ) 0.5 R 0 , respectively. A wide-strain-range G evaluation method with comprehensive consideration of the initial consolidation condition and the cyclic loading pattern was established, and the applicability of the proposed method was verified.