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

Abstract

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 P₀' and the stress ratio of anisotropic consolidation R₀ (= σ₁/σ₃), 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 (α₀). A remarkable finding is that the maximum dynamic shear modulus G_max and G/G_max–γ_zθ curve is affected significantly by the initial consolidation condition (P₀′ or R₀) but is insensitive to changes in the cyclic loading pattern (δ and α₀). G_max increases with increasing P₀′ or R₀, and the nonlinearity of the G/G_max–γ_zθ curve decreases with increasing P₀′ or R₀. 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 (P₀′/P_a)(R₀)^0.5 and (P₀′/P_a)^0.5R₀, 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.

Keywords:

• Marine sandy silt
• dynamic shear modulus
• initial consolidation condition
• cyclic loading pattern
• G evaluation method

Disclosure statement

The authors declared that they have no conflicts of interest to this work.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (52008206, 51978335) and the China Postdoctoral Science Foundation (2021M690279).