Abstract:

Using the self-vibration column apparatus, the experimental investigation on the 165 undisturbed clayey and silt soil samples obtained from 41 boreholes in Xuzhou urban area were conducted to evaluate the characteristics of dynamic shear modulus ratio G/G₀ and damping ratio l with the shear strain amplitude γa . Special focus is given to the influence of effective confining pressure, plasticity index, and geological age on the G/G0-γa  and λ-γa  curves of Q₃ and Q₄ clay soils, Q₄ silty clay soil and Q₄ silt soil. The results indicate that the larger the effective confining pressure is, the larger the plasticity index is, the newer the geological age is when the depth is similar, and the weaker the nonlinearity of soils is. The upper and lower envelopes of the G/G0-γa  and λ-γa  test data of three soils were proposed. The influence characteristics of soil type, effective confining pressure, plasticity index, and geological age on the G/G0-γa  and λ-γa  curves of three soils were quantitatively analyzed, and the corresponding empirical formulas for predicting G/G0-γa  and λ-γa  curves were established. The results are beneficial to understand the dynamic characteristics of various soils in Xuzhou urban area, and have a helpful reference for the evaluation of seismic site effects in this area.

Key words: soil dynamic characteristics, dynamic shear modulus, damping ratio, empirical formula