An approach for predicting multi-support seismic underground motions in layered saturated soil under surface water. Issue 115 (December 2018)

• Record Type: Journal Article
• Authors: Liu, Guohuan; Yu, Haitao; Liu, Yaqiang; Lian, Jijian
• Is Part Of: Soil dynamics and earthquake engineering. Issue 115(2018)
• Page Start: 104
• Page End: 118
• Publication Date: 2018-12
• Subjects: Saturated soil under surface water -- Multi-support seismic motions -- Transfer function -- Power spectral density -- Cross-coherence function; Soil dynamics -- Periodicals; Earthquake engineering -- Periodicals; Sols -- Dynamique -- Périodiques; Génie parasismique -- Périodiques; 624.176205
• DOI: 10.1016/j.soildyn.2018.08.009
• Languages: English
• ISSNs: 0267-7261

Abstract

Abstract: Simulation of multi-support (i.e. spatially variable) seismic underground motions in sea areas plays a significant role in the seismic analysis of cross-sea structures such as cross-sea bridges or subsea tunnels. However, existing approaches for predicting multi-support seismic motions mainly focus on the dry site soils without overlying surface water. This paper proposes an approach for predicting multi-support seismic underground motions in layered saturated half space under surface water, subjected to oblique incident P waves. The transfer function in saturated soil under surface water, as the theoretical basis of the subsequent numerical simulation, is first derived based on wave propagation theory and the calculated reflection coefficients of P wave–induced P1, P2, SV waves in saturated soils. The derived transfer function is further employed to deduce and obtain the underground (sub-seabed) power spectral density function and response spectrum function. The two obtained functions, combined with the additional cross-coherence function, are subsequently employed to construct the cross power spectral density matrix and thus to simulate multi-support seismic underground motions. The solutions are validated against the target power spectral density, target response spectrum and target cross-coherence functions. A parametric analysis is presented where the effects of the soil thickness, the incident angle and the overlying water depth are investigated. Results show that the soil thickness, incident angle and overlying water depth have significant influences on the amplitude of transfer functions, which further affect the ratios between seismic ground and underground motions. Highlights: Theoretically required transfer function in saturated soil under surface water is first derived. PSD matrix to predict multi-support seismic motions in saturated soil under surface water is obtained. Program for simulating multi-support seismic motions in layered saturated soil under surface water is developed. Parametric analysis of the effects of soil thickness, incident angle and overlying water depth on the predicted seismic motions is investigated.