Seismic Response of Submarine Slopes

2003 ◽  
Author(s):  
Giovanna Biscontin ◽  
Juan M. Pestana
Keyword(s):  
Site Response ◽  
Depth Profiling ◽  
Small Strain ◽  
Computer Code ◽  
Strength Properties ◽  
Response Analysis ◽  
Cohesive Soils ◽  
Sloping Ground ◽  
Ground Conditions ◽  
Analysis Computer

The geological profile of submerged slopes on the continental shelf typically includes soft cohesive soils with thicknesses ranging from a few meters to tens or hundreds of meters. The response of these soils in simple shear tests is largely influenced by the presence of an initial consolidation shear stress, inducing anisotropic stress-strain-strength properties which depend also on the direction of shear. In this paper, a new simplified effective-stress-based model describing the behavior of normally to lightly overconsolidated cohesive soils is used in conjunction with a one-dimensional seismic site response analysis computer code to illustrate the importance of accounting for anisotropy and small strain nonlinearity. In particular, a simple example is carried out to compare results for different slope inclinations. Depth profiling of the maximum shear strains and permanent deformations provide insight into the mechanisms of deformation during a seismic event, and the effects of sloping ground conditions.

κ0 for soil sites: Observations from KiK-net sites and their use in constraining small-strain damping profiles for site response analysis

2019 ◽  
Vol 36 (1) ◽  
pp. 111-137 ◽  
Author(s):  
Boqin Xu ◽  
Ellen M Rathje ◽  
Youssef Hashash ◽  
Jonathan Stewart ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Strong Motion ◽  
Small Strain ◽  
Site Amplification ◽  
Site Response Analysis ◽  
Response Analysis ◽  
One Dimensional

Small-strain damping profiles developed from geotechnical laboratory testing have been observed to be smaller than the damping inferred from the observed site amplification from downhole array recordings. This study investigates the high-frequency spectral decay parameter ( κ0) of earthquake motions from soil sites and evaluates the use of κ0 to constrain the small-strain damping profile for one-dimensional site response analysis. Using data from 51 sites from the Kiban-Kyoshin strong motion network (KiK-net) array in Japan and six sites from California, a relationship was developed between κ0 at the surface and both the 30-m time-averaged shear wave velocity ( V s30) and the depth to the 2.5 km/s shear wave velocity horizon ( Z2.5). This relationship demonstrates that κ0 increases with decreasing V s30 and increasing Z2.5. An approach is developed that uses this relationship to establish a target κ0 from which to constrain the small-strain damping profile used in one-dimensional site response analysis. This approach to develop κ0-consistent damping profiles for site response analysis is demonstrated through a recent site amplification study of Central and Eastern North America for the NGA-East project.

scholarly journals Stress-independent parameters for stress-strain relationship and damping in nonlinear one-dimensional seismic site response analysis

2021 ◽  
Vol 15 (1) ◽  
pp. 14-29
Author(s):  
Nghiem Manh Hien
Keyword(s):  
Finite Element ◽  
Site Response ◽  
Computer Code ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Ground Acceleration ◽  
Maximum Shear Strain ◽  
Seismic Site Response ◽  
Independent Parameters ◽  
Modulus Reduction

The modulus reduction and damping curves represent the nonlinear behavior of soil under cyclic load. In the literature, those curves were produced from lab tests of soil at particular confining stresses. This study developed a set of parameters that can be used to normalize the modulus reduction and damping curves to be stress-independent. The proposed formulations for the stress-independent parameters were implemented in the finite element code SRAP and validated through producing shear modulus reduction and damping curves that match the existed ones. Nonlinear 1D seismic site response analyses were conducted for centrifuge experiments to verify the developed computer code. Comparisons of the analysis results between SRAP and another computer code were presented in terms of maximum and minimum displacement, peak ground acceleration, maximum shear strain profiles, and response spectra. Keywords: backbone curve; hysteretic damping; dynamic soil model; stress-independent parameters; finite element method; nonlinear 1D seismic site response analysis.

The effect of soil nonlinearity on high-frequency spectral decay and implications for site response analysis

2021 ◽  
pp. 875529302098199
Author(s):  
Boqin Xu ◽  
Ellen M Rathje
Keyword(s):  
Shear Strain ◽  
High Frequency ◽  
Site Response ◽  
Small Strain ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Large Strains ◽  
Soil Nonlinearity ◽  
Equivalent Linear ◽  
Generate Surface

This study uses recorded ground motions at soil sites over a range of shaking intensities to investigate the effects of soil nonlinearity on the high-frequency spectral decay, as quantified by the parameter [Formula: see text]. Equivalent-linear site response analyses indicate that [Formula: see text] should increase significantly with increasing shear strain and ground motion intensity due to increases in soil damping. However, using more than 2500 motions from 32 sites, this study shows that [Formula: see text] does not vary systematically with the induced shear strain but instead remains at its small-strain value. This observation indicates that high-frequency components of motion are consistent with small-strain damping, rather than the strain-compatible damping used in site response analysis. It is demonstrated that equivalent-linear site response analyses for large strains can be modified to generate surface motions with more realistic high-frequency content by scaling the predicted surface motion to fit the small-strain [Formula: see text] or by employing frequency-dependent soil properties that account for the frequency dependence of the induced strains.

Simplified Model for Small-Strain Nonlinearity and Strength in 1D Seismic Site Response Analysis

2016 ◽  
Vol 142 (9) ◽  
pp. 04016042 ◽  
Author(s):  
David R. Groholski ◽  
Youssef M. A. Hashash ◽  
Byungmin Kim ◽  
Michael Musgrove ◽  
Joseph Harmon ◽  
...  
Keyword(s):  
Site Response ◽  
Small Strain ◽  
Simplified Model ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Seismic Site Response

scholarly journals Linear One-dimensional Site Response Analysis in the presence of stiffness-less free surface for certain power-law heterogeneities

2020 ◽  
Author(s):  
Joaquin Garcia-Suarez ◽  
Domniki Asimaki
Keyword(s):  
Free Surface ◽  
Power Law ◽  
Site Response ◽  
Small Strain ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Physical Explanation ◽  
One Dimensional ◽  
Soil Deposits ◽  
Heterogeneous Soil

We revisit previous results in small-strain One-dimensional Site Response Analysis of heterogeneous soil deposits. Specifically, we focus on sites whose shear modulus distribution is described by means of a power law that yields zero stiffness at the free surface. First, we show that in some cases (which we characterize in detail) considerations of energy finitude should prevail over considerations of vanishingtractions at the free-surface, as these may pose acuter constrains. We re-evaluate previous contributions in light of this result. Second, we analyze the previously-reported occurrence of “energy accumulation in upper layers”, providing a physical explanation for it. In passing, we supply estimates of the natural frequencies, and compare these with our previous results.

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