Adjustment of spectral pseudo-static approach to account for soil plasticity and zone seismicity

The concept of the spectral pseudo-static procedure has been developed at the Université de Sherbrooke as an alternative to the conventional pseudo-static approach for the seismic stability analysis of clayey slopes. The destabilizing effect of an earthquake is approximated, in the new approach, by an inertial force that hyperbolically varies with depth while being proportional to the maximum acceleration of the seismic event. Its results have been rigorously verified against available static and dynamic laboratory tests, and have been extensively validated by a series of simulations performed using the computer code FLAC. Good agreements have been achieved between the results of the spectral pseudo-static procedure and complete numerical analyses, in terms of the computed safety factors and the critical slip surfaces. This implies that the spectral pseudo-static approach can be integrated into available limit equilibrium (LE) software providing a useful tool to examine the effect of dynamic soil characteristics on the proposed seismic coefficient profiles. The herein-reported study extends the previous endeavors to examine and quantify the effect of plasticity index (PI) (0%, 15%, 30%, 50%, and 100%) on the proposed formula of seismic coefficient profile using the same numerical modelling and assumptions. Original analyses were carried out considering earthquakes compatible with the seismicity of Quebec City (zone 4), and they have been repeated in the current study for earthquakes compatible with other regions having different seismicity (zones 2, 3, and 5). Based on the results of the current analyses, side-formulas were established between the spectral pseudo-static coefficient on ground surface for any value of soil plasticity index (PI) and the corresponding coefficient originally used in the main formula (PI = 30%).

[1]  C. Hsein Juang,et al.  Normalized Shear Modulus and Material Damping Ratio Relationships , 2005 .

[2]  Xiangwu Zeng,et al.  The influence of phase on the calculation of pseudo-static earth pressure on a retaining wall , 1990 .

[3]  E. Cascone,et al.  Coupling of topographic and stratigraphic effects on seismic response of slopes through 2D linear and equivalent linear analyses , 2014 .

[4]  Farshid Vahedifard,et al.  Evaluation of simplified methods for predicting earthquake-induced slope displacements in earth dams and embankments , 2013 .

[5]  J. Bray,et al.  Pseudostatic Coefficient for Use in Simplified Seismic Slope Stability Evaluation , 2009 .

[6]  G. Magiera,et al.  A sensitivity study of seismic structure-soil-structure interaction problems for nuclear power plants , 1982 .

[7]  Behzad Fatahi,et al.  Fully Nonlinear versus Equivalent Linear Computation Method for Seismic Analysis of Midrise Buildings on Soft Soils , 2014 .

[8]  G. Atkinson.  Earthquake time histories compatible with the 2005 National building code of Canada uniform hazard spectrum , 2009 .

[9]  J. Locat,et al.  Corrélations entre des propriétés mécaniques dynamiques et statiques de sols argileux intacts et traités à la chaux , 1987 .

[10]  Roberto Paolucci,et al.  A macro‐element model for non‐linear soil–shallow foundation–structure interaction under seismic loads: theoretical development and experimental validation on large scale tests , 2012 .

[11]  Mahmoud N. Hussien,et al.  Framework to assess pseudo-static approach for seismic stability of clayey slopes , 2018, Canadian Geotechnical Journal.

[12]  R. Dobry,et al.  Effect of Soil Plasticity on Cyclic Response , 1991 .

[13]  Juan M. Mayoral,et al.  Seismic response of high plasticity clays during extreme events , 2015 .