INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS Int. J. Numer. Anal. Meth. Geomech., 2003; 27:669–683 (DOI: 10.1002/nag.293) Simplified estimation of seismically induced settlements E. Vincens 1,n,y , P. Labb! e 2 and B. Cambou 1 1 MSGMGC, Ecole Centrale de Lyon, 36, Av Guy de Collongue, 69134 Ecully Cedex, France 2 International Atomic Energy Agency, Wagramerstr., 5, Wien 1400, Austria SUMMARY This paper proposes a predictive expression of settlements for a dry sand deposit overlying a bedrock and subjected to a seismic motion. The proposed formula combines geometrical and mechanical properties of the soil profile with classical characteristics of the input motion. One of the main concepts developed herein consists in regarding the input motion and the dynamical response as samples of random processes; another key concept consists in the common densification curve from Sawicki. The model introduces a parameter k identified by means of an extensive set of accelerograms. The main advantage of the proposed method consists in allowing fast comparisons of earthquake induced settlements for different soil and motion characteristics and therefore quantifying the damage power of a time-history input motion. Copyright # 2003 John Wiley & Sons, Ltd. KEY WORDS: sand; densification; cyclic behaviour; random process; response spectra; damage 1. INTRODUCTION The main causes of disorders are often related to changes in soil properties appearing in sandy soil deposits, due to a possible liquefaction (see knowledge obtained from the Kobe Earthquake, [1]). Nevertheless, these disturbances are not necessarily linked to water presence in the subsoil, and may occur in dry and loose sandy deposits [2–4]. In the latter case, settlements are only related to a granular rearrangement which tends to confer a more dense structure to the soil deposit. In the past, some authors have proposed methods to estimate the amount of seismically induced settlements in dry sands by using numerical methods [5] or suggesting simplified procedures [6–8]. These latter procedures differ not only from the way the input motion is treated but also from the rapidity of each process to provide the final amount of settlement: * Finn and Byrne [5] proposed a numerical method where the seismic input motion is a time history recording at the base of the soil profile. The in situ distortion field is computed using an equivalent linear elastic method. Within each layer, each half-cycle of strain response Received 13 November 2002 Revised 12 March 2003 Copyright # 2003 John Wiley & Sons, Ltd. y E-mail: eric.vincens@ec-lyon.fr, vincens@ec-lyon.fr n Correspondence to: E. Vincens, Ecole Centrale de Lyon, MSGMGC, 36 Av Guy de Collongue, 69134 Ecully Cedex, France.