A comparison of numerical methods for multi-tied walls Paolo Carrubba *, Pietro Colonna Universita Á di Padova, Dipartimento di Ingegneria Idraulica, Marittima e Geotecnica, Via Ognissanti 39, 35129 Padova, Italy Received 28 April 1999; received in revised form 8 March 2000; accepted 17 March 2000 Abstract Simpli®ed and analytical approaches are currently used in the analysis of multi-propped walls; the former assume the soil to be everywhere at failure, whereas the latter take into account soil±structure interaction. The aim of the paper is to compare the results obtained by methods of analysis with increasing degree of complexity: comparisons between equivalent reaction, subgrade reaction and full ®nite element analysis are shown for multi-tied dia- phragm walls in dry sand. Soil parameters were assumed constant in the analysis, while wall geometry, wall stiness and anchors prestressing were varied according to current retaining wall practice. Results of analysis show that, if a proper selection of geotechnical data is made, simpli®ed and analytical approaches give comparable values for wall embedment, maximum bending moment and anchor load. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Multi-tied wall; Dray sand; Simpli®ed methods; Numerical methods 1. Introduction The use of multi-propped walls has become increasingly widespread for temporary and permanent support of vertical excavations, especially when horizontal displace- ments must be prevented. A wide range of technologies is currently available for braced or tieback walls; however, when deep excavations are involved, a continuous wall is generally cast in situ in its ®nal dimension before excavation is carried out (slurry-trench, tangent-pile, secant-pile); the wall is subsequently propped during the excavation stages with struts or ground anchors. If props are closely spaced, the bending moment decreases and steel beams can be used. Computers and Geotechnics 27 (2000) 117±140 www.elsevier.com/locate/compgeo 0266-352X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0266-352X(00)00007-0 * Corresponding author. Tel.: +39-049-827-7907; fax: +39-049-827-7988. E-mail address: carrubba@geomar.ing.unipd.it (P. Carrubba).