Influence of length effect on embankment slope reliability in 3D

• Published in: International journal for numerical and analytical methods in geomechanics Vol. 42; no. 7; pp. 891 - 915
• Main Authors: Felix, Darve, Hicks, Michael A., Li, Yajun
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.05.2018
• Subjects: Clay; Clay soils; Computation; Embankments; Failure modes; Failure surface; Finite element method; finite elements; Height; Length; length effect; Predictions; Probability theory; random fields; Reliability; Shear strength; Slope; slope reliability; Slopes; Soil; Soils; Solutions; spatial variability; Variation
• ISSN: 0363-9061; 1096-9853
• DOI: 10.1002/nag.2766

Summary Embankment slopes composed of spatially variable soils have a variety of different failure modes that are affected by the correlation distances of the material properties and the geometry and total length of the slope. This paper examines the reliability of soil slopes for embankments of different length and uses parallel computing to analyse very long embankments (up to 100 times the embankment height) for a clay soil characterised by a spatially varying undrained shear strength. Based on a series of analyses using the 3D random finite element method (RFEM), it is first shown that the reliability of slopes of various length can be efficiently computed by combining simple probability theory with a detailed 3D RFEM analysis of a representative shorter slope of length 10 times the slope height. RFEM predictions of reliability indices for longer slopes are then compared with results obtained using Vanmarcke's (1977a) simplified 3D method and Calle's (1985) extended 2D approach. It is shown that these methods can give significantly different results, depending on the horizontal scale of fluctuation relative to the slope length, with RFEM predicting a lower slope reliability than the Vanmarcke and Calle solutions in all cases. The differences in the solutions are evaluated and attributed to differences in the assumed and computed failure surface geometries.