Contents lists available at ScienceDirect Computers and Geotechnics journal homepage: www.elsevier.com/locate/compgeo Research Paper Effects of scour-hole dimensions on lateral behavior of piles in sands Yunjie Lin, Cheng Lin ⁎ Department of Civil Engineering, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 Canada ARTICLE INFO Keywords: Pile lateral behavior Local scour Sands Modified p-y curve method FE analyses ABSTRACT Scour is a process of soil erosion around foundations caused by currents and waves, which can severely com- promise the performance of the foundations. The scour process forms a scour hole around the foundation. The existence of the scour hole has been considered by many design standards for pile foundations such as those from the US Federal Highway Administration (FHWA) and American Petroleum Institute (API). However, these standards recommend different procedures to evaluate lateral responses of piles subjected to local scour that forms three dimensions of scour hole. This paper presents a series of three-dimensional finite element (FE) parametric analyses to examine the feasibility of the standard methods (FHWA and API) as well as an analytical solution proposed by the authors through varying scour-hole dimensions, soil properties, and pile properties. The results showed that the analytical solution provided conservative results while the standard methods provided mixed results compared with the FE analyses. The loss of pile lateral capacity due to scour was more significant in dense sands than in loose sands (approximately 10% more). For a given relative scour depth, the increase in pile diameter increased the scour-induced loss of pile lateral capacity. 1. Introduction Scour is a process of removing soils around foundations by currents and waves, which is a major cause of failures of many water-related infrastructures such as bridges and marine structures. The damage of scour is most severe in the extreme weather events such as floods, storm surges, and hurricanes. Therefore, evaluation of vulnerability of bridges and marine structures to scour is always associated with the floods and hurricanes [1]. The scour-induced failures are predominantly due to the loss of soil supports to the foundations and the deterioration of foun- dation elements, which cause the reduced foundation capacity, parti- cularly the lateral capacity. This is because the lateral capacity is mainly dependent on the soils at shallow depths which are easily scoured away. Scour at pile foundations generally consists of general scour (ero- sion across the riverbed or seabed) and local scour (development of a scour hole around the foundation). In general design practices for es- timation of pile capacities, local scour is often simplified as general scour (i.e., removing the entire soil layer across the river channel to the maximum local scour depth). Although such a design practice is simple, it is too conservative and thus unnecessarily expensive [2]. In recent years, the importance of scour-hole dimensions for pile capacities has been increasingly recognized. For example, a number of studies in- cluding three-dimensional (3D) numerical simulations and centrifuge tests have been conducted to evaluate the effect of scour-hole dimen- sions on lateral behavior of piles [2–6]. However, the 3D numerical simulations and centrifuge model tests are relatively complicated and time-consuming and thus are not widely used in routine engineering design. A more practical way to consider scour-hole dimensions in calcu- lation of pile lateral behavior is the use of modified p-y curve methods [6–9], which will be discussed in more detail. One of these methods includes estimating the changes in vertical effective stress around the piles due to local scour and then incorporating the estimated stress changes to modify the existing p-y curves. In this method, the calcula- tion of vertical effective stress around piles after scour is essential. The methods to calculate vertical effective stress around piles are available in the US Federal Highway Administration (FHWA) design methods for drilled shafts (denoted as FHWA-DS) and driven piles (denoted as FHWA-DP), and the American Petroleum Institute Geotechnical and Foundation Design Considerations (denoted as API) [10–12]. However, these standard methods (i.e., FHWA-DS, FHWA-DP, and API) vary considerably in terms of the calculation of vertical effective stress sur- rounding piles, which therefore result in appreciable difference in cal- culated pile lateral responses [8]. Moreover, these methods are ap- plicable to only a certain range of scour-hole dimensions. Realizing the limitations inherent in the standard methods, the authors [8,13] de- veloped an analytical solution for estimation of vertical effective stress https://doi.org/10.1016/j.compgeo.2019.02.028 Received 26 November 2018; Received in revised form 21 February 2019; Accepted 26 February 2019 ⁎ Corresponding author. E-mail address: chenglin918@uvic.ca (C. Lin). Computers and Geotechnics 111 (2019) 30–41 0266-352X/ © 2019 Elsevier Ltd. All rights reserved. T