Inﬂuence of non-breaking wave force on seismic stability of seawall for passive condition B. Giridhar Rajesh, Deepankar Choudhury n Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India article info Article history: Received 29 August 2014 Accepted 15 January 2016 Available online 2 February 2016 Keywords: Seawall Factor of safety Sliding Overturning Non-breaking wave abstract Proper design of seawall in earthquake prone region is one of the major concerns in geotechnical earthquake engineering. This paper presents the stability analysis of seawall under the combined action of earthquake forces, non-breaking wave force, hydrostatic and hydrodynamic forces and uplift force. Stability of seawall is assessed in terms of its factor of safety against landward sliding and landward overturning modes of failures. Seismic passive earth resistance has been calculated using pseudo-static approach. A detailed parametric study has been conducted to study the effect of non-breaking wave height, depth of water on seaward and land ward sides, soil and wall friction angles, and horizontal and vertical seismic accelerations. The factor of safety against overturning mode of failure decreases by about 52%, for a change in the ratio of non-breaking wave height to the depth of water on seaward side from 0 to 0.60. Present study shows that the seismic stability of seawall is more sensitive to non-breaking wave height, soil friction angle, wall friction angle and horizontal seismic acceleration. Proposed closed- form solutions and design charts can be used for the seismic design of seawall for passive case under the combined action of earthquake and non-breaking wave forces. & 2016 Elsevier Ltd. All rights reserved. 1. Introduction Gravity type seawalls are the most common type of construc- tion used to defend shoreline against wave attack. Poor perfor- mance of the many seawalls can be noticed from the past major earthquakes like Loma Prieta in 1989, Northridge in 1994, Kobe in 1995, Bhuj in 2001, South Asian Sumatra in 2004 and Tohoku in 2011 (Werner, 1998; Dakoulas and Gazetas, 2008; Sheth et al., 2006; Cilingir et al., 2011; Kang et al., 2014). The movement of a seawall can be either seaward side or landward side depending on various factors such as the weight of the seawall, the combination of forces acting on the seawall and the strength of the backﬁll and foundation soil (Ghalandarzadeh et al., 1998; Dakoulas and Gaze- tas, 2008). The present study deals with the landward movement of seawall during the earthquake which has not been received much attention so far. Two seawalls of Kobe port during the 1995 earthquake had experienced similar mode of failure (Gha- landarzadeh et al., 1998; PIANC, 2001). Landward overturning of seawall due to 1993 Hokkaido Nansei-Oki earthquake tsunami has been reported by Shuto and Matsutomi (1995). The seawall on the Ryoishi coast, Iwate Prefecture has also failed by landward over- turning due to the 2011 Great East Japan Earthquake and Tsunami (Kato et al., 2012). In the normal conditions, i.e., when there is no earthquake, seawalls will be continuously experiencing wave for- ces which are time varying in nature. When these waves overtop the seawall, they might cause lee ward scour leading to loss of passive resistance from the backﬁll. This in turn with wave forces on the seaward side might cause landward movement of the seawall (USACE, 2005). So, seawall must be designed to be safe against landward movement as well. The wave forces acting on seawalls can be divided into non-breaking wave forces, breaking wave forces and broken wave forces. This paper focuses on the stability of seawall under the inﬂuence of non-breaking wave force in succession with earthquake forces. Seawall will be subjected to a non-breaking wave force when the depth of water at the wall is greater than 1.5 times the maximum design wave height. Most of the seawalls support the submerged backﬁll, in such cases an extra hydrodynamic pressure will be generated during the seismic event in addition to the lateral earth pressure on landward side and the hydrodynamic pressure from water on the seaward side. Due to the complications of the combination of these forces acting simultaneously, the design of seawall becomes challenging to the geotechnical engineers. In the present study, seismic design of gravity type seawall subjected to the combined action of earth- quake forces, non-breaking wave force, hydrostatic and hydro- dynamic forces and uplift force using the pseudo-static method is presented. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/oceaneng Ocean Engineering http://dx.doi.org/10.1016/j.oceaneng.2016.01.006 0029-8018/& 2016 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ91 22 2576 7335/8335; Fax: þ91 22 2576 7302. E-mail addresses: bgrajesh@iitb.ac.in (B. Giridhar Rajesh), dc@civil.iitb.ac.in, dchoudhury@iitb.ac.in (D. Choudhury). Ocean Engineering 114 (2016) 47–57