اثر مرزی بر پاسخ لرزه ای یک شیب خاک سه بعدی با بنیاد فونداسیون سطحی در بالا Boundary Effect on the Seismic Response of a Three-dimensional Soil Slope with a Shallow Foundation on Top

1. Introduction Seismic failure of slopes and geotechnical structures (e.g., shallow foundations, retaining walls, bored piles, sheet pile walls, tunnel cut-and-cover walls, tunnel linings) has been a major cause of human and material losses and has also been the subject of much research (Bouckovalas and Papadimitriou, 2005; Azizian and Popescu, 2006; Kourkoulis et al., 2010; Taiebat et al., 2011; Tripe et al., 2013; Azzam, 2015; Karimi and Dashti, 2015; Liu et al., 2015). In some cases, geotechnical structures are constructed adjacent to an earth dike or sloping surface such as footings for bridge abutments near river dikes on sloping embankments (Kourkoulis et al., 2010; Azzam, 2015). Excessive permanent deformation of shallow foundations on top of slopes under earthquake loading has been widely observed (Choudhury and Subba, 2006; Kourkoulis et al., 2010; Azzam, 2015). Numerous experimental studies on the seismic behavior of a shallow foundation on a level ground have been performed, including shake-table experiments (Maugeri et al., 2000; Paolucci et al., 2008; Shirato et al., 2008; Drosos et al., 2012; Karimi and Dashti, 2015) and centrifuge tests (Gajan et al., 2005; Bienen et al., 2007; Gajan and Kutter, 2009; Raychowdhury and Hutchinson, 2009; Deng and Kutter, 2012; Trombetta et al., 2013). Up to now, very few studies have been conducted on the dynamic behavior of a shallow foundation on top of a slope. Compared to a physical experiment, the Finite Element (FE) method is a less expensive and less time-consuming way, and offers the advantage of conveniently simulating more influencing factors. In this environment, a number of seismic behaviors of shallow foundations resting on top of slopes have been adequately analyzed via the FE method (Choudhury and Subba, 2006; Kourkoulis et al., 2010; Azzam, 2015). The seismic response problems in geotechnical earthquake engineering practices involve boundary values. Therefore, boundary conditions can play an important role in the development of internal stresses on the soil slope and can affect the seismic bearing capacity of the shallow foundation. Literatures about the boundary effects on the dynamic characteristics of a soil slope as well as a shallow foundation founded near 3D slop crests are few. In the following sections, the numerical framework for simulating the seismic response of a 3D soil slope and the dynamic settlement of a shallow foundation on top of the slope are described. Emphasis is placed on the boundary effect on the seismic slope response, and then the boundary effect on the seismic settlement of the shallow foundation is discussed. Finally, insights and conclusions are drawn based on the reported results.