Seismic Analysis of Soil-Nailed Walls Using the Modified Pseudo-Dynamic Method

Determination of seismic response of geotechnical structures is important for safe design in a seismically active area. The dynamic behavior of geotechnical structures is complex, and therefore the use of different methods helps to understand this dynamic behavior. Numerical methods allow to well describe the complex dynamic behavior of geotechnical structures. However, the time-consuming, determination of several different parameters, radiation conditions, and difficulty in interpreting the results are the reasons for limiting the use of these methods in the technical community. The pseudo-static method is the most common method for analyzing seismic stability in geotechnical engineering. This method is independent of time and does not consider the dynamic nature of the earthquake load. Also, some soil parameters such as damping or compressive and shear wave velocity are not considered. To overcome these drawbacks, the pseudo-dynamic method was developed by Steedman and Zeng [1]. Sarangi and Ghosh [2] used the pseudo-dynamic method to determine the seismic stability of nailed vertical excavations in medium dense to dense sand. However, the boundary conditions are not included in the pseudo-dynamic method. Therefore, the pseudo-dynamic method has been modified again to satisfy the boundary conditions [3]. Recently, Kokane et al. [4] using the modified pseudo-dynamic method presented a solution for nail tensile force and inertial forces acting on failure wedges. However, the formulation used in this article is very difficult to develop. In this paper, the modified pseudo-dynamic method is used to analyze the seismic stability of nailing soil walls. Because the modified pseudo-dynamic formulation has been formulated to calculate the seismic pressure of a nail-free wall, the modified pseudo-dynamic formulation first is rewritten for the wall system with nail reinforcement, to calculate the seismic active pressure. Using pseudo-dynamic acceleration components derived by Belleza [3] and conducting an analytical process, the proposed formulation is obtained for the active seismic soil pressure coefficient and the safety factor corresponding to the general stability of soil-nailed walls. In the proposed formulation both Qh and Qv as horizontal and vertical inertial forces of the failure wedge are considered. Then, using the try and error iteration method, the critical angle of failure, seismic active pressure, and seismic safety factor are obtained. The main innovation of this study is to apply the modified pseudo-dynamical method for a nailed soil wall, however, as another innovation, seismic pressure on the wall is calculated taking into account the tensile force of the nails. It should be noted that in the available analytical methods, the seismic pressure of the wall has been calculated without regard to the nail tensile force. In the following, to validate and verify the proposed analytical method, a comparison between the presented analytical results with the results of the shaking table and the available analytical methods is carried out, which shows the high accuracy of the proposed method than other analytical methods. Finally, with a numerical example, a parametric study is carried out to verify the effect of various soil and nail parameters on the seismic stability of the nailed walls, and the coefficient of seismic active pressure. References 1. Steedman, R. and Zeng, X. (1990) The influence of phase on the calculation of pseudo-static earth pressure on a retaining wall. Geotechnique, 40(1), 103-112. 2. Sarangi, P. and Ghosh, P. (2016) Seismic analysis of nailed vertical excavation using pseudo-dynamic approach. Earthquake Engineering and Engineering Vibration, 15(4), 621-631. 3. Bellezza, I. (2015) Seismic active earth pressure on walls using a new pseudo-dynamic approach. Geotechnical and Geological Engineering, 33(4), 795-812. 4. Kokane, A.K., Sawant, V.A. and Sahoo, J.P. (2020) Seismic stability analysis of nailed vertical cut using modified pseudo-dynamic method. Soil Dynamics and Earthquake Engineering, 137, 106294.