Contents lists available at ScienceDirect Computers and Geotechnics journal homepage: www.elsevier.com/locate/compgeo Research Paper Wave propagation and ground vibrations due to non-uniform cross-sections piles driving Omid Tavasoli a, ⁎ , Mahmoud Ghazavi b a Department of Civil Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran b Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran ARTICLE INFO Keywords: Field testing Pile driving Ground vibration Pile geometry Finite difference method ABSTRACT Piles are normally installed into the ground using appropriate hammers which cause different environmental problems such as noise, air pollution and ground vibration. In this paper, the ground vibrations due to the drivability of cylindrical, tapered and semi-tapered piles are investigated using field testing and numerical analysis and the results are compared and discussed. It is concluded that the application of non-uniform cross- section piles increase the driving process efficiency, reduce energy consumption and decrease the noise pollution by reducing the operation time. This, the application of tapered piles should be considered in practice from the viewpoint of allowable ground vibrations. 1. Introduction Despite the benefits of pile driving technique, this process has ser- ious environmental problems and disadvantages such as air and noise pollution and ground vibrations caused by hammer impacts. Other problems, for instance, the possibility of swelling, penetration or lateral displacement of surrounding soil occur during this process and three types of waves including spherical, cylindrical and superficial waves create in the ground due to hammer impacts [1]. Spherical waves propagate from the tip of the pile, while cylindrical waves move lat- erally from the shaft and surface waves reproduce through refraction of the waves at a critical distance from the pile in the ground [1,2]. When the hammer strikes the pile head, tension waves with a certain fre- quency and amplitude propagate in the pile and then release into the surrounding soil. The main effects of emission of these tension waves during pile driving are wave propagation in the pile, pile-soil interac- tion along the pile shaft and toe, wave propagation within the ground and dynamic soil-structure interaction due to dynamic response of ad- jacent foundations and the development of vibrations in structures. Dynamic effects of pile driving on surrounding medium depend on various factors including driving system and hammer specification, the pile geometry, pile materials, soil specifications, nearby structure types, soil-structure interaction, and the distance between the vibrating piles and nearby structures. One most important factor affecting the vibra- tions is the pile impedance which is directly related to the geometry and shape of the pile. Another important factor is the energy of driving hammer which always is known as an effective factor. However, there is ambiguity in defining this energy. Each hammer has a nominal energy which transfers to the pile-soil system and adjacent structures. The transferred energy ratio is defined as the energy transmitted through air, anvil, pile pad, hammer pad, and so on. The soil properties have important role in the amount of wave dissipation. Such properties affect damping characteristics which depend on the type of soil, grain size distribution, hardness, moisture content and temperature [2]. Analyses of uniform shaped piles during pile driving have been in- vestigated comprehensively in the literature (Smith [3]; Chow and Smith [4]; Coutinho et al. [5]; Mabsout and Tassoulas [6]; Mabsout et al. [7]; Ghazavi et al. [8]). Axial load-carrying characteristics of ta- pered piles have been studied in the literature by Wei and El-Naggar [9], static loads, harmonic vibrations and the kinematic response of such piles under earthquake loading was also evaluated by Ghazavi [10–12] and Ghazavi and Ahmadi [13,14], Rybnikov [15] and Sakr et al. [16] which reported that the tapered pile had a better perfor- mance than a cylindrical pile. The behavior of piles with varying sec- tions during driving was investigated by Ghazavi and Tavasoli [17], using pile-soil modeling by finite difference method, and concluded that the change in the geometry of the pile section has a direct effect on the rate of pile’s residual set and velocity. Tavasoli and Ghazavi [18] performed numerical analysis and real tests on the drivability of pre- casted cylindrical and tapered piles with open and closed-ended con- ditions. They reported that in closed or open-ended pile cases, the ta- pered pile had a final penetration more than a cylindrical pile, and https://doi.org/10.1016/j.compgeo.2018.08.010 Received 8 June 2018; Received in revised form 6 August 2018; Accepted 12 August 2018 ⁎ Corresponding author. E-mail address: o.tavasoli@iauet.ac.ir (O. Tavasoli). Computers and Geotechnics 104 (2018) 13–21 0266-352X/ © 2018 Elsevier Ltd. All rights reserved. T