Geomechanics and Engineering, Vol. 26, No. 4 (2021) 333-343 https://doi.org/10.12989/gae.2021.26.4.333 333 Copyright © 2021 Techno-Press, Ltd. http://www.techno-press.org/?journal=gae&subpage=7 ISSN: 2005-307X (Print), 2092-6219 (Online) 1. Introduction For construction of a structure on very thick saturated clay layers results into excess pore water pressure dissipation over long period of time. To accelerate the process of consolidation, vertical sand drains or prefabricated vertical drains (PVDs) can be installed at predetermined locations so that the water can drain out from the clay layer under superimposed load. Such observations were reported by Das (1985) and Smith and Smith (1998). Yoshikuni and Nakanodo (1974) included the effects of smear and well resistance for radial consolidation under static loading condition. Such theories were continued to be studied and improved by many researchers like Indraratna and Redana (2000), Walker and Indraratna (2006), Lu et al. (2011) and Zhang et al. (2019). These authors proposed radial consolidation models for static load incorporating parametric variations like variable discharge capacity, equal Corresponding author, Professor E-mail: sramendu@gmail.com a Assistant Professor E-mail: monideepapaul@gmail.com b Assistant Professor E-mail: bakshi.kaustav@gmail.com, Kaustav.bakshi@iiti.ac.in strain with resistance. The cohesive soil deposit below different civil engineering applications like highway, railway and runway embankments, ocean banks is subjected to rapid long-term cyclic loading [Yasuhara et al. (1995) and Samang et al. (2005)]. The consolidation theories developed for static loads predicted settlement for such soil deposit and the results differ significantly from the field measurements which indicate the requirement of consolidation studies under cyclic loads [Wilson and Elgohary (1974)]. The previous studies from Conte and Troncone (2006) and Ma et al. (2020) adopted low frequency cyclic loads but those were limited to one-dimensional consolidation along vertical direction only. Tang and Onitsuka (2000), Conte and Troncone (2009), Hsu and Liu (2013), Yazdani and Toufigh (2012), Deng et al. (2013), Kelly (2014), Amiri et al. (2018) studied consolidation through radial drainage by PVDs under linear time dependent loading considering well resistance and smear action. Zhu and Yin (2001), Leo (2004), Walker and Indraratna (2009) reported consolidation of soil along vertical and horizontal drainage under ramp load. Attya and Indraratna (2007), Indraratna et al. (2009, 2010 and 2016), Ni et al. (2014) conducted experimental investigation on cohesive soil and studied the pattern of pore water pressure generation under high frequency cyclic loading. Bai and Shi (2017) also reported experimental studies on consolidation behavior of saturated clay due to thermal loading cycles and observed significant volume reduction due to a series of heating – cooling cycles. An analytical model for radial consolidation prediction under cyclic loading Monideepa Paul 1a , Kaustav Bakshi 2b and Ramendu Bikas Sahu 3 1 Department of Civil Engineering, Heritage Institute of Technology, Kolkata-700107, India 2 Department of Civil Engineering, Indian Institute of Technology Indore, Madhya Pradesh 452020, India 3 Department of Civil Engineering, Jadavpur University, Kolkata- 700032, India (Received April 15, 2020, Revised May 17, 2021, Accepted August 4, 2021) Abstract. The excess pore pressure increases under undrained cyclic loading which cause decrease in effective stress followed by possible failure in the soft soil. With the inclusion of vertical drains radial drainage allows quick dissipation of excess pressure during cyclic loading and thereby failure of foundation soil may be avoided. The present study aims for analytical closed-form investigation on soft cohesive deposit under radial flow consolidation through vertical drains with no smear when subjected to long-term rapid cyclic loading. The mathematical formulation of pore pressure including degree of consolidation under cyclic loading is developed by using Green’s functions technique. Results obtained from the proposed formulation are in good agreement when compared with published field data which confirms its correctness to predict consolidation under cyclic loading. Once the proposed model is validated, it is applied to investigate the effect of vertical drains on variation of pore pressure ratio with number of loading cycles. The findings indicate that the pore water pressure generates slowly at the outermost boundaries of the vertical drains for initial number of loading cycles. The magnitude of pore water pressure accumulation increases and then dissipates for higher number of loading cycles. The variation of degree of consolidation for different frequencies of a unit cell of a prefabricated vertical drain is also furnished. Keywords: cyclic stress ratio; effective confining pressure; frequency; number of cycles; plasticity index; pore water pressure; radial consolidation