Contents lists available at ScienceDirect Geotextiles and Geomembranes journal homepage: www.elsevier.com/locate/geotexmem Radial consolidation of PVD-Installed normally consolidated soil with discharge capacity reduction using large-strain theory Ba-Phu Nguyen, Yun-Tae Kim * Department of Ocean Engineering, Pukyong National University, Busan, 608-737, Republic of Korea ARTICLE INFO Keywords: Geosynthetics Discharge capacity Large-strain PVD-Installed deposit Radial consolidation Soil disturbance ABSTRACT The radial consolidation rate of prefabricated vertical drain (PVD)-installed soft deposits is known to be closely related to the PVD discharge capacity, which usually decreases during consolidation. Conventional solutions for radial consolidation of PVD-installed deposits have been developed to consider discharge capacity reduction using small-strain theory, in which the volume compressibility coefficient and soil permeability were assumed to be constant. This paper formulates a general expression for discharge capacity reduction with time in numerical analysis based on large-strain theory. Soil disturbance effects caused by PVD installation, such as a nonlinear distribution for radial hydraulic conductivity, are captured in the proposed solution. The proposed solution was applied to field data from a test embankment at Saga Airport. The proposed solution provides a good result which is close to the measured data. 1. Introduction To improve soft clay deposits, a prefabricated vertical drain (PVD) is frequently used to accelerate consolidation and increase shear strength (Hansbo, 1981; Kim and Lee, 1997; Chai et al., 2001; Li and Rowe, 2001; Shen et al., 2005; Rowe and Taechakumthorn, 2008; Chung et al., 2014; Lam et al., 2015; Jang et al., 2015; Kim et al., 2018a, 2018b; Nguyen et al., 2018). To reduce the time required for consolidation of thick soft deposits, PVDs are typically installed using a steel mandrel, thereby reducing the lengths of drainage paths. During consolidation of clay deposits, pore water flows horizontally toward the drain and the collected flow then moves vertically in the drain toward permeable drainage layers. Therefore, the effectiveness of PVD improvement method is closely related to PVD discharge capacity (q w )(Chai and Miura, 1999; Tran-Nguyen et al., 2010). Although PVD accelerates a consolidation rate, its discharge capacity usually decreases with con- solidation time as well as depth which results in delay of the con- solidation rate (Hansbo, 1983; Rixner et al., 1986; Miura and Chai, 2000; Aboshi et al., 2001; Chai et al. 2001, 2004; Bo, 2004; Chu et al., 2006; Deng et al., 2013, 2014; Indraratna et al., 2016). The reduction of discharge capacity of PVD is induced by many factors in field: squeezing of the filter sleeve into core channels, thus reducing channel cross-sectional areas; creep deformation of PVDs; clogging of drainage channels due to soil particles; folding of PVD when subjected to large strains. The reduction of discharge capacity is also investigated for other vertical drain improvement methods such as sand drains, stone columns, pervious concrete piles and permeable pipe piles. The dis- charge capacity of these approaches also reduced with time, being si- milar to PVDs (Suzuki and Yasuhara, 2007; Weber et al., 2010; Suleiman et al., 2014; Ni et al. 2017, 2018). Several analytical solutions have been developed to estimate the effects of discharge capacity reduction on consolidation. Chai et al. (1995) and Kim et al. (2018a) conducted the analytical solutions con- sidering the discharge capacity reductions with depth. Deng et al. (2013, 2014) provided a series of analytical solutions considering dis- charge capacity reductions over time and depth. Indraratna et al. (2016) provided a closed mathematical solution to consider discharge capacity reduction due to degradation of natural PVDs in highly acidic clay. Generally, all previous solutions considered discharge capacity reductions using small-strain theory; the volume compressibility coef- ficient and soil permeability were assumed to be constant. Recently, Lu et al. (2015) developed a simple analytical solution for nonlinear con- solidation of a vertical drain with coupled radial-vertical flow, in which well resistance effects were considered. However, PVD discharge ca- pacity reductions over consolidation were ignored. Although Kim et al. (2018a) used numerical analysis to consider discharge capacity varia- tion with depth, it remains difficult to formulate a general expression for discharge capacity during consolidation employing numerical ana- lysis. In addition to PVD discharge capacity reduction, soil disturbance https://doi.org/10.1016/j.geotexmem.2019.01.008 Received 2 August 2018; Received in revised form 28 December 2018; Accepted 30 December 2018 * Corresponding author. E-mail address: yuntkim@pknu.ac.kr (Y.-T. Kim). Geotextiles and Geomembranes 47 (2019) 243–254 0266-1144/ © 2019 Elsevier Ltd. All rights reserved. T