Ballast Mechanical Performance with and without Under Sleeper Pads
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-2043-5
Geotechnical Engineering
Ballast Mechanical Performance with and without Under Sleeper Pads Yunlong Guo
a
, Jianxi Wang
b
, Valeri Markine
a
, and Guoqing Jing
c
a
Section of Railway Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2628CN, Netherlands School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China c School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China b
ARTICLE HISTORY
ABSTRACT
Received 12 November 2019 Revised 20 April 2020 Accepted 28 June 2020 Published Online 15 September 2020
With the train speed and axle load increasing, excessive stresses are produced and transmitted to the ballast layer, inducing rapid ballast degradation. To solve this issue, the under sleeper pads (USPs) have been widely applied between sleepers and ballast particles as the elastic layer. In this research, laboratory tests using half-sleeper track were carried out to study the ballast bed performance with or without the USPs under static and cyclic loading. Results show that applying the USPs reduces the track stiffness and can decrease the settlement. However, installing the USPs increases the ballast bed acceleration and the sleeper vertical acceleration. The contact areas of sleeper-ballast with USPs are over 5 times as those without USPs. The USPs assist reducing ballast degradation mainly by avoiding the ballast particle breakage at the sleeper-ballast interface and can increase the stress distribution at the longitudinal direction.
KEYWORDS Ballast USPs Cyclic loading Settlement Breakage
1. Introduction The increasing train speed and axle load lead to the several degradation and deformation of ballasted tracks. It is already known that the track settlement is significantly affected by ballast degradation (Li et al., 2002; Guo et al., 2019b). Consequently, mitigating ballast degradation is urgent and necessary not only for improving the track capacity and performance but also for reducing maintenance costs and increasing track service time (Xiao et al., 2017). Recently, the geo-inclusions have been successfully applied in ballasted tracks, such as polyurethane, geogrid and geocell (Indraratna et al., 2013; Indraratna et al., 2018; Jing et al., 2019). The main purpose of applying these geo-inclusions is to improve performance and reduce degradation of the ballast layer by restricting the ballast relative movements. Additionally, it has been demonstrated that these geomaterials are able to enhance track stability (lateral and longitudinal sleeper resistance) and decrease the plastic deformation (Indraratna et al., 2014; Chen et al., 2015; Qian et al., 2015; Jing et al., 2018). However, maintenance and material costs are the main concerns when applying these materials.
CORRESPONDENCE Guoqing Jing
[email protected]
ⓒ 2020 Korean Society of Civil Engineers
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