Field performance of a peat railway subgrade reinforced with helical screw piles

Abstract

Rail tracks on peat subgrades can experience significant deflections, some of which have led to derailments. A potential ground stabilization strategy is to use screw piles to reduce rail displacements; however, limited research has been undertaken to investigate the effect of these piles and their performance under cyclic train loading. A field site was instrumented and monitored before and after screw pile installation. The piles were instrumented with strain gauges, piezometers were installed in the peat, and high-speed cameras were used to measure track and subgrade displacements. The load carried by each instrumented pile was approximately 50–60 kN 3 weeks after installation, but reduced to approximately 30 kN after 6 months. Although 1 year’s worth of piezometric data were collected before installation of the piles, it is difficult to conclusively attribute the changes in pore pressures to the piles, particularly because the piezometric data collected after the pile installation were only available for the 7 months that exhibit the period of greatest seasonal fluctuations. The track support system deformations showed no significant difference pre- and post-pile installation. Therefore, based on the monitoring data at this site, it appears that the designed transfer of load from the ties to the piles through arching within the ballast layer was not realized.

A Critical Review on the Performance of Pile-Supported Rail Embankments under Cyclic Loading: Numerical Modeling Approach

“…Due to the limited results available, no relationship could be established between the pile's orientation and the amount of axial load borne. On the basis of the monitoring data at this location, it appeared that the expected load transfer from the ties to the piles by arching within the ballast layer was not accomplished [121].…”

“…This research showed that it is possible to refine a pre-designed reinforcement solution and verify the feasibility and design approach of the piling technique using full-scale experimentation. Wheeler et al [121] evaluated the field performance of helical screw pile-supported peat railway subgrade located on the CN Rail Lévis subdivision in southeastern Quebec. The piles were mounted with strain gauges to determine the corresponding axial strains, piezometers were placed in the peat to monitor static and dynamic pore water pressures before and after installation of the piles, and track and subgrade displacements were measured using high-speed cameras before and after installation of the piles.…”

A review of the advancement of helical foundations from 1990- 2020 and the barriers to their expansion in developing countries

“…In another field study, Cannon conducted dynamic loading tests on helical piles of different sizes and lengths under different ground conditions [162]. Also, several recent works were conducted by Wheeler amount of rail displacement due to the passage of the train [213]. Elkasabgy and Naggar studied the effect of lateral vibration on helical piles in clay [217].…”

Bridge transition monitoring: Interpretation of track defects using digital image correlation and distributed fiber optic strain sensing

“…For example, Digital Image Correlation (DIC) techniques have been successfully applied to measure track displacements at the locations of high-quality subgrade, poor quality subgrade, and track transitions in order to gain an improved understanding of how the monitored tracks behaved. 4,13–17 Additionally, Rayleigh backscatter-based distributed fiber optic strain sensors have been successfully used to measure rail strains at a sampling rate and spatial resolution that permitted the calculation of rail stresses, rail deflection profiles, and rail seat forces for several consecutive sleepers. 18,19…”

“…More recently, DIC has been used in conjunction with a system of synchronized high-speed cameras to measure vertical displacements of rails, sleepers, and ballast, as well as longitudinal displacements of rails with sub-pixel accuracy. 15–17,21…”