Geosynthetic-Reinforced Soil Structures for Railways: Twenty Five Year Experiences in Japan
F. Tatsuoka, M. Tateyama, J. Koseki and T. Yonezawa
ABSTRACT: Geosynthetic-reinforced soil retaining walls (GRS-RWs) have been constructed for a total length more than 135 km mainly for railways, including high-speed train lines. A full-height rigid (FHR) facing is constructed, firmly connected to the reinforcement layers, after a full-height wrapped-around GRS wall has been constructed and the major residual deformation of the backfill and supporting ground has taken place. A number of this type GRS RWs performed very well during the 1995 Kobe Earthquake and the 2011 Great East Japan Earthquake. The seismic design code has been revised to be prepared for such level seismic loads as experienced during the 1995 Kobe EQ. A number of conventional type RWs and embankments that collapsed during these and other earthquakes, heavy rains, floods and storm wave actions were reconstructed to this type GRS RWs. A couple of new bridge types comprising GRS structures have been developed. The latest version is GRS integral bridge, which comprises a continuous girder integrated to the top of the facings of a pair of GRS RWs without using bearings. The first prototype was constructed for a high-speed train in 2012 and three others were also constructed to restore bridges that fully collapsed by great tsunami during the 2011 Great East Japan EQ.
Enhancement of Rail Track Performance through Utilisation of Geosynthetic Inclusions
Buddhima Indraratna, Sanjay Nimbalkar, and Cholachat Rujikiatkamjorn
ABSTRACT: In coastal regions of Australia, high population density and increased traffic volumes have led to rapid expansion of rail transport. Use of artificial inclusions such as polymeric geosynthetics for enhanced soil-structure interaction and rubber shock mats for absorbing energy with the aim of reducing particle breakage is described in this paper as a cost-effective option. This paper highlights the results of a laboratory study on the deformation of coal fouled ballast stabilised with geogrids, at various degrees of fouling. A novel Track Process Simulation Apparatus (TPSA) was employed to reproduce realistic rail track conditions under cyclic loading, and the Void contaminant index (VCI) was used to assess the level of ballast fouling. The beneficial aspects of the geogrid inclusion are discussed in the paper. Laboratory results showed that biaxial geogrids can reduce the deformation of fresh ballast, but their effectiveness diminishes with an increase of VCI. A threshold value of VCI was proposed in view of track maintenance. Comprehensive field trials were executed on two fullscale rail tracks in the towns of Bulli and Singleton in New South Wales. These trials facilitated the evaluation of the relative performance of different types of geogrids, geocomposites and shock mats installed in fully instrumented track sections. Field trials showed that the use of recycled ballasted in rail tracks was a feasible and effective alternative. The performance of geogrids and geocomposite was found to be associated with their geometrical and mechanical properties as well as with the type of subgrade. The distributions of vertical and lateral stresses in the track were also assessed. In addition, effects of magnitude of axle load and train speed on stress distributions were studied.
KEYWORDS: Railway Tracks; Deformation; Degradation; Geosynthetics; Ballast; Fouling
Railway Track Transition Dynamics and Reinforcement Using Polyurethane GeoComposites
P. Woodward, O. Laghrouche and A. El-Kacimi
ABSTRACT: The change in railway track stiffness from ballasted track to a fixed track structure, such as concrete slab-track or a fixed bridge deck, can cause significant track geometry issues, particularly for high-speed and heavy haul. The change in track stiffness generates additional track forces at the ballast interface in an area that can be very difficult to maintain, due to the tamper’s inability to lift the track on the fixed geometry side. In this paper the transition problem is investigated using DART3D, a 3-dimensional finite element program that can simulate the train-track coupling behaviour over the transition. The application of a 3-dimensional polyurethane reinforcement technique is then presented as a designable means to control the ballast migration behaviour in the transition zone to reduce dy amic effects from problems like hanging sleepers. The paper then discusses the impact of using this type of ballast reinforcement through numerical simulation. Application of the technique at Tottenham Hale Junction UK is presented to illustrate the application of the system to real track transitions.
How to Overcome Geotechnical Challenges in Implementing High Speed Rail Systems in Australia
H. Khabbaz and B. Fatahi
ABSTRACT: Although there are a few medium speed rail systems in Australia, there is not a passenger rail transport with the high transit speed, seen in other countries. This paper firstly summarises lessons learnt from other countries, experienced high speed rail (HRS) for many years. Then, the challenges associated with implementing HSR systems in Australia are explained. The main challenges include selection and design of proper tracks, geographical issues, environmental concerns, economics and project costs and construction procedures. The second part of the paper presents the effective solutions to the geotechnical challenges associated with HSR systems. Various approaches are presented to improve the ballast layer properties and enhance the track formation bearing strength, stiffness, resiliency and dynamic properties. Employing concrete slab (ballast-less) tracks is also taken into consideration for HSR systems, and their performance is compared to ballasted tracks.
Maintenance Model for Railway Substructure
Ali Ebrahimi, James M. Tinjum, and Tuncer B. Edil
ABSTRACT: A maintenance model for railway substructure is proposed by combining a ballast deformation model presented in this study and a previously developed railway track subgrade model. This model is used to predict the deformation of railway track and to estimate a schedule for ballast maintenance and tamping. The prediction of the permanent deformation of fouled railway ballast is based on an empirical ballast deformation model and a statistical technique called “Support Vector Regression – SVR”. Both approaches are based on data obtained from a large-scale cyclic triaxial (LSCT) apparatus for the fouled ballast. The empirical deformation model of railway ballast incorporates the strong correlation between the plastic strain rate of ballast under cyclic loading with fouling and stress conditions (overall prediction R2=0.89). The concept of statistical learning regression (i.e., Support Vector Regression, SVR) was implemented to compare the predictions from the statistically based model with those from the empirical deformation model. The results show a strong correlation (R2=0.98) between the predicted and calculated rate of plastic strain of ballast by SVR. The maintenance planning model in this study was developed based on the empirical deformation model of ballast and predicts the intervals between corrective maintenance activities (e.g., tamping) and necessity for preventive maintenance activities (e.g., undercutting or drainage systems, etc.) in the railway track.
KEYWORDS: Railway Track, Maintenance, Ballast, Fouling, Statistical Method
Dynamic Behaviour of Railway Ballasted Track Structures in Shaking Table Tests and Seismic Resistant Performance Evaluation in Japan
T. Ishikawa, S. Miura and E. Sekine
ABSTRACT: This study presents an experimental, analytical and numerical studies to elucidate the dynamic response of ballasted track structures subjected to horizontal seismic motions. First, a series of shaking table tests for one-third small-scale model ballasted tracks was performed. As the results, it was revealed that the existence of grouted layer had a serious influence on the seismic performance of ballasted track structures. Next, numerical simulations of the shaking table tests were conducted with a newly proposed analytical procedure which utilizes FE analysis considering the cumulative strain characteristics of ballast. As the results, it was revealed that as the analytical procedure could roughly estimate the residual displacement of railroad ballast after seismic motions, it was effective to evaluate the seismic performance of ballasted track structures for practical use.
Mechanical Properties of Polyurethane-Stabilized Ballast
A. Keene, J.M. Tinjum and T.B. Edil
ABSTRACT: Ever increasing volume, tonnage, and speeds on rail systems are stressing rail substructure to levels never before evaluated or considered in depth. To improve maintenance techniques for problematic railway elements (e.g., bolted rail joints, intersections, bridge approaches), an in situ method involving ballast layer reinforcement with polyurethane is proposed. Ballast is a crucial material for structural support of the rail tracks. The structural integrity of highly fouled ballast (i.e., containing fine particles) can be compromised leading to track instability and ultimately train derailments. An application using polyurethane void filling and particle bonding technology has been developed and has the potential to mitigate impacts of ballast fouling, enhance rail freight capacity, and improve track-substructure maintenance efficiency. The purpose of this paper is to present the mechanical properties of Polyurethane-Stabilized Ballast (PSB) (e.g., compressive and flexural response), compare these properties to other materials commonly used in transportation infrastructure (e.g., natural aggregates, cement-stabilized soil), and address the suitability and compliance of PSB for use in track infrastructure. PSB has mechanical properties similar to cement-stabilized soil (i.e., displays flexural strength), but has much greater compressive strength than ballast, which is critical for stabilization of track substructure. Ease of injection and the negligible curing period for PSB makes it an attractive option for railway maintenance, especially for time-sensitive maintenance activities, such as intersections and bridge approaches.
Dependency of Cyclic Plastic Deformation Characteristics of Unsaturated Recycled Base Course Material on Principal Stress Axis Rotation
A. Inam, T. Ishikawa, and S. Miura
ABSTRACT: Nowadays, in order to economize the cost of pavements, recycled crusher-run (recycled concrete) that is recycled material is employed as base course material instead of natural crusher-run (andesite). Therefore, mechanical response of recycled crusher-run is required to evaluate in order to construct quality roads with minimum cost. In this research paper, an attempt is made to determine strength-deformation characteristics of unsaturated recycled crusher-run material, under various loading conditions and saturation degrees. In addition, cyclic plastic deformation behaviour of two types of materials that are natural crusher-run (andesite) and recycled crusher-run (recycled concrete) is compared and analysed. A series of laboratory element test were carried out by using multi-ring shear apparatus, which can take in to account the rotation of principal stress axis. The experimental results show that, cyclic plastic deformation considerably enhances due to the rotation of principal stress axis under repeated axial and shear loading tests. Moreover, cyclic plastic deformation of recycled crusher-run material increases to some extent when compared with natural crusher-run material under same experimental condition
Quickness Test Approach for Assessment of Flow Slide Potentials
V. Thakur and S. A. Degago
ABSTRACT: Sensitive clays are known to result in massive flow slides and thereby resulting in loss of human lives and damaging nearby transportation infrastructures. Flow behaviors of these clays are usually characterized by their undrained shear strength at their fully remolded state. Therefore, assessment of flow slides in sensitive clays is directly related to their remolded shear strength. In other words, the extent of flow slides is crucially influenced by the remolded shear strength of the sensitive clays. However, a seemingly small variation in remolded shear strength has significant alteration in the flow behavior of sensitive clays. This paper study this aspect using a novel and pragmatic test procedure referred to as the quickness tests. This test amplifies the smaller range of remolded shear strength in term of parameter called quickness. The test has an advantage of giving a better visualization about the behavior of sensitive clays. Based on relevant Norwegian landslides data, a quickness based criteria to asses the potential for occurrence of flow slides is proposed.
KEYWORDS: sensitive clays, landslides, flow slides, remolded shear strength, quickness
Cement Stabilization for Pavement Material in Thailand
S. Horpibulsuk, A. Chinkulkijniwat, A. Suddeepong, A. Neramitkornburee and C. Suksiripattanapong
ABSTRACT: Highway pavement generally consists of base and sub-base, which are constructed from suitable materials. When no suitable materials are available and it is expensive to bring the materials from distant sources, an alternative way which is widely practiced in Thailand is to stabilize the in-situ soil by cement. This method is economical and the engineering properties of the soil-cement mixture can be controlled. The strength and resistance to deformation increase with time. Two types of pavement material, widely used in Thailand, are lightweight cemented clay and pavement recycled material. The effects of water content, cement content, air content and curing time on engineering properties (unit weight, strength and compressibility) of lightweight cemented clay are illustrated. The equations to assess the engineering properties are presented. The equations facilitate the determination of cement content and air foam content to attain the target strength, unit weight and compressibility characteristics using a few trial data. The statistical analysis result of the field strength development of the pavement recycled materials is presented. Mixing process in this technique plays a minor role on the field strength reduction. Curing condition is a major role controlling the field strength development. For engineering and economic viewpoints, the satisfactory curing water is required after pavement stabilization.
KEYWORDS: lightweight cemented soil, pavement recycled material, cement stabilization, pavement material
Stone Columns Field Test: Monitoring Data and Numerical Analyses
Marcio Almeida, Bruno Lima, Mario Riccio, Holger Jud, Maria Cascão, Felipe Roza
ABSTRACT: This paper presents a case study of a field test performed on a set of 16 stone columns (4 × 4 square mesh, 1.85 m spacing, 1.0 m diameter, and 11.25 m length) loaded with iron rails applied during approximately one month. Extensive instrumentation comprising 28 instruments was used for monitoring the field test area. The objective of this study was to verify the performance of foundation improvements with stone columns for a future ore stockyard. The field test was also useful to calibrate a numerical model for predicting the behaviour of the permanent stockyard. Two- and three-dimensional finite element analyses were carried out and the results of field measurements and numerical calculations were compared. In general the numerical calculations of vertical and horizontal displacements reproduced the field measurements with satisfactory accuracy up to limit state conditions. Calculations of excess pore pressure and total horizontal stresses had less satisfactory agreement, and some reasons are provided for this. The yield of stone columns provided by 3D analysis appears to be more realistic than that provided by 2D analysis.
Numerical Analysis of Response of Geocell Confined Flexible Pavement
Ram Babu and G. L Sivakumar Babu
ABSTRACT: Geocell is one of the recent forms of reinforcing material that is increasingly used in applications in flexible pavements. In the present work, the benefit provided by geocell- reinforcement to the flexible pavement in terms of settlement as well as fatigue and rutting strains reductions are analysed. A simple composite model for geocell-reinforced soil is proposed to represent the three dimensional structure. To investigate the behaviour of geocell reinforcement in the flexible pavement, a series of numerical analyses are carried out to understand the effect of secant modulus of geocell material, aspect ratio, thickness of geocell-reinforced layer, and type of subgrade material and the results are presented in this paper. The results of the analysis are useful in development of guidelines for the design of flexible pavements in using geocells.
KEYWORDS: Geocell reinforcement, Composite model, Flexible pavements, Parametric study
