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

Vol. 42 No. 3 September 2011

Building Damage Assessment for Deep Excavations in Singapore and the Influence of Building Stiffness

K.H. Goh and R.J. Mair

ABSTRACT: One of the biggest issues for underground construction in a densely built-up urban environment is the potentially adverse impact on buildings adjacent to deep excavations. In Singapore, a building damage assessment is usually carried out using a three-staged approach to assess the risk of damage caused by major underground construction projects. However, the tensile strains used for assessing the risk of building damage are often derived using deflection ratios and horizontal strains under ‘greenfield’ conditions. This ignores the effects of building stiffness and in many cases may be conservative. This paper presents some findings from a study on the response of buildings to deep excavations. Firstly, the paper discusses the settlement response of an actual building – the Singapore Art Museum – adjacent to a deep excavation. By comparing the monitored building settlement with the adjacent ground settlement markers, the influence of building stiffness in modifying the response to excavation-induced settlements is observed. Using the finite element method, a numerical study on the building response to movements induced by deep excavations found a consistent relationship between the building modification factor and a newly defined relative bending stiffness of the building. This relationship can be used as a design guidance to estimate the deflection ratio in a building from the greenfield condition. By comparing the case study results with the design guidance developed from finite element analysis, this paper presents some important characteristics of the influence of building stiffness on building damages for deep excavations.

KEYWORDS: Building Damage Assessment, Deep Excavations in Singapore, Building Stiffness

DOI: 10.14456/seagj.2011.10

Vol. 42 No. 3 September 2011

Concept and Design Methodology of Redundancy in Braced Excavation and Case Histories

G. Zheng, X.S. Cheng, Y. Diao, and H.X. Wang

ABSTRACT: The conventional design methodology of deep excavation retaining structure generally proceeds elements by elements, consequently, the retaining structures are/may be lack of redundancy. This could lead to catastrophic collapse of retaining system. It is necessary to introduce the concept of redundancy into the design of retaining structure and develop the design methodology based on redundancy. In this paper, redundancy of deep excavation retaining structure is classified into five aspects. Necessity and importance of each aspect are explained. A method to evaluate and quantify the retaining structure redundancy is presented through the analysis of an example. Two typical case histories are studied to reveal the redundancy problems that may exist. Finally, a series of measures are proposed to increase the redundancy of deep excavation retaining structure.

KEYWORDS: Concept and Design Methodology, Redundancy, Braced Excavations

DOI: 10.14456/seagj.2011.11

Vol. 42 No. 3 September 2011

Three-Dimensional Deformation Behavior of an Over-sized Excavation in Shanghai Clay

ABSTRACT: In this paper, a case study regarding the excavation of the largest excavation in Shanghai soft clays (Zhongsheng Shopping Mall) is investigated through field studies and numerical modelling. To reduce the excavation induced deformation and construction time, a combination of excavation support schemes, the central part by bottom-up method and the peripheral part by top-down method, is used in this construction project. Extensive field performance data, including wall deflections and ground surface settlements, were collected. Construction sequences are summarized and correlated with the measured data. Three-dimensional effective stress elasto-plastic finite element analysis is conducted to examine the wall deflections and ground surface movements. A comprehensive comparison with the field observations has demonstrated the capacity of numerical models for the predictions of wall deflections and ground surface settlements. Numerical studies indicate that both the wall deflection and ground surface settlement are affected by the excavation corner as well as the length and the shape of the wall. Parametric studies of two construction sequences reveal that the deformations of the wall and soil are larger due to the circumstance that some supports are not installed in time during excavation. Zone excavation exerts a slight effect on the wall deflection for the wall panels near the centers of the excavated zones, but causes less wall deflection for the wall panels near the corners of the excavated zones.

Keywords: Over-sized excavation, combined method, deformation, three-dimensional, finite element analysis

DOI: 10.14456/seagj.2011.11

Vol. 42 No. 3 September 2011

Numerical Study on the Movement of Existing Tunnel Due to Deep Excavation in Shanghai

J. J. Chen, J. H. Wang, G. W. Xiang, S. L. Wen, and Y. Du

ABSTRACT: Adjacent excavation can have significant impact on the stress and deformation of existing tunnels. Several construction techniques have been proposed to reduce the movement of a metro tunnel due to two adjacent excavations in Shanghai. To evaluate the effectiveness of these different methods, the interactive impact of the two adjacent excavations on the crossing tunnel is studied numerically in this paper. The 2D FEM numerical analysis uses the Cam-clay model to simulate the behaviour of soft clay and considers the nonlinear performance of the soil-wall interface and the excavation sequences. The analysis investigates the influence of various factors, including the excavation procedure, installation of resistance piles, and relationship between the tunnel and the retaining wall of excavation. The results show that the crossing tunnel heaves during excavations because the distance between the two adjacent excavations is very small and the diaphragm walls for the original tunnel are used as the retaining structure of the new excavations. This predicted trend is verified by field measurements. The parametric study shows that dividing the whole dividing the whole excavation into several pit excavations and installing resistance piles tied to the tunnel can decrease the vertical displacement of the tunnel effectively.

KEYWORDS: Numerical Study, Movement, Existing Tunnel, Deep Excavation, Shanghai

DOI: 10.14456/seagj.2011.12

Vol. 42 No. 3 September 2011

Observed Performance of Diaphragm Wall Construction

C.Y. Ou and L.L. Yang

ABSTRACT: This study presents the behavior of ground movement induced by the construction of diaphragm wall based on the results of full-scale field tests or panel tests in the construction of the Taipei mass rapid transit system. Two typical test results are presented to understand the general characteristics of ground movement induced by the construction of one wall panel and multiple wall panels. Moreover, the panel test results from the other contracts are also summarized. Results show that the ground settlements after the completion of the whole diaphragm wall construction were much larger than those measured from panel tests because ground movement during the “normal” construction was heavily affected by construction factors. Use of panel test results to evaluate ground settlements might result in a misleading conclusion. Use of the envelope, as established in this study, was a rational way to evaluate ground settlements at the present stage. Besides, the maximum ground settlement of panel tests occurred was about 0.05~0.07 times the trench depth (D) percent and the primary settlement influence zone fell within a normal distance of 0.6D from the panel. The maximum ground settlement after the completion of the whole diaphragm wall construction was about 0.13D(%). The ground settlement beyond 1.5D ~ 2D was found to be insignificant.

KEYWORDS: Observed Performance, Diaphragm Wall Construction

DOI: 10.14456/seagj.2011.13

Vol. 42 No. 3 September 2011

Performance of Construction with New Pneumatic Caisson Method in Shanghai Soft Ground

F.L. Peng and H.L. Wang

ABSTRACT: In the new pneumatic caisson method (NPC), soil excavation and removal is completed remotely by workers on the ground. In 2007, this method was successfully applied in a tunnel shaft in Shanghai. Combined with the construction example, field monitoring and measuring has been conducted. Typical monitored results, such as the working pressure, lateral earth pressure, reaction pressure, and ground movements, were presented and analyzed. In addition, a numerical approach considering the soil disturbance during construction was proposed to predict the soil movements induced by the NPC construction. It was successfully implemented in the three-dimensional finite element method (FEM) codes. Calculated soil movements were examined and verified by the field measurements. In the meantime, these results were compared with the ones obtained from the two-dimensional approach proposed by the authors in the previous study. Results showed that, they agreed well with each other, and in general the three-dimensional analysis results approached the actual situation more closely.

KEYWORDS: Performance of Construction, New Pneumatic Caisson Method, Shanghai Soft Ground

DOI: 10.14456/seagj.2011.14

Vol. 42 No. 3 September 2011

Technologies of Micro-disturbance Construction of Pipe-Jacking

W. Q. Ding, B. Li, S. L. Yuan and J. K. Ge

ABSTRACT: As a mature subsurface excavation method, pipe-jacking has already been widely used in many fields of city construction. The fact that the construction environment becomes more and more complicated requires micro-disturbance pipe-jacking. Combining the successful micro-disturbance construction of the pipe-jacking part of Shanghai Expo Power Cable Tunnel, some methods such as the preparations before construction, disturbance controlling during different construction phases and many specific construction technologies are summarized. During pipe jacking, a lot of measures like keeping the stabilization of the excavation surface, controlling the pipe jacking speed, adopting new sludge lubricating sleeve technologies, achieving precise attitude control and conducting timely slurry replacement. It is hoped that this will be helpful to the later micro-disturbance pipe-jacking.

KEYWORDS: Micro-Disturbance Construction, Pipe-Jacking

DOI: 10.14456/seagj.2011.15

Vol. 42 No. 3 September 2011

Design and Construction of InJe Tunnel, the Longest Road Tunnel of Korea

S. M. Cho, S. D. Lee, and Y. J. Kwon

ABSTRACT: Inje Tunnel, an 11 km-long twin-tunnel will be the longest road tunnel of Korea. Two parallel tunnels including two vertical shafts and one inclined shaft are under construction. Details of the tunnel design including geotechnical characteristics, cross-section of the excavation, reinforcement, drainage, ventilation operation, safety facility corresponding with a tunnel fire, and portal planning are introduced. Various analyses that systematically make comprehensive utilization of available data obtained from geotechnical investigations were applied for the optimal evaluation of ground conditions. The typical NATM excavation scheme by a combination of drilling, blasting and reinforcement has been undertaken. Steel-fiber mixed shotcrete, steel rib with Lattice girder, and rock bolt were designed for the reinforcement. Ventilation plan using the inclined shaft and vertical shafts are summarized considering traffic conditions and emergency situations. Current construction procedures are also briefly described.

KEYWORDS: Design and Construction, InJe Tunnel, the Longest Road Tunnel, Korea

DOI: 10.14456/seagj.2011.16

Vol. 45 No.1 March 2014

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.

KEYWORDS: Geosynthetic-Reinforced Soil Structures, Railways, Twenty Five Year Experiences, Japan

DOI: 10.14456/seagj.2014.40