The first International Symposium on Geotechnical Engineering for High-speed Transportation Infrastructure (IS-GeoTrans) will be hosted in Hangzhou between October 26 to 28, 2012, to provide a platform for international exchange of expertise. The theme of IS-GeoTrans 2012 is Safe and comfortable high-speed transportation infrastructure. It intends to provide a venture to discuss the challenges and critical issues in the development and maintenance of high speed transportation infrastructure. The goal is to catalyze the advancement in geotechnology and to prompt scholarly exchange.

In this paper, both measurements and numerical simulations of railway induced vibration are discussed. A measurement campaign has been carried out along the high-speed railway track in Lincent, Belgium. The experimental determination of transfer functions and vibration velocity during train passages are discussed. A numerical model is introduced to predict the transfer functions and the vibration velocity during train passages. The comparison of experimental and numerical results demonstrates the importance of accurate numerical models and input data. The results are obtained in the framework of the development of a hybrid prediction method, where numerical and experimental data can be combined to improve the prediction accuracy for railway induced vibration.

Railway transitions experience differential movements due to differences in track system stiffness, track damping characteristics, foundation type, ballast settlement from fouling and/or degradation, as well as fill and subgrade settlement. This differential movement is especially problematic for high speed rail infrastructure as the ‘bump’ at the transition is accentuated at high speeds. Identification of different factors contributing towards this differential movement, as well as development of design and maintenance strategies to mitigate the problem is imperative for the safe and economical operation of both freight and passenger rail networks. This paper presents the research framework and initial instrumentation details from an ongoing research effort at the University of Illinois at Urbana-Champaign. Three bridge approaches experiencing recurrent geometry problems were instrumented using multidepth deflectometers (MDDs) and strain gages to identify different factors contributing to the development of differential movements.

This paper presents an overview on the wide-ranging track structure studies at the Tampere University of Technology (TUT), Finland dealing with the key aspects of track geotechnics related to high-speed passenger traffic on ballasted tracks. Special attention is paid to ballast and sub-ballast, while also considering frost action, embankment stability, track stiffness, track geometry and transition zones. As a result, this paper states that understanding the ballast degradation mechanism and its consequences and assessment of its condition occupy an important role in the construction and maintenance of a smooth high-speed rail line. The choices related to building the sub-ballast also have a dramatic impact on later track deformations and maintenance needs. In cold climate, especially where seasonal frost occurs, understanding and taking into account the frost action mechanism is crucial. Especially in the maintenance and rehabilitation planning of existing tracks, high-class analyses of ground penetrating radar data and its integrated analysis with other data can yield considerable benefits.

There are many issues surrounding the performance of critical assets on high-speed ballasted railway lines. At assets like switch & crossings and bridge transitions high track forces can be produced resulting in higher ballast settlements and hence track misalignments. The latter result in higher track forces and hence more settlement, leading to the need for increased track maintenance to ensure comfort and safety. Current technologies for solving issues like ballast movement under high-speed loading regimes are limited. However, a technique that has been well used across the UK and now increasingly overseas to stabilise and reinforce ballasted railway tracks is the application of in-situ polyurethane polymers, termed XiTRACK. This paper discusses how this technique can be used to solve these types of long-standing issues and presents actual polymer application profiles at two typical critical sites, namely a junction and a transition onto concrete slab-track.

Transportation agencies spend millions of dollars annually to repair civil transportation infrastructure including pavements, earth structures and approach slabs distressed by soft compressible soils and expansive soils. Several research studies performed at the University of Texas at Arlington (UTA) focused on stabilizing these problematic soils so that they will provide better and more stable support to the transportation infrastructure. This paper focuses on a summary of two major distresses and mechanisms, and remedial measures for addressing these distress problems. A combined lime-cement stabilization method is fully evaluated in providing better support of pavement infrastructure, and these results are described here. Another major transportation infrastructure problem involving bridge approach slabs requires different treatment methods, and these results are briefly described. As a part of the recently completed research study assessments, both shallow and deep soil treatment methods for stabilizing soils are fully evaluated for their effectiveness in arresting the distress posed to the pavements and bridge approach slabs. These results along with a few future research needs are presented in this paper.

City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation, affecting the surface environment and the safety of the tunnels. Due to its strong dispersion, sandy cobble strata can be easily disturbed by shield tunneling. Based on the project of the Chengdu Metro Line 1, field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves, ground loss ratios and construction influence zones. The discrete element method (DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level. Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil. The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.

In this study, ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions. In our model, wave propagation in the infinitely extended ground is dealt with using a simple, yet efficient gradually damped artificial boundary. Based on the assumption of invariant geometry and material distribution in the tunnel’s direction, the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number. Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number. The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform. The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum. A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.

Pipes, especially buried pipes, in cold regions generally experience a rash of failures during cold weather snaps. However, the existing heuristic models are unable to explain the basic processes involving frost actions. This is because the frost action is not a direct load but one that causes variations in pipe-soil interactions resulting from the coupled thermo- hydro-mechanical process in soils. This paper developed and implemented a holistic multiphysics simulation model for freezing soils and extended it to the analysis of pipe-soil systems. The theoretical framework was implemented to analyze both static and dynamic responses of buried pipes subjected to frost actions. The multiphysics simulations reproduced phenomena commonly observed during frost actions, e.g., ice fringe advancement and an increase in the internal stress of pipes. The influences of important design factors, i.e., buried depth and overburden pressure, on pipe responses were simulated. A fatigue cracking criterion was utilized to predict the crack initialization under the joint effects of frost and dynamic traffic loads. The frost effects were found to have detrimental effects for accelerating fatigue crack initialization in pipes.

In this paper, a semi-analytical method for the analysis of pile-supported embankments is proposed. The mathematic model describes the cooperative behavior of pile, pile cap, foundation soil, and embankment fills. Based on Terzaghi’s 1D consolidation theory of saturated soil, the consolidation of foundation soil is calculated. The embankments with two different types of piles: floating piles and end-bearing piles are investigated and discussed. The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented. It is found that it takes a longer time for soil consolidation in the embankment with floating piles, compared with the case using end-bearing piles. The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles, compared with the case of floating piles.