Railway ballast, which form an integral part of railtracks, is highly susceptible to subsistence due to both vibration transmitted by the passing trains, as well as the breakage of the ballasts themselves with repeated impact. The resulting subsistence necessitates regular monitoring and maintenance, involving cost- and time-consuming remedial actions, such as stone-blowing and ballast renewal. It would therefore be desirable if measures could be taken to minimize the wear and tear effect of the rail traffic, consequently to prolong the lifespan of the ballast layer. This paper describes the exploratory work on rubber inclusions to address this problem. The rubber elements were derived from the inner tubes of motorcycle tyres, cut and shaped accordingly to produce various configurations for the study. Granitic stones of suitable size were sieved and used as representative samples of typical ballast as the tests were mainly carried out with a standard direct shear test setup, i.e. shearbox measuring 60 mm x 60 mm. The rubber tubes were cut and shredded to produce strips and shreds respectively, and the elements were arranged in various pre-determined configurations within the simulated ballast layer. The direct shear test results indicated that rubber inclusion could effectively improve the shear resistance of ballast to various degrees, though the configurations clearly played an important role in the improvement observed. Both strips and shreds were found expedient in deformation control with increased ductility of the composites, with potential to absorb impact and reduce breakages of the ballasts. Both mechanisms contributed to the reduced overall subsistence, accompanied by an increase in the shear resistance. As such, the present study indicates a promising application of the material in improving the performance and longevity of existing ballast layer in railtracks. Nonetheless, considering that the test setup is but a static, scaled down simulation, without dynamic loading which mimics the rail traffic, it is necessary to conduct further investigations in instrumented full-scale setups for verifications prior to filed implementation.

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When ballasted tracks have a high-mix ratio of fine particles, track maintenance effect by tamping is difficult to sustain because such work impairs the density of the ballast, and the initial settlement of the ballast tends to occur. In particular, in the case of the ballast with a high-mix ratio of fine particles, the settlement tends to be large because the strength of the ballast decreases in saturated condition. Therefore, we developed a repair method of sustaining the repair effect to ballasted tracks with a high-mix ratio of fine particles without the ballast renewal. In this repair method, ballasted tracks are tamped by a tie-tamper after throwing in repair material consisting of polymer and reaction material. This method prevents the strength decrease of ballast in the rain by mixing this repairing material and the ballast with a high-mix ratio of fine particles under sleepers, resulting in the reduction of the proceeds of the track settlement. In this study, the authors performed a direct shear test to evaluate the strength properties of this repairing material. The authors then performed a full-scale model test to confirm the validity of the method. The results confirmed that this technique is an effective approach to repair ballasted tracks.

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At the runway expansion project in the Fort Lauderdale-Hollywood International airport in Florida (FLL project), there are complicated geotechnical issues that lots of cavities in the limestone-loose sand mixed ground are existing in the shallow area. The Broward County Aviation Department (BCAD), the owner of the project, has required to collapsing the cavities and compacting the runway foundation to secure the take-off and landing of aircrafts. Mammoth Vibro-Tamper (MVT) was proposed and accepted as the alternative to the originally specified Deep Dynamic Compaction (DDC) for the runway with its length of 2.4km and area of 477,000 m2. In this report, the shallow compaction effect and vibration reduction effects by MVT are presented in comparison with the DDC.

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The 2011 off the Pacific coast of Tohoku Earthquake occurred on March 11. When the earthquake occurred, there were a number of frozen subsurface zones in cold districts, such as Hokkaido. However, any experimentally-verified case of deformation and collapse modes of embankment was not available in respect to the seismic performance of a frozen embankment. This study examined the earthquake resistance of embankment in cold districts by providing shake to a model embankment on which the surface layer had been frozen after adding seepage water. Additionally, a similar experiment was conducted for a model embankment on which the surface had not been frozen.

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Lots of high-speed railway subgrades have been built in the severely cold region in China. The water-proof and drainage system with frost heave prevention structure and micro frost heave coarse-grained filling material with good frost-resistance performance have been widely used in these regions, which can generally solve the problem of high-speed railway subgrade frost heave in the seasonally frozen region. However, the long period monitoring of high-speed railway subgrade indicates that there are still some frost heave problems existing in the seasonally frozen region and this can cause the irregularity problem to the high-speed railway lines which cannot be totally ignored. A new experimental system has been built, which can investigate the frost heave characteristic, the permeability and the water retention capacity of coarse-grained soil. The influence of the fine particles filling material, the permeability and the water content to the frost heave deformation have been tested and analyzed. The water retention ability of different soil is also analyzed. Based on the characteristic of water movement of subgrade in the frozen period and the interactive affection among the water, ice and soil particles; the frost heave development mechanism of micro frost heave coarse-grained filling material is discussed. This achievement can provide scientific evidences, in order to optimize and improve the frost heave prevention filling material and structure.

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In 2010 temperature and moisture sensors were made and installed into the pavement and subgrade of the "Astana-Burabay" highway (North region of the Kazakhstan). In 2013 similar sensors were used for the "Atyrau-Aktobe" (West region) and "Almaty-Bishkek" (South region) highways. In the present paper the study results of subgrade frost penetration of the above stated highways are given. For each highway a subgrade frost penetration starting and finishing times are determined; frost penetration and thawing graphs are constructed; frost penetration and thawing rate values are determined; dependence of the amount of unfrozen water from the value of negative temperature and initial moisture is established.

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Rigid pavement has advantages of long life with durability and less maintenance cost, which can be justified the higher initial cost when we consider costs over the whole life of pavement. We have little information, however, about the displacement or deformation of rigid pavement laying on a frost susceptible subgrade in cold regions. This paper shows a simple analytical method to estimate a deformation of rigid pavement, supposing a frost heave and a frost depth of subgrade and using FEM. The results are compared with the surface deformation data of rigid pavement of the airport apron constructed on a local frost susceptible subgrade soil. This analytical method is shown to be useful for rigid pavement design in cold regions.

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