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Nowadays requirements for strength and stability of railway subgrade are increased. It is due to raising of train speed and axle load. Some sections of subgrade that were previously considered stable do not satisfy safety requirements. In this regard, superstructure reinforcing solutions need to be developed. This paper highlights ballast and subgrade reinforcement applications of geogrids in railway infrastructure. In recent years, geosynthetics are widely used for this purpose. Geosynthetics influence on the stress-strain state of subgrade is an important and extremely urgent problem. The paper describes recent research efforts in field studies, which helped to identify geosynthetics reinforcement influence on ballast layer.

The article deals with the problem of strengthening of the subgrade located on the sections that have the interchange of cars with the axle load of 25 tons and more. The issues of the subgrade behaviour were studied on the example of the Eastern test site with regard to geotechnical and permafrost conditions for the construction and maintenance of subgrade. The main directions to the subgrade strengthening are referred to the following: 1) Strengthening of the top of subgrade; 2) Providing the stability of the sloping parts of subgrade; 3) Providing the carrying capacity of the weak, including thawing, roadbeds.

When flowable solid bulk commodities are transported, their distribution in a vehicle cargo space may change due to a dynamic load, mainly due to intensive braking. This cargo movement causes changes of a load of particular vehicle axles, what may result in overloading of axles mainly in a front part of vehicle/combination, although the vehicle/combination was loaded correctly. This article quantifies the influence of intensive braking on axle load changes during a transport of cement and selected types of gravel. It is based on practical braking tests which were done for purposes of the quantification of this influence.

Before the widespread use of high-speed rail ballastless track needs to be tested in real conditions at high speed and small axial load. Experimental railway track of “VNIIZhT” makes it possible to carry out tests at high axial load, low speed but that does not fully meet the real fields of application of ballastless track. To resolve this contradiction it proposed to apply the methodology of forecasting resource of ballastless track under real operating conditions basing on the results of tests on an experimental ring using mathematical modeling. The proposed algorithm and methodology allow applying results of observation of degradation of tested ballastless track design on the Test Loop (Scherbinka railway station) to the network section where laying of any ballastless track design for mixed traffic is planned. In the longer term this methodology will give opportunity to take into account changes of operational factors on a section, including impact of increase of axle load or train speed on durability of track design.

The main purpose of this paper is to propose a procedure intended to improve the efficiency of the analytical road pavement design method, by employing the necessary courses according to the effective traffic volume, composition and axle load spectra on a road sector. The approach is based on measuring traffic data using a weigh-in-motion (WIM) system, for 36 months, on an important multilane highway in Romania. A designed application software was an essential traffic data processing tool. Pavement design was carried out using the Romanian standardised procedure, as well as using coefficients calculated with the employed software, based on collected traffic data. The latter represents the proposed design methodology, which led to a 15% reduction in asphalt thickness and a 10% thickness reduction for the stabilised course. The obtained results emphasised the technical, economic and environmental advantages of the proposed design approach.

Correia et al. [1] , developed an expression to model the force distribution due to axle loads, with respect to the moving referential. The above force distribution was used for Finite Element Analysis using PLAXIS 3D. A code is developed in MATLAB to generate a matrix of dynamic multipliers for each static point load applied along the railway track with each time step. The amount of load applied is equal to the axle load of the train resulting from the solution of the Winkler Beam for the movement of a load. The results can be used for gauging the effect of changing various geological and physical parameters on the distribution of force due to axle load. Once calibrated to geotechnical and physical data corresponding to sites above actual underground train tracks, the model can be used to predict the effect of vibrations on existing infrastructure.

A low volume road (LVR) structural design has two phases: first one is selection of appropriate construction materials and second is the determination of layer thicknesses under the certain traffic and environmental conditions with considering the subgrade bearing capacity. Pavements are prompted to serve the traffic without reaching the terminal serviceability index over its design life. Rut accumulation (plastic deformation) is the most common pavement deterioration type of flexible pavements. Therefore the main goal of the design is prevent rutting. Many low volume road design manual assume that plastic deformation occurs only in subgrade. Construction of overlying layers by selective high performance materials according to the related material and construction specifications is the reason of this assumption. In fact, the assumption is not much reasonable especially for with no, or thinly overlaid low volume road pavements, where the major structural strength is comprised of unbound granular pavement materials and where the principal distress mechanism is rutting in the aggregate layers. Subgrade bearing capacity and the traffic are the main input parameters in the design stage of low volume roads. Subgrade bearing capacity is expressed with California Bearing Ratio (CBR) or Resilient Modulus (Mr). The “traffic” term is determined by Equivalent Standard Axle Load (ESAL) repetitions which is often admitted as 80 kN single axle load. Although it is not too difficult to determine an axle load for an individual vehicle, it becomes quite complicated to determine the number and types of axle loads that a particular pavement will be subjected over its design life. For calculation of Load Damage Factors of different vehicle types, which have various axle load and configurations, a generalized fourth-power law has been used for more than a half century. The objective of this study is to indicate the limitations and difficulties faced on reliably applying a power law relationship in design of LVRs with no, or only thin seals. If a power law relationship to be used due to its simplicity, several parameters must be considered in selection of the power value. Such as stress dependent behavior of unbound granular materials and the selected distress type.

In order to fulfill green requirement (reduction of CO 2 emissions given by French “Grenelle”), a great need appears concerning roll-on roll-off efficient technology. Heavy seam welded structures manufacturer has to present an optimized product to fulfill this requirement. In this purpose, the Modalohr system overcomes several challenges: transport 4m height and 38 tons semi- trailer in UIC kinematic gauging with a low floor rail vehicle, use of conventional large wheel bogie with maximum axle load, 9 million kilometers running over 30 years service life. For cost effectiveness, the compact vehicle design uses welded assembly and avoids systematic full penetration welds which may require costly preparation machining. The idea is to develop a one shot FEA which provides both global structural bending and torsional vehicle behaviors and also the fatigue focus on each joint for both weld toe and weld root. The local stress analysis requires too much effort and the structural stress using appropriate inclined shell element in a global system model complies such requirement. A home made tool implements these techniques. LOHR “Seam Sim” development deals with the partial automation of the FEA model generation based on the following key points: solid weld feature are generated in CAD, FEA model automation idealization is achieved without additional manual operation. Postal 2 post processing tool has been developed to allows standard FEA code results processing for both static and fatigue assessment. The final display is a scalar stress safety margin map associated for each element to the appropriate criterion over the system depending on the area type; plain metal, sheet metal edges, weld toe, weld root, bolt connection … “Seam Sim” theory [2] , [3] and Verification & Validation (V&V) has been presented during last fatigue Design conference in 2011 [4] , today's aim is to present a highly fatigue demanding industrial application. Loads are applied at a system level to fulfill EN12663-2 standard and additional manufacturer load cases (including longitudinal dynamic fatigue load for 1050m long train and lifting, boarding kinematic load cases). The fatigue results are focused on each detail.

Coal rock creep is an inevitable phenomenon in coal mining, fluid seepage is involved in coal rock creep in coal mine, and coal rock creep and fluid flow interact. To determine the coal rock creep–seepage law, in this paper, CSCG-160-type gravity hydraulic constant load creep seepage test system developed by China University of Mining & Technology (Beijing) is used to carry out creep seepage test with step loaded axle load in certain condition of confining pressure for raw coal rock sample; in the test, coal rock-related deformation (axial strain, volumetric strain) in the creep process is measured and seepage is recorded. By analysis of the test result, the creep deformation – seepage law during coal rock creep seepage is obtained. The study result of very important practical guiding significance for dynamic disaster and water damage prevention and control of gas in coal mine.

To analyze the influence of structure type on passing ability of car transport vehicle combination, the four basic vehicle combination models of two typical structure types, such as car transport semi-trailer road train and car transport vehicle combination with center axle trailer, have been built by using TruckSim. The turning circle test and the adaptability test on highway have been simulated on dry pavement to analyze the relationship between the structure type and the turning passing ability. The results show that the structure parameters have significant influence on the passing ability of car transport vehicle combination; three of the vehicle combination models can meet the requirements of GB 1589-2004“Limits of dimensions, axle load and masses for road vehicles”; all the four basic vehicle combination models will take up the lane beside itself when running on the up to and including third-grade highway/ramp.

Many of the world's railways run on ballasted track, which has for nearly 200 years provided a stable support for train operation. However, with trafficking the geometry of the track deteriorates, mainly as a result of the development of differential settlement of the track-bed (ballast and sub-base). When the geometry defects become too severe, maintenance is needed to realign the track to enable the continued safe running of trains. Maintenance is a major cost associated with ballasted railway track, which usually takes the form of tamping. However, tamping damages the ballast, resulting in a diminishing return period between maintenance interventions until eventually the track-bed requires full renewal. A major component of the differential settlement can be attributed to the ballast layer. However, differential settlement of lengths of track cannot easily be modelled or predicted either computationally or experimentally. Thus the total plastic (permanent) settlement is often used as a proxy for the potential for the development of differential settlement along a length of track in the field. Many empirical models have been developed to predict ballast settlement, usually as a function of the number of train axle passes and/or the cumulative load. However, these models may produce very different results, perhaps indicating that the input variables have not been adequately formulated. This paper describes some current empirical ballast settlement models, and evaluates them using experimental data generated using the Southampton Railway Testing Facility (SRTF). This apparatus represents a section of track consisting of a single sleeper bay 650 mm wide, confined by rigid sides that enforce plane strain conditions. The paper summarises the strengths and weaknesses of the existing models, and suggests variables that could be taken into account to improve them.

Quasi-static and dynamic loads from train-traffic are applied to the entire track system: super-structure, substructure and subsoil. Due to lack of maintenance of the track bed, the dynamic loads on the track system causes an accumulation of excess pore water pressure within the sub-structure. Furthermore, a pumping effect exerted on the track system, which depends on the axle load and velocity of the vehicle, may cause in mud hole formation, rising of the underlying soil, ballast contamination and the clogging of gravel bed pores. Consequently, the subgrade resistance is reduced and hence the system loading capacity. The main objective is to detect mud holes as early as possible by non-invasive, non-destructive measurements to avoid costly interim or long term treatments. The present publication focuses on the comparison of vertical velocities due to a moving train load in the absence of water, thus eliminating any complexities arising from any variation in the pore pressure. Due to the large velocity of the trains, elastic and plastic deformations might develop in the vicinity of the track-subgrade system. In the current publication, a simplified numerical simulation of one axle of an ICE train traversing along the rail track with various speeds have been simulated.