To quantitatively investigate the morphological features of railway ballast, a new statistical index, Curvature Index (CI), was presented. With a set of 584 digitized railway ballast particles obtained through 3D scanning, the statistical distribution functions of CI and existing global shape indices (i.e., long axis, middle axis, short axis and sphericity index) were obtained. Then, based on Proper

Deep foundations are very important elements in the routine design of railways and bridges when the loads applied due to these important structures are higher than the bearing capacity of the soil. However, the methods currently available to calculate the bearing capacity of driven piles embedded in clay have been developed based on empirical factors derived from limited tests. Hence, further assessment

A volume-shear coupling mechanism is imperative for developing high-speed railways in very cold regions. A series of consolidated drained static triaxial experiments were carried out to investigate the effect of freeze-thaw (F-T) cycles on the stress-strain features of coarse-grained materials (CGM) typically used at the bottom layer of subgrade for high-speed rail tracks in China. Mathematical expressions

The Optimal Recycling of Reclaimed Asphalts in low-traffic Pavements (ORRAP) project concerns a cold recycling of 100% Reclaimed Asphalt Pavement (RAP) without binder addition, in base and subbase layers of low-traffic pavements. The mastic coating of aggregates induces a viscoelastic behaviour and changes the resilient modulus with frequency and temperature. This modulus is obtained with repeated

A new prefabricated vertical drain (PVD) with wings has been proposed, and its behaviour has been investigated using laboratory model tests and finite element analysis (FEA). The new PVD uses wings that are aligned perpendicularly to the surface of the PVD and is thus named WPVD. The wings increase the contact area of a WPVD with soil and serve as a horizontal drainage channel, and this can be more

Differential settlements can affect transition zones between bridges and road embankments in countries where very compressible soft soil layers are widespread in the subsoil. The related damage makes these locations the most maintenance-prone locations, resulting in high direct and indirect costs for the road owner and the road users as well. Accordingly, approaches capable of analysing current conditions

The aim of this research is to study the effect of temperature and stress levels on the permanent strain of blends of two types of recycled waste materials, namely recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP). RAP was mixed with RCA in different percentages of up to 80% by dry mass. A three-stage repeated load triaxial (RLT) testing procedure was employed for evaluation of

The disposal of waste tyres in a landfill has been outlawed in Europe since 2000, with some exceptions being made for construction works. Since then, tyre-derived products have been widely used in road applications. One of these applications is in tyre bales, comprising 100–140 car vehicle tyres compressed into a lightweight block and secured by galvanised steel tie wires running around the length

The piled-raft foundation in soft clay ground for high-speed trains has suffered serious settlement due to cyclic train loading in recent years. It was urgent to implement countermeasures to improve the natural ground. In this research, firstly, a ground treatment technique was proposed to reduce permanent train-induced deformation. Permeation grouting was injected into the bearing strata of group

The aim of this study is to understand the local mechanisms related to creep behavior of a typical clay under triaxial loading. The investigation concerns both normally consolidated and overconsolidated specimens of remolded kaolin clay. The macroscopic results showed that both dilatancy and contractancy could occur during creep depending mainly on the clay behavior prior to the creep test. The magnitude

The increased popularity of using a deep cement mixing (DCM) column as a ground improvement element in soft ground has brought about the need to identify how the targeted strength and stiffness values defined in guidelines can be achieved considering the water content and the incorporated cementitious materials. This paper addresses this important aspect by studying the strength and stiffness variations

Ballast/fines mixture is often found in railway substructure and the overall behaviour of tracks is strongly dependent on the mechanical behaviour of this mixture. Since directly testing such mixture with large grains is limited with common laboratory equipment, the consideration of a model material at smaller size is advisable. Parallel gradation method is widely used for this purpose. This study

This paper presents the results of using rigorous modeling artificial neural network and genetic algorithm to examine the proper stabilization of very weak subgrade soils at high moisture contents. The experimental database was performed in Louisiana transportation research center for four types of soft soil, 125 samples data were prepared and used in development ANN and genetic algorithm models. For

Continuous heave was observed in a High-Speed Railway subgrade section, which caused severe track irregularity and damage to the concrete structure. After exploring the current relevant research and the construction information of the heave section, this paper addresses the causes and characteristics of the deleterious heave. Displacement and temperature sensors were installed in field to investigate

Soil properties play important role to the metro tunnel settlement induced by traffic load of metro operation. Numerical studies on this topic are still rare due to the lack of accurate dynamic constitutive models of clay. In this study, a new critical state based bounding surface plasticity model for natural structured clays is first developed. It is able to consider the initial and induced anisotropy

Based on long-term, continuously monitored data of an expressway, this paper analyzes the influence of pavement types on thermal stability of block-stone embankments with variations of temperature, heat flux, heat budget change, freeze-thaw cycles, permafrost table, and thawing plate area. Results show that closer to the ground, the annual average temperature of the block-stone embankment with asphalt

Previous studies showed that the permanent strain of interlayer soil in the French conventional railway substructure is highly dependent on the volumetric coarse grain content fv (volumetric ratio of coarse grain to total sample). This study developed a fatigue model allowing the effects of coarse grain content fv, stress state and number of loading cycles N on permanent strain to be accounted for

Ballast layer is a part of railway foundation that its behavior is affected by the properties of constituent particles. The shape of the particles, which affects ballast behavior, is an important characteristic that is represented by angularity and sphericity indexes. In this study, the macro- and micro-mechanical shear behaviors of railway ballast are investigated by using Discrete Element Method

This paper aims to demonstrate the anisotropic behaviour of railway ballast via true-triaxial tests. To do so, a novel, large-scale, true-triaxial testing apparatus (GeoTT) is designed and constructed. It consists of six hydraulic actuators, designed to apply a distributed stress to large granular cubic test specimens with dimensions: 500 mm × 500 m × 500 mm. To show the capability of the new facility

High sulfate expansive soils present special challenges during stabilization. Traditional stabilizers such as lime and cement which are rich in calcium are ineffective in controlling shrink/swell behavior of these soils due to formation of the expansive mineral, ettringite. In this study, two geopolymers synthesized from aluminosilicate sources, fly ash and metakaolin, were investigated to determine

A rail track system comprises a number of components and, in order to analyse and predict track behaviour, it is essential to understand the function of each component as each will have a major influence on overall track performance. Historically, rail track substructure, particularly the subgrade, has been given less attention than the superstructure despite its importance in track design. This paper

Geomaterials exhibit elastoplastic behaviour during dynamic and repeated loading conditions. These loads are induced by the passage of a train or vehicle which then generates recoverable (resilient) deformation and/or permanent (plastic) deformation. Modelling this behaviour is still a challenge for geotechnical engineers as it implies the understanding of the complex deformation mechanism and application

RoadCem (RC) is an additive produced based on nanotechnology and comprises of synthetic zeolites and alkali earth metals as some of its components. The geotechnical properties of a soil stabilized by adding RC to partly replaced cementitious materials are studied. Various combinations of the additives were investigated with the objective of reducing the amount of OPC by 50% by an inclusion of RC and

This study provides a new interpretation of 3D particle geometry that unravels the ‘interrelation’ of the four geometry parameters, i.e., morphology M, surface area A, volume V, and size L, for which a new formula, M = A/V × L/6, is introduced to translate the 3D particle morphology as a function of surface area, volume, and size. The A/V × L of a sphere is invariably 6, which is placed in the denominator

This paper identifies the fundamental driving factors for the mobilization of mud pumping in railway substructure beneath ballastless slab track. Physical model tests on a compacted gravel layer overlying a permeable layer were performed under different conditions in terms of fines content, moisture (i.e., unsaturated, saturated with and without surface ponding), load patterns, and slit width between

The noncoaxiality of the principal stress direction and plastic principal strain increment has been broadly recognized as an influencing parameter for design of soil structures. Here we performed a series of systematic hollow cylinder experiments to study the effects of stress anisotropy on the noncoaxiality of dense Babolsar and Toyoura sands. A total of 25 undrained torsional shear tests were carried

In this paper, three-dimensional numerical modeling is performed to study the effects of strike-slip fault movement on the performance of shotcrete and segmental linings in shallow tunnels that transversely cross the fault. For this purpose, a parametric study is conducted on lining thickness, soil geo-mechanical properties, tunnel depth, and fault dip angle to assess their influence on the tunnel

The drainage performance of unbound granular material (UGM) is an important consideration in pavement design because premature failures can occur due to the presence of excess moisture in UGM layers. Recently, transportation agencies have been evaluating their granular base and subbase drainage and mechanical performance to ensure sufficient drainage capacity while maintaining adequate structural support

The main aim of this research was to investigate the mechanism of deformation of buried pipe under traffic moving load and the suitability of the modified Spangler-Iowa formula, coupled with the Boussinesq theory of load transmission through elastic media in predicting the deformation of these buried structures. This study employed reduced-scale physical model tests in a geotechnical centrifuge, numerical

The prediction of the ground vibration transmitted from tunnels to neighbouring buildings is a vital step in the assessment of the ground-borne noise in buildings. In empirical models it is commonly assumed that the level of ground vibration reduces monotonically with the distance away from the tunnel alignment. In reality, a ‘shadow’ zone is observed above the tunnel. This is first illustrated using

This study aims to establish an elasto-plastic constitutive model under repeated loads for unbound granular materials (UGM) used in the pavement. Shakedown theory was employed to analyze the deformation behavior of UGM at different stages. The prediction models of plastic strain rate and resilient strain were fitted with the loading repetitions, axial stress, and other factors. Based on the typical

The discrete element method (DEM) has been confirmed as an effective numerical method for modelling railway ballast, and successfully used to analyse a wide range of ballast-related applications (e.g. geomaterials). However, there still exists some aspects under development. Among them, the model calibration can be the most significant one (morphology, degradation and contact model). Because reliable

The volume of Construction and Demolition Wastes is dramatically increasing around the world, mainly in urban areas, giving rise to environmental damage. In Tehran, producing 50,000 tons of the construction and demolition wastes (CDW) has made the lack of suitable sites for the disposal. This study aims were to evaluate the physical and mechanical properties of the CDW to possibly use in road construction

In recent years, the use of construction and demolition (C&D) materials as alternative aggregates in geotechnical engineering applications, such as embankments, pavement subbase layers and geosynthetic-reinforced structures has raised increasing attention from researchers and practitioners worldwide. On the other hand, geosynthetics, particularly geogrids and high strength geotextiles, are used as

Wadell’s ‘true’ Sphericity is a traditional 3D particle geometry descriptor that quantifies the shape by comparing the particle’s surface area to the surface area of a sphere having the same volume as the particle. Despite the simplicity of definition and the capability to characterize the 3D shape, the true Sphericity has not been employed in the engineering practice due to the technical difficulty

The reuse of Computer Numerical Control (CNC) milling waste spirals is becoming a challenging task for numerous countries because of the annual increase in steel production integrated with the CNC machines. This paper presents the results of a study of some geotechnical properties of a low plasticity clay (CL) mixed with steel CNC milling waste spirals. The spirals had been first coated with zinc (galvanization)

Faulting is one of the primary distresses in Jointed Concrete Pavement (JCP), due to the combined effects of ambient environmental factors, load transfer and repeated traffic loads. The combined effects induce the various stages of the increasing size of faulting. It is found that the earliest progression of faulting in the pre-erosion stage is caused by the plastic deformation of the base layer. An

Composite sleepers and bearers formed of polymers and sometimes steel or fibre reinforcement are an alternative to traditionally used timber or prestressed concrete counterparts. Composite materials offer the combined benefits of the compliant sleeper/ballast contact of timber with the longer service life of concrete. However, composite and timber sleepers have lower bending stiffness compared with

Soil Water Characteristic Curve (SWCC) is an essential tool to determine the properties of unsaturated geomaterials, including shear strength, permeability and volume change. Although many SWCCs have been measured using laboratory testing, field studies of the subject are very limited. In the current study, six (6) sets of sensors were installed at different depths and locations of a highway embankment

This paper aims to develop a time domain analysis method capable of accurately simulating the vehicle-soil-track interaction phenomenon in a computationally rigorous manner. The proposed method takes full account of wave propagation effects in the subsoil half-space through the development of a systematic frequency dependent lumped parameter assembly. A robust multi-objective optimization methodology

Dynamic behavior of subgrade soils greatly affects the serviceability of a railway/highway line, where the critical dynamic stress (σcri) mainly determines the dynamic stability of a subgrade. In this study, a series of large-scale dynamic triaxial tests on saturated specimens with different confining pressures (σ3) and dynamic deviatoric stresses (σd) were performed to investigate the dynamic stability

Coal combustion by-products, “ash” in various forms have been used extensively to stabilize soils partially due to their relatively slow rate of hydration, pozzolanic reactions and competitive price compared to portland cement. This paper is based on a case study where fluidized bed ash was used to stabilize a subgrade soil causing extensive ettringite formation that resulted in significant structural

Volumetric behavior of intact and compacted loess under isotropic compression and wetting was investigated through stress- and suction-controlled triaxial tests. To assist in the interpretation of test results, X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimeter (MIP) tests were carried out to determine the mineral composition and the microstructure of the

More effective and sustainable use of natural resources besides the mitigation of environmental impacts induced by their extraction could be achieved by reusing construction and demolition (C&D) materials. C&D materials are increasingly being used in pavement bases/subbases as a reliable alternative to virgin quarry materials. The behaviour of flexible pavements under dynamic loads conveyed from traffic

It is a good practice to change the soil properties when dealing with inappropriate soils in geotechnical engineering, which is referred to as soil improvement. In this study, the effect of lignosulfonate (2% weight ratio of soil as an optimum percentage), stabilizer and PP fibers (0.4, and 0.8% weight ratio of stabilized soil) as reinforcement on the soil durability of clayey sand was investigated

In expansive soils, tensile strength and tensile stress are two main factors that control the development of cracks due to drying shrinkage. Numerous experimental methods and theoretical models have been proposed for the measurement and prediction of tensile strength. However, there are only few studies that focus on the measurement and prediction of tensile stresses in expansive soils. Understanding