Conference Agenda

Bitumen is a natural product, in which its use for waterproofing dates back to ancient times. A bituminous geomembrane (BGM) is manufactured by impregnating a polyester geotextile with an elastomeric bitumen compound. The geotextile provides a high mechanical resistance, while the bitumen provides the waterproofing properties and ensures longevity of the frame-work by protecting the geotextile. The durability of a BGM is measured in terms of how its key components, their mechanical and low permeable properties are subject to biodegradation by bacteria in various buried applications.

Some example project applications in the domain of transportation will be described to illustrate these advantages where the bearing capacity of subgrades of over-consolidated soils can be improved by waterproofing unstable foundations in the presence of water. The infrastructure of the main tarmac runway at St. Georges airport in Utah and a railway track in Nebraska, both in USA will be described.

Random fibre reinforcement of granular soils with flexible polymeric fibres increases their shearing resistance and ductility. However, the potential advantages of fibre reinforcement are not limited to monotonic loading conditions. Recent research has shown that fibre re-inforcement has the potential to reduce the permanent settlement of granular materials subject to cyclic loading, such as railway ballast. Ballast is still widely used on railways, as ballasted tracks are still predominant worldwide and are compatible with high-capacity and high-speed applications. Under repeated train passages, ballasted track settles differentially hence costly maintenance operations are required periodically to restore the correct rail level. Full-scale tests in the Southampton Railway Testing Facility (SRTF) have shown that the addition of a moderate amount of thin polyethylene strips to ballast can reduce the permanent settlement with marginal influence on track stiffness, provided that the fibres are sufficiently narrow not to disturb the natural arrangement of the ballast grains. As with fibre reinforced soils, the performance of fibre-reinforced ballast is expected to be influ-enced by the characteristics of both the host material and reinforcement. This study pre-sents the results of full-scale tests carried out in the SRTF using different materials for the fibres and ballast. The fibres were obtained from polypropylene rope to replicate at a much larger scale the polypropylene filaments often used for the reinforcement of sands. The ballast was coarser and settled significantly less. The design of the reinforcement was informed by packing tests, as suggested by earlier tests using strip fibres. Thin fibres, with a small influence on the packing of the grains, were found to reduce the permanent set-tlement and had little influence on track stiffness.

This paper focuses on evaluating local stiffness enhancement near a geogrid installed at the base/subbase interface of full-scale pavement test sections at the FAA’s national air-port pavement test facility (NAPTF) in USA. The investigated test pavements comprised of the north section stabilized with a square aperture geogrid and the south control section with no geogrid. Inductive coil sensors and pressure cells were embedded in both sections. A full-size dual-tridem gear applied realistic moving wheel loads on the pavement surface. Pavement responses including layer deformations from coil sensors and applied pressure from earth pressure cells were measured during traffic loading. Modulus characteristics of the subbase layer were then estimated based on the sensor measurements during traffic passes. The study findings indicate higher layer stiffness consistently estimated in the geogrid-stabilized pavement section when compared to the values in the control section due to heavy aircraft gear loads.

Railway has multiple advantages of reliable service, fast and versatile to both passenger and cargo as compared to other modes of transportation infrastructure. However, the efficiency and safety of railway engineering are dependent on the track structure. This paper evaluates the contribution of the multi-functional composite geotextile to the railway track, through a labora-tory test carried out at Southwest Jiaotong University, Chengdu, in collaboration with interna-tional industry practitioners. The contributions are assessed through the quantification of the traffic improvement as well as the reduction in ballast and sub-ballast fouling for three sets of simulated cyclic train loading test model, Model 1 as control, with Model 2 and Model 3 using different types of multi-functional composite geotextiles. The findings validate the reduction of vertical deformation and reduction of fouling by using multi-functional composite geotextiles, ultimately allowing the railway track to support additional train traffic and longer lifespan.

<p>Geosynthetics are materials currently used in the railways applications. The system developed with the company which has the Concession Contract for the management of the Italian railway infrastructure, is using the geosynthetic as a base layer where to spray a pure polyurea membrane, a fast-curing waterproofing product used since decades all over the world to waterproof roofs, decks and hydraulic structures.</p>

<p>This system shows all its benefits in maintenance applications, where an existent bridge should be <br /> re-waterproof in a very short time, with a minimum impact on the railway traffic. During these operations, where the main task is to create a continuous waterproofing layer which would protect the existing structure from the water percolation, the rails and the ballast are removed to uncover the bridge structure.</p>

<p>The main problem in these job-sites is the presence of several defects (like irregularities or moisture in high quantity) in all existent bricks or concrete bridges, due to their old age. The new waterproofing layer should manage these factors and the use of a geosynthetic, mechanically fixed to the structure, would offer a formwork where to apply a tough in-situ waterproofing layer made by polyurea.</p>

<p>A polyurea is the reaction product between an isocyanate and a mixture of reactive amines. A waterproofing membrane designed according to this technology shows excellent mechanical properties. Moreover, it is completely watertight after a few seconds from its application, without overlaps and its outstanding puncture resistance is assuring that no damages will occur during the operations to replace the ballast in its original position.</p>

<p>Mapei’s experience in the railway field and its expertise in construction chemicals have led to an excellent solution which has successfully being used in a lot of job-sites.</p>

ABSTRACT: Installation damage tests were carried out on several geosynthetics of various types and from different manufacturers. The testing procedures included conditioning products in a field installation at low temperatures, under specific Nordic conditions (crushed rock, compaction) followed by laboratory tensile testing of the exposed and un-exposed geosynthetic samples. The results of the individual tests were evaluated, and the results interpreted anonymously regarding the different geosynthetic versus the typical de-sign approach in similar Nordic conditions at positive temperature.

The paper presents research result of geosynthetics applications in railway structure with focus on ballast and subballast stabilization. Previous investigations have indicated the influence of geosynthetics on ballast bearing capacity and its deformation behavior, but field results of railway track geometry needs to be made. In addition, long-term behavior of stabilized track structure has not clearly indicated yet. In this study the influence of geosynthetics in ballast layer on long-term behavior estimated by the state of the track geometry. For this purpose, rail spotter and track leveling were used. The results have shown that deflection accumulation rate over time on the section with geosynthetics is 1.8 times lower than on the usual one, and the unevenness of track lowering is 1.7 times lower. Ballast stabilization with geomaterials in any case reduces the cost of current maintenance, the most complete difference in labor costs is felt starting from 4 years of post-repair operation.

<p>Inclusion of geosynthetic reinforcements within the granular base layer has been shown to substantially improve the overall performance and life of pavements. This effect has been demonstrated in several applications, and the mechanisms through which such an improvement can be achieved have been clearly described for the past 40 years by many authors. However, because of the complexity of the reinforcement mechanisms, quantifying this effect, either in terms of increased design life or reduction of the pavement thickness, is not simple. Because of this, available design methods still rely heavily on empirical test results from large scale lab tests or field trials. The growing need for a sustainable use of plastic materials has led manufacturers to develop innovative geosynthetics capable to give the maximum possible performance with the lowest possible weight. This paper provides an overview of the development of a biaxial geogrid characterized by a three-dimensional shape designed to improve the interaction with the granular aggregate. The shape of the ribs in the machine direction was designed to enhance its performance within the aggregate layer by providing resistance to the plain strain/stress condition present in roads. This new geometry improves the moment of inertia when compared to traditional biaxial geogrids, the result of which is greater transverse stiffness, greater resistance against bending of ribs oriented in the machine direction, and greater confinement of the material in the cross-machine direction.</p>

<p>A series of tests were run on various biaxial geogrid designs, some of which were characterized by tall vertical ribs in machine direction. Laboratory tests included pull-out, composite stiffness tests, static plate bearing test, cyclic plate load tests, full-scale wheel load tests using an accelerated pavement tester (APT). This paper summarizes the results of these tests, showing the advantage of the three-dimensional biaxial geogrids over traditional planar geogrids.</p>

<p>Perranporth to Newquay Cycleway project is solution for a ramp construction to be formed on top of an existing historic railway embankment. The ramp is located in tree root protection to provide the approach to foot bridges. According to the British Standard BS5837:2012 the design in Tree Root protection areas should not need any excavation and compaction of soil. Area close to existing tree root should be protected and undisturbed during construction. Therefore, it is required to use systems to prevent tree and their root during and after construction traffic.</p>

<p>A Cellweb system was designed to protect tree root zone that allow drainage, nutrient and gas exchange necessary for root growth. The system decreases pressure effect on soil and tree roots by dissipated the loads and transferring laterally to subgrade soil instead vertically. </p>

<p>Therefore, the reinforced embankment with a stack Cellweb system filled with clean angular stone were used as a solution for a foot bridge that allowing tree roots growth at the same time. The height of the embankment was 1.5m with slope angle 70deg. The Rivel Mesh system as a rigidity formed face was used to achieve slope stability during construction and protect embankment face against sliding. In the other hand, embankment slope faces were filled with top soil and vegetated. while the face was protected from erosion by covering with Erosion Contol landlok and wrapped around at each layers of soil. </p>

<p>The design is included some of key element. Cellweb system to protect tree roots from excavation and compaction also reduces pressure to subgrade soil. Rivel mesh system were used to achieve slope side stability. Also, Erosion control landlock were used to protect slope sides against erosion at long term. Geotextile used as a pollution and separation control and Sleeve-It were used as supported fence for ramp.</p>

<p>As part of large-scale field tests, a range of twelve mechanically bonded nonwoven geotextiles made of polypropylene staple fibres from various manufacturers were tested about their robustness against installation loading in their function as separation layers between soft subsoil and coarse-grained base course material. Four different installation situations were simulated on large scale test fields. Base course materials ranging from round-grained, sandy gravel to sharp-edged, stony gravel were used for this purpose. The impact by site traffic was controlled based on the ruts resulting from truck crossings. A suction excavator was used to gently reveal the geotextiles.</p>

<p>All samples were visually assessed for damage and then classified. The energy absorption and the derived damaging work were used to evaluate the mechanical changes based on both, wide-width tensile tests and static puncture tests. Half of the exposed samples remained with more than 80% of their original performance. Almost all materials didn’t exceed 50% of performance loss after the tests. A classification system should quantify the complexity of the soil-geosynthetic-system where geotextiles are used as separation layers. The tests have shown that strength alone is not enough to assess geotextiles as separators between coarse grained subbase layers and soft soils and to avoid damage. The evasion principle should be followed instead. For this purpose, it is necessary to consider the deformability. The energy absorption together with the minimum elongation ability provides a good basis for this. Against this background, a proposal for an update of the current classification system was made.</p>