Conference Agenda

<p>The growth of geosynthetic hydraulic product types, structures, and associated performance has been impressive. Geosynthetics routinely replace traditional materials such as soil and stone layers to provide for important engineering functions including drainage, filtration and erosion and sediment control, all while providing greener engineering options resukting in lower carbon footprints. The growth of product structures and performance behaviors has challenged the standardization community to keep pace with measurement technologies appropriate to capture both short and long term product performance. Along the way, many testing tools and measurement procedures have been developed, and many more are in development.</p>

<p>This paper will review the many geosynthetic hydraulic structures and their specific applications. The important work ISO TC221 and ASTM International Committee D35 to standardize measurement technologies will be presented, including summary descriptions for:</p>

<ul>

<li>ISO 18198, Determination of long-term flow of geosynthetic drains</li>

<li>ISO 12958-1, Determination of water flow capacity in their plane – Part 1: Index test</li>

<li>ISO 12958-2, Determination of water flow capacity in their plane – Part 2: Performance test</li>

<li>ASTM D4716, Standard Test Method for Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant Head</li>

<li>ASTM D6574, Standard Test Method for Determining the (In-Plane) Hydraulic Transmissivity of a Geosynthetic by Radial Flow</li>

<li>ASTM D 6918, Standard Test Method for Testing Vertical Strip Drains in the Crimped Condition</li>

<li>ISO 18325, Test method for the determination of water discharge capacity for prefabricated vertical drains</li>

<li>ISO TC 18228-8, Design using geosynthetics — Part 8: Surface erosion control</li>

<li>ASTM D7101, Standard Index Test Method for Determination of Unvegetated Rolled Erosion Control Product (RECP) Ability to Protect Soil from Rain Splash and Associated Runoff Under Bench-Scale Conditions</li>

<li>CEN TS 17445, Geosynthetics — Standard test for the simulation of rainfall-induced erosion on the surface of a slope protected by geosynthetic erosion control products</li>

</ul>

Geotextile tubes is a popular solution for dewatering applications. During the dewatering process, infill material such as soil slurry or sludge material investigation is pumped into the geotextile tubes through the inlet port at high pressures, and thus significant amount of tension forces can be developed at the inlet port sleeve and connecting parts of the tube. The inlet port sleeves are typically made from high strength geotextiles to withstand the high tensile force, but this high tensile force can also be exerted at the seam connection between the inlet port sleeve and body of geotextile tube body, and at geotextile body material in proximity of this seam connection. Geotextile rupture or tearing could occur at these locations during high pressure pumping. Therefore, it is important to determine its resistance to tearing. The factors that affects its tearing strength should also be evaluated. So far, only limited studies have been done on this aspect. Hence, a new tensile test setup was developed to simulate the application of tensile forces on the inlet port sleeve and surrounding geotextile material during slurry pumping.

The setup consists of a housing to clamp a portion of the geotextile tube body, and a circular drum that connects to the inlet port sleeve. Strain gauges were installed on the various critical locations on the geotextile test specimen both on geotextile tube body and inlet port sleeve. Several types of inlet port designs were tested, and the critical tearing strength of these inlet ports were analysed. Test results suggest that the seam design connecting the inlet sleeve and geotextile body is a key factor in deciding the critical tearing strength of an inlet port design.

<p>Carbon fiber composite grid fabric can be used as a uni-directional or bi-directional load member depending on the high strength and structure of the carbon fiber, so that no additional process is required and the facility investment cost is reduced. In this study, we fabricated carbon fiber composite yarn with appropriate stiffness and ductility and manufacture the hybrid grid for seismic resistance by strengthening and designing to have an optimum grid structure. For seismic resistance test was done by the SIM (stepped isothermal method) as a creep test. Five isothermal exposures of 23, 37, 51, 65, 79 °C were employed for the SIM procedure. The creep tests were performed at 40, 50 and 60% of ultimate tensile strength (UTS). To simulate a seismic event, tensile loads of 80, 90 and 100% of the UTS were applied during the 23 °C step and after the 79 °C step. The strength and elongation of the above four grids designed to derive the optimal fineness and fabric structure required for the fabrication of the reinforcing grid were measured. Comparing the tensile strength and elongation, it can be concluded that the thicker the fiber, the stronger the tensile strength can be obtained, and the structure of specimen can be considered to be favorable to the weft direction elongation. Creep strain exhibits an initial decrease at each elevated temperature step. The final strain was approximately 7.9%, similar value as that obtained from the application of the seismic load midway through 23°C temperature step. Creep strain decreased after seismic event cause of recovery force, after that strain increased again. After same condition of seismic event in different times, strain finally overlapped. Normally, seismic event has no effect on long-term property but in specific condition, a seismic event may reduce the creep property of grid fabric.</p>

<p>A series of large-scale direct shear tests and cyclic shear tests were conducted on the staggered stacking soilbags. The influences of the number of cyclic shears, vertical stress, and amplitude of shear displacement during the cyclic shearing process on the dynamic deformation characteristics and shear strength of the staggered stacked geotechnical bags were explored. The results show that the shear failure of the interface between the soilbags before and after the cyclic shear basically conforms to the Mohr-Coulomb failure criterion. Under low vertical stress, the dynamic parameters of the interface between the soilbags change slightly as the number of cycles increases. As the vertical stress increases, the dynamic shear modulus of the interface between the soilbags increases, while the damping ratio remains unchanged. As the amplitude of horizontal shear displacement increases, the damping ratio of the interface between soilbags gradually increases, and the dynamic shear modulus decreases. After the cyclic shear test, the increase in the shear strength of the interface between the soilbags increases with the increase of the vertical stress.</p>

The Liner system in leach pads projects is especially valuable and implies a considerable part of the capital expenditure for these types of projects. As well as the overliner material, sometimes represent a big challenge to find a nearby and adequate material source capacity. The overliner must meet specific geotechnical properties to provide drainage and liner protection, been critical a controlled maximum coarse size and sieve distribution to avoid puncture failure in the liner system and provide efficient drainage.

This paper includes the summary of two recent studies developed for one of the biggest copper leaching operations in Chile, consisting in an expansion of the secondary leaching process with more than 168 million tons capacity and 120 m maximum high of the leached ore deposit, and a Low-Grade Oxide dump leach expansion of 85 m high, with large surface of lining and high demand of overliner material where natural sources are almost unavailable.

The studies assessed the feasibility of using granular materials with a maximum particle size greater than 2" as overliner, as well as the viability of increasing the vertical load to which the liner is subjected. It is important to consider that these analyses were based solely on the integrity of the liner system under higher vertical loads and did not evaluate specific variables of each project that may affect its overall slopes stability.

Different HDPE geomembranes were tested and obtained high puncture resistant and low to moderate deformation for different liner thickness cases up to 185 m total ore height equivalent load. Comparing this results to the resistances and deformations that were obtained under theoretical calculations, the assessed HDPE geomembranes can offer better resistance than what was expected, demonstrating the improvement in technology and components that the materials used for their manufacture have had in the last years.

Ultra-lightweight foamed glass aggregate (UL-FGA) is a lightweight and insulating fill material used in the construction of retaining structures, embankments and general grade-raising fill, bridge abutments, and foundation slabs throughout Europe as well as in North America. UL-FGA is granular material that has dry bulk densities ranging from 180 – 240 kg/m3 and a closed cell structure which provides good insulation properties and minimal water absorption. This sustainable material has a favorable carbon footprint in part because it is manufactured using recycled glass cullet. Most UL-FGA applications require a separation geotextile fabric to be installed in conjunction with the UL-FGA as the geotextile is critical in maintaining the UL-FGA layer’s ultra-lightweight and highly insulating properties over the design life of the project. Additionally, there are UL-FGA applications where the UL-FGA layer is providing water storage and thus the filtration characteristics of the geotextile need to be understood. This paper summarizes the characteristics of geotextiles serving the separation and/or filtration functions in various UL-FGA applications over the design life of the project.

This study investigated particle displacement and rotation (motion) in reinforced triaxial tests conducted on transparent sand. Individual particles were segmented from laser-illuminated sections through the specimens by using a neural network. State boundary lines between probable and improbable particle motions were drawn. The reinforced specimen was stronger than the unreinforced, despite having a similar volumetric strain response. By comparing the particle motions it was found that unreinforced specimens buckled and thus the lower strength. Preliminary results suggested that at a given applied axial strain particle rotation increased when lateral restraint was increased

<p>The study in question is based on experience made on nonwoven lines consisting mainly of the following manufacturing phases:<br />- opening of the fiber<br />- carding<br />- folding<br />- pre-punching<br />- needling 1<br />- needling 2<br />- calandering<br />The raw material considered is made of high tenacity polypropylene fiber. The study starts from the analysis of the fiber resistance trend in reference to the EN ISO 5079 toughness test, in order to characterize the behavior of a mixture of up to three types of fibers. The specific processing characteristic of the production line is represented by specific mechanical tensile resistance values obtained on the nonwoven geotextiles with reference to EN ISO 10319. Subsequently, the loss of resistance of the mixture due to the different toughness and elongation of the three components of the mixture is determined. Moreover, the weighted resistance values of the individual components of the mixture are calculated in order to determine the toughness of the mixture itself. Starting from the toughness of the mixture, as estimated above, the resistance of the resulting nonwoven geotextiles is linearly obtained. In order to evaluate this model, the values of a historical series of production control tests were processed.</p>

<p>This article presents the study of the durability of two distinct polypropylene woven geotextiles (G1, with a lower percentage of protective additive against ultraviolet radiation and G2, with a higher percentage) exposed to two climatic cycles of field exposure (2016 summer until end of 2017 spring and other cycle beginning in 2018 winter until end of 2019 autumn). The exposure took place in the city of Varginha, South of Minas Gerais, Brazil, latitude 21 ° 33’05’’S. The local atmospheric dynamics was monitored using meteorological station data, with ultraviolet radiation estimated as 4.2% of the accumulated global radiation measured. The durability analysis was performed by tensile strength before and after exposure, individually, as well as the cumulative effect on the total exposure time. The relevance of the work is in the development of a proposal for an exponential mathematical model to evaluate the durability of polypropylene woven geotextiles exposed in the field, since exposure to the environment is of considerable complexity. It was found that the sum of resistance losses of the isolated periods cannot be considered equivalent to resistance loss for the total exposure period, due to the accumulation of damages that the material is subjected throughout its exposure. There was also a greater loss in the second exposure cycle compared to the first, justified by the damage that the polymer matrix structure had already accumulated during winter and spring. It was concluded that the durability of intact geosynthetics exposed to weathering factors presents itself differently due to different atmospheric dynamics, since each period or season presented its peculiarities.</p>