Conference Agenda

The world population grows decade after decade increasing the food demand. During this time drought becomes more accentuated so irrigation must be more efficient. Many irrigation ca-nals are built of soil with a poor waterproofing quotient and concrete sections which, after 15 years or less, meet seepage through cracking. Geosynthetic lining is the solution. The main challenges irrigations districts face when lining canals are having to shut them off during con-struction. Therefore, it is important that the choice of material enables easy and fast installa-tion in diverse weather conditions, is economically competitive and can withstand time when left exposed to the elements and easy to maintain. Through case studies, this paper demon-strates that bituminous geomembranes (BGM) meet and exceed these challenges. The paper reviews briefly their characteristics as uniquely qualified for usage when lining canals: low Manning and thermal coefficient, density greater than 1, and proven longevity when left ex-posed.

<p>Impact of stones on a geotextile, for example during construction of a coastal engineering structure, can damage the geotextile. Using the results of laboratory tests, it was shown that, apart from the robustness of the geotextile and is maximum elongation, the friction between the falling stone and the geotextile and between the geotextile and the subsoil is of importance for the risk of damage on the geotextile. Furthermore, it was found, as could be expected that the shape of the stone has a large influence. An analytical calculation model was developed and compared with the results of numerical calculations.</p>

<p>Recently field tests have been performed using one geotextile or a composite. Stones of different sizes were used in these tests. Tests were performed on a subsoil of sand and clay.</p>

<p>In the paper, the results of these tests will be compared with the results of the analytical model.</p>

<p>This paper presents the results of implementing erosion control techniques with geosynthetics (Geomats, Geocell and geogrid mattress) on Brazilian Hydroelectric Power Plants (HPPs) reservoirs. Different erosion control techniques were applied in 2016 in 3 experimental units installed in the margins of the Porto Colômbia and Volta Grande HPPs, located in the Rio Grande basin on the border of São Paulo and Minas Gerais states, where 14 experimental sections corresponded to techniques exclusively with geosynthetics (with an approximate area of 150 m²). The performance of the analyzed sections was assessed qualitatively using a performance matrix that collected and summarized data over a monitoring period of four years, considering the variables: stream-bank integrity against erosion; vegetative cover growth, structural integrity, need for maintenance, aesthetics and landscape integration, and regrowth of native vegetation. The performance was also assessed by differential bathymetry studies performed in 2016 and 2020 in the HPPs margins. This work highlights the benefits of implementing geosynthetic materials in margin erosion control techniques, taking advantage of its properties, ease of installation and durability, and evidence the importance of monitoring the techniques to know the long-term performance. The erosion control technique with a geogrid mattress showed the best results in all the analyzed sections.</p>

<p>The Nordic countries in Europe are faced with specific challenges when it comes to construction. Next to specific soil conditions, these regions are faced with significantly lower temperatures during wintertime than other regions in Europe. To confirm that the current best practices for geosynthetic installation are also applicable to these specific cold conditions or that new guidelines should be implemented for these specific conditions, full scale field testing has been conducted recently within the ROUGH project. A job site in the north of Finland was prepared to perform installation damage testing on nonwoven geotextiles used as filtration/separation geotextile in a drainage trench. Laboratory evaluation of the characteristics before and after installation provides a good view of the impact of installation in Nordic conditions: cold climate and typical Nordic soils.</p>

Fabric formed concrete revetments are being applied in several fields of application. This can be erosion protection, sealing, mechanical protection or as ballasting element for e.g. pipelines. These applications require different performance of the concrete mattress. Despite the long history of more than 50 years, there are still unknown technical parameters in terms of concrete filled geotextile mattresses. This paper will therefore explain the contribution of concrete mattresses to the tensile strength of concrete, which has been carried out at the University of Applied Sciences in Münster. Above it, it will demonstrate the applicable ice load on a concrete mattress, as well as the hydraulic roughness of a concrete filled mattress. Additionally showed reference applications will underline the relevance of concrete mattresses in hydraulic engineering.

Local scour around bridge piers is one of the most diffused causes of failure for river bridges since it considerably modifies the geometry of the riverbed around the foundation. Countermeasures have been proposed in terms of both bed armoring and flow-altering de-vices. In this field, the use of Geosynthetics can provide innovative solutions, with envi-ronmental, economic and technological benefits compared to more traditional approaches. In the paper some flume experiments, run in clear-water flow conditions on a circular pier in a homogeneous granular riverbed, are described. The tests included four runs where the area around the pier was covered with innovative “Geo-carpet” systems made by plastic nets with different mesh size, and one reference test on an unprotected pier. The results, at least for a single hydro-dynamic condition, showed the efficiency of the Geo-carpets on the reduction of the scour depth and volume, and pave the way to future experiments in-vestigating different geometries and flow conditions (including live-bed scour).

<p>Interaction between soils and nonwoven geotextiles is very important in applications of these materials as filters in geotechnical and geoenvironmental engineering. Filters are used to prevent the erosion of soils in contact with the filter without impeding the flow of seeping water through the soil. A nonwoven geotextile should retain soil particles without causing excessive clogging inside the geotextile openings. Significantly, the mechanism of soil-nonwoven geotextile interaction is very complex. Generally, it depends on the geotechnical characterization of the base soil and on the physical and hydraulic parameters of nonwoven geotextiles. Several methods have been presented by researchers for assessing the filtration behaviour of soil-nonwoven geotextile systems. These include the hydraulic conductivity ratio test, long-term flow test and the Gradient Ratio test. Without any doubt, the Gradient Ratio test is the most commonly used method for measuring filtration compatibility of soil-geosynthetic systems. This paper presents laboratory method for the study of evaluation of interaction between internally unstable soil and needle-punched nonwoven geotextiles, with particular reference to the applications of these materials as filters. The need for improvements in laboratory test for a better understanding of soil-nonwoven geotextile interaction and modifying filtration criteria for nonwoven geotextiles is highlighted.</p>

In this study, the compatibility of internally unstable soils with two nonwoven geotextile filters was analysed by means of a method proposed by the Authors in a recent research. The method is based on a geometrical, experimental and micro-structural approach that considers the geotextile pore size distribution and its filtration opening size, the soil grain size distribution and its critical diameter of suffusion, the results of long-term filtration tests and the scanning electron microscope images of geotextile microstructure. The meth-od application allowed the Authors to better evaluate the soil/geotextile filter compatibility under critical/severe conditions.

The contact between wastewater and geotextiles can lead to the development of biofilm due to microorganisms’ activity resulting in the decrease of void ratio in the geotextile ma-trix (bioclogging). This phenomenon reduces the lifespan of geotextiles in works such as sanitary landfills, mining lagoons or wastewater stabilization ponds. However, geotextiles can also promote the removal of wastewater’s compounds such as suspended solids, or-ganic compounds, nitrogen (N) and phosphorus (P). The objective of this research is to evaluate the bioclogging evolution in two types of non-woven geotextiles of different weights after contacting with a wastewater. Laboratory experiments were carried out in permeameters colonized with wastewater biomass and fed with domestic synthetic wastewater (300 mg COD/L, 30 mg N-NH4/L, 6 mg P-PO4/L, C/N:4 and C/P:20). The re-sults show rapid biofilm adhesion to both geotextiles and good stabilization conditions of the biofilm, but clogging was not significant for 80 days of contact. Removal of COD, N and P was slightly higher for the GT300 (around 82%, 55% and 36%, respectively), but considered good for both geotextiles.

The paper presents the results of tests on a family of products for erosion control on riv-er/channel banks: geomats reinforced with double twisted steel wire meshes or with polypro-pylene geogrid; and reinforced geomats combined with geocontainer mattresses. The allowable resistant shear stress and allowable water velocity have been evaluated by testing in a flume according to ASTM D6460. Two different experimental campaigns have been carried out, to evaluate the performance of products both in unvegetated and vegetated conditions, both at short and at long flow duration. The analysis of test results allowed to define the surface of al-lowable shear stress vs the elapsed time t (years) from installation and the duration of flow D (hours). The procedure for getting the design curves of allowable shear stress vs flow duration at different times t is illustrated. The obtained charts allow the design according to the princi-ples set in ISO 18228-8.

<p>Geotextiles have been successfully applied in the filtration function in road works for more than 50 years, composing drainage systems or acting as a separating element, in which the filtration and separation functions are associated. Recently, they have also been applied to protect pavement layers from increasing the moisture content, in which the structure and the hydrophobic characteristics of the geotextile are of great relevance. This hydrophobic characteristic is provided by both the raw material and its structure and prevents water from penetrating the pores of the unsaturated geotextile unless a positive pressure equals to or greater than the water penetration resistance occurs. Such water penetration resistance is a property of the geotextile related to the hydrostatic pressure that it supports until the passage of water occurs. During the manufacturing process, either by adding lubricating oils or through a chemical finishing composition, nonwoven geotextiles from staple fibers may have their hydraulic properties temporarily modified, making them hydrophilic or considerably reducing the intrinsic characteristic of hydrophobia. This article presents a discussion on the factors that influence this behavior and experimental results to evaluate the influence of the type of soil at the interface and the characteristics of the geotextile, considering its pore distribution and its water penetration resistance. Through experiments in nonwoven geotextiles, either hydrophobic or hydrophilic, it is possible to observe the influence of the fabric condition on the water penetration resistance, and how the initial condition of a virgin nonwoven geotextile with a water penetration resistance near to zero may change when the flow causes the leaching of surface additives.</p>