Bioengineering Techniques Adopted for Controlling Riverbanks’ Superficial Erosion of the Simplício Hydroelectric Power Plant, Brazil

Mechanical and Thermoanalytical Study of Polypropylene Geomats Exposed in the Field and the Laboratory

A Hydroelectric Power Plant (HPP) presents erosion problems on reservoir slopes and margins. Geomats are a biotechnical composite technology increasingly used to protect soils against erosion. Survivability or durability of geomats is essential for successful application. This work analyses the degradation of geomats exposed in the field for more than six years. These geomats were used as erosion-control treatment in a slope at HPP Simplício in Brazil. The degradation of the geomats in the laboratory was also analysed through exposure in a UV ageing chamber for 500 h and 1000 h. Degradation was quantitatively evaluated by testing the tensile strength of the geomat wires and thermal tests such as thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed that the geomat wires exposed in the field had a greater decrease in resistance compared to the samples exposed in the laboratory. In the samples collected in the field, it could be observed that the degradation of the virgin sample occurred earlier than in the exposed samples, contrary to what was observed in the TG tests carried out with the samples exposed in the laboratory. The DSC analysis showed that the samples had similar behaviours for the melting peaks. This evaluation of the wires of the geomats was presented as an alternative to analysing the tensile strengths of discontinuous geosynthetic materials such as the geomats.

Sustainability in Geotechnics through the Use of Environmentally Friendly Materials

The reduction in the exploitation of non-renewable natural resources is nowadays widely recognized as a pressing need for a more sustainable society. Moreover, the increase in waste valorization and reuse of waste materials are undoubtedly important steps forward for environmental sustainability. Geotechnical design being part of typical civil engineering projects can play a major role in the sustainability of the built environment. Thus, a Special Issue was proposed focused on the use of environmentally friendly materials in geotechnical solutions, highlighting the relevance of geotechnics to reduce our carbon footprint. Their main purpose to collect and publish original research papers pointing out the use of sustainable materials in geotechnics has been achieved, through the great interest of the research community and a high number of submissions. This editorial summarizes the papers published during the 2020–2021 biennium, highlighting their main conclusions.

Geomats Used to Control Erosion on Reservoir Margins in Brazilian Hydroelectric Power Plants

Erosion on reservoir margins causes losses in the production of energy in Hydroelectric Power Plants (HPPs), making it necessary to implement control techniques that ensure the reduction in sediment deposits inside reservoirs. Among these techniques, geomats (geosynthetic erosion mats) are widely used to control erosion processes in slopes and watercourses. This material protects the margins both in the short and long term, contributing to strengthening the vegetation’s roots developed in the erosion areas. This paper studies the performance of geomats (with and without sack gabion) installed in six margin sections distributed in three experimental units of the Brazilian HPPs called Porto Colômbia and Volta Grande. The geomat performance was evaluated over four years of monitoring through a qualitative evaluation matrix and differential bathymetry. The influence of ultraviolet (UV) radiation on the degradation of geomats installed in each section (natural conditions), as well as on geomat ultraviolet-aging samples in the laboratory (accelerated conditions), was also evaluated using differential scanning calorimetry (DSC). The results showed no significant difference in performance between using the erosion control technique consisting only of geomats and the technique consisting of geomats and sack gabion. The highest bathymetric difference value obtained in the present study was 1.62 m in the experimental unit VG1, controlled with geomat without the application of sack gabion on the margin.

Semi-Rigid Erosion Control Techniques with Geotextiles Applied to Reservoir Margins in Hydroelectric Power Plants, Brazil

In Brazil, hydroelectricity represents close to 70% of the energy consumed in the country. However, hydroelectric plant operations may be affected by the deposit of sediments for erosive processes on reservoir margins. This study presents the results of implementing two semi-rigid erosion control techniques installed on reservoir margins of two Brazilian Hydroelectric Power Plants (HPPs). These techniques were the gabion and gabion mattress used as a mixed technique and geogrid mattress technique. This paper highlights the importance of implementing geotextiles in the construction process of these erosion control techniques, taking advantage of their separation properties. The performance of the techniques was evaluated using qualitative performance variables and by differential bathymetry studies performed in 2016 and 2020 in the experimental units installed in each HPP. Moreover, the degradation of the geotextiles in each installation was evaluated through thermal analysis. The erosion control techniques that showed the best results were gabion and gabion mattress. Regarding the exhumed geotextiles, thermal analyses have shown that the commercial geotextiles that were used can withstand temperatures of up to 200 °C leading to no changes to their structure.