Conference Agenda

<p>In 2020 Studio Speri has been engaged from Enel in the design of the maintenance project of two reservoirs (Sillico reservoir, constructed in 1940’ and Lombrici reservoir, constructed in 1950’). They are both located in Tuscany, in the district of Lucca (Italy). The scope of the work is the <strong>rehabilitation of the reservoirs impervious facing</strong>, both on the bottom and on the: natural slopes, embankments and concrete structures that define the reservoirs.</p>

<p>The existing facings of the reservoirs, made of concrete slabs, have failed due to <strong>differential foundations settlements</strong>. Both reservoirs are constructed in a complex geological contest. Sillico foundation is composed of compressible alluvial soils. Lombrici foundation is a doline, made of residual soil upon a limestone bedrock subjected to karst phenomena. The reservoirs have experienced cracking of the concrete facing several times. The rehabilitations have been done always through the restauration of the rigid impervious facing, without solving the problem definitively.</p>

<p>In order to achieve the best standard of waterproofness, the designed solution consists in the construction of a <strong>flexible geosynthetics impervious facing system</strong>. The new facing will be placed both upon the existing concrete slab (in the zones where they are not damaged or collapsed) and upon granular soil material (in the zones where the existing concrete facing has failed). The total area to be waterproofed is almost 4’600 m² (2’700 m² for Sillico reservoir and 1’900 m² for Lombrici reservoir).           </p>

<p>The facing is composed by an <strong>impervious geocomposite with a draining geocomposite</strong> for the drainage of the possible infiltrations. The impervious geocomposite is made of a 2.5 mm PVC geomembrane, heat sealed with a 500 g/m² geotextile. The geodrain is made of a geogrid, heat sealed with a 500 g/m² geotextile. Particular care has been taken in the design of the anchorage and sealing system.  </p>

<p>The authors of this paper have over five decades of combined knowledge on Geosynthetic Clay Liners (GCLs). This paper will cover both the engineering and performance capabilities of GCLs but also provide readers the dos and don’ts experienced by the authors over the course of their work exposure while working on GCLs on various projects worldwide since the early 90s. Kent von Maubeuge has been directly involved with GCLs since the early 90s when needlepunched GCLs were entering the market and has seen the growth of this geosynthetic material used on various applications while providing assistance on various research studies and testing done on GCLs over the course of the last three decades. Bruno Herlin has been directly involved with GCLs since 2000 with the direct responsibility of overseeing GCLs for his organization and has witnessed the what, where, when, who, and why a GCL should be used and how they should be used but also the dos and don’ts of their installation techniques. The paper will also cover the myths of GCLs. Both authors have had a history of sharing information between themselves on GCLs over the last five decades and are now going to share this information for the next generation to have in their GCL ‘bag of tricks’ to avoid mistakes made in the past but to also feel confident that GCLs do indeed work and can performance effectively as a proven barrier.</p>

<p>Downstream components of spillover section of any dam face the challenge of energy absorption or dissipation. Fatigue under impacts or dynamic loads is obvious which causes deterioration in such components over a period of time and therefore periodical repairs become essential. Conventional methods for such repairs are mainly based on impact resistant materials which have their own limitations whereas solutions with usage of geosyntheitcs are based on devising a system to resist impact rather than depending merely on some material. This fundamental distinction between principles of repair methodology underlines the benefits of geosynthetics. Their usage can not only help effectively repair the damaged components but also enhance their performance in several ways. Cost economy, faster execution and longevous life of repaired components are the main benefits if geosynthetics are applied with due understanding of the causes of damage and behavior of respective dam components under dynamic loads. The paper focuses on issues related to energy dissipation in the dam downstream and presents case studies of old Indian dams whose components subjected to dynamic loads have been repaired with application of geosynthetics.     </p>

<p>Defence against natural hazards is important for the preservation of the Alpine region as a living and economic area as well as a recreational area for present and future generations. Of specific importance are protective structures against natural hazards such as rockfall and avalanche events.</p>

<p>Construction in alpine regions requires special measures concerning design, execution and the selection of construction methods and materials. Especially for rockfall and avalanche protection, aspects of safety, construction costs and material availability as well as the limited construction time are of crucial importance. All these factors play an important role in design and execution. Examples are given to show how the use of suitable geosynthetics can lead to an economically and technically optimal solution for such protective walls.</p>

<p>For rockfall protection structures, the Austrian guideline ONR 24810 provides a technical planning basis that deals with protective structures against natural hazards. ONR 24810:2020 – “Technical rockfall protection - Terms, actions, design and structural solutions” provides guidance on the design and practical implementation of rockfall protection dams. These are used in cases where slope geometry and available space permit such a structure. Dams have advantages over nets, especially in terms of service life, construction costs and - depending on the design - energy absorption capacity. Before starting the design, the structure must be assigned to a certain defined type.</p>

<p>The design of avalanche protection dams in the fall zone is more complex. If an avalanche cannot be prevented in the area of origin, structures are erected in its fall-path or in its runout area to deflect the avalanche in another direction (deflection dam), to limit the lateral extent of the avalanche (guide dam) or to stop the avalanche completely (arrest dam).</p>

<p>In the paper, design, dimensioning, and execution are presented on the basis of selected projects</p>

<p>Of the civil infrastructure sectors, the environmental sector is the one which is growing the fastest as we seek to address the multiple issues posed by man-made pollution and population growth. Landfill industry needs to keep increasing both in terms of its capacity and its ability to safely dispose of the remaining waste and ensure that the existing landfill remain safe. The key task facing governments and landfill operators is one of maximizing the space available within landfills and safely containing the waste to ensure it will not contaminate groundwater or watercourses or pose threats in terms of instability or the build-up of potentially explosive gases.</p>

<p>Geosynthetics form a key part nowadays of the toolbox that the landfill designer and operator has available. They enable fill to be safely contained and leachates and gases to be safely collected. Geosynthetics maximize the space available within the site. They also reduce the need for mineral exploitation by reducing the need for thick clay liners, granular collectors, and filter systems.</p>

<p>A part of rainwater goes through the covering layer of soil and creates water pressure in the soil which would reduce the stability of the soil and increase the risk of direct sliding. That’s why a drainage layer is always recommended on top of the geomembrane. In some conditions, therefore, the upper part of the multilayered geosynthetic system located on top of the smooth geomembrane has to include a drainage layer and also a soil-gripping layer. Multifunctional geocomposites are available on the market which incorporates drainage, reinforcement, protection, and soil gripping in one product, and has been in use now for more than 15 years.</p>

<p>The paper introduces these multiple functions in the landfill capping system with the help of an existing project case study followed from its feasibility until the execution phase.</p>

<p>This paper presents the study case related to combination of geosyntethics used as riverbank slope normalization located in Cimanggis residential are, West Java, Indonesia. The combination of gabion, geogrid reinforcement combined with wiremesh facing and geocomposite of geotextile non woven-geogrid slope protection were applied along the section of the riverbank slope. The riverbank slope section spans 390 meters along Cikeas river where it will later become access road and near the crest will be constructed housing area. Slope stability analysis was conducted to determine the value of the slope safety factor with the aim of concluding what preventive and security measures could be. From the results of the analysis, it showed that the 13 meters high slope of the Cikeas river’s safety factor was below the criteria stated in Indonesian National Standard for Geotechnic Design Requirements with a safety factor 1.20 (the slope safety factor must be above 1.50). The combination of geosythetics were applied in the program and yield the safety factor up to 1.74 which indicated safe slope. This design also considered the earthquake pseudostatic load, where the result of the safety factor was 1.13 and fulfilled the criteria stated in Indonesian National Standard for Geotechnic Design Requirements (the slope safety factor must be above 1.10). The combination of those geosynthetics application worked effectively for normalizing the river bank slope.</p>

<p>The ‘Museum of the Future’ in Dubai is one of the most innovative buildings in the world, which is designed in three main parts, namely the lower green hill, the middle building, and the top elliptical void structure. As per the architectural design, the green hill is designed as a smooth transition from ground, in the form of an earthen vegetated mound which eventually should cover the embedded three-story podium structure. As a result, the green hill had to be constructed as claddings around the base structure rather than as a solid earth hill. Three different types of geosynthetic green systems were used to recreate the different slopes, which included reinforced soil for steep slopes, heavy revetement with geocells for moderate slopes, and rolled erosion control mats for gentle slopes. In most cases, the available thickness of soil layer was only 30 cm, complicating the design and construction of the geosynthetic systems. To ensure the stability of the geosynthetic green cover systems for moderate and gentle slope cases, continuous veneer reinforcement was installed below the thin soil fills, using double-twisted wire mesh netting that was anchored to the concrete structure at the top of the cover system. Due to existing space constraints, the soil reinforcement had to be anchored to the concrete structure in most of the cases for reinforced soil slopes. Additionally, a layer of geosynthetic drainage composite was installed below the entire surface area of the green cover system to enable easy drainage of the continuous irrigation water expected from the gardening activities.</p>

<p>Through the successful case reference of the ‘Museum of the Future’ project in Dubai, this paper sheds light on the possibilities, opportunities and challenges associated with the use of sustainable geosynthetic systems in iconic projects for landscaping and architectural applications.</p>

Over the past thirty years, geomembranes (GMs), especially high-density polyethylene (HDPE) ones, were used as impervious materials to provide a barrier to water and oxygen in many mine site reclamation cover systems around the world. The physical stability of these GM remains a major concern as it affects their performance to control fluid flows. Considering that HDPE GMs can crack even while being in the elastic domain, a maximum allowable strain (MAStrain) was fixed at 4% to avoid stress cracking. The MAStrain corresponds to a maximum allowable stress that must not be exceeded. This paper assessed the chemical and mechanical properties of exhumed GMs from two cover systems (S1 and S2) installed 13 and 20 years, and the impact of the tensile properties on the MAStrain. The results show that the geomembrane remains in the first degradation stage and no negative impact was found on the mechanical properties. The tensile behavior of the exhumed GM indicates a gain of stiffness that reduces the MAStrain.

<p>The iconic Angkor Wat Temple towers a landscape of meandering canals and rice fields and is encased in a huge 5km-long reservoir-moat. Beside its architectural relevance, the complex served as water storage and expansion basin to balance the tropical floods. Along the slopes of the moat embankments a protective staircase is set out of massive squared laterite and top carved sandstone blocks. The core of the embankment is made of silty sand layers compacted by hand. Due to the low density-state of the fill and to the fluctuating moat water-level, diffused portions of the embankment steps collapsed along the time, mainly following a roto‐translational slide mechanism. In 1997, after a period of intense rains, a major event involved the front steps of the Temple at its west-entrance, a portion of embankment that had been previously restored in the 1960´s. According to the back analyses carried out, the instability was caused by an unbalanced overthrust on the soil mass of the embankment, that built up through the water pressure within the embankment soil. The proposal of a geosynthetic-based reinforcement of the embankment took into account that the geosynthetic layers inserted in the soil mass could provide not only an increase of the shear strength of the fill body, but also a diffused drainage out of its compacted mass. In fact, the local Agency for the management of the Archaeological Park registered an increasing frequency in the embankments collapse events in the whole area of Angkor in the last 30 years, as more extreme climate conditions - higher rainfall peaks – have been taking over. The presented geosynthetic-based restoration proved its good performance at a distance of 20 years after its implementation, both in terms of behavior and impact in the Cultural Heritage context.</p>

This paper focuses on the application of Bituminous Geomembrane (BGM) for the water-proofing of new and existing earthen canals. The start of its application is about half-century back when USBR first time applied BGM in canal waterproofing and the first time BGM was used in waterproofing of a large dam by Coletanche in 1978 in France.

In India, the first appli-cation of BGM has been done in one kilometer stretch of Pench Canal in Nagpur district, Ma-harashtra which was given as a pilot project to Yooil Infra to arrest the seepage and enhance the stability of the canal. The area comprises expansive soil which has been problematic for canal banks stability, concrete lining failures, heavy seepage through banks and breaching of banks at different reaches of canal. The BGM application resulted in a complete stoppage of seepage through that section of the canal and no stability related problem was observed due to the elimination of drawdown conditions while and after the full flow of canal during mon-soon.

BGM is unique due to its properties of being flexible, high puncture resistance, practi-cally impermeable, resistant to thermal expansion, UV resistant, non-biodegradable, low maintenance cost and overall exceptional durability.

This paper gives the technical assessment of slopes of the canal with the existing concrete lining, outlining possible reasons for the fail-ure of concrete lining and remedy with the impervious bituminous geomembrane.