APLICACIONES DE GEOMEMBRANAS y GEOSINTHETIC CLAY LINERS GCL S

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1 APLICACIONES DE GEOMEMBRANAS y GEOSINTHETIC CLAY LINERS GCL S 1 Seminario Argentino sobre Uso de Geosintéticos Buenos Aires Centro Cultural Borges Sergio A. Reyes Reyes & Asociados S.R.L. INGENIERIA Y MEDIOAMBIENTE

2 The Performance of Engineered Landfill Covers and Liners Hydraulic Performance - Restrictions Promote a Degradation Cycle Avoid Pollutant Transport into GW : Single Liners, Single Composite Liners Double Simple Liners, Double Composite Liners Influence of Geomembranes and GCL s on methane uncontrolled dispersion covers!!!!! Conclusions

3 Liner Design: Bottom Barrier A. Compacted Clay B. Geomembranes.are They Useful?? C. Leachate Collection System D. Bentonite E. Geosynthetic Clay Liners What s their Advantage??? Bentonite? Trash LCS GM 0.6 m CCL Subbase

4 Traditional Landfill Goal: Keep Liquids Out Cap CH 4, CO 2.. Or NO GASES?? Buried Waste (little decomposition) Liner and Leachate Collection system Leachate to Treatment Plant

5 Long term aquifer protection A balance between low and high infiltration cover design philosophies should be attempted (Rowe et. al., 1997). According to Rowe et al. high infiltration into the landfill during the OPERATIONAL PHASE and SOME TIME AFTER WASTE DISPOSAL CEASES may be allowed.

6 POOR OR LACK OF COMPACTION PROMOTES, CHANNELING, FISSURING AND CRACKING : PREFERENTIAL PATHS THIS IN TURN LEADS TO CONCENTRATED (EXCESSIVE) INFILTRATION: POORLY HOMOGENIZED

7 Can we construct better Covers?????

8 Certainly.Not an Easy Task

9 Bioreactor Landfill Goal: Add Liquids Cap CH 4, CO 2 Leachate Recirculation Buried Waste (rapid decomposition) Liner and Leachate Collection System Schematic Shows Anaerobic Operation Leachate to Treatment Plant

10 Early Surface Infiltration Systems

11 What low and high infiltration means? The concept varies from site to site not only because of rainfall differences but also as a consequence of : Landfill layout. Regional elevation contours Cover slope and Const. Characteristics Run off characteristics of the catchment area All play a key role.

12 HOWEVER, THE MOST IMPORTANT FEATURE IS the REMOVAL EFFICIENCY OF THE BOTTOM DRAINAGE SYSTEM

14 The volume of infiltrated water must be effectively limited and distributed through a less permeable homogenizing cover. BIOREACTOR TENDENCY

15 Horizontal Trenches for Leachate Recirculation

17 CLAY Size ( < 2µm ) Mica Sheets (Plate like) Particles. Cohesive Nature of Fine Soils related to content of clay like minerals (kaolinite, illite, montmorillonite (Ca, Na,) clorite o vermiculite.)

18 CLAY Clay Minerals are negatively charged on surface due to Isomorphous substitution. As a result of uneven distribution of electrical charges and water dipoles ions are hydrated (+ s to n s and viceversa). Hydrated Cations (+ Ves.) attracted to clay particles (-Ves.). Double layer. Free Water attempts to migrate into de Difuse Double Layer (osmosis) to equilibrate concentracions (water is the transport agent) Expansion / Swelling. The higher the Electrolyte Conc. (ions/cm 3 ) the thinner the DDL results and less interaction.. Less Swelling.

19 CLAY Osmotic Swelling pressure can exceed 1000 Kpa..specially with highly compacted clay or dry clay causing expansion and SOFTENING. IF Salt conc. In pore water is high lower swelling pressures. Viceversa High Osmotic pressure, fast swelling, Vol. Increase, Softening,.LOWERS k.. Na + bentonites!!! However, Organic (Water) Soluble Liquids have a similar effect, low dielectric constant (Є ~ 2 vs 80 for water) DDL Disappears k INCREASES. Cations interchange can induce swelling ( thickness of DDL). e.g : 2 N A+ substituting 1 C ++ a.

20 Montmorillonitic clays Charge Deficiency Relatively low in outer layer - 0,3 e - /unit cell). Does not fix K +. Weak layer bonding + Hydrated Cations = expansion /Swelling. C.E.C. aprox. 100 meq / 100 g. Properties Desert Zones from Volcanic Ash. Severe Swelling and Shrinking. Either Low..or High K.and!!! Ca ++ Ø res = 2º Na ++ Ø res = 0º - 3º.

22 Now taking into account the Mass transfer equation based on Fick s First and Second law the total mass flux responds to the following equation (C.Shackelford 1988,89) J n s c D n c x D R d = 1 + (ρ b /n) * K p m n c x

26 Polymers Thermoplastics Linear molecules with a ball or chain structure Shape retained by physical strength Strength lost and can be shaped when heated Thermosets Closed three dimensional molecular structure Shape retained by chemical bonding Can be softened by heating but retain their form Very stiff material Elastomers Comparatively open 3D molecular structure Shape retained by chemical bonding Can be softened by heating but retain their form Higly flexible materials

27 Common polymers used to manufacture Geotextiles Polyamides (Nylon) Additives are used to : Control Degree of polymerization (= chains of monomers=viscosity) Protect the polymer against light (UV light breaks down polymer) Resistant to Thermo oxidation

28 Common polymers used to manufacture Geotextiles Polyester (PETP) Degree of polymerization must be carefully controlled (viscosity) Good for Reinforcement Good Creep Characteristics

29 Common polymers used to manufacture Geotextiles Polyolefins There are two types Polyethylene Polypropylene

Common polymers used to manufacture Geotextiles Polyolefins Polyethylene (PE) LDPE (density 920 930 kg/m³) LLDPE (density 925 945 kg/m³) HDPE (density 940 960 kg/m³) Better Physical Characteristics

30 Common polymers used to manufacture Geotextiles Polyolefins Polyethylene (PE) LDPE (density kg/m³) LLDPE (density kg/m³) HDPE (density kg/m³) Better Physical Characteristics from LDPE to HDPE HDPE is more Rigid and Stronger, + Resistant to Chemical Attack Degree of crystallinity controls physical properties Cristallinity = Regular Chain or Highly polar = Higher Density Branching = Deviation from Linear Chain = Lower Cristallinity (density) HDPE low Branching so Geotextiles and Geomembranes

31 Common polymers used to manufacture Geotextiles Polyolefins Polypropylene (PP) Prone to Branching with other Monomers (e.g. Ethylene) Quite Creep Suceptible Much more suceptible to oxidation.additives quantity!! Against ageing

Geosynthetic Fibres Polyester may have higher E and better creep characteristics...sinks in water PP performs well wet and dry.floats UV light sensitive 85 % loss when exposed to sunlight + 3 months.

32 Geosynthetic Fibres Polyester may have higher E and better creep characteristics...sinks in water PP performs well wet and dry.floats UV light sensitive 85 % loss when exposed to sunlight + 3 months. Polyamide (Nylon) reduces 30 % strength when soaked PE depends on molecular weight...degree of crystallinity (density) Non wovens (spraying fibres on a platform ) FS strain 50 to 150 % Plastic Meshes (geogrids) from PP or PE from extrusion reinfcnt. Wovens (interlacing yarns...long. WARP.CS FILL Less strain to Failure used for reinfcnt.

36 What`s the Role of Difussion Coefficients for Geomembranes??? What`s the Mass Flux Thru Them?? F = S gf D g Δ cf /t GM

38 Geosynthetic Clay Liners GCLs are thin, prefabricated sheets (rolls) of clay trapped between two other media usually geotextiles. The clay may be bonded to a geomembrane sheet. GCLs are used for waterproofing, and have been used as a clay liner in landfills.

39 Types of Geosynthetic Clay Liners (GCLs) Bentonite + Adhesive Adhesive bound bentonite to upper and lower GX Bentonite Stitch bonded bentonite between upper and lower GX Bentonite Needle punched bentonite through upper and lower GX Bentonite + Adhesive Adhesive bound bentonite to a geomembrane Courtesy J. Zornberg

40 Uses of GCLs in landfill sites A liner component Hydraulic barrier A cover component Hydraulic barrier Gas barrier

41 Landfill Cover systems GM Cover Soil GCL Advantages Can be a composite GCL/GM Liner Gas containment by GCL & GM GM protects GCL from Desiccation & Penetration by roots Disadvantages Potential interface slippage between GM & GCL on slopes Higher cost than with single component liner

45 Landfill Single Liner systems GM Leachate collection system GCL Advantages Composite Liner system leads to very low seepage rate GM provides protection to GCL Disadvantages Thin liner system vulnerable to puncture Thin liner system has limited chemical attenuation capacity

46 Landfill Double Liner systems GM Leachate collection layer GM GCL Advantages Composite Liner virtually impermeable GM s provide protection to GCL Disadvantages Thin liner system vulnerable to puncture Thin liner system has limited chemical attenuation capacity

GM GM Landfill Double Liner systems with leak detection layer Leachate collection layer GCL Leak detection layer CCL Advantages Double liner with leak

47 GM GM Landfill Double Liner systems with leak detection layer Leachate collection layer GCL Leak detection layer CCL Advantages Double liner with leak detection GCL can be constructed with light weight equipment No consolidation water from GCL Disadvantages High cost Leak detection layer must be pumped to remove liquid

48 Dry GCL Hydrated GCL 48

49 Gravity roll release: GCLs panels lowered downslope by slowly releasing harness assembly Moving roll pull: One end of roll placed at site perimeter, GCL roll suspended from equip. moving backward 49

50 Minimum overlap seam: 150 to 300 mm depending on product and site conditions Ex: for Needle punched GCL, Dry bentonite is added using a lime spreader or line chalker 50

51 Other issues: Premature wetting of GCL by rain Shrinkage of GCL upon drying Shrinkage of GCL-delay in placement of cover material Patches Placement next to rigid structures Pipe penetrations 51

53 THANK YOU VERY MUCH FOR YOUR KIND ATTENTION!!!!

Geosynthetics. Nanjundaswamy P. Dept. of Civil Engineering S J C E, Mysore

Geosynthetics. Nanjundaswamy P. Dept. of Civil Engineering S J C E, Mysore Geosynthetics Nanjundaswamy P. Dept. of Civil Engineering S J C E, Mysore What are Geosynthetics? GEO Soil, Rock or other Geotechnical material SYNTHETIC Man made Polymeric material Used to enhance, augment