Lesson 8-Geosynthetics Flashcards
5 major types of geosynthetic products:
- Geomembrane
- Geosynthetic Clay Liner
- Geotextiles
- Geonets
- Geogrids
-also known as flexible membrane liner (FML)
-one of the five major types of geosynthetic products used in landfill engineering
Geomembrane
Relatively thin sheets of flexible thermoplastic or thermoset polymeric materials that are manufactured and prefabricated at a factory and transported to the site.
Geomembrane
Primary function of geomembrane in landfill engineering is as a
liquid and/or vapor barrier
Are made of one or more polymers along with other ingredients such as carbon black, pigments, fillers, plasticizers, crosslinking chemicals, processing aids anti-degradants and biocides.
Composition of Geomembrane
The polymers used to manufacture _________________ include a wide range of plastics and rubbers differing in properties.
Composition of Geomembrane
Category of Polymeric Materials: (Composition of Geomembranes)
- Semi-crystalline thermoplastics – such as:
a. HDPE – high density polyethylene
b. LLDPE – linear low density polyethylene
c. VLDPE – very low density polyethylene
d. fPP – flexible polypropylene
2.Thermoplastics – such as:
a. PVC – polyvinyl chloride
3.Thermoplastics elastomers – such as:
a. CSPE – chlorosulphonated polyethylene
The thickness of geomembranes range from __________ to __________
0.75 mm to 3.0 mm
The recommended thickness for all the geomembranes is _______________ except for HDPE which should be at least __________ to allow extrusion for seaming.
0.75 mm, 1.50 mm
The most widely used geomembrane in waste management industry
HDPE- high density polyethylene
What are the salient features of HDPE:
a. Chemical resistance – landfill leachates pose no threat to a liner made of HDPE
b. Low permeability
c. Ultraviolet resistance – carbon black and antioxidants provide a synergistic effect
Geomembrane designed for waste containment applications requiring greater flexibility than HDPE. Lower weight allows to conform to nonuniform surfaces.
LLDPE- Linear lower density Polyethylene
Salient features of LLDPE:
a. Multi-axial tension properties – exhibits high out-of-plane elongation, allowing it to conform to differential settlement without jeopardizing the integrity of liner.
b. Puncture resistance – provides excellent puncture resistance due to its flexibility.
c. Chemical resistance – also resistant to leachate and other chemicals.
One of the polyolefin family of polymers which is often reinforced with an open weave fabric called scrim.
fPP- flexible polypropylene
Salient features of fPP:
Chemical resistance – chemical resistance is quite good in this product.
b. Ultraviolet
c. Installation Survivability – with tear resistance being high, puncture, impact characteristics are comparably high as well.
One of the original geomembranes used for waste containment applications. Components are: resin, plasticizers, filler, and pigment.
PVC – polyvinyl chloride
Salient features of PVC:
a. Flexibility – exhibits excellent out-of-plane flexibility and conformance to irregular subgrades.
b. Seameability – can be seamed by solvent method or thermal techniques.
c. Constructability – the easiest to install of all the geomembranes.
They are scrim reinforced and they have been used for essential all-barrier (waterproofing) applications, including landfill liners and covers.
CSPE – chlorosulphonated polyethylene
Salient features of CSPE:
a. Chemical resistance – excellent.
b. Ultraviolet resistance – excellent.
c. Installation Survivability – seaming can be performed by both thermal and solvent methods.
Use of geomembrane with an underlying
compacted clay liner (CCL) provides the optimal
liner system. This approach is referred to as a _______________
composite liner system