Barriers

 

  Liner types

  Functions

  Construction

 

 

Liner types

 

Bottom barriers should provide impermeabilization to leachate, prevent biogas from escaping into the environment, provide mechanical support for the waste mass, and avoid accumulation of leachate by means of the filtration, drainage and collection system located above the bottom barrier.

Side barriers in landfills constructed below surface level should provide impermeabilization to leachate and to external water fluxes, mechanical resistance to water pressure, drainage of leachate and, if necessary, external water, and prevent lateral migration of biogas.

Top cover should prevent biogas from escaping into the environment, avoid or reduce rainwater infiltrations through a combination of sealing and drainage functions, and provide support for aftercare options such as vegetation and erosion control.

 

 

Functions

 

The functions of barrier system components are as follows: lining, leachate percolation and drainage (horizontal flow and vertical flow), reinforcement, mechanical protection, separation, erosion control, water filtration and drainage, and biogas migration control.

 

Construction

 

Lining components in barrier systems should be designed specifically according to the type of material used.

The emplaced clay liner should be carefully engineered and controlled both in laboratory tests and in the field in order to present a homogeneous performance. During the construction phase particular care should be devoted to compaction and moisture control. Existing clay strata should be considered as a raw material and remoulded and processed in order to respect proper design parameters.

Mechanical support of synthetic liners should be adequate to avoid localized subsidence and/or differential settlement which 

can determine failure of the liner or significantly change the slope. The supporting soil for the synthetic liner should be shaped according to the design slope, well compacted and rolled.

After emplacement, lining should be controlled according to a well-defined Quality Control Procedure.

 

 

 

Drainage

 

It is important to have flexible structures that can adapt themselves to settling and horizontal landfill movement and can resist to potential damage by operating machines.

Leachate drained from the bottom of the landfill, has to be collected continuously in order to avoid leachate hydraulic head over the barrier system. According to some guidelines, in order to avoid accumulation, leachate should not be pumped but collected and conveyed only by gravity.

 

Casella di testo:

University of Padua

IMAGE Department

 

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Biogas

 

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