Abstract
Leachate containment in Denmark has through years been regulated
by the DIF Recommendation for Sanitary Landfill Liners (DS/R 466).
It states natural clay deposits may be used for membrane material
provided the membrane and drainage system may contain at least 95%
of all leachate created throughout the lifetime of the landfill.
Presently, the recommendation is under revision partly because
this clause was considered not to be sufficient to secure drink
water quality in underlying aquifers - a necessary containment of
at least 99% is foreseen. The revision should consequently take
into account advective ion transport as well as diffusion.Clay
prospection for clays rich in smectite has revealed large deposits
of Tertiary clay of very high plasticity in the area around
Rødbyhavn on the Danish island Lolland. The natural clay contains
60 to 75% smectite, dominantly as a sodium-type. The clay material
has been evaluated using standardised methods related to
mineralogy, classification, compaction and permeability, and
initial studies of diffusion properties have been carried out.
Furthermore, at a test site the construction methods for
establishing a 0.15 to 0.3m thick clay membrane have been tested
successfully. At natural watercontent w = 40 to 45% it is possible
to establish a homogeneous membrane with hydraulic conductivity k
<5 E-12 m/s giving an extreme low transport by advection.
The hydraulic conductivity measured in oedometer tests used for
establishing swell and deformation properties showed to be very
dependent on the stress level. It varies from k = E-11 to 2 E-13
m/s at vertical stresses from 5 to 4800 kPa and is clearly related
to a reduced effective porosity diminishing with stress.
Preliminary diffusion tests indicate a similar influence on the
effective diffusion coefficient being much lower than anticipated
using the total porosity. These properties are of major importance
to the future use of clay membranes for containment of hazardous
waste. In order to explain these properties microstrutural
investigations were initiated to establish boundary conditions for
evaluation of relevant transport processes.Consequently, this clay
material may be used as raw material to be compacted for membrane
purposes in a natural wet condition using high compaction effort
comparable to Modified proctor energy. It fulfils the requirements
that are presently proposed in the new Danish Recommendation for
Landfills and a number of other applications that are foreseen for
clay embedment of hazardous waste.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the Symposium on Microstructural modelling og natural and artifically prepared clay soils with special emphasis on the use of clays for waste isolation |
| Place of Publication | Lund |
| Publisher | Roland Pusch |
| Publication date | 1998 |
| Publication status | Published - 1998 |
| Event | Workshop on Microstructural modelling of natural and artificially prepared clay soils with special emphasis on the use of clays for waste insulation - Lund, Sweden Duration: 1 Jan 1998 → 1 Jan 1998 |
Workshop
| Workshop | Workshop on Microstructural modelling of natural and artificially prepared clay soils with special emphasis on the use of clays for waste insulation |
|---|---|
| Country/Territory | Sweden |
| City | Lund |
| Period | 01/01/1998 → 01/01/1998 |
| Other | No exact date found. |