3012
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
4 GEO-ENVIRONMENTAL PROBLEMS IN LANDFILLS
WITH HIGH ORGANIC CONTENT
(ii) Higher moisture content will increase the self weight of
waste body especially under leachate recirculation. As indicated
by Eq.6,
F
S
will decrease with an increase of
W
i
.
4.1
Leachate generation
As mentioned in section 2.2, the difference between the initial
moisture content and the field capacity of the Chinese MSW is
greater than that of western countries, which is the main factor
causing high leachate production. Simulation result (see Figure
7) also shows that MSW with higher organic content and
moisture content has larger leachate production. Therefore,
calculation of leachate production in landfills with high organic
content MSW cannot neglect the effect of initial moisture
content and moisture release via decomposition of organic.
Under certain circumstances (e.g. clogging of leachate
collection system, etc.), high leachate mound might be resulted
due to the high leachate production in Chinese landfills.
(iii) During the bio-hydro-mechanical coupled process, the
cohesion and friction angle mobilized at a certain strain level
tend to change with an increase of waste age (see Figure 3).
This makes the determination of
F
S
even more complex.
5 CONCLUSION
Engineering properties of landfilled MSWs with high organic
content in Asian developing countries are distinguished from
those in developed countries. Numerical study through the
BHM coupled model showed that landfilled MSWs with higher
organic content tend to have larger leachate production, long-
term settlement and possibility of slope failure. The model
developed can be used to study the application of bioreactor
landfilling technologies in landfills with high organic content.
4.2
Settlement in landfills
The biodegradation-induced settlement rate is highly dependent
on the decomposition condition of landfill. Under optimum
biodegradation condition, Figure 8 shows that both samples will
accomplish their settlement within about 5 years. Therefore, if
the condition is adjusted via leachate recirculation or air
injection, most settlement would occur during landfilling stage,
which can significantly decrease post-closure settlement of
landfill. Figure 8 also shows that instant settlements (i.e.,
t
= 0)
of the two samples are close to each other. It is mainly due to
the relatively higher
C
6 ACKNOWLEDGEMENTS
The work was supported by the National Natural Science
Foundation of China (Grant Nos. 10972195, 51010008), and the
National Basic Research Program of China (“973” Project)
(Grant No. 2012CB719800)
C
’
for Orchard Hills sample which is pre-
shredded before tests. However, MSW from Qizishan landfill
has much more long-term compression, which indicates the
necessity of accelerating the biodegradation-induced settlement
of landfills with high organic content.
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+ cos
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Figure 9. Method of slices Figure 10. Ejection of leachate/gas
