HYDRAULIC CONDUCTIVITY BEHAVIORAL DEVELOPMENT ON ARTIFICIAL VEGETATION SUBSTRATES (MADE BY COAL FLY ASH, GRAVEL G5 AND CLAY) FOR THE COAL MINING RECLAMATION PROJECT ”OBERDORF“ GKB-BERGBAU GMBH KÖFLACH AUSTRIA

Convention Bandung 2004 (CB2004)
The 33rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist
Horizon Hotel, 29-30 Nov, 1 Oct 2004, Bandung

HYDRAULIC CONDUCTIVITY
BEHAVIORAL DEVELOPMENT ON
ARTIFICIAL VEGETATION SUBSTRATES

(MADE BY COAL FLY ASH, GRAVEL G5 AND CLAY)

FOR THE COAL MINING RECLAMATION
PROJECT ”OBERDORF“ GKB-BERGBAU
GMBH KÖFLACH AUSTRIA

Anggoro Tri Mursito

Research Centre for Geotechnology, Indonesian Institute of Sciences (LIPI)

Abstract

The open pit coal mine “Oberdorf” located about 30 km north of Graz is the
biggest one in Austria. Coal production will cease in 2004 leaving an area of
350 hectares of which about 80% have to be recultivated and/or reclaimated.
The key issue of this research is to develop an optimized substitute for the
missing biologically active topsoil, which was dumped during mining activity, as
well as to figure out adjusted vegetation in dependence from the composition of
the “artificial” soil.

An artificial soil mixed made out of electrical-coal power plant wastes (fly ash)
and material from the mine (clay and gravel G5) has been created for the
reclamation of open pit mine site. Physico-chemical properties were measured
over time to examine them in a chronosequence of 22 plots (each 400m2) with
systematically changing mixtures (1,2 and 3 components of varying proportions
were established and planted. In the field plots, available nutrient content was
initially high but established only for some of plots. Due to ecological function
measurement, physical parameter, which is hydraulic conductivity, is one of
several physic properties will have to be monitored and analysed.

According to the development value of the year of 2003 (spring) shows that
increasing of water permeability classes (class 6) is leaning to the direction of
fly ash and tegel composition. Class 5 are only in the trial plot number 5 and 9.
Only in one trial plot which is drop in class 4 (trial plot 16), but it is still classified
into “good” class (according to “Arbeitskreis Standortskartierung, 1996”). The
trial plot number 1 has also classified into class 6, because the substrate
composition in this trial is only 100% of gravel. It has to be the highest class, but
it is not always the highest value of water permeability. All the trial plots are
classified into high to very-very high. Compared results between initial (spring, 2000) and recent measurement (spring, 2003) is shown that extremely
increased in the trial plot 3 and 13. In the year of 2003, in trial plot number 3
and 13 are suddently flare up to 4 classes (from class 2 to 6). As we can see in
the CT images of one component substrate (100 % of tegel) shows that cracked
structures clearly appear as a results of decreasing precipitation in the last
winter and also highly increasing of temperature as well. High percentage of
cracked means that water can easily flows. Most of the trial plots are increasing
of classes due to the season differences. The others (trial plot number 1, 5, 6
and 9) remain in the same class. Same grade doesn’t means that same value of
water permeabilty as well, but e.g. trial plot 1 has same class compared to the
result in 2000 and that means very very high.