Paper/Poster/Presentation Title
Keywords
Fly Ash, Hydraulic Conductivity, Darcy Hydraulic Testing, Infiltration tests
Start Date
25-6-2018 3:40 PM
End Date
25-6-2018 5:00 PM
Abstract
Large volumes of fly ash are generated by the coal-fired power stations and are currently disposed onto waste dumps, with limited space. Therefore, a need for an alternative ash disposal method arises. Limited studies has been conducted to understand the change in the hydraulic properties of ash under different backfilling conditions. This study focus on generating input data to model different fly ash backfilling scenarios into opencast coalmines and to determine its influence on the receiving environment.
Laboratory (Darcy Up-flow) and field (Auger hole) tests were conducted to determine the change in hydraulic conductivity over time with fly ash from two power stations in Mpumalanga. Darcy up-flow column tests were conducted with acid mine drainage (AMD) on ash pre-cured to 40, 50 and 60% moisture content.
Test results showed: 1) Laboratory hydraulic conductivity values for early time (1st week) ranges between 0.1 – 0.5 m/d and decreases over a 20 week period to 0.001 – 0.007 m/d.; 2) Ash-1 shows a consistent relationship between curing moisture content and hydraulic conductivity; 3) Ash-2 however, showed a more inconsistent relationship that may be due to the heterogeneous particle size distribution causing preferential pathways; 4) Field tests results showed reducing hydraulic conductivity values ranging between 0.2 – 0.9 m/d for freshly dumped ash and 0.01 – 0.5 m/d for 20 year old ash; and 5) fly ash initially neutralizes AMD (pH-2.5) to pH-11. Some acidification from pH-11 to pH-4 is observed throughout the testing. The geochemical processes along the flow path decreases the hydraulic conductivity with time.
GENERATING HYDROGEOLOGICAL MODELLING INPUT DATA FROM LABORATORY AND FIELD TESTS FOR FLY ASH MONOLITH DEPOSITION IN COAL MINE BACKFILLING, MPUMALANGA, SOUTH AFRICA.
Large volumes of fly ash are generated by the coal-fired power stations and are currently disposed onto waste dumps, with limited space. Therefore, a need for an alternative ash disposal method arises. Limited studies has been conducted to understand the change in the hydraulic properties of ash under different backfilling conditions. This study focus on generating input data to model different fly ash backfilling scenarios into opencast coalmines and to determine its influence on the receiving environment.
Laboratory (Darcy Up-flow) and field (Auger hole) tests were conducted to determine the change in hydraulic conductivity over time with fly ash from two power stations in Mpumalanga. Darcy up-flow column tests were conducted with acid mine drainage (AMD) on ash pre-cured to 40, 50 and 60% moisture content.
Test results showed: 1) Laboratory hydraulic conductivity values for early time (1st week) ranges between 0.1 – 0.5 m/d and decreases over a 20 week period to 0.001 – 0.007 m/d.; 2) Ash-1 shows a consistent relationship between curing moisture content and hydraulic conductivity; 3) Ash-2 however, showed a more inconsistent relationship that may be due to the heterogeneous particle size distribution causing preferential pathways; 4) Field tests results showed reducing hydraulic conductivity values ranging between 0.2 – 0.9 m/d for freshly dumped ash and 0.01 – 0.5 m/d for 20 year old ash; and 5) fly ash initially neutralizes AMD (pH-2.5) to pH-11. Some acidification from pH-11 to pH-4 is observed throughout the testing. The geochemical processes along the flow path decreases the hydraulic conductivity with time.
Stream and Session
F3: Modelling and Decision Making Under Uncertainty