Description:
Cracks manifested on the north batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia in November 2013. The crack opened varies from trace to approximately 150 mm wide was located at about 20 m back from the coal face and extended for approximately 50 m on the eastern side and terminated 10 m away from the access road. Site investigations and remedy measures were implemented immediately after the cracking. This study involves in a three dimensional modeling on the cracking mechanism using finite element method (FEM) encoded in Plaxis 3D software program. From the study, it was found that the initial model based on north batter being stable for many decades tended to lead a circular critical path while the model after overburden removal showed a trend of block sliding. The safety factor of initial north batter was 1.38 through safety analysis while it was decreased to 1.17 for the coal batter after overburden removal. But the simulated shear and tensile strains indicated that the coal batter after overburden removal in fact experienced block failure. Furthermore, the simulated location of cracking was in good agreement with the actual location, and the simulated heave of the coal seam was in good agreement with the experience in Victoria brown coal open pit mining The observed vertical crack would be a combined action of the overburden removal and the groundwater flow in the unconfined aquifer.
Description:
Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data.
Description:
Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data.