Description:
After a 26-mm precipitation in February 2014, noticeable ground movements were recorded on the north batter of Maddingley brown coal open pit, Victoria. To investigate the rainfall effect on the stability of the brown coal batter with opened cracks, a three-dimensional geologic model was developed, and the finite element program encoded in Plaxis 3D was employed to conduct a complex two-phase (fluid-solid) coupled numerical simulation. It was found that the simulated deformations were well agreed with the field survey data. There were ground movements along the length of cracks on both sides of the crack with larger movement towards the pit bottom. The coupled effect of hydrostatic forces from the crack in the rear of the batter and from the clay layer underlain the batter caused the block to slide, or batter failure. From the results, it revealed that both short-term high rainfall intensity precipitation and long enduring low rainfall intensity precipitation could cause the brown coal batter with opened cracks instable.
Description:
Australian Research Training Program (RTP) Scholarship Federation University Australia George Collins Memorial Scholarship.
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.
Description:
The study is supported by the Australian Research Training Program (RTP) Scholarship and Federation University Australia George Collins Memorial Scholarship
Description:
With the increased size of excavation due to long-term open cut mining, batter instability has become a major geo-hazard in Victorian Brown Coal Open Pits where facilitate some largest brown coal mining operations in the world. Block failure is a unique failure mode in Victorian brown coal mines, which is often associated with cracks and rainfall. Maddingley Brown Coal Mine (MBC) is located in Bacchus Marsh, Victoria, Australia. Slope instability has also been a major geo-problem since the open pit mining commenced in MBC in 1940s. Making clear the cracking mechanism and the correlations between rainfall and batter instability have important implications in better understanding and predicting batter failures in Victorian brown coal mines. In this research, three-dimensional geologic models were developed to investigate the mechanism of brown coal batter instability. The finite element program encoded in Plaxis 3D was employed to conduct the complex two-phase (fluid-solid) coupled numerical simulations. The results revealed the cracking mechanism of coal batter and the effects of rainfall on batter stability. It was found that the brown coal batter with overburden tends to lead a circular critical path while the batter after overburden removal shows a trend of block sliding as interpreted by the shear and tensile strains simulated. The existence of joints and the hydrostatic water pressure in the joints could adversely affect the stability of brown coal batter towards block failure. Precipitation can increase the deformation, excess pore pressure, total pore pressure, active pressure and decrease the matric suction, and thereby decrease the shear strength, effective stress, and batter stability. The results from the three-dimensional hydro-mechanically coupled finite element study were well agreed with the field monitored data, theoretical calculations, and Victorian brown coal mining experience.
Description:
The precipitation and evaporation records from 1972 to 2013 were analysed at five stations in central Victoria, Australia. The stations formed a north-south transect of sites across a distinct climatic gradient spanning the dry inland plains, the Great Dividing Range and the southern coastal zone. The focus was on the March November 'Growing Season' when typically higher available moisture is critical for a variety of agricultural practices and water management across the region. Growing season rainfall trends were fairly consistent across all stations with ongoing declines generally observed in all months with the exception of November, with the most notable declines in April, May and October. Pan evaporation recorded display greater variation between stations with both significant positive and negative trends evident within the season across the station network. The influence of El Nino Southern Oscillation and Indian Ocean Dipole on rainfall and pan evaporation was statistically significant, increasing through winter and peaking in spring at all stations. The Southern Annular Mode displayed marked intraseasonal influence which appeared to be highly location dependent. Interestingly, the tropical climate drivers displayed a stronger relationship with pan evaporation than rainfall over the analysis period. This highlighted the potential benefits of taking a broader terrestrial water balance (TWB) perspective of both pan evaporation and rainfall, a concept previously termed 'Effective Rainfall'. Critically, this study shows the importance of understanding regional variation in TWB elements with respect to local topography and geographic location, as well as intraseasonal variations within the overall growing season.
Description:
The precipitation and evaporation records from 1972 to 2013 were analysed at five stations in central Victoria, Australia. The stations formed a north-south transect of sites across a distinct climatic gradient spanning the dry inland plains, the Great Dividing Range and the southern coastal zone. The focus was on the March November 'Growing Season' when typically higher available moisture is critical for a variety of agricultural practices and water management across the region. Growing season rainfall trends were fairly consistent across all stations with ongoing declines generally observed in all months with the exception of November, with the most notable declines in April, May and October. Pan evaporation recorded display greater variation between stations with both significant positive and negative trends evident within the season across the station network. The influence of El Nino Southern Oscillation and Indian Ocean Dipole on rainfall and pan evaporation was statistically significant, increasing through winter and peaking in spring at all stations. The Southern Annular Mode displayed marked intraseasonal influence which appeared to be highly location dependent. Interestingly, the tropical climate drivers displayed a stronger relationship with pan evaporation than rainfall over the analysis period. This highlighted the potential benefits of taking a broader terrestrial water balance (TWB) perspective of both pan evaporation and rainfall, a concept previously termed 'Effective Rainfall'. Critically, this study shows the importance of understanding regional variation in TWB elements with respect to local topography and geographic location, as well as intraseasonal variations within the overall growing season.