Study on the stability of brown coal batter with opened cracks on Maddingley brown coal mine

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.