Brown Coal in Victoria, Australia and Maddingley Brown Coal Open Cut Mine Batter Stability

Brown coal is young, shallowly deposited, and widely distributed in the world. It is a fuel commonly used to generate electricity. This paper first reviews the resources and characteristics of brown coal in Victoria, Australia, and its exploitation and contribution to the economy or power supply in Victoria. Due to the shallow depth of the brown coal seam, e.g. very favorable stripping ratio, open pit mining is the only mining method used to extract the coal at low cost for power generators. With the large-scale mining operations, cases of batter failure were not rare in the area. From the comprehensive review of past failures, overburden batter tends to fail by circular sliding, coal batter tends to fail by block sliding after the overburden is stripped due to a weak water-bearing layer underneath the coal seam and tension cracks developed at the rear of the batter, and batter failure is typically coincided with peak raining seasons. Secondly, the paper reviews the case study of Maddingley Brown Coal (MBC) Open Cut Mine batter stability, including geology, hydrogeology, and hydro-mechanically coupled numerical modelling. The modelling employs three-dimensional finite element method to simulate the MBC northern batter where cracks were observed in November 2013. The comprehensive simulation covers an overburden batter, a brown coal batter, two rainfall models, and a buttressed batter. The simulated results agree well with observed data, and it is found that the rainfall at the intensity of 21mm substantially lowered the factor of safety of the coal batter

Rainfall affected stability analysis of Maddingley brown coal eastern batter using plaxis 3D

Rainfall is a common factor that triggers the instability of Victorian Brown Coal (VBC) open pits which facilitate some of the largest brown coal mining operations. There has been no relevant study on rainfall-induced slope instability of VBC open pits in literature. In this paper, a three-dimensional (3D) two-phase (fluid-solid) coupled finite element method (FEM) was employed to investigate the stability of Maddingley Brown Coal (MBC) eastern batter under different rainfall conditions. It was found that the batter tends to lead a circular failure path during large rainfall. With the increase in either precipitation period or rainfall intensity, the deformation, excess pore pressure and active pressure increased, while the matric suction decreased. The hydrostatic force in the confined aquifer underlying the brown coal seam increased during rainfall; meanwhile, the resisting force decreased. As a result, the shear strength decreased and thereby the stability of the batter decreased. The safety factor and the critical failure path of the eastern batter simulated in this study were consistent with the previous study on the Northern batter. This study is a strong supplement to the literature on rainfall-induced instability of VBC batters. In the meantime, it is significant to provide a reference to the application of sophisticated 3D numerical modelling for studying slope instability of brown coal and similar mineral deposits. © 2020, Saudi Society for Geosciences.The study is supported by the Australian Research Training Program (RTP) Scholarship and Federation University Australia George Collins Memorial Scholarshi

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.Australian Research Training Program (RTP) Scholarship Federation University Australia George Collins Memorial Scholarship

Stability study on the northern batter of MBC Open Pit using Plaxis 3D

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

Noradrenaline released from locus coeruleus axons contracts cerebral capillary pericytes via α2 adrenergic receptors

Noradrenaline (NA) release from locus coeruleus axons generates vascular contractile tone in arteriolar smooth muscle and contractile capillary pericytes. This tone allows neuronal activity to evoke vasodilation that increases local cerebral blood flow (CBF). Much of the vascular resistance within the brain is located in capillaries and locus coeruleus axons have NA release sites closer to pericytes than to arterioles. In acute brain slices, NA contracted pericytes but did not raise the pericyte cytoplasmic Ca2+ concentration, while the α1 agonist phenylephrine did not evoke contraction. Blocking α2 adrenergic receptors (α2Rs, which induce contraction by inhibiting cAMP production), greatly reduced the NA-evoked pericyte contraction, whereas stimulating α2Rs using xylazine (a sedative) or clonidine (an anti-hypertensive drug) evoked pericyte contraction. Noradrenaline-evoked pericyte contraction and capillary constriction are thus mediated via α2Rs. Consequently, α2Rs may not only modulate CBF in health and pathological conditions, but also contribute to CBF changes evoked by α2R ligands administered in research, veterinary and clinical settings

Efficient C2 Continuous Surface Creation Technique Based on Ordinary Differential Equation

In order to reduce the data size and simplify the process of creating characters’ 3D models, a new and interactive ordinary differential equation (ODE)-based C2 continuous surface creation algorithm is introduced in this paper. With this approach, the creation of a three-dimensional surface is transformed into generating two boundary curves plus four control curves and solving a vector-valued sixth order ordinary differential equation subjected to boundary constraints consisting of boundary curves, and first and second partial derivatives at the boundary curves. Unlike the existing patch modeling approaches which require tedious and time-consuming manual operations to stitch two separate patches together to achieve continuity between two stitched patches, the proposed technique maintains the C2 continuity between adjacent surface patches naturally, which avoids manual stitching operations. Besides, compared with polygon surface modeling, our ODE C2 surface creation method can significantly reduce and compress the data size, deform the surface easily by simply changing the first and second partial derivatives, and shape control parameters instead of manipulating loads of polygon points

Adaptive phase-field modelling of fracture propagation in poroelastic media using the scaled boundary finite element method

A scaled boundary finite element-based phase field formulation is proposed to model two-dimensional fracture in saturated poroelastic media. The mechanical response of the poroelastic media is simulated following Biot's theory, and the fracture surface evolution is modelled according to the phase field formulation. To avoid the application of fine uniform meshes that are constrained by the element size requirement when adopting phase field models, an adaptive refinement strategy based on quadtree meshes is adopted. The unique advantage of the scaled boundary finite element method is conducive to the application of quadtree adaptivity, as it can be directly formulated on quadtree meshes without the need for any special treatment of hanging nodes. Efficient computation is achieved by exploiting the unique patterns of the quadtree cells. An appropriate scaling is applied to the relevant matrices and vectors according the physical size of the cells in the mesh during the simulations. This avoids repetitive calculations of cells with the same configurations. The proposed model is validated using a benchmark with a known analytical solution. Numerical examples of hydraulic fractures driven by the injected fluid in cracks are modelled to illustrate the capabilities of the proposed model in handling crack propagation problems involving complex geometries. © 2023 The Author(s

Focusing on the patterns and characteristics of extraordinarily severe gas explosion accidents in Chinese coal mines

Extraordinarily severe gas explosion accidents (ESGEAs) (thirty fatalities or more in one accident) have a high occurrence frequency in Chinese coal mines. There are 126 ESGEAs that occurred in China from 1950 to 2015, and they were investigated through statistical methods in this study to review the overall circumstances and to provide quantitative information on ESGEAs. Statistical characteristics about accident-related factors, such as gas accumulation, ignition sources, operating locations, accident time, coal mine regions and coal mine ownership, were assessed in this paper. The statistical analysis shows that disorganized ventilation fan management was the most frequent cause of gas accumulation in ESGEAs, while illegal blasting was the most prominent cause of the ignition source in ESGEAs. Furthermore, ESGEAs were found to occur frequently in certain provinces (e.g., Shanxi, Henan and Heilongjiang) and during November and December of the year. Moreover, most accidents and the largest death tolls generally occur in state-owned coal mines. Based on the results of statistical studies, some countermeasures were proposed in this study

Spatially Variable Coal Slope Stability Analysis using Image-Based Scaled Boundary Finite Element Method

Slope stability analysis is a challenging task when complex stratigraphies, complex geometries and spatially variably soil parameters are considered. Numerical methods, such as the finite element method are commonly used in slope stability analyses, however, these methods require significant user input when meshing geometries consisting of heterogeneous and spatially variable materials. This paper presents a numerical technique combining the scaled boundary finite element method and image-based meshing for slope stability analysis. The inputs for the analyses require images detailing the stratigraphy and the spatial variation of the material properties. Quadtree decomposition is applied to simultaneously generate meshes and consider the spatial variation of material properties directly from the images through a mapping technique. The stability of slopes is analysed assuming an elastoplastic Mohr-Coulomb constitutive model for the soil. The shear strength reduction technique is applied to evaluate the shear reduction factor iteratively to define the factor of safety of the slope. Coal slopes at Yallourn open-pit mine, Victoria, Australia was considered, forming the basis of a case study to demonstrate the applicability of the presented method

Exposure to combustion generated environmentally persistent free radicals enhances severity of influenza virus infection

© 2014 Lee et al. Background: Exposures to elevated levels of particulate matter (PM) enhance severity of influenza virus infection in infants. The biological mechanism responsible for this phenomenon is unknown. The recent identification of environmentally persistent free radicals (EPFRs) associated with PM from a variety of combustion sources suggests its role in the enhancement of influenza disease severity. Methods: Neonatal mice (\u3c seven days of age) were exposed to DCB230 (combustion derived PM with a chemisorbed EPFR), DCB50 (non-EPFR PM sample), or air for 30 minutes/day for seven consecutive days. Four days post-exposure, neonates were infected with influenza intranasally at 1.25 TCID50/neonate. Neonates were assessed for morbidity (% weight gain, peak pulmonary viral load, and viral clearance) and percent survival. Lungs were isolated and assessed for oxidative stress (8-isoprostanes and glutathione levels), adaptive immune response to influenza, and regulatory T cells (Tregs). The role of the EPFR was also assessed by use of transgenic mice expressing human superoxide dismutase 2. Results: Neonates exposed to EPFRs had significantly enhanced morbidity and decreased survival following influenza infection. Increased oxidative stress was also observed in EPFR exposed neonates. This correlated with increased pulmonary Tregs and dampened protective T cell responses to influenza infection. Reduction of EPFR-induced oxidative stress attenuated these effects. Conclusions: Neonatal exposure to EPFR containing PM resulted in pulmonary oxidative stress and enhanced influenza disease severity. EPFR-induced oxidative stress resulted in increased presence of Tregs in the lungs and subsequent suppression of adaptive immune response to influenza