Diesel particulate matter investigations in underground coal mines

A number of underground coal mines are using diesel-powered vehicles as the main source fuel for the transport. The primary concern with these diesel-operated vehicles is the diesel particulate matter (DPM), because it is known to be a carcinogenic agent after prolonged exposure. A well-designed ventilation system is necessary to dilute DPM, so that air quality is maintained to statutory guidelines. This paper outlines details of DPM characteristics, its health effects on miners, coal mine ventilation guidelines and some research investigations that underpin the control of DPM flow in underground coal mines

Selection of fan(s) to dilute DPM for multi-seam board and pillar coal mines using Hardy Cross and CPM methods

Multi-seam coal mining comprises of a large number of working sections. A well-organized ventilation system is necessary to supply adequate air quantities to all working sections and to dilute diesel particulate matter (DPM) within the statutory limits. In this paper, an attempt has been made to optimize fan(s) operating points in a multi-seam mine using a combination of Hardy-Cross and critical path methods. Selection of parallel fan sizes was further explored using computational fluid dynamics (CFD). Simulation results show that operating two surface parallel fans results in low total air power and low fans pressur

Effect of boundary condition on shear behaviour of rock joint

The presence of inherent discontinuities within a rock mass poses significant influence on its shear strength-deformation characteristics. Therefore, it is important to study the rock joint performance within the laboratory for the safe and economical design of underground structures (such as mine roadways) in jointed rock mass, stability analysis of jointed rock slopes and foundation design on a fractured rock mass. To study the rock joint mechanics and principles governing its shear behaviour, this research is focused on the behaviour of natural rough rock joint within the laboratory under Constant Normal Load (CNL) and Constant Normal Stiffness (CNS) boundary condition using servo-controlled direct shear apparatus at the University of Wollongong, Australia. It was observed from the experimental results that the CNS testing procedure truly simulates the shearing mechanism of an actual field unlike CNL, and the shear strength evaluated rock joint is underestimated under the CNL boundary condition. Also, the shear strength envelope under CNS exhibits non-linearity in contrast with the bilinear strength envelope under CNL boundary condition

Analysis of Diesel Particulate Matter Flow Patterns in Different Ventilation and Operational Conditions of Underground Mines

Diesel-operated vehicles are commonly used by personnel in underground mines. Although these vehicles facilitate travel within the mine, their main disadvantage is that they generate diesel particulate matter (DPM), a known carcinogenic agent. This calls for research to control the spread of DPM in underground mines in order to ensure the safety of mine personnel. In this article, the flow patterns of DPM generated by two types of diesel-operated vehicles are modeled using computational fluid dynamics (CFD) simulations. The simulation results are validated using field experimental measurements. The models show that if the vehicle is stationary, DPM particles are dispersed towards the center of the gallery and occupy the entire cross section of the road way. Vehicle movement induces air currents that may result in the miners being exposed to high DPM concentrations. The results show that if the DPM and the intake air counter-flow (flow in opposite directions), the DPM spread occurs throughout the entire cross-section of the roadway. This research is expected to contribute to the formulation of effective DPM control strategies in underground mines

Diesel particulate matter investigations in underground coal mines

A number of underground coal mines are using diesel-powered vehicles as the main source fuel for the transport. The primary concern with these diesel-operated vehicles is the diesel particulate matter (DPM), because it is known to be a carcinogenic agent after prolonged exposure. A well-designed ventilation system is necessary to dilute DPM, so that air quality is maintained to statutory guidelines. This paper outlines details of DPM characteristics, its health effects on miners, coal mine ventilation guidelines and some research investigations that underpin the control of DPM flow in underground coal mines

Precursory localization and development of microfractures along the ultimate fracture plane in amphibolite under triaxial creep

In a triaxial creep experiment in amphibolite, we clearly found a precursorylo calizationa nd developmento f microfracturesa long the final fracture planeu singa n AE (acoustice missions) ourcelo cation technique.T he precursorylo calizationo f AE hypocenters first nucleatedn ear a pre-existingm acroscopidc efecta ndt hene xtendedg raduallya longt hef inalf racture plane prior to failure. On the other hand, no significant precursorylo calizationo f AE hypocenteros n the final fracture plane before failure has been reported in rock samplesf ree of pre-existingm acroscopidce fects. This differencein AE occurrencep atterns beforef ailure could be explainedb y the differencein the degreeo f damage in the portion of the rock surrounding the localization zone when it nucleates

Design and field trials of water-mist based venturi systems for dust mitigation on longwall faces

Dust generation from longwall chock movement and the Beam Stage Loader/crusher (BSL) is a major source of air contamination on modern longwall faces. If not controlled effectively, much of these respirable dust particles would disperse quickly into the longwall due to high face ventilation velocities, contributing significantly to higher dust levels. A new water mist based venturi system has been developed for the purpose of suppressing respirable dust from longwall chock movements close to the maingate (MG). The unit is powered by compressed air and water using an ultrasonic nozzle embedded in a venturi body. The ultrasonic nozzle is capable of producing ultra fine water mist with droplet sizes ranging from 1 to 100 μm. Laboratory tests indicate that the ultrasonic nozzle (MAL-1300-B), when combined with a 70 mm (diameter) x 143 mm (length) venturi body, was can produce an optimum spray covering a distance over 10 m. Further tests show that a combination of air supply at 6 bar and water at 4 bar produces the optimum water mist thrust with inducted air velocity over 8 m/s. The venturi system was built as a stand alone unit using fire resistant and antistatic materials and can be easily hooked under the chock canopy with a magnetic base. The system can be powered by compressed air and water supplied to the longwall face and adjusted with the spray angle to achieve the droplet size and velocity needed for dust suppression and diversion. Computational Fluid Dynamics (CFD) modelling was undertaken to gain a better understanding of face ventilation and dust flow patterns to optimise the spray orientation of the venturi system for field trial installation. CFD modelling results show that the operating conditions of sprays with the best mitigation performance vary according to the source of dust, a better dust mitigation effect can be achieved when the venturi units on longwall chock are installed at 20o down towards the floor and tilted 45o along the face. Field trials were conducted at two underground longwall mines in QLD and NSW. Three venturi units were installed on Chock No 6 on the longwall with an additional unit trialled at the BSL to mitigate dust from longwall outbye. Dust measurements with real time monitoring Personal Dust Monitor (PDM) and gravimetric samplers indicate dust mitigation efficiency up to 30% has been achieved in both trials

Slope stability prediction using the Artificial Neural Network (ANN)

Slope failure is a significant risk in both civil and mining operations. This failure phenomenon is more likely to occur during the high rainfall season, areas with a high probability of seismic activity and in cold countries due to freezing-thawing. Further, a poor understanding of hydrogeology and geotechnical factors can contribute to erroneous engineering designs. Several Limit Equilibrium Methods (LEMs) and numerical modelling tools have been developed over the years. However, the highlighted success of the Artificial Neural Networks (ANNs) in other disciplines/sectors has motivated researchers to implement ANNs to forecast the Factor Of Safety (FOS). This paper aims to develop ANNs to predict the value of the FOS for slopes formed by (i) uniform one soil/rock material and (ii) formed by two soil/rock materials. Each of these slopes contains three sub-models with 6, 7 and 8 input material parameters. Thousands of FOS values were generated for each sub-model using LEMs by randomly generating material input parameters. Over 80% of generated FOS values were used to train ANNs and the remaining 20% were used to for validation. The one-material models performed better than the two-material models overall. The first sub-model from the one-material models and the third sub-model from the two-material models exhibited the best performance compared to the other sub-models, achieving Mean Square Error (MSE) of 8.35E-04 and 5.10E-3, respectively. The third sub-model from the one-material models and the first sub-model from the two-material models have a MSE of 2.00E-3 and 9.80E-3, respectively. The second sub-models have shown the lowest performance compared to the other models. The minimal errors between LEMs and ANNs have led to the conclusion that ANN can be used as a tool for a quick and first-pass analysis by design engineers without undertaking rigours, complex, time-consuming and tedious computation of FOS using LEMs. An actual field-tested database can be usedto predict real-world slope failures

Optimum Auxiliary Fan Location to Control Air Recirculation

This paper presents the optimum auxiliary fan(s) location to control air recirculation in dead-end workings where diesel-powered vehicles operate. Investigations were conducted with various secondary fan locations from the dead-end crosscut with varying the intake air quantities using a 30 m3/s capacity twin 75 kW auxiliary fan and 45 m3/s capacity twin 110 kW auxiliary fan to control air recirculation and DPM. The results showed that if the drive intake airflow rate matches the fan capacity, air recirculation will occur even when the fan is located 10 m away from the crosscut entry. Results also showed that if the intake drive air quantity was greater than or equal to 150% of fan capacity, no recirculation was observed when the twin 75 kW fan location was at least 5 m and the twin 110 kW fan location was at least 10 m away from the dead-end crosscut access