The mechanics of bolt drilling and theoretical analysis of drilling parameter effects on respirable dust generation

The evaluation analysis on the airborne dust regional pollution of the anchor drilling operation in the tunnel

The anchor drilling operations generate massive airborne dust particles in the tunnel heading face that raises the pneumoconiosis morbidity and explosion risk. In this paper, a full-scale tunnel physical model is constructed to study the effect of the wind velocity and drilling site position on the airborne dust regional pollution scope based on the actual anchor drilling craft. The research indicates that the four extensive vortex areas keep the dust suspension at 14 m from the heading face and make the deposition dust particle refloat. The average respirable dust rate reaches the maximum value at section 5 m and presents a gradual decline as the dust particle migrates along the outlet direction. Raising the wind velocity contributes to alleviating the airborne dust pollution in the anchor drilling operation. As the wind velocity increases from 3 to 24 m/s, the high dust concentration area and number higher than 200 mg/m³ pose overall decrease trends, and the average dust concentration displays a linear decrease until 26.14-58.65 mg/m³ around the anchor worker head. Moving the drilling site positions closer to the exhaust air duct aggravates the airborne dust pollution in the front breathing zone. As the anchor drilling operation switches from the return air side to the supply air side, the dust concentration area ascends by 59.4-84.4% in the personnel respiratory space.

Study on dust control technology of mobile spray combined with full-section fog curtain in return airway of header working face

For the problem of coal dust pollution in the return air lane of the comprehensive mining working face of soft rock mines.Based on the principle of supersonic siphon pneumatic atomization dust control, mobile vehicle-mounted pneumatic spraying combined with full-section fog curtain dust control technology is proposed to address the coal dust pollution problem in the return air tunnel of the comprehensive mining working face of soft rock mines. This technology has a wider spraying range, stronger wind resistance and lower energy consumption.Using the k-ε turbulence module and the fluid flow particle tracking module of COMSOL simulation software, a three-dimensional numerical model of the return air tunnel was established. The effect of wind flow characteristics on the diffusion range of coal dust and fog droplets was analysed, and the dust transport pattern and dust control effect of the new technology were obtained for different cross-sectional return airways. The results show that the velocity of the wind flow is continuously decayed by the slope, and the dust of different particle sizes is distributed differently by the inertial force. Coal dust with particle sizes larger than 6.5 μm accumulates below the structure at a lower velocity, and coal dust with particle sizes smaller than 4.5 μm is mostly suspended above the structure at a higher velocity. The device effectively stops the transport of dust and covers the whole section of the roadway, and the dust removal efficiency reaches 96.53%~97.93%, which provides relevant theoretical support and treatment means for the control of dust pollution in the return airway of coal mines.

A Comprehensive Roof Bolter Drilling Control Algorithm for Enhancing Energy Efficiency and Reducing Respirable Dust

In underground coal mines, the drilling process in roof bolting operation could generate excessive amount of respirable coal and quartz dusts. Improper drilling control might also pose safety hazard and interrupt production. Therefore, an automated, high-efficiency drilling control system with safety features can be beneficial to the bolter personnel. In this research, a comprehensive drilling control algorithm has been developed to reduce the generation of respirable dust and to increase the drilling energy efficiency based on laboratory drilling test results and safety considerations. Specific energy is used to evaluate the energy efficiency. In addition, the ratio between specific energy and rock uniaxial compressive strength can be used as a basis for determining the rational drilling bite depth-typically a determined high one permissible by the driller power and drill steel. The test results show that to achieve and maintain a desired drilling bite depth for good drilling performance, a combination of relatively low rotational rate and a rationally high penetration is preferred. By monitoring the drilling rate, the system is able to evaluate the bit wear condition and improve drilling safety. In this paper, the developed drilling control algorithm for achieving a rational drilling bite depth is demonstrated. By adapting this drilling control algorithm, the drilling efficiency and bit condition can be monitored in real time, so the system can maintain a relatively high energy efficiency, generate less respirable dust, and avoid drilling failure.