Study on environmental pollution caused by dumping operation in open pit mine under different factors

The drill-and-blast method is widely used for the excavation of hard rock tunnels. Toxic gases such as carbon monoxide and nitrogen oxides are released immediately after blasting by the detonation of explosives. To provide a safe working environment, the concentration of noxious gases must be reduced below the threshold limit value according to health and safety regulations. In this paper, one-dimensional mathematical models and three-dimensional CFD numerical simulations were conducted to analyze the concentration, propagation and dilution of the blasting fumes under different operating conditions. Forced, exhaust and mixed ventilation modes were compared to determine the safe re-entry times after blasting in a 200 m-long tunnel excavated using the top-heading-and-benching method. Based on the numerical simulations, carbon monoxide was the most critical gas, as it required a longer ventilation time to reduce its concentration below the threshold limit value. The safe re-entry time reached 480 s under the typical forced ventilation mode, but was reduced to 155 s when a mixed ventilation system was used after blasting, reducing the operating costs. The reduction of the re-entry time represents a significant improvement in the excavation cycle. In addition, the results obtained show that 1D models can be used to preliminary analyze the migration of toxic gases. However, to reliably determine the safe re-entry times, 3D numerical models should be developed. Finally, to verify the accuracy of the CFD results, field measurements were carried out in a railway tunnel using gas sensors. In general, good agreements were obtained between the 3D numerical simulations and the measured values.

/pdf/concentration-propagation-and-dilution-of-toxic-gases-in-1fm0zs7p.pdf

Concentration, Propagation and Dilution of Toxic Gases in Underground Excavations under Different Ventilation Modes

Parameter analysis of jet tunnel ventilation for long distance construction tunnels at high altitude

Dust pollution during shotcrete process in high-altitude tunnel based on numerical simulation

Numerical investigation on temperature–humidity field under mechanical ventilation in the construction period of hot-humid tunnel along the Sichuan–Tibet Railway

Study on CO diffusion law and concentration distribution function under ventilation after blasting in high-altitude tunnel

Traditional compound pendulum jaw crushers have many disadvantages such as low efficiency and uneven broken materials. This paper proposes a new biaxial compound pendulum jaw crusher to solve these problems. This paper presents the kinematic and dynamic performance of the new crushers, introduces its structure and layout features, derives the equations involving position, velocity, acceleration and kinetics, describes a workspace of the jaw crusher, analyzes the travel characteristic values and crushing force of movable jaw plates, and optimizes its structural and motion parameters through a multi-objective genetic algorithm. After the optimization process, the novel jaw crusher has little force on each hinge and large force on movable jaw plates. Specifically, the forces in the X-direction are 120,300 N for hinge C, 120,200 N for hinge D, and 195,000 N for hinge N; the forces in the Y-direction are 167,100 N, 162,800 N, and 197,900 N accordingly, while the breaking force of the movable jaw plate is 229,6...

Zhong Jiang

Papers

Study on CO diffusion law and concentration distribution function under ventilation after blasting in high-altitude tunnel

Research on the biaxial compound pendulum jaw crusher based on seven-bar mechanism: