Abstract
Forced ventilation or newly built vertical shafts are mainly used to solve ventilation problems in large underground cavern groups. However, it is impossible to increase air supply due to the size restriction of the construction roadway, resulting in ventilation deterioration. Based on construction of the Jinzhou underground oil storage project, we proposed both a summer ventilation scheme and winter ventilation scheme, after upper layer excavation of the cavern is completed and connected with the shaft. A three-dimensional numerical model validated with field test data was performed to investigate air velocity and CO concentration. Fan position optimization and the influence of temperature difference on natural ventilation were discussed. The results show that CO concentration in the working area of the cavern can basically drop to a safe value of 30 mg/m3 in air inlet and exhaust schemes after 10 min of ventilation. Since there is inevitably a back-flow in the winter ventilation scheme, it is necessary to ensure that airflow is always moving towards the shaft. Optimal placement of the axial flow fan at the shaft bottom is on the central axis of the cavern, 5 m away from the shaft. The greater the temperature difference, the better the natural ventilation effect of the shaft. The natural ventilation effect of the shaft as an outlet in winter, is better than that of the shaft as an inlet in summer.
Highlights
The strategic reservation of oil and natural gas is an important means to ensure a safe and stable supply of energy and normal operation of the country
This paper aims to reveal a reasonable path of construction ventilation for large-scale underground cavern groups in winter and summer
It can be seen that carbon monoxide (CO) gas in the vicinity of the middle step moves toward the connecting roadway with the increase in ventilation time
Summary
The strategic reservation of oil and natural gas is an important means to ensure a safe and stable supply of energy and normal operation of the country. Compared with traditional underground engineering such as railway tunnels, highway tunnels, and hydraulic tunnels, the water sealed caverns often have characteristics such as a large section, multiple working faces, high required air volume, and serious pollution. These characteristics put forward high requirements for the rapid and safe construction of underground water sealed caverns and some practical engineering problems that urgently need to be solved. Ventilation time and pollutant concentration are two important indexes for evaluating ventilation schemes in tunnel construction. Rational design and optimization of the ventilation scheme for the underground cavern group is key technology and directly related to project progress and safety of construction workers [10]
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