Study on the coupling pollution law of dust and gas and determination of the optimal purification position of air duct during tunnel excavation

Analysis of the Stability of the Double-Hole Complementary Ventilation and Ventilation Network of the Tunnel Constructed by Drilling and Blasting Method

“…Combining ( 6), (8), and (9) gives discriminant (10): (10) Through numerical simulation, the flow Qm of A-A, B-B, C-C, and D-D sections in the four branches is obtained, as well as the resistance hm of each branch and the air flow resistance Rm of each branch, and then the air flow resistance Rm of each branch is substituted into Equation (10) for theoretical calculation, and the air flow direction of the double-hole tunnel can be determined by the K obtained. According to the law of energy balance of the loop, Equation ( 3) can be obtained:…”

“…In Figure 10, the resistance h m of each branch decreases as L t increases. Combined with the data in Figures 9 and 10, the air flow resistance R m of each branch can be calculated, and then K is obtained according to the discriminant Equation (10), which are summarized in Table 3.…”

“…In Figure 10, the resistance hm of each branch decreases as Lt increases. Combined with the data in Figures 9 and 10, the air flow resistance Rm of each branch can be calculated, and then K is obtained according to the discriminant Equation (10), which are summarized in Table 3. It can be seen from Table 3 that the Rm of each branch decreases with the increase of Lt, but the degree of decrease is different, resulting in an obvious difference in the K. When Lt = 80 m, Qa > Qu, K = 0.69 < 1; Qa < Qu, K = 0.009 < 1, it indicates that the air flows from the advance side tunnel to the undercut side tunnel.…”

“…In the selection of ventilation methods for long highway tunnels, full diameter air flow ducts are mostly used to match high-power forced ventilations in foreign countries [7], while in China, inclined shafts, parallel pilot tunnels, and shafts are usually built and a combination of forced and roadway ventilation methods are adopted [8,9]. Through numerical simulation and on-site monitoring, scholars discussed the above ventilation measures and ventilation effects, and summarized the air flow and pollutant migration laws in the tunnel under the forced ventilation method [4,10,11]. At the same time, the correction coefficients of key parameters such as air flow demand, fan efficiency, air flow 2 of 17 duct leakage rate, and air flow duct resistance during tunnel construction ventilation are also studied, which provides theoretical guidance for tunnel construction [12][13][14][15][16].…”