Abstract: Tunnel excavation using an integrated tunneling and support machine generates continuous dust emission at the tunnel face. This emission adversely impacts the respiratory health of in-tunnel workers and the spatial visibility inside the tunnel. Existing research on tunnel dust primarily focuses on tunnels constructed using the drill-and-blast method. However, the dust generation mechanism of mechanically excavated tunnels notably differs from that of drill-and-blast tunnels, making it necessary to conduct targeted research on dust generation. Therefore, a case study is conducted on the Wujiawan Tunnel of the Chengdu-Chongqing Central Line Project. The dust concentration in each construction procedure of the tunnel excavated by an integrated machine is synchronously monitored using multiple dust concentration meters, and dust removal tests inside the tunnel are performed with dust suppression vehicles. The main conclusions are as follows: (1) During tunnel mechanical excavation and shotcreting, the peak dust concentration within 100 m behind the tunnel face reaches 18 mg/m³ and 13 mg/m³, respectively, and the maximum dust concentration in the tunnel reaches 9 times the allowance in the specification. (2) During tunnel construction, the maximum proportions of PM10 concentration in total dust reach 72.4% and 62.4%, respectively. The distribution patterns of PM10 concentration are consistent with the total dust concentration. (3) When the dust collector is set on the upper bench, the dust reduction effect is not good; however, when it is set on the lower bench, the total dust and PM10 concentration within 50 m behind the dust removal vehicle are considerably reduced, and the average dust removal efficiency reaches 44%. (4) Mechanical dust suppression in the tunnel cannot fulfill purified air quality requirements, necessitating auxiliary dust suppression measures.

Key words: tunnel, boring and support integrated machine, mechanical excavation, dust concentration, dust removal test