English：

To explore the dispersion law of harmful gases under the pressure ventilation mode in thetraditional pipe jacking operation, the smoke diffusion test was carried out on the tunnel face of the pipejacking operation site by using the smoke generating device. The smoke diffusion velocity in the pipe andthe carbon dioxide concentration field in the pipe and the working well were tested and analyzed,respectively. The test results indicate that under the traditional press⁃in ventilation operation mode, thesmoke diffuses at a speed of 3. 25m / s and the smoke diffuses in the pipeline at a speed of 1.3m / s. Oncean electrical fire or gas pipeline rupture accident occurs, it is difficult for personnel to effectivelyevacuate. A negative pressure gas seal induced pipe jacking operation environment protection system wasdeveloped, and its key control parameters were studied by theoretical analysis and model testing. Theresults indicate that the influence of air supply angle, air supply speed, and the distance between airoutlet and tunnel face on ventilation effect decreases in turn. The new system can reduce harmful gas toless than 10%, and for harmful gas leakage accidents, the concentration of harmful gas can be reduced toa safe value within 15minutes.