Drilling and blasting tunneling method

1, full-face excavation method, one-time drilling and blasting of full-face excavation section, excavation and molding, and full propulsion. When the tunnel is high, it can also be divided into upper and lower parts to form steps, synchronous blasting and parallel excavation. When geological conditions and construction conditions permit, full-face tunneling method is preferred.

2, pilot tunnel method, first part of the excavation section as a pilot tunnel, and then gradually expand the excavation of full-face tunnel. This is a construction method with small and medium-sized machinery as the mainstay when the tunnel section is large and it is difficult to adopt full-face excavation due to geological or construction conditions. The cross section of the pilot tunnel should not be too large, and it should be suitable for ballasting of ballasting machinery, transportation of ballasted vehicles, installation and construction safety of feng shui pipes. The free surface can be increased when the pilot tunnel is excavated and blasted, which is beneficial to find out the geological and hydrogeological conditions of the tunnel and create conditions for tunnel ventilation and drainage. According to geological conditions, groundwater conditions, tunnel length and construction conditions, determine the lower pilot tunnel, upper pilot tunnel or middle pilot tunnel. After the pilot tunnel excavation, the expansion excavation can be carried out after the full length of the pilot tunnel excavation, or it can be operated in parallel with the pilot tunnel excavation.

3, the division excavation method, in the case of poor stability of surrounding rock, generally need support, excavation of large section of the tunnel, you can first dig a part of the section, timely support, and then gradually expand the excavation. When excavating a tunnel by drilling and blasting, it is generally regarded as a tunnel excavation cycle from the first drilling sequence, through the processes of charging, blasting, ventilation, smoke dispersion, slag discharge and so on, to the end of the second drilling sequence. Try to compress the operation cycle time and speed up the excavation. In 1980s, some countries used the drilling and blasting method to excavate tunnels with a cross-sectional area of about 100㎡ in medium-hard rocks, with an average excavation speed of about 200m per month. In the Lubuge Hydropower Project in China, a diversion tunnel with a diameter of 8.8m was excavated, with an average monthly footage of 23 1m and a maximum monthly footage of 373.7m