Study on optimization of blasting scheme for fast tunneling of small section tunnel

To solve the problems of poor stability of surrounding rock, over-break or under-break of excavation and excessive blasting vibration speed during blasting excavation of small section tunnel in southwest China, the blasting parameters are optimized and analyzed from three aspects:water pressure blasting, quasi-parallel cutting form and millisecond delay blasting, and the optimal millisecond delay range with good vibration reduction effect is given theoretically.The results show that the use of water pressure blasting technology and quasi-parallel cutting form can improve the blasting effect and form a better tunnel profile and cutting effect, but it cannot control the blasting vibration velocity.The principle of millisecond delay disturbance vibration reduction in tunnel is analyzed from the point of view of waveform superposition, and the optimal millisecond delay theoretical range of 23-46 ms is obtained.The field verification shows that the 25 ms is selected as the delay time of adjacent holes in bad sections, and 45 ms delay time setting of tunnel section between cutting holes and relief holes, relief holes and bottom holes can control the vibration speed below 1 cm/s, with good vibration reduction effect.