Study on vibration response characteristics of kilometre deep shaft induced by frozen soil blasting in ultra deep alluvium

With the increasing demand for underground resources in China, the construction of ultra-deep shafts is becoming more and more popular. In order to stabilize the shaft wall and reduce the collapse of the shaft wall during the shaft excavation, the freezing method is generally used in the construction. However, the vibration generated during blasting will still have a certain impact on the stability of the shaft wall. In severe cases, even collapse will occur, causing certain casualties, delaying the construction progress and increasing the project cost. In order to solve such problems, based on the research background of 704.6 m deep alluvium frozen soil blasting excavation project in the west wind shaft of Zhaogu No. 2 Coal Mine, the vibration monitoring of deep shaft frozen soil blasting shaft wall was carried out, and combined with the ANSYS/LS-DYNA analysis software, the three-dimensional numerical model of shaft multi-stage blasting was established to deeply explore the vibration response law of shaft wall under frozen soil blasting excavation in the frozen topsoil section. The monitoring results show that the waveform of each section of the time-history curve of shaft wall vibration caused by frozen soil blasting is obviously distinguished. The blasting of segment 3 auxiliary holes with large charge and dense blasthole distribution has the greatest impact on shaft lining vibration, but they are all within the safety range which is 8.39 cm/s. For the cutting blasting segment, the shaft wall is mainly affected by longitudinal wave to produce vibration, and the vertical vibration velocity is greater than the radial and tangential vibration velocity. During auxiliary blasting, with the increase of free surface, the force generated by blasting gradually extends to the horizontal direction, the radial vibration velocity of the shaft wall gradually dominates, and the vertical vibration velocity decreases relatively. Based on one-dimensional elastic wave theory, the relationship between the vibration velocity of the shaft wall caused by blasting and the concrete stress is analyzed. The calculation results are less than the tensile strength of concrete. The reliability and accuracy of the model are verified by comparing the numerical simulation results with the measured vibration velocity waveform, and the vibration velocity in the vertical direction of the particle closest to the wellbore is 23 cm/s, which is within the safe range. The research ideas and methods can provide certain reference for the construction and vibration control of the same type of shaft blasting in frozen soil.