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超深厚冲积层千米立井冻土爆破井壁振动响应特性研究

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

  • 摘要: 随着我国对地下资源需求的不断增大,超深立井施工逐渐普遍化。在立井开挖时为了稳固井壁且减少井壁坍塌,一般会选用冻结法施工,但爆破时产生的振动仍然会对井壁的稳定性造成一定的影响,严重情况下出现的塌方现象,会造成一定的人员伤亡、延缓施工进度等危害。为解决此类问题,以赵固二矿西风井704.6 m深厚冲积层冻土爆破掘进工程为研究背景,开展深大立井冻土爆破井壁振动监测,并结合ANSYS/LS-DYNA分析软件建立立井多段爆破三维数值模型,深入探索冻结表土段冻土爆破开挖下井壁的振动响应规律。研究结果表明:冻土爆破引起井壁振动的时程曲线各段波形区分明显,段装药量大、炮孔分布密集的3段辅助孔爆破对井壁振动影响最大,合速度为8.39 cm/s,均在安全范围以内;掏槽爆破时,井壁主要受纵波影响产生振动,垂向振速大于径向和切向振速;辅助爆破时,随着自由面增大,爆破产生的作用力逐渐向水平向扩展,井壁径向振速逐渐占优,垂向振速相对减小;运用一维弹性波理论,分析了爆破引起井壁的振动速度对混凝土应力之间的关系,计算结果小于混凝土抗拉强度;对比数值模拟结果与实测振速波形,验证了模型的可靠性和准确性,并通过模拟分析获得离井壁最近质点垂直方向的振动速度为23 cm/s,在安全范围内。研究思路与方法成果可为同类型立井冻土爆破的施工与振动控制提供一定参考。

     

    Abstract: 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.

     

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