隧道爆破围岩应力变化过程中天然气运移研究

发布时间：2018-10-21 18:43

【摘要】：目前,对于隧道施工过程中天然气的研究和分析,主要集中在成因机制、爆炸危害以及防治技术上,对于隧道施工过程中天然气的运移理论却少有论及,因此,难以准确判断天然气的运移模式和聚集方向,给隧道施工带来严重的不确定性和危害性。本文结合玄真观隧道的具体资料,研究了隧道爆破以及围岩应力变化过程中岩体内产生裂隙的方式和范围,并且分析了隧道开挖过程中天然气的运移模式。本文主要取得了以下几个方面的的成果： (1)利用勘察以及施工过程中获得的实验结果,分析了隧道的瓦斯级别,综合判定勘察期间隧道为低瓦斯隧道,施工过程中隧道为高瓦斯隧道。分析认为隧道瓦斯级别前后不一致的原因有三个：一是由于爆破作用在岩体中形成裂隙,岩体中的天然气通过裂隙进入隧道并聚集；二是由于围岩应力变化过程中产生了裂隙,岩体中的天然气通过裂隙进入隧道并聚集；三是由于岩层中的吸附气体在岩层物理环境改变时解析为游离气体进入隧道并聚集：最终使隧道成为高瓦斯隧道。 (2)根据隧道爆破资料,计算出爆破过程中围岩内产生裂隙的范围为504.7mm。根据爆破作用方向与围岩中节理面的关系,分析了围岩不同部位爆破裂隙的发育规模。得出：隧道拱顶和下部围岩中不易形成规模较大的裂隙,隧道左、右两侧围岩中容易沿节理形成规模较大的裂隙。. (3)利用有限元分析软件,对隧道开挖过程中围岩应力进行了数值模拟。模拟结果为：上台阶开挖后,隧道左、右两侧围岩中出现了压应力集中,而拱顶出现了拉应力；下台阶开挖后,隧道拱顶出现了压应力集中,而中、下部围岩中出现了拉应力。 (4)结合隧道爆破围岩应力变化过程中裂隙区产生方式和范围以及天然气运移规律,分析了隧道开挖过程中围岩内天然气的运移模式。研究认为：裂隙发育区内,赋存在岩体中的游离态天然气,在集中应力或分子扩散力或两种力的作用下,沿着裂隙向浓度较低或者压力较小的区域运移,运移速度较快或者很快；非裂隙区内,赋存在岩体中的游离态天然气,在集中应力或分子扩散力或两种力的作用下,只能通过地层中原有孔隙、节理向浓度较低或者压力较小的区域运移,运移速度较慢或者极慢。 (5)根据裂隙区岩石体积和岩石的储集物性计算出天然气溢出速度为1.99m3/min,根据回风中天然气的浓度计算出天然气溢出速度为2.565m3/min。分析计算结果得出隧道为高瓦斯隧道。
[Abstract]:At present, the research and analysis of natural gas in tunnel construction mainly focus on the formation mechanism, explosion hazard and prevention technology. However, there is little discussion on the theory of natural gas migration during tunnel construction. It is difficult to accurately judge the migration mode and accumulation direction of natural gas, which brings serious uncertainty and harm to tunnel construction. Based on the concrete data of Xuanzhengguan tunnel, this paper studies the mode and scope of cracks in rock during tunnel blasting and stress change of surrounding rock, and analyzes the migration mode of natural gas during tunnel excavation. The main achievements of this paper are as follows: (1) by using the experimental results obtained in the course of investigation and construction, the gas level of the tunnel is analyzed, and the tunnel is judged as a low-gas tunnel during the survey. The tunnel is a high gas tunnel during construction. It is concluded that there are three reasons for the inconsistency of tunnel gas levels: first, because of the blasting action forming cracks in the rock mass, the natural gas in the rock mass enters the tunnel and accumulates through the cracks; the other is because of the cracks in the process of the stress change of the surrounding rock mass. The natural gas in the rock mass enters the tunnel through the fissure and accumulates; The third reason is that the adsorbed gas in the rock layer is resolved into the free gas into the tunnel when the physical environment of the rock layer changes and accumulates: finally, the tunnel becomes a high-gas tunnel. (2) according to the blasting data of the tunnel, The range of cracks in the surrounding rock during blasting is calculated to be 504.7 mm. According to the relation between blasting action direction and joint surface in surrounding rock, the development scale of blasting crack in different parts of surrounding rock is analyzed. It is concluded that it is not easy to form large scale cracks in the arch roof and the lower wall rock of the tunnel, and. (3 is easy to form along the joints in the left and right side rock of the tunnel.) the finite element analysis software is used. The stress of surrounding rock during tunnel excavation is simulated numerically. The simulation results are as follows: after the excavation of the upper steps, the compressive stress concentration appears in the surrounding rock on the left and right sides of the tunnel, and the tensile stress appears in the arch roof, and after the excavation of the lower steps, the compressive stress concentration appears at the top of the tunnel arch, but in the middle, (4) combined with the generation mode and range of crack zone and the law of natural gas migration during tunnel blasting, the migration mode of natural gas in surrounding rock during tunnel excavation is analyzed. It is considered that the free natural gas in the fractured area, which exists in the rock mass, moves along the fissure to the area with lower concentration or lower pressure under the action of concentration stress or molecular diffusion force or two kinds of forces. Migration is faster or faster; free natural gas stored in rock masses in non-fissured areas can only pass through the original pores in the strata under the action of concentrated stress or molecular diffusion or both forces. The joints migrate to areas where the concentration is lower or the pressure is low, (5) based on the volume of rock and the physical properties of rock in the fractured area, the gas spill velocity is calculated to be 1.99 m3 / min and 2.565m3 / min based on the concentration of natural gas in the return air. The analysis and calculation results show that the tunnel is a high gas tunnel.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U452.11;U455.6

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