隧道先后行洞开挖步距间隔的施工影响分析

Analysis on construction influence of excavation step interval of tunnel

针对分离式隧道的先后行洞在不同的步距间隔情况下开挖对隧道围岩稳定性的影响进行研究。运用有限元软件ABAQUS,并且选用D-P屈服准则对分离式隧道左右洞开挖的过程进行数值模拟,结合实际工程分析隧道开挖过程中的围岩应力分布、塑性区域和位移变化。研究结果表明,先行洞在开挖步距小的情况下会对后行洞产生较大的竖向应力,开挖前拱顶处产生3.01 MPa,开挖后拱顶处产生1.55 MPa,出现塑性区域范围较大,塑性应变值为0.24 mm,隧道位移变化量同样大于开挖步距大的情况。由研究结果得出,分离式隧道在开挖过程中应避免在先行洞开挖步距小的情况下对后行洞进行开挖,施工现场应根据实际工程围岩情况合理调整两洞之间的开挖步距。

The effect of excavation on the stability of the tunnel envelope at different step intervals is studied for the successive cavities of a separated tunnel.The finite element software ABAQUS is used,and the D-P yield criterion is selected to numerically simulate the process of excavation of the left and right holes of the separated tunnel,and to ana lyze the stress distribution,plastic region and displacement changes of the surrounding rock during the excavation of the tunnels with the actual project.The findings show that,the first tunnel in the case of small excavation step will pro duce a large vertical stress on the later tunnel,3.01 MPa at the top of the vault before excavation and 1.55 MPa at the top of the vault after excavation,with a large range of plastic region and a plastic strain value of 0.24 mm,and the change in tunnel displacement is also larger than that of a large excavation step.According to the results of the study,the excavation of separated tunnels should be avoided in the excavation process with a small excavation step for the first tunnel,and the excavation step between the two tunnels should be reasonably adjusted according to the actual pro ject surrounding rock conditions at the actual construction site.