不同间距下溶洞对分离式隧道稳定性的影响

Influence of karst caves with different spacing on stability of separated tunnel

为了解分离式隧道中间存在溶洞时溶洞对隧道稳定性的影响,通过FLAC3D分析了岩溶区溶洞对分离式隧道围岩应力与变形的变化规律。结果表明:溶洞会对分离式隧道顶部、底部围岩的应力及变形产生较大影响。当分离式隧道之间存在溶洞时,在隧道顶、底部一定范围出现拉应力集中区,其中拉应力最大值多分布在隧道顶部,但底部拉应力增长快;围岩的压应力则增幅不大,且最大值分布在隧道之间而非洞壁处;围岩的剪应力均有所增加;围岩的位移有所增加且隧道顶部附近围岩有较大程度的位移增长。当隧道间距增大时,洞壁附近围岩的最大拉应力、压应力及上下两侧位移量均有所下降。当隧道间距在1倍隧道开挖断面宽度时,溶洞对隧道的影响较显著,而当间距大于1.5倍宽度时可忽略不计。

Numerical analysis software FLAC3D is used to analyze the influence of the stability of the wall rock of the karst cave in the separation tunnels.The stability change caused by the distance changing separation tunnel is analyzed.The results show that the stress and deformation of the surrounding rock at the top and bottom of the separated tunnel are impacted by the caves.When there are karst caves between separated tunnels,the tensile stress concentration area will appear in a certain range at the top or bottom of the tunnel.The maximum tensile stress is mostly distributed at the top of the tunnel,but the rapidly increases area of the tensile stress is distributed at the bottom.The increase of compressive stress in the surrounding rock was small,and the maximum value occurred between the tunnels rather than at the walls.When the shear stresses in the surrounding rock increased,the displacement of the surrounding rock increased.A large increase in the displacement of the surrounding rock is located near the top of the tunnel.When the distance between the tunnels increases,the maximum tensile stress,compressive stress,and displacement of the surrounding rock near the cave wall will decrease.When the tunnel is as the wide as the separation tunnel excavation section,the influence of karst cave on the separation tunnel is more significant,and the impact of the cave on the tunnel is significant too.When the spacing is greater than 1.5 times of the separation tunnel width,the impact can be neglected.