| Tunnel collapse caused by Karst caves occurred several times in the construction ofXiaobatian Highway tunnel which built in karst region, that makes great deal of damage totunnel. Taking K26+691～K26+975miles of Xiaobatian tunnel as engineering background,this paper aims at discussing the influences on construction because of the existing ofconcealed karst cave in the roof of tunnel.The content have finished in paper contains:(1)By studying the thesis and reference about tunnel construction technology in karstregion, the mechanism of karst, development process, classification, the influence on tunnelconstruction of karst and the treatment technology of karst cave are summarized.(2)The numerical model with existing of concealed karst cave in the roof of tunnel andthe comparative model without karst cave though the ANSYS software system are modeledrespectively, the analysis on bend method is carried out. So the influence on surrounding rockand primary support of karst cave in Xiaobatian can be studied.(3)By modeling different distance between tunnel and karst cave, the deformation ofsurrounding rock and primary support in construction using bend method is analysed.Through the above research and analysis, the conclusions of this paper are mainly:(1) With the existing of concealed karst cave in the roof of Xiaobatian tunnel, the verticaldisplacement of tunnel primary support reduced by1.6percent.(2)The safety factor of tunnel vault, arch shoulder and foot of side wall is reduced.Especially, the safety factor of tunnel vault is reduced by3.4percent.(3) With the existing of concealed karst cave in the roof of Xiaobatian tunnel, the verticaldisplacement of tunnel vault, arch shoulder, arch foot, side wall, foot of side wall and tunnelinverse reduced, and the horizontal displacement of these part increased. Especially, thehorizontal displacement of arch shoulder and arch foot is increased by7.2percent and2.9percent respectively.(4) With the existing of concealed karst cave in the roof of Xiaobatian tunnel, the stressin surrounding rock near tunnel vault increased.(5)With the distance between tunnel and karst cave increased, the influence onsurrounding rock and primary support of karst cave in Xiaobatian is reduced.The conclusion can provide certain guidance for the construction of Xiaobatian tunnel.With the existing of concealed karst cave in the roof of Xiaobatian tunnel, the horizontal displacement of arch foot increased, so plentiful attention should be taken on tunnelmonitoring measurement in case of taking proper measures when too much displacementgrowth occurred in arch foot. Besides, in consideration of the reducing of the safety factor oftunnel vault, strengthening measures can be applied necessarily. |
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