Study On The Stability Of Slope On Tunnel Entrance

The construction of tunnel entrance can't avoid the geological disaster such as landslide, collapse, unsymmetrical pressure, debris flow and avalanche on. Tunnel entrance is the first construction of tunnel construction, as the safe of tunnel entrance relate the entrance to tunnel and safe construction. The failue pattern of slope on tunnel entrance is put forward with method of engineering geological analysis. The stability of two typical slope on the tunnel entrance such as slope in parallel with tunnel and slope be orthogonal with tunnel are analysisd with FEM software FLAC. The main research work of this dissertation is as follow:①The factors which affect the stability of slope on tunnel entrance and failue model of slope on tunnel entrance are analysisd with the method of engineering geological analysising. The factors which affect the stability of slope on tunnel entrance include stratum and lithology, geological structureand crustal stress, rock structure, affect of engineer construction, water, shake and climate etc. the failue model of slope on tunnel entrance include collapse failue, slide failue, plane failue, partial slump failue and wedge failue.②The affect of the excavation of two separated tunnel to the stability of slope on tunnel entrance and in parallel with tunnel is analysisd with FEM software FLAC. According to analysis, the stress character, displacement character and stability of slope after the excavation of tunnel are elicited.③The affect of excavation method, angle of slope and tunnel depth to the stability of slope are analysisd: the affect of excavation of left tunnel first to the stability of slope is a little more than the affect of excavation of right tunne first to the stability of slope; the affect of the change of slope angle to the stability of slope is small when the slope angle is less than 35°,but the affect sharp increase when the slope anglge is more than 35°and less than 55°; The excavation of tunnel's affect to the stability of slope is great.④Taking the slope on Daping tunnel entrance as example, the stability of nature state, excavation of tunnel entrance and the excavation of tunnel are analysis with FEM software FLAC3D. The bedding rock on Daping tunnel entrance is shaly sandstone, the upper of it is constructing soil, and the stability of itself is bad. The excavation of tunnel elicite the minishing of skid-resistance, and that reduces the stability of slope. The excavation of tunnel shapes the inner free-face, the rock above tunnel sink and drive the landslide body slip forward.