| Slope stability of tunnel hole is one of the key issues in the tunnel construction, especially high-intensity earthquake problem. In "5.12" wenchuan earthquake, a lot of damage to the tunnel are mainly concentrated in tunnel hole, YongJiaShan railway tunnel is also in high-intensity region. Longmen pre-piedmont active fault (Guanxian-Jiangyou fault) goes through YongJiaShan shatter slope rear rim. Studies of the Slope stability under high-intensity earthquake location will be necessary. This paper has used both geologieal and Numerieal Simulation method, Through stress-strain and different monitoring time-history curves of displacement,acceleration and speed under dynamic action, analyze the stability of YongJiaShan railway import tunnel shatter slope comprehensively. Conclusion is that under seismic dynamic, the mid-rear rim of YongJiaShan unstable slope will be destruction. It is Irrational about this railway line selection. Suggestion is to adjust the line position. The main research conclusions are as follows:(1)Longmen pre-piedmont active fault fracture zone has mainly high carbonation floitite, mylonite and fault gougeis,which belongs to the large-stone rock fragment with well graded. Microscopic structure is very well developed, scratching, cracks or rupture signs such as can be seen everywhere. Shearing test for 121KPa measured its cohesion, shearing Angle 31.7°;Compression test compression modulus measured for 13.64 MPa. Summarizing literature think longmen piedmont fault belt a single fracture of the mountain earthquake recurrence period at least in 2000~3000 years.(2)The import tunnel is loose slope ,which below bedrockfell is the Limestone. Longmen pre-piedmont go through from slope rear rim. In "5.12" wenchuan earthquake, rear rim of slope produced a certain width by the ripping. Causative factor influence, such as rainfall along the interface base will be deformation trend.(3)Using the research area near seismic dynamic parameters, there is the study of the slope dynamic response characteristics under 3-d numerical simulation software FLAC3D. The results show that the slope acceleration amplification coefficient increases with the elevation, especially in the horizontal acceleration increase the most obvious.Slope near the near-fault margin of acceleration value is 11.5 m/s2. (4)Under the seismic dynamic process, displacement of horizontal and vertical direction dis time-history curves is not as seismic reciprocating motion but enlarging trend. With the increase of elevation, displacement also can increase accordingly; at the same elevation, slope table displacement is larger than inside.(5)Under seismic dynamic role , slope overburden interface produced a certain stress concentration, especially in rear rim of slope body with the value of 1MPa.Based on the rigid body limit equilibrium theory searching most dangerous sliding surface, slope unstable coefficient in earthquake condition, will be from a natural 1.048 down to 0.876, and be in not steady state.The slope mid-rear rim of YongJiaShan unstable slopes will be destruction, which is consistent with FLAC3D numerical simulation correlation analysis.(6)It is Irrational about this railway line selection.Suggestion is to adjust the line position. Railway line and seismic fracture belt should be adequate security distance, and if possible with the larger Angle through the fault zone. Strengthen the monitoring of slope especially rear rim. |
