ANALYSIS ON CHARACTERISTIC AND FORMATION MECHANISM OF LARGER DEFORMATION FOR THE TUNNEL OF CHENGDU-LANZHOU RAILWAY

The larger deformation of soft rock tunnel of the Chengdu-Lanzhou railway presented not only the common larger deformation characteristics, such as the lining crack, steel torsion, transect of tunnel reduced in size, and so on; but possessed the regional particularities of the tectonic conditions were intricate and active, for the Chengdu-Lanzhou railway pass through the following three tectonic elements of Longmen Mountain tectonic belt, Songpan-Ganzhi fold tectonic belt and west Qinling Mountains fold structural belt included 10active faults; of the formation lithology condition were extremely weak and cracked, for the 70 percent of rock mass of Chengdu-Lanzhou railway were soft rock of slate, phyllite, schist and carbon slate, suffered seriously by the tectonic and took on the intense crumpled deformation and strong crushing cracked; of the Wenchuan seismic effect were outstanding, for the Chengdu-Lanzhou railway run through the Wenchuan 512 meizoseismal area, the seismic wave damaged to rock mass, which resulted to reduce integrity of rock mass and increase water permeability of rock mass. The crustal stress field of Chengdu-Lanzhou railway were extremely complex, with the tectonic stress field characteristic of obvious high crustal stress. The formation mechanism of larger deformation of the Chengdu-Lanzhou railway were the interaction of the complex tectonic stress, soft and cracked formation lithology, bias of disadvantage discontinuous surface and softening effect of groundwater, summarized the three kinds of the loose large deformation, squeezed large deformation and structural large deformation in high stress field. And the conclusions of this paper is great guiding significance for the building Chengdu-Lanzhou railway and others tunnel construction in similar engineering geological conditions.