STUDY ON THE ENGINEERING GEOLOGICAL PROPERTY OF THE SOFT ROCK TUNNEL IN MID-YUNNAN WATER DIVERSION PROJECT

According to further study on geological characteristics, physical and mechanical properties, water physical properties and rheological property of the soft rock in the central area of Yunnan province. It is concluded that the red-bed soft rock shear strength, compressive strength is lower. with the increase of clay mineral and shale content, the physical and mechanical properties were gradually decreased.the muddy rock strength was reduced by 30%～40% when water-saturated, the fine sandstone and siltystone loss of it is 20%～30%.The disintegration and expansibility is controlled by the clay mineral and shale content. the test shows that the red-bed soft rock creep effect is obvious, the long-term compressive strength is 70% of the uniaxial compressive strength, Long-term shear strength values compared with the direct shear test of internal friction Angle decreased about 20%, cohesion was reduced by 60%. basis on many engineering experience and academic achievements, combined with the Engineering geological property and long-term strength of the soft rock in the central area of Yunnan province, this paper puts forward the evaluation methods of the soft rock tunnel extrusion and surrounding rock classification. To provide evidence for the discriminant of large deformation of soft rock in the tunnel.