Researches on calculation method of support and support-anchorage union to unstable rock

As a typical geologic disaster in the Three Gorges Reservoir,unstable rock is classified into falling unstable rock,sliding unstable rock and toppling unstable rock in view of unstable modes.Shear fracture along controlling fissure is the failure mechanism for falling unstable rock and sliding unstable rock,while tension fracture is that for toppling unstable rock around turning point.It is proved in much practice that support is the best measure when some conditions are satisfied, especially for falling unstable rock and toppling unstable rock.Loads acting on unstable rock mass can be divided into self-weight,fissure pressure in controling fissure and earthquake forces,and three are three load combinations.Based on the allowable bearing capacity of support mass and equilibrium theory of unstable rock mass, the authors have established calculation method for support to falling unstable rock and for support-anchorage union to toppling unstable rock. These methods can calculate geometrical dimensions of support and anchorage pile or rope numbers.The proposed methods have been successfully applied in hundreds of unstable rocks in the Three Gorges reservoir for two years. All the methods in the paper are adopted by “The Design Technique Standard of Landslide, Bank Collapse, Unstable Rock in Chongqing City (the Three Gorges Reservoir)”.They are valuable for controlling unstable rock disasters in the Three Gorges Reservoir.