RESEARCHES ON DEFORMATION AND FAILURE CHARACTERISTICS OF AN UNDERGROUND POWERHOUSE WITH COMPLICATED GEOLOGICAL CONDITIONS BY DDA METHOD

As a numerical modeling approach,discontinuous deformation analysis(DDA) method was employed to analyze effects of different factors on the deformation characteristics of an underground powerhouse.The effect factors mainly consist of stress lever coefficient,rock reinforcement,joint structure pattern and strength properties of joints in surroundings,etc..It has been shown that DDA model can get reasonable results with different simulation cases.The deformation of surrounding rock mass is closely relevant with rock stress conditions assumed beforehand.As the surrounding rock mass has the characteristics of hard and soft rocks being formed alternatively,where the multi-layer of shear zones exists between them,the displacements of sidewall have larger increasing intervals compared with those of roof arch displacements of the powerhouse when horizontal stress increases;and the discontinuous sliding along surfaces of shear zones will occur normally.Reinforcement with rock bolts will bring favorable effects on rock surroundings in controlling deformation and stress distribution properties.If a series of key blocks collapse,the joint intersections in surrounding rock mass,in some cases,will exert negative effects on the stability of powerhouse.On the other hand,for joint intersections being under stable state,unstable deformations of rock surroundings will occur when the joint strength is reduced to some extent.This paper presents some relevant results with DDA method,and some problems associated with DDA have been discussed.