STABILITY AND DEFORMATION OF DEEP AND THICK OVERBURDEN DUE TO CHANGED SEEPAGE CONDITIONS AFTER RESERVOIR IMPOUNDING

The impact of seepage field on deep and thick overburden mainly manifests in the physical,chemical and mechanical aspects of the ground.In this paper,a deep and thick overburden in typical place of Lu-dila hydropower reservoir banks on Jinsha River is used as examples of stability analysis after reservoir impounding.The site has a detailed ground investigation.The ground investigation includes geological structure,material composition,hierarchical feature,physical and mechanical properties,grain composition and infiltration parameters.Using those data,the deformation of deep and thick overburden is computed with a three-dimensional finite element program.The seepage aspect to the deep overburden is analyzed.The results show that after the river water level elevates 5 meters,the seepage changes.Under the effect of osmotic pressure,the deformations on the parallel and perpendicular direction to the river are different.The largest deformation on the parallel direction to the river is 50 cm.The largest deformation on the perpendicular direction to the river is 133 cm.The largest decrease in production is 188 cm.Such a large deformation can cause deep overburden damage,thereby affect its upper buildings and road safety.