Study of combined bearing characteristics of lining and surrounding rock for hydraulic tunnel under internal water pressure

Internal water pressure is one of the main kinds of loads acting on hydraulic tunnel,which consists of lining and surrounding rock.The axisymmetrical model is adopted and the corresponding formulas are carried out.The radial stress on interface is assumed as the flag to tell the combined bearing capability of lining and surrounding rock.Then the influence of rock permeability and deformation modulus on the combined bearing characteristic of lining and surrounding rock is discussed.The design method and process are described in detail.According to the limit of maximum width of concrete crack,a program to calculate pervious lining stresses and to carry out the reinforcing bars design is developed and compiled.A certain tunnel is analyzed as an example and a certification of design program is provided.Finally some conclusions are drawn as follows.Rock permeability is as important as deformation modulus in tunnel lining structure design.The possibility of lining deviating from rock becomes larger when rock permeability becomes poorer and deformation modulus softer.And the possibility of lining deviating from rock also becomes larger when the concrete cracked.A great amount of steel can be saved through the reinforced concrete lining scheme than the steel lining one.To enhance rock integrity and impermeability,some advices are suggested,such as reducing excavation disturbance,adopting fine and complete consolidation grouting.