Study On The Distribution Law Of Water Pressure On The Composite Lining And The Stress Characteristics Of Structure Of Subsea Tunnel

With the increasing demand for sea-crossing traffic,as one of the main methods of sea-crossing traffic,the subsea tunnel has been widely used.In order to ensure the safety of construction,the subsea tunnel is often deep buried under the seabed.Water inrush and high water pressure on lining are the main problems in subsea tunnel construction.Its purpose is to control the water inflow and reduce the water pressure on lining.The key to the construction of the subsea tunnel is to adopt a reasonable and reliable waterproof and drainage system.At the same time,accurate calculation the water pressure on lining and the internal force of the structure are very important.The paper is based on the subsea tunnel of Qingdao Metro Line 8.The law of water pressure on lining and internal force of the lining structure are systematic studied in this thesis.Its research method include theoretical analysis,numerical calculation and field test.The main contents of this thesis are listed as following:(1)Based on the investigation of waterproofing and drainage systems of typical subsea tunnel,the conception and composition of water and drainage system are discussed.When the water level is high,the tunnel with composite lining should limit the water flow and take drainage measure.Its purpose is to control the water inflow and reduce the water pressure on lining.(2)According to the simplified seepage field calculation model of subsea tunnel,the analytical formula for water pressure and its reduction factor of subsea tunnel initial support.Combined with numerical calculation,the effects of influencing factors such as water level,permeability coefficient of surrounding rock,thickness of grouting circle,grouting effect,thickness and permeability coefficient of initial support on the water pressure and reduction foctor of the initial support.Considering the actual engineering situation,it is deem that the main influencing factors of the water pressure reduction factor are the permeability coefficient of surrounding rock,the thickness of the grouting circle and the grouting effect.A table of water pressure reduction factor suitable for Qingdao subsea tunnel is presented.(3)The influence of seepage on internal force and deformation of lining structure is analyzed by numerical calculation.The results show that the seepage has a significant effect on the internal force and deformation of lining structure.Therefore,the calculation value of the internal force of the lining should be increased appropriately when using the water pressure reduction factor method to design the lining structure.(4)Using the F5 structural fracture zone of Qingdao Metro Line 8 subsea tunnel as engineering back ground,the internal forces of the lining structure were calculated by selecting different water pressure reduction factor.The variation of quantity of reinforcement and safety factor of lining structure is analyzed.With the increase of the water pressure reduction factor,the quantity of reinforcement required by lining will increase obviously,and the safety factor of lining structure will decrease continuously.When the water pressure reduction factor is less than 0.4,the existing design scheme can meet the safety demand.