Effect Of Weak Intercalation And Surrounding Rock Creep On Thermal Stress Of Hydraulic Tunnel Concrete

Hydraulic tunnel is widely used in hydropower engineering construction.In recent years,the problem of cracks in lining concrete has been paid more and more attention.The research shows that the thermal stress is one of the important reasons for the cracking of lining concrete.For the analysis of thermal stress of hydraulic tunnel lining concrete,in the previous finite element calculations it was assumed that the surrounding rock is uniform and does not include the surrounding rock creep.In fact,the surrounding rock is cut by discontinuities such as rock joint and weak intercalation,and has creep characteristics.However,few relevant studies consider weak intercalation and surrounding rock creep.Therefore,it is necessary to conduct a more detailed study to consider the effect of weak intercalation and surrounding rock creep on the thermal stress of hydraulic tunnel lining concrete.Takes a circular water conveyance tunnel as the engineering background,it is assumed that the surrounding rock contains a weak intercalation with a uniform layered distribution.Studies the effect of the intercalation and surrounding rock creep on the thermal stress of the hydraulic tunnel lining concrete.Based on the calculation principle of elastic creep thermal stress,using the finite element method of ANSYS and its APDL and UPFs secondary development,the thermal stress of hydraulic tunnel lining concrete is simulated by threedimensional finite element method.This paper detailed analyzes the effect of the thermal stress of the lining concrete from penetrating and drive weak intercalation's the angle,the distance from the excavation contour,the thickness,and the elastic modulus.Considering surrounding rock creep,the effect of surrounding rock creep on thermal stress of lining concrete is analyzed under the condition of uniform surrounding rock and surrounding rock with weak intercalation.The effect of concrete creep on thermal stress is significant,so concrete creep is considered in the simulation process.According to the simulation results,combining comprehensive influence factors,the main characteristics of the effect of thermal stress of hydraulic tunnel lining concrete considering the weak intercalation and surrounding rock creep are as follows: The penetrating weak intercalation increases historical maximum of the first principal stress of concrete in a certain range,the increase rate is about 3.02%~106.11%,mainly on the external surface of lining;The drive weak intercalation generally decreases historical maximum of the first principal stress of concrete,the reduction range is about 0.95%~11.57%;Considering the uniform surrounding rock creep,historical maximum of the first principal stress of concrete decreases about 0.22%~5.86%;Considering the surrounding rock creep with penetrating weak intercalation,historical maximum of the first principal stress of concrete decreases by about 3.10%~9.12%,and increases by no more than 0.30% in special position;Considering the surrounding rock creep with drive weak intercalation,historical maximum of the first principal stress of concrete decreases by about 1.68%~10.43%,and increases by no more than 0.14% in special position.Therefore,in the simulation calculation of the thermal stress of hydraulic tunnel lining concrete,the penetrating weak intercalation should be considered,and the drive weak intercalation can even be ignored.Considering the surrounding rock creep,the interaction between surrounding rock and lining can be reasonably simulated.It provides a reference for the temperature control and crack prevention of hydraulic tunnel lining concrete.