Study On Influence Mechanism Of Lining Defects And Bearing Capacity Of Highway Tunnel Lining

With the development of community economy and technology,China's highway tunnel construction rank first in the world.Meanwhile,the disease problem in operating tunnel are gtadually emerging.In the southwestern regions of China,due to poor construction environment,the quality of tunnel is more difficult to control than other regions,which resulting in severe challenges for tunnel operation and maintenance.However,for the defects of tunnel lining,related research about the mechanism and bearing capacity of tunnel mechanical properties is lacking.And the theoretical system and calculation method have not yet been formed.Thus,this paper combined Large field experiments,laboratory model tests,,theoretical analysis and numerical simulation,and studied the influence mechanism of tunnel mechanical properties.Moreover,the calculation of bearing capacity under different defect condition was also discussed.The above research played an important role in the construction,maintenance,operation and management of highway tunnels,especially in Yunnan and southwestern China.The main contribution of this paper are summarized as follows.(1)Based on the statistical analysis of the detection results,the main types of tunnel lining defects and their distribution are revealed,and the cause of lining defects are also analyzed.Furthermore,a 1: 1 scale tunnel lining model with typical defects was established,and large-scale outdoor tests was carried out by using 2D and 3D geological radars,which obtained a standard map of geological radar with typical defects.(2)Given that the weight of lining has little effect on the ultimate bearing capacity,and the frictional force on the test model on smooth ground is negligible.Meanwhile,considering that horizontal loading is safer and more stable than vertical loading,to make the experiment reflect the actual working state of the lining,and simulate the constraints and loading of the surrounding rock on the lining,we developed a horizontal tunnel lining model test device,which is composed of reactionforce frame,electro-hydraulic system,stratum restraint system,and arch foot fixtures.This device has the characteristics of clear force,simple structure,convenient operation,reliable,and high efficiency.(3)The laboratory tests of NC lining with lining voids,lining thinning and combined defects were carried out,and the mechanical properties,deformation evolution law and bearing capacity of NC lining with defects were systematically studied.Then,the mutual verification of numerical simulation and NC lining model test was realized.Besides,the influence law of defects,load and formation parameters on the mechanical properties of NC lining was also thoroughly revealed.(4)We carried out an indoor model test study on the RC lining with void defects at the dome and abutment,and systematically studied the mechanical properties,deformation evolution law and bearing capacity of the RC lining with defects,which revealed that the RC lining has higher integrity and better ductility than NC lining.Based on the above study,the mutual verification of numerical simulation and RC lining model test was realized,we also revealed the influence rule of the parameters such as cavity range,position,and stratum stiffness on the mechanical properties of RC lining.(5)Given that the engineering requirements,a toolbox based on machine learning algorithm for calculating the bearing capacity of tunnel lining was designed and implemented.This toolbox contains five types of machine learning regression algorithms,and each type contains two models.Simultaneously,NC and RC lining bearing capacity simulation datasets were established,which can tackle the problem of high costs of physical test and time consuming for finite element analysis.Eventually,according to the data-driven method,the bearing capacity of tunnel lining can be calculated more efficiently and accurately.