Study On Mechanical Pro Perties Of Concrete PiPe Joint With Large Section In Long Distance PiPe Jacking Engineering

The topographic condition of Chongqing is mountainous,and the connection between the water supply groups is not close enough.In order to improve the connection between the water supply groups and ensure the urban water supply,it is necessary to construct a large number of long-distance and large-section water supply pipelines between the groups.Considering the requirements of water supply quality and the soft and hard rock as the main surrounding rocks in Chongqing area,concrete pipes were selected for the project to be constructed by pipe jacking method.in the construction of long distance and large section concrete pipe jacking,and due to the characteristics of large jacking force and complex bearing force,stress concentration tends to occur at the pipe jacking joint,leading to local crushing failure of the pipe joint.In view of this,this paper,relying on an engineering project in Chongqing,analyzes the stress characteristics of long-distance concrete pipe jacking joints with large section through theoretical derivation,field monitoring test and numerical simulation.The main research contents and results are as follows:(1)Through theoretical derivation,the ultimate bearing capacity of concrete pipe joint is studied when the ultimate compressive strain is reached.And the ultimate bearing capacity formula of concrete pipe jacking joint under axial pressure is obtained.Further,the ultimate bearing capacity formula of concrete pipe jacking joint when deflection occurs is analyzed and the law between ultimate bearing capacity and opening length of the deflection is obtained.(2)Through field monitoring test,the axial stress at different positions of each pipe joint among different relays was studied,and the axial stress at deflection position of concrete pipe joint under different jacking forces was analyzed,and the law of linear change of axial stress of pipe joint with jacking force was obtained.(3)Through numerical simulation method,the stress of concrete jacking pipe socket during jacking is analyzed,and the law of stress of joint socket changes with deflection angle and the influence law of jacking force on the stress of joint socket during deflection is obtained.It is also found that when the jacking force reaches a certain value,the concrete pipe jacking joint appears local crushing phenomenon,and the ultimate deflection angle of the concrete pipe jacking joint under different bearing capacity is further analyzed.By comparing the axial pressure and the bias pressure,the law of stress amplification factor(the bias stress/axial compressive stress at the same position with the same jacking force)changing with the jacking force is obtained,and according to the simulation results,the range of safety factor of jacking force for reference is 3.44-4.33.(4)The influence of the thickness,Poisson’s ratio and elastic modulus of the concrete pipe jacking gasket and the jacking ring on the force of the pipe jacking joint is analyzed by numerical simulation method,and the influence curve of the parameters of the gasket and the jacking ring on the axial force of the socket and the jacking ring is obtained.Combined with the results of numerical simulation and engineering practice,the parameter optimization ranges of gasket and jacking ring are given for reference in Practical engineering,and the obtained optimized parameters are applied to practical engineering application,and good engineering application results are obtained.