| With the rapid development of social productive forces and the continuous advancement of science and technology,the level of urbanization in various regions of our country has continued to rise,the number of urban populations has also continued to rise,and the demand for urban living space has increased.Nowadays,people are vigorously developing the aboveground space,so the rational development and utilization of underground space is getting more and more attention from people from all walks of life.Among the various projects for the development of underground space,urban subway projects have contributed greatly to alleviating the pressure of ground transportation in large cities.With the construction and operation of a large number of subway projects,studying the time-varying reliability of subway shield tunnel structures can predict the reliability during the construction and operation of the project,improve the quality of the project and reduce the cost of maintenance.The main content of this paper is the reliability of the soil and segment structure at the end of the construction of the subway shield tunnel during construction and service.After considering the influence of time factors,the reliability of the shield tunnel segment structure was studied.The specific research contents are as follows:1.According to the relevant background of the research topic of this paper,the research significance of this paper is proposed.Through the study of structural reliability theory,the factors affecting the reliability of subway shield tunnel construction are analyzed,and at the same time,the time-varying reliability of the structure is studied by considering the role of time.According to the two limit states of structural bearing capacity and normal use,combined with the failure mode of concrete carbonization corrosion,five function functions Zi during shield construction and tunnel service period are established.2.The principle of shield construction and the purpose and method of soil reinforcement at the end of the shield are stated,and the advantages and disadvantages of commonly used soil reinforcement methods are compared and analyzed.Taking a bid section of the Shenyang subway as the research background,using ABAQUS to calculate the stress and deformation of the soil body and the segment structure during the construction process of the reinforced soil through the shield tunnel.The results show that after the soil body is strengthened,the ground settlement decreases by 60%,the arch settlement decreases by 56%,and the invert arch uplift value decreases by 39%.By setting different material parameter changes of the reinforced soil,the change of the soil displacement during the tunnel construction process is analyzed,and the sensitivity of parameters such as internal friction angle and elastic modulus is obtained.The calculation and analysis results show that the sensitivity of the internal friction angle is the largest among the five parameters of the studied reinforced soil.3.After considering the randomness of the parameters,the combination of MATLAB and ABAQUS,the Latin hypercube command in MATLAB software was used to randomly sample the 26 random variables identified in this paper,and the interface function was written to use the sampling results to basically Variable substitution,cycle calculation 300 times,get the maximum surface settlement,maximum surface uplift,maximum stress and deformation of the segment under different variables and bring it into the corresponding structural function Zi for calculation,when Zi <0 is regarded as Failure,count the number of failures and calculate the failure probability,and finally check the standard normal distribution table to obtain the corresponding reliability index value.During the service of the shield tunnel,the reliability index of the tunnel was reduced from 4.09 to 2.88 in the unreinforced soil area;in the soil reinforcement area,the reliability index of the tunnel was reduced from 4.54 to 2.93. |
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