Research On Fuzzy PID Control Technology Of Shield Excavation Face Stability In Composite Stratum

Recently,urban density continues to increase,and the utilization of urban space has been paid more attention.In order to alleviate the pressure of ground traffic,the development of underground space has become a new direction for urban construction,and subway construction is becoming more and more in line with the needs of urban construction.In the construction of subway tunnels,the shield tunneling method is widely used due to its low disturbance and high safety.With the progress of technology,the diameter of tunnel section began to develop toward the direction of large section,there will be geological conditions such as composite strata during the construction process,how to ensure the stability of shield tunnel excavation face under complex geological conditions during the shield construction process is one of the core issues in shield tunneling construction.This thesis takes the stability control of shield tunnel excavation face as the main research object,relying on a certain subway shield tunnel project in Wuhan,through theoretical analysis and modeling simulation to study the stability control of shield tunnel excavation face in composite strata under the condition of soil uncertainty process,has made certain theoretical value and engineering significance research progress,the main research result is as follows:1、Summarize the basic principles of the face stability in the shield excavation,analyze the evolution process of the stability state of the shield tunnel excavation face,Considering the uncertainty of the soil mass,based on the upper bound theorem of the limit analysis method,a spiral failure model for the instability of the excavation face of the composite stratum is constructed,and obtain the limit support pressure value under each level of reliability index through the MATLAB programming calculation program combining with the reliability theory.2、Analyze the composition of the shield tunneling thrust control system,through the research and simplification of the basic principles of the shield tunneling machine’s hydraulic propulsion system,obtain the transfer function of each element and establish the mathematical model of the shield thrust control system which with hydraulic flow as input,shield thrust pressure as output,and external pressure on the excavation surface as the external load module.Fully considering the characteristics of the shield machine’s working environment,the fuzzy PID control algorithm is designed to optimize and improve the PID algorithm.Through simulation verification,it is concluded that the designed shield thrust control algorithm can better meet the requirements of the shield machine thrust control system.The calculation process of the ultimate support pressure solution and the shield thrust control simulation model are combined to form a complete set of shield excavation face stability control process,which can ensure the safe progress and effective control of the tunneling process.It is of great significance to ensure the construction safety of shield tunneling in composite strata.