Study On The Influencing And Governing Factor For Large-size Shield Tunneling In Composite Stratum

The rapid increase in demand for infrastructure construction in the process of urbanization has led to a serious shortage of urban land resources,and the contradiction between space supply and demand has become increasingly prominent.More and more large-diameter shield tunnel boring machines are used in the construction of underground space projects.As the diameter of shield excavation increases,the probability of encountering composite strata is greatly increased,and its construction is more complicated and riskier than tunnel excavation in uniform strata.Under the condition of sparse geological drilling samples,the geological environment is difficult to accurately perceive and predict,making the stability control of shield tunneling a challenging engineering problem.Shield operators need to identify the key influencing parameters of excavation efficiency,stability and safety,and adjust these parameters in time during the shield tunneling process to avoid possible unfavorable conditions such as shield instability.In order to assist shield operators in reasonable control of shield construction parameters,this paper uses digital construction,global sensitivity analysis,artificial intelligence and other related theories,methods and technologies to affect the impact of large-diameter or superlarge-diameter shield tunneling in composite stratum from three aspects Factors and controlling factors were analyzed and studied,including: the correlation study of shield construction parameters and rock and soil quality under the condition of composite strata,the study of geological parameter processing methods under the condition of composite strata,and the prediction of surface settlement and shield machine performance under the condition of composite strata.Research on parameter control of shield machine:(1)Research on the correlation between shield construction parameters and rock and soil quality under complex stratum conditions.In previous research,a BIM-based shield big data management platform was developed.Based on the data stored in the system,a research method for the correlation between shield construction parameters and geological parameters in composite strata was proposed.This research proposes a global sensitivity method based on random response surfaces,combining Generalized Polynomial Chaos Expansions(GPCE)proxy model and global sensitivity analysis(GSA)to establish a sensitivity analysis framework,quantitatively and Qualitatively describe the relationship between shield construction parameters and shield excavation surface stability,shield attitude and ground settlement,and then fully explore the hidden information of data stored in the BIM-based shield big data management platform.The results show that the GPCEGSA method can effectively identify the construction parameters that have an important impact on the performance of the shield machine during the construction process,and the key construction parameters have different influences on the tunneling performance of the shield machine in different geology.(2)Research on the rock and soil quality data processing method and the prediction of surface settlement and shield machine performance under the condition of complex strata.Propose a multi-layer soil system transformation method for the processing of complex stratum geological parameters,which is used to convert composite stratum rock and soil quality data,and solve the problem of insufficient geotechnical parameter interpretation when constructing input and output index systems in the machine learning process;proposes decision-making based on gradient enhancement The prediction model of composite stratum surface settlement and shield machine performance based on the tree(GBDT)algorithm.The optimization algorithm is used to optimize the model,and the generalization ability of the model is explored.The results show that the multi-layer soil system conversion method for data processing can effectively reduce data redundancy and improve the accuracy of the prediction model.The prediction accuracy of the prediction model after hyperparameter optimization is significantly improved,and it has good generalization ability.(3)Research on shield parameter control under composite stratum conditions.This study uses statistical analysis of the settlement monitoring data of a certain project in Wuhan,sets settlement grading control standards for the settlement control of the upper soft and lower hard composite stratum,and predicts the control level of the ground settlement caused by tunnel excavation in advance according to the ground settlement prediction model,combined with the shield Research on the correlation between construction parameters and geology,and propose appropriate control measures for different control levels.Combining the research results of this paper and related materials,the method of shield construction parameter control in soft stratum,upper soft and lower hard stratum and composite rock formation is summarized and combed.