Study On Digital Decision Support For Cutterhead And Cutting Tools Maintenance Of Super-large Diameter Shield In Composite Strata

With the development of the city,human habitation,commerce and transportation gradually extend to the underground space.Shield method is widely used in underground engineering because of its advantages of less environmental impact and higher safety.In recent years,the development of human underground space has been increasing rapidly,and the demand of large-diameter shield tunnels construction has been increasing.The excavation of large section of large-diameter shield tunneling also leads to the normal condition of encountering complex geological conditions of multiple strata,which brings a series of engineering challenges such as difficult maintenance of cutterhead and cutting tools,increased risk of instability in tunneling and low efficiency of assembling super-large segments.Among them,the super-large diameter shield(more than 14 m in diameter),especially the important channel in the sea,the city underground fast-driving road,often under the soft hard tunneling construction in highly abrasive composite strata,the buried depth deeper,environment more complex,the cutterhead and cutting tool wear problem is particularly prominent.How to evaluate and detect the in-service cutterhead and cutting tool efficiently,how to reasonably balance the relationship between the cutting tool replacement frequency and the engineering tunneling efficiency cost,and how to effectively analyze the mass data of the shield tunneling parameters and support the maintenance of the cutterhead and the decision of cutting tool replacement,it is urgently needed to be further studied.In view of this,by studying the cross-scale modeling of super-large diameter shield construction,the framework design of digital management and control system based on cross-scale BIM model,the digital decision support for shield construction and so on,this paper proposes a set of digital control process for shield tunnel construction,and takes cutterhead and cutting tool wear prediction and cutting tool replacement decision as examples to carry on the selective analysis.It mainly includes the following studies:1.Put forward the concept of cross-scale BIM modeling,and took a super-large diameter shield tunnel project of a city as an example for modeling.The cross-scale BIM modeling goes beyond the traditional meso-scale modeling of the tunnel body structure,and also includes the macro-scale modeling of the surrounding environment and the geological space modeling,and the meso-scale modeling of the core construction equipment(eg: shield tunneling machine).2.Put forward a digital management and control system framework based on crossscale BIM,which integrates data management,analysis and construction decision-making functions.The system includes dynamic maintenance subsystem of in-service cutterhead of shield construction,which can support the input,view,statistics and export of cutting tools data.In order to strengthen the function of data management,based on VBA language(Visual Basic for Applications,a general automation language used to extend the function of Windows Applications),the information entry interface of manual cutting tool data collection is developed to form two structured storage forms with different levels of detail.3.With the support of the digital management and control system based on the crossscale BIM,five construction pilot applications were completed,in which the prediction of cutting tool wear in shield tunneling and the decision analysis of cutting tool replacement further considering the tunneling efficiency of the project were mainly introduced.The former is based on cutting tool data in the form of detailed structured storage,shield and geological parameter data to complete cutting tool consumption analysis,wear coefficient analysis and wear prediction based on XGBoost algorithm.The latter is based on cutting tool data in the form of brief structured storage,shield and geological parameter data to define a cutterhead wear index with weight coefficient of single cutting tool yield and build the mathematical model of penetration and cutterhead wear,total extrusion,torque and rotational speed.The comprehensive cost and two kinds of cutting tool replacement strategies were illustrated.The simulation models of cutting tool wear and shield tunneling process were established by using system dynamics and discrete events in the software Any Logic,and the cutting tool replacement decision was analyzed by combining with the mathematical model used to calculate penetration,cutting tool life and tunneling efficiency.The digital management and control system based on cross-scale BIM can better meet the actual needs of the project and provide effective construction guidance,which is of great significance to ensure the safety and success of the super-large diameter shield tunneling project in composite strata,and to save the project cost and time limit.At the same time,it also provides the implementation path and method framework for the whole life cycle data sharing of the underground structure during construction and operation.