Study On Schedule Risk Of TBM Construction Project Based On Bayesian Network Method

In recent years,the construction range of underground tunnel engineering is becoming larger and larger,and the mechanical execution of tunnel TBM is becoming more and more frequent.The risk problem of project schedule is becoming more and more conspicuous.The risk evaluation before construction plays an important role in the work out the construction schedule and the completion of the project on schedule.Therefore,it is especially important to determine a scientific assessment method for progress risk evaluation.In the tunnel construction project,schedule control is a schedule target set under the reasonable control of funds and quality,and the schedule target out of control will inevitably impact the quality and safety of the project,so it is of great crucial to study the schedule risk of the tunnel project.In the first place,the theory of risk management and TBM construction schedule risk management is recommened,and the construction way,features and process flow of TBM are analyzed.The frequently-used risk analysis ways are simply introduced and compared,and the methods are compared and selected.By comparing the characteristics of tunnel TBM construction with its matching level,and through contrastive analysis,the research method most matching with the tunnel project schedule risk research system is finally selected.Secondly,literature analysis was used to classify tunnel TBM construction schedule risks into six categories: controllable factors,human,material,machine and pipe,and non-controllable factors,geology and technology.The risk origins of these six types of secondary indicators were discerned by WBS-RBS way,and 54 risk factors were initially recognized.The experts scored 32 risk factors.An objective,reasonable and operable risk assessment index system for tunnel TBM construction progress has been established.Then,the interpretative structure model is used to construct the causal layer among the second-level indicators of geological factors,human factors,material factors and management factors respectively.For equipment factors and technical factors,the equipment system division principle is used to analyze the reasons for the lag of the project schedule,and the risk network topology diagram of TBM construction schedule is obtained.Finally,the network relationship topology was imported into the Bayesian software Genie,and the prior probability was obtained by using the expert rating.The conditional probability and the posterior probability and grade of tunnel TBM construction progress lag were calculated by the software,and the main factors causing the occurrence of TBM construction progress risk were determined.Finally,the application procedure of the above evaluation model is expressed in detail in combination with the Double-Three Tunnel Project of Northern Xinjiang Water Supply Phase II Project.According to the occurrence of the project schedule risk,the precautionary steps are worked out.Integrated with the theory and practice,the construction delay early warning model with practical value is established,which attests to the scientificity and feasibility of the model.