Schedule Risk Analysis And Simulation Optimization Research On Complex Long Distance Diversion Tunnel With Deep Shaft

Complicated long shaft diversion tunnel plays a significant role in the reasonable and effective use of underground space.Because of its unique engineering structure and complicated construction environment,the long shaft diversion tunnel is easy to cause the pressure difference between the upper and lower flat caves and the long distance ventilation and smoke dissipation difficulty,the process duration and the logic change.And the construction method of drilling and blasting method and TBM method are complex and complex.The above-mentioned construction difficulties and problems make the long-distance water diversion tunnel construction of long shaft is an extremely complicated process,which is the research of tunnel construction process analysis poses a great challenge.Although traditional whole process simulation technology can optimize construction scheme and describe construction process,it can not scientifically select ventilation parameter,analyze logical relationship uncertainty and activity duration uncertainty.Moreover,initial system cannot output influence level that mechanical configuration and other related parameters make on construction period.Therefore,this thesis conducts an in-depth study on the problems mentioned above,which provides theoretical basis and technical assistance for construction management of complex long distance diversion tunnel with deep shaft,and obtains the research results as follows:1.Considering the complex construction conditions,the much construction interference and other objective conditions during the construction of long distance diversion tunnel with long vertical shaft,scientific value of the ventilation parameters and uncertainty analysis of model's logical relationships and active time is considered into the initial simulation model in order to make an optimization of the traditional simulation model.Long-distance diversion tunnel construction has some difficulty column such as construction front long,high strength construction,excavation volume,and complex construction conditions.So the construction process is complex.In the current long-distance diversion tunnel construction simulation model,simulation parameters rely more on experience and expert engineering analogy to select,which is a certain lack of relevance;and construction risks on construction progress is not considered in modeling process.In response to these problems,ventilation simulation module was added into the simulation model in order to develop realistic ventilation program of works.And schedule risk analysis module is added into the simulation model in order to identify effectively changes in the logical relationship and active time caused by risk events.The two modules optimizates long-distance diversion tunnel construction simulation models and increases the accuracy and reliability of the model simulation results.2.Considering the deficiency that traditional ventilation time in drilling and blasting method is determined with empirical approach,and combining the construction ventilation characteristic of the long distance diversion tunnel with deep shafts,this thesis proposes a method to determine the construction ventilation time based on the Euler-Euler two–phase numerical simulation..Traditional ventilation time in drilling and blasting tunnelling is almost all determined with empirical approach,which is difficult to quantificationally estimate the efficiency of smoke exhaust,and hard to predict the airflow track and the diffusion process of poisonous gas in the underground caverns.The construction of complex long distance diversion tunnel is featured with plenty of blasting faces,long ventilation distance,and superior difficulty in removing toxic gas with deep shafts.The existing two-phase flow researches primarily concentrate on the Euler-Euler simulation of a single diversion tunnel.Only a small number of them analyze Euler-Lagrange construction ventilation in the cross distribution tunnels,which can not reveal the concentration space distribution and migration rule of the contaminant of the construction ventilation in the cross distribution tunnels with deep shafts.Therefore,an Euler-Euler two–phase turbulence model is established with the consideration of the cross distribution tunnels and the draught head of deep shaft.The scientific ventilation time is obtained,which provides scientific basis for optimized simulation parameter and engineering practice.3.Considering the deficiency that current schedule risk analysis mainly focuses on the uncertainty of activity duration and neglects the uncertainty of logical relationship,this thesis puts forward the schedule risk analysis method of complex long distance diversion tunnel with deep shaft,which takes both logical relationship uncertainty and activity duration uncertainty into consideration.Construction of complex long distance diversion tunnel with deep shaft is featured with long construction period,high construction intensity and crisscrossing and intensive layout,and is a complicated system.Due to the unique structure and complex construction environment,the construction of deep shaft faces complex excavation technology,diverse geologic conditions and other problems.There exist plenty of uncertain factors during the construction of long distance diversion tunnel.These factors will not only affect activity duration,but bring about risk events,which lead to the change of logical relationship between activities and finally affects construction schedule.Current schedule risk analysis mainly focuses on the uncertainty of activity duration,but neglects the influence on construction schedule which is made by the variation of logical relationship.In light of this,fully considering the characteristic of complex long distance diversion tunnel with deep shaft,this thesis analyzes tunnel construction schedule risk from the aspects of logical relationship uncertainty as well as activity duration uncertainty.When compared with the current schedule risk analysis method,the risk analysis method proposed in this thesis,which considers both logical uncertainty and activity duration uncertainty,can realize more comprehensive risk analysis,and provide scientific guidance for the construction schedule management of complex long distance diversion tunnel with deep shaft.4.For the issue that construction period was affected by process duration and construction parameters,multivariate sensitivity analysis of long-distance diversion tunnel construction period is implemented based on range analysis.Long-distance diversion tunnel construction period is random and uncertain.Previous studies lack analysis for multivariate impact on construction period,which offeres limited guidance on the actual construction.In response to these problems,range analysis of data solution and multivariate sensitivity analysis are adopted to analysis the influence level of construction parameters on long-distance diversion tunnel construction with long vertical shaft.It judges the duration of the simulation process and all the simulation parameters may affect the duration of the critical path on the degree of influence on the duration of the,on the basis of tunnel construction schedule risk analysis.Compared with the current study,this method could determine all possible factors impact on the construction schedule of the simulation,and identify the key parameters on the construction process and construction period significantly affect,which provides a comprehensive basis for science to manage the development and construction of site construction organization plan.5.In this thesis,a long distance diversion tunnel is chosen to conduct application research,which proves the feasibility of theory and method mentioned above.Taking a long distance diversion tunnel as a case study,apply the theory,method and technology of above research into practical engineering.(1)Taking the ventilation process of drilling and blasting construction of a vertical shaft in a hydropower station's long distance diversion tunnel as a case study,adopt the Euler-Euler two–phase turbulence model to conduct simulation,and compare measured data and simulation results so as to verify the reliability of ventilation mathematical model.Meanwhile,analyze the grid sensitivity of long distance tunnel's grid model to obtain the reasonable meshing scheme.Additionally,through analysis of simulation results,study the airflow field and the diffusion as well as migration rule of noxious and dust,obtain the relationship between ventilation duration and excavation length,then finally optimize the construction simulation scheme.(2)With the combination of practical engineering,adopt probabilistic branch method to analyze logical uncertainty resulted from geological risk and use statistical clock method to make analysis of logical uncertainty from equipment risk.Moreover,adopt optimistic duration,most likely duration,pessimistic duration as well as 0.75 percentile to determine ? distribution of activity duration,then adopt rejection technique to conduct random sampling in order to realize the uncertainty analysis of activity duration.(3)On the basis of consideration of scientific value of ventilation parameters and uncertainty analysis of logical relationships and activity time,long distance tunnel construction simulation with long vertical shaft in carried on.The total duration,key path,resource intensity and some other simulation output can be obtained.And some risk parameters like probability of completion,completion risk,the most critical step of the line and criticality can be obtained too.These provide a scientific guidance for complex long tunnel with vertical shaft construction schedule management.(4)Relying on long-distance diversion tunnel construction process dynamic simulation model,and on the basis of tunnel construction schedule risk analysis,long-distance diversion tunnel construction period multivariate sensitivity analysis is implemented.It analyzes impact of single project activity duration on total duration of fluctuations,and impact of construction parameters on single project activity duration.Range analysis was used to analyze the two impacts on critical path.This method could determination the degree of influence of simulation model for the entire duration of the simulation parameters,and could recognize the key construction process and construction parameters,which provide a theoretical basis for the construction schedule and on-site construction time schedule control.