Numerical Simulation Of Ventilation And Optimization Of Construction Scheme For The DiversionTunnels

The construction scheme optimization is an important research problem and the construction of the diversion tunnel is extremely complex. Construction ventilation, which is an important restriction factor of construction schedule, needs advanced theory to optimize construction scheme. The theoretical analysis of numerical simulation for the ventilation in the diversion tunnel and optimization of construction sccheme based on the ventilation simulation are presented. It integrates with advanced theories and methods from the hydraulic and hydroelectric engineering science, systems engineering, geographical information system and computational fluid dynamics.In general, the following four achievements are obtained in this dissertation:(1) Determination method of ventilation parameters based on CFD is presented. And the construction ventilation models for diversion tunnel are set up. The quantitative construction ventilation time is obtained by solving mathematical model. It overcomes disadvantages of the qualitative engineering analogy and empirical method of ventilation time. It offers the theoretical basis to construction schedule simulation and construction scheme optimization.(2) The 3-D transient quasi-single phase models and a 3-D two phase flow model are proposed together with k-εequations. The effect of inter-phase drag, lift force and virtual quality force are considered in the momentum source of dust diffusion model. The effect of buoyancy is considered in the momentum equation of the CO transport model. The 3-D dust concentration field in the diversion tunnel with 50m long is simulated using the 3-D quasi-single phase models and a 3-D two phase flow model. The simulated results show that the trend of the dust migration and velocity based on the 3-D transient quasi-single phase models is well in agreement with that based on 3-D two phase flow model. Compared with the two phase flow model and the 3-D transient quasi-single phase models, the time reaching the standard of ventilation is almost the same. Consequently, the dust diffusion in explosion processes of the diversion tunnel is simulated using a 3-D quasi-single phase models. The reliability of the models is analyzed.(3) The optimization of construction scheme based on the numerical simulation of ventilation is presented. Based on the numerical simulation of ventilation, a new method called the visual dynamic simulation technique for construction process is presented, which combines visualization simulation technology, and network plan and optimum technique. It provides powerful technical measures for comprehensive analysis of the interaction and restriction of the construction duration, the intensity of excavation, the traffic of construction site and the construction scheme optimization.(4) The diversion tunnel of a hydropower station is taken as a case. The ventilation in different excavation progresses is simulated. The distributions of the wind velocity, wind pressure, CO concentration and dust concentration are analyzed respectively. Using the data-fitting method, the relation between ventilation time of blasting of the diversion tunnels and excavation progress is established. The construction simulation and schedule optimization are researched based on the optimized ventilation time. The feasible construction period, reasonable construction scheduling and optimized construction intensity are obtained to optimize the construction scheme.