Euler-Lagrange Simulation Of TBM Ventilation Considering Heat Transfer Of Surrounding Rock In Deep-Buried Headrace Tunnel

During the TBM construction of deep-buried headrace tunnel,it is very difficult to decrease temperature and control the dust due to the thermal storage effect,the heat transfer of surrounding rock and the dust produced during construction process.Ventilation is an important method to improve the TBM construction environment and ensure the construction safety.Ventilation simulation,which is an effective way to obtain the distribution characteristics of air-flowing field and temperature field and the law of dust particle migration,can appropriately provide suggestions for on-site cooling and dust suppression system.However,most related researches are limited to consider the influence of convective heat conduction between vent air and surrounding rock,and ignore thermal conduction inside surrounding rock.In addition,the three-dimensional distribution feature of fractures inside the surrounding rock is usually neglected in study of surrounding rock heat transfer.Hence,it is urgent to analyze the influence mechanism of heat transfer of surrounding rock with fractures in TBM ventilation of deep-buried headrace tunnel.According to the fundamental of Computational Fluid Dynamics,Geology and Heat Transfer,this paper carries out in-depth research of above issues and gain results as follows:(1)Firstly,the polygonal discrete fracture network model of deep-buried headrace tunnel surrounding rock is established based on 3D fracture stochastic modeling theory.Then,the effective thermal conductivity of deep-buried headrace tunnel surrounding rock is derived through analyzing the fractal characteristic of 3D fracture network.Accordingly,the heat transfer model of surrounding rock considering influence of both heat conduction within surrounding rock and heat exchange coupling between wind flow and surrounding rock is established.Finally,the Euler-Lagrange two-phase flow model for TBM ventilation is put forward on the basis of Euler-Lagrange two-phase flow model with RNG k-? two-equation turbulence model and discrete phase model.The stochastic particle trajectory model is used to simulate the particle phase,in which the effects of turbulent stochastic diffusion and gas solid coupling on dust particle transport are considered.In addition,the discretization scheme of the governing equations is discussed and the SIMPLEC algorithm is selected to solve discrete equations.(2)To verify the accuracy,consistency and effectiveness of established model,the comparison between field experimental data,simulation results of established model and other traditional models is carried out,in which error indicators are adopted,such as the mean absolute percent error,the root mean square error,the ratio of percentage deviation and correlation coefficient.(3)The proposed model is applied to a real project.The law of heat exchange between vent air and surrounding rock,and the distribution feature of tunnel and surrounding rock temperature field are revealed.The distribution characteristics of airflowing field within the tunnel and the law of dust particle migration inside the TBM are obtained.Furthermore,parameters of ventilation cooling and dust suppression system are optimized.The research results can provide the theoretical guidance and technical support for engineering practice.