Research On Construction Simulation Optimization Of Complex Deep Buried Diversion Tunnel Group Based On Ventilation Simulation

The criss-cross cavern layout,complex construction schedule and resource optimization are characteristics of the complex deep buried diversion tunnel group,and its construction process is a multi-level and multi-process dynamic cycle.In addition,the heat transfer effect of high ground temperature surrounding rock leads to further deterioration of ventilation environment,lower labor productivity and endanger the life safety of workers.At present,the ventilation parameter values in the simulation study of the diversion tunnel are based on the engineering experience or the numerical simulation of isothermal ventilation confined to a single ventilation scheme.Meanwhile,most of the existing tunnel construction simulation ignores the dynamic change characteristics of the simulation parameters,and a few studies have been limited to the use of Bayesian updating methods,which is difficult to accurately describe process parameter change.Therefore,how to consider the influence of high ground temperature surrounding rock and the dynamic change of ventilation demand in the optimization of ventilation parameter as well as how to describe the dynamic evolution of construction simulation parameters with the construction propulsion are important subjects to be solved urgently in the field of construction simulation optimization of the complex deep buried diversion tunnel group.This paper makes an in-depth study on the problems mentioned above and obtains the following results:1.The influence of high ground temperature heat transfer and the dynamic change of ventilation scheme are not synthetically considered in determining the value of construction ventilation parameters in the existing research of complex deep buried diversion tunnel group construction simulation,and parameter updating methods are hard to accurately describe the dynamic evolution characteristics of construction parameters.Therefore,optimization theory and method of complex deep buried diversion tunnel group construction simulation are proposed.Ventilation parameter value selection in traditional complex deep buried diversion tunnel group construction simulation research is based on engineering experience or confined to isothermal ventilation simulation with single ventilation scheme,lacking overall consideration of influence of high ground temperature heat transfer and dynamic change of ventilation scheme.Besides,most of the existing tunnel construction simulation researches ignore the dynamic change features of simulation parameters with construction advance.And minority researches are limited to using Bayesian parameter updating technique,which is hard to precisely describe the parameter changing process.Therefore,optimization theory and method of complex deep buried diversion tunnel group construction simulation are proposed.Firstly,construction simulation optimize process in which the ventilation parameter value optimization selection and construction parameter dynamic update are synthetically considered.Then the complex deep buried diversion tunnel group construction simulation optimization model is established by couple CPM model and CYCLONE model.Finally,construction intensity statistics and resource balance optimization method is proposed to provide theoretical support of complex deep buried diversion tunnel group construction organization design and project management decision.2.Current studies on the numerical simulation of tunnel surrounding rock thermal conduction mostly regard the homogeneous rock thermal conductivity as the surrounding rock thermal conductivity,and there lacks the research on the effective thermal conductivity of tunnel surrounding rock that considering the rock mass as fractured media.This paper proposes a method of analyzing the surrounding rock effective thermal conductivity of complex deep buried diversion tunnel group based on fractal analysis of 3D fracture network.Current studies on the numerical simulation of tunnel surrounding rock thermal conduction mostly consider the homogeneous rock thermal conductivity as the surrounding rock thermal conductivity,and these studies focus on field testing,2D thermal conduction numerical simulation and porous media modeling and simulation,so there lacks the research on the effective thermal conductivity of tunnel surrounding rock considering the rock mass as fractured media.To solve these problems,this paper proposes a method of analyzing the surrounding rock effective thermal conductivity of complex deep buried diversion tunnel group based on fractal analysis of 3D fracture network.Firstly,the surrounding rock exposed fracture traces log data of actual complex deep buried diversion tunnel group is collected,and based on the probability and statistics theory,the geometric parameters of the fracture is estimated and the 3D fracture network is stochastically modeled with Monte Carlo method;Secondly,based on the fractal theory,the fractal dimension of the 3D random fracture network is calculated with cubic covering method;Finally,the mathematical expression of surrounding rock effective thermal conductivity is derived based on the fractal characteristic of the 3D fracture network,and this research provides a theoretical foundation for improving the mathematical model of complex deep buried diversion tunnel group construction ventilation simulation considering the influence of surrounding rock thermal conduction.3.In view of the actuality that synthetically consideration of heat conduction within surrounding rock and heat exchange coupling between wind flow and surrounding rock in the research of complex deep buried diversion tunnel group construction ventilation two-phase turbulent flow model is scarce,a complex deep buried diversion tunnel group construction ventilation two-phase flow simulation method considering the influence of surrounding rock heat transfer is put forward.At present the research of diversion tunnel construction ventilation two-phase flow simulation converges on isothermal ventilation,besides the existing non-isothermal two-phase flow simulation of deep buried diversion tunnel research is restricted to considering the heat exchange between wind flow and surrounding rock,and ignores the important influence of high ground temperature heat transfer on construction ventilation.Aiming at those problems,a complex deep buried diversion tunnel group construction ventilation two-phase flow simulation method considering the influence of surrounding rock heat transfer is proposed,and a complex deep buried diversion tunnel group construction ventilation two-phase turbulent flow model considering the influence of heat conduction within surrounding rock and heat exchange coupling between wind flow and surrounding rock is established.Firstly the surrounding rock heat transfer model is improved by equivalent thermal conductivity coefficient of surrounding rock obtained through analysis of three-dimensional fracture network fractal theory.Then reasonable simulation parameters,such as ventilation pattern,ventilation quantity and so on,are confirmed by considering the intricate cavity layout of complex deep buried diversion tunnel group and ventilation requirements changing with construction advance.Moreover,in order to obtain rational grid generation scheme and time step value,Grid Convergence Index(GCI)and Variate Percentage Change(VPC)are used to analyze the independence of grid and time step.Finally,the reliability of mathematic model is verified by field measured data to provide theoretical basis for getting optimal values of ventilation simulation parameters.4.Considering the problems that current tunnel construction simulation researches mostly ignore the dynamic evolution characteristics of construction parameters,the current parameter updating methods have low updating frequency,and the results cannot describe the change characteristics of the simulation parameter accurately.The dynamic updating method for simulation parameters of complex deep buried diversion tunnel group based on adaptive chaos differential evolution-support vector machine is proposed.In the current researches of tunnel construction simulation,most of them ignore the dynamic evolution characteristics of construction parameters,the existing few simulation parameter updating studies are limited to use the Bayesian updating method which assuming that the simulation parameter values obey the normal distribution,this leads to the inconsistency between the hypothesis distribution and the real distribution,the low frequency of parameter updating and the difficulty in accurately describing the nonlinear variation of simulation parameters.Aiming at the above problems,the dynamic updating method for simulation parameters of complex deep water diversion tunnel group based on adaptive chaos differential evolution-support vector machine is proposed.Firstly,adaptive scaling factor and Chaos theory are adopted to improve the Differential Evolution algorithm,and the Adaptive Chaos Differential Evolution algorithm(ACDE)is proposed;Secondly,based on the original time series of site construction parameters,the parameter optimization of support vector machine(SVM)is optimized by ACDE,and the construction simulation parameter prediction model based on adaptive chaotic differential evolution algorithm support vector machine(ACDE-SVM)is constructed;Then the error index is used to evaluate the performance of the model,and compared with the simulation results using the conventional simulation method and the Bayesian updating method,the superiority and applicability of the dynamic updating method of simulation parameters based on ACDE-SVM is verified.5.Based on practical engineering,the construction simulation optimization application of complex deep buried diversion tunnel group is realized by using the theory and method of the construction simulation optimization of complex deep buried diversion tunnel group which comprehensively considering the optimization of ventilation parameters and the dynamic updating of simulation parameters,and the feasibility of the theory and method mentioned above is verified.Taking a complex deep buried diversion tunnel group engineering as the research case,the theories and methods mentioned above are applied to practical project.Firstly,based on the ventilation requirements of complex deep buried diversion tunnel group in different construction periods,different ventilation schemes are formulated;Secondly,based on the fractal analysis of the three-dimensional fractured network,the equivalent thermal conductivity of the surrounding rock is obtained.The simulation methods of ventilation two-phase flow of complex deep buried diversion tunnel group under the consideration of surrounding rock heat transfer is used to simulate the cooling process of ventilation in different ventilation schemes,and then the turbulence structure characteristics of the wind field are analyzed,and the heat transfer of surrounding rock in tunnel,the heat exchange law between surrounding rock and airflow and the regulation of migration and change of pollutants are discussed,Finally,it reveals the internal relationship between ventilation time and excavation length under different construction ventilation schemes,and optimizes the values of simulation ventilation parameters;Thirdly,based on the original time series of site construction parameters,the construction simulation parameters prediction model based on ACDE-SVM is adopted,and the dynamic prediction analysis of the construction simulation parameters of complex deep buried diversion tunnel group is carried out;Lastly,based on the optimized simulation ventilation parameters and the construction simulation parameters prediction time series,the construction simulation optimization model is adopted to realize the construction simulation optimization of complex deep buried diversion tunnel group,and provide theoretical guidance and technical support for the arrangement of construction schedule and the control of site construction period.