Temperature Analysis Of Construction Space Of Tunnel Face And Numerical Simulation Research

With the gradual development of tunnel construction in the direction of growth and deep burial,the high temperature problem caused by surrounding rock,equipment,personnel and other factors during the construction process has become more and more serious.Safety work,etc.are closely related.Therefore,in order to deal with the problem of high temperature in the tunnel,it is necessary to understand the variation law of air temperature during tunnel construction,especially the temperature law of the near the tunnel construction face space.Based on theoretical analysis,this paper establishes a mathematical model of the temperature of air micelles in the tunnel,and combines the heat conditions in the study area to obtain a temperature calculation model for the tunnel space near the face of the tunnel construction.The change law is studied,and the results can provide a reference for the design and optimization of the ventilation scheme.The main research conclusions and results are as follows:(1)By analyzing the tunnel construction situation and related literature,considering the influence of gravity,buoyancy,swirl and other factors in the construction process,the renormalization model is used to simulate the tunnel construction ventilation,and the grid-independent analysis and method verification are carried out.When the number of grids reaches 983170,it meets the accuracy requirements.The simulation results of the example are compared with the field data in the literature,and the average relative error is 3.77%,and the temperature change law is consistent.It is considered that the numerical simulation method can be used for subsequent related content simulation research.(2)The mathematical model of air temperature per unit volume is established by studying the heat change process of air micelles.The calculation area and the heat calculation method in this area are determined.Combined with the established mathematical model of air temperature,the calculation model of space temperature near the tunnel face in steady state is obtained.According to the requirements of relevant specifications for tunnel construction,the air volume required for the simulated tunnel construction is calculated to be 34.46m~3/s,and the numerical simulation conditions are determined.(3)The space average air temperature of the tunnel face under different working conditions is studied.The space average air temperature of the near tunnel face meets the requirements of the code and the air supply volume is between 30 m3/s and 35 m3/s,which is consistent with the temperature calculation model established by theory.The increase of air supply leads to the decrease of the average air temperature in the space,but the decrease of temperature decreases gradually.The increase of surrounding rock temperature leads to the increase of average air temperature in space,but the increase of air temperature is basically the same under different air supply modes.The increase of ventilation distance will weaken the cooling effect of low-temperature efflux.When the ventilation distance exceeds 33.6 m and 46.5m respectively,the efflux will terminate and produce backflow.(4)By changing air supply volume,surrounding rock temperature and ventilation distance,the spatial temperature variation rule of the tunnel face under different air supply modes is studied.The following conclusions are drawn:1)in the vertical height,the average air temperature decreases first and then rises.In the case of side air supply,the decreasing rate is greater than the rising rate,while in the case of top air supply,the decreasing rate is less than the rising rate.2)On typical sections,the lateral air supply with different air supply volumes has the least influence on the height temperature of the duct axis,while the top air supply has the greatest influence on the height temperature of the duct axis.The influence degree of air temperature at different sections under different surrounding rock temperatures is in the same order:working breathing height below 2 m>working breathing height above 2m>air duct axis height.Under different ventilation distances,the influence of side air supply and top air supply on different sections is very different.3)In terms of temperature difference between head and foot,under different air supply volumes,the comfort of personnel with side air supply is better when working below 2 m,and the comfort of personnel with top air supply is better when working above 2 m;Under different temperature of surrounding rock,the comfort of personnel in top air supply mode is better.There are great differences in the comfort level of operation under different ventilation distances.(5)By comparing the calculated and simulated values of the space average air temperature at the face of the near tunnel construction,the average relative errors under different air supply modes are 5.16%and 3.06%,respectively.There are still some errors in the air temperature calculation model,which need to be modified.Therefore,by adding additional terms to the original calculation model and fitting nonlinear curve data,a more accurate calculation formula was obtained,with the average relative errors reduced to 2.56%and 2.17%,respectively.