| High ground temperature heat damage is a common geological problem in deep buried long tunnel engineering.The high ground temperature in the tunnel will lead to quality,progress,safety and other problems,therefore,it is necessary to study the temperature distribution characteristics in the tunnel area and predict the high temperature heat damage section.This can provide theoretical guidance and reference for the actual design and construction of tunnel engineering.In this paper,the temperature field and geothermal distribution characteristics of Lulang tunnel are studied.Through a large number of documents and data,we have a deep understanding of the regional geological background,and based on the field investigation data of Lulang tunnel,combined with landsat-8 remote sensing image,the surface temperature of tunnel area is retrieved,and the distribution characteristics of surface temperature are summarized.By analyzing the measured borehole temperature data in the tunnel site,fitting the borehole data and predicting the temperature,the distribution characteristics of tunnel ground temperature are obtained.ANSYS is used to analyze the two-dimensional geological model of Lulang tunnel,the temperature field of Lulang tunnel and the temperature change curve along the track are simulated,and then the high temperature damage section is identified.The main results are as follows:(1)The atmospheric correction method is used to process the thermal infrared remote sensing data to obtain the characteristics of land surface temperature distribution.The surface temperature of Lulang tunnel and its surrounding area is obviously different in different seasons.The retrieved surface temperature in winter is lower than that in summer,the specific performance is: in winter,the temperature of most parts of the remote sensing area is below 10℃,within the range of tunnel mileage,the surface temperature does not exceed 20℃;In summer,The regional temperature is concentrated in the range of 15 ～25℃.Within the tunnel mileage,the temperature does not exceed 30℃.In winter and summer,the surface temperature of the tunnel area conforms to the seasonal characteristics,and there is no abnormal high temperature area.(2)The borehole data of the tunnel study area reveal the temperature changes of different trends.From the scatter plot of borehole data,it can be divided into two kinds of curves: linear growth and nonlinear growth.In view of the two kinds of growth trend of borehole temperature data,this paper uses the geothermal gradient method as the coefficient of linear fitting method and least square method.The linear and nonlinear temperature data are fitted respectively,and the prediction formula of each borehole is obtained.Through calculation and comparison,the average linear fitting error is 5.95%,and the average nonlinear fitting error is 4.77%,in a certain depth range,it can be used for temperature prediction.(3)After the borehole data are digitized,the temperature field of the tunnel rail bottom depth is interpolated,and the temperature distribution characteristics of the tunnel elevation are obtained.Within the mileage range of Lulang tunnel,the mileage above 30℃accounts for 19.32% of the total length of the tunnel.The mileage section above 30 ℃ is located in the middle of the tunnel area,The closer to the two ends of the tunnel,the lower the temperature will be.The mileage between 20 ℃ and 30 ℃ accounts for 37.6%,and the mileage below 20 ℃ accounts for 43.4% of the total length of the tunnel.By using the finite element simulation software ANSYS,the specific temperature distribution characteristics of Lulang tunnel in the whole mileage section are calculated and simulated,and the temperature change curve along the tunnel track is obtained.The results of finite element numerical simulation show that,In Lulang tunnel line,there is a certain high ground temperature and heat damage.The highest temperature of rail bottom is 37.2℃.Identifing two mileages with slight heat damage.When the temperature of tunnel construction environment is higher than 28℃,it will have a negative impact on person,equipment and materials.It is necessary to take cooling measures and control the temperature to ensure the safety of engineering construction. |
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