Study On The Evolution Law Of Thawing Temperature Field On Frozen Wall Of Tunnel

Compared with other construction methods,artificial freezing construction technology has many advantages,such as good impermeability and zero pollution to the adjacent environment.It is widely used in tunnel construction in complex environment.Among them,the evolution law of thawing temperature field of frozen wall during freezing construction is always the focus of attention in actual construction.Taking the local horizontal freezing construction of Beijing Fuba subway tunnel as the engineering background,this paper studies the evolution law of tunnel natural thawing temperature field considering freezing wall temperature gradient by using the combination of theoretical analysis,model test and numerical simulation.The main research contents and conclusions are as follows:(1)Using the method of similar model test,the distribution law of thawing temperature field of tunnel frozen wall is studied.In the test,3 key layers are set,and 9 temperature measurement points are arranged in each layer for monitoring,so as to obtain the development of temperature field of frozen wall in natural thawing period.After thawing for 85 min,it is found that the thawing temperature fields of the three layers have the same distribution law,and the spacing of isotherms has been reduced to less than 0.2℃,the soil temperature is basically consistent with the ambient temperature(20℃),and there are small temperature fluctuations near the thawing area of the freezing pipe.(2)Using ABAQUS finite element software,the distribution law of thawing temperature field of tunnel frozen wall is numerically simulated.It is found that after actively freezing for 38 days,the thickness of frozen wall meets the actual construction requirements.After thawing for 50 days,the frozen wall disappeared completely and the formation temperature returned to the original ground temperature.(3)Considering the temperature gradient of frozen wall,the temperature gradient is transformed into the heat conduction equation by using Fourier law,and then the analytical solution of tunnel natural thawing temperature field is established.The analytical results of the thawing temperature field are compared with the model test and numerical simulation results.The analysis results show that with the increase of thawing time,the thawing temperature difference of the soil obtained by the three research methods gradually decreases,the isotherm distribution is gradually dense,and the maximum temperature difference along the vertical measuring points of the freezing pipe is about 1.5℃.The distribution law of the thawing temperature field calculated by the analytical solution is basically consistent with the model test and numerical simulation results,which verifies the reliability of the analytical solution of the thawing temperature field.Artificial freezing method is more and more widely used in tunnel engineering.The research results of this paper have a certain reference value for the design and construction of tunnel freezing method construction engineering.Figure[57]table[10]reference[79]...