| Traffic pressure becomes larger and larger with accelerating in the process of urbanization.Development of underground space used for building subway to alleviate the traffic pressure has already becomes the inexorable trend.For condition of complex formation with rich water soft soil,existed engineering risk of leakage and sand boil,etc. While opened path nearby subway and shield tunneling in construction process of freezing engineering,so using liquid nitrogen freezing to rush emergency in the project is very necessary.But the method is seldom applied in underground engineering,so combined with specific engineering in this paper, analysis and study for restoration application of liquid nitrogen freezing on tunnel engineering.Firstly, analyzes technological process based on physical properties of liquid nitrogen and combined with thermodynamic theory by using finite element and finite difference method, setting up finite element equation of frozen soil wall temperature field and equation of coupled thermo-mechanical. Using software of ANSYS to numerical simulation, obtained that can be excavated after freezing between 10 and 20 days, then it is proved the validity and feasible of software by comparing between calculated results and data of temperature measurement.And simulation of coupled thermo-mechanical and tunnel excavation based on temperature field, according to the calculated results, explaining displacement and stress which from frozen and excavated were concentrated on tunnel segment, tunnel excavation has little influence of on frozen soil wall which posses sufficient intensity and integrity.Based on theoretical analysis and numerical simulation in this paper,showed that liquid nitrogen rapid freezing in the special freezing engineering for auxiliary and rush emergency is feasible and safety reliability,the results is of certain guiding significance to tunnel special restoration of engineering constructing. |
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