Study on bilateral freezing temperature field and surface frost heaving deformation of long connected aisle of underground railway

Based on the long connected aisle of a section of Fuzhou Metro Line 2,the development rules of ground freezing temperature field and surface frost heave are studied under the double-sided freezing mode.The measured analysis of the temperature field shows that the temperature field development of the stratum can be divided into three periods. The temperature of the soil in the early stage of the positive freezing decreases rapidly,and the development rate of the frozen wall in the excavation area and the non-excavation area is about 1.1; the soil is slowly cooled by the latent heat of phase change in the later positive freezing; the temperature of the soil during the maintainable freezing period tends to be stable,but the excavation area is disturbed by construction,and the temperature has a certain degree of recovery. Using ANSYS finite element software and considering the latent heat of phase change of soil,the finite element model is established. Compared with the measured values of temperature,the two methods are basically consistent. The surface frost heave monitoring research shows that the key area of surface frost heaving of the connected aisle is the middle part which surface uplift value and growth rate are both larger than the hole mouth,and the final uplift value is about 1.28 times of the hole. Fitting the development of surface frost heaving in this area and the frost heave distribution of the section,the fitting results are consistent with the measured values.