Study On Soil Frost Heaving And Temperature Field Induced By Artificial Horizontal Freeze Cross Passage

For the cross passage using artificial freezing construction, the mechanical nature of frozen soil not only generates dramatic changes, but also frozen soil is accompanied by the formation of freezing and thawing, and the amount of freezing and thawing caused by artificial freezing method may damage underground pipeline and the instability of foundation, then tilt the adjacent buildings (structures), produce cracks, the main tunnels will also produce a series of adverse effects due to freezing. So the temperature field development of frozen soil curtain should be control well, and the strength and stability of frozen soil curtain must satisfy excavation requirements. It is very important to study on frost heaving and temperature field of cross passage by artificial horizontal freezing method.In this study, by the research of freezing and thawing,temperature field of frozen soil, we can draw valuable conclusions, which have certain guiding significance and establish theoretical foundation to further promote the application of freezing method to cross passage. Some valuable conclusions are drawn as follows:1. Numerical simulation for the cross passage construction using is carried out by using the code FLAC^3D. Based on appropriate parameters for models, some results are obtained:①In the construction process, we have numerical calculation to surface deformation which is produced by freezing and thawing, the results will be compared with the Project and the results are anastomotic, so conclusions can guide construction.②Determine the distribution of freezing temperature field, and study the two adjacent freezing pipes overlapping time and time which reaching the necessary thickness of frozen soil curtain, the results will be compared with the Project and the results are anastomotic, so conclusions can guide construction.③Study the impact of frost heaving to main tunnels by the construction of freezing, and frozen soil curtain suffered force. The construction of cross passage produces additional deformation in three directions to main tunnels, so measures must be adopted to control deformation.④Simulate the impact of surface deformation of cross passage by excavation, at the same time calculate the safety factor of frozen soil curtain to determine whether the design parameters can meet the requirements of excavation. The results shows that soil excavation has a little impact to surface deformation, we can ensure that under the condition of thickness and intensity of frozen soil curtain, the construction of cross passage is safe.2. Mechanism of freezing and thawing and analysis of influencing factor, a theoretical analysis of the freezing temperature field of the mathematical model to determine the temperature distribution rule. One pipe freezing zone temperature shows the distribution of logarithmic curve and cooling zone temperature shows the distribution of aligning; the temperature is basically smooth in the middle of two pipes freezing temperature field.3. Finally, influence of factors such as depth of cross passage, thickness of frozen soil ring, and soil excavation radius on the ground surface is studied. Some measures against soil freezing and thawing are summaried.