The Formatting Characteristics Research Of Freezing Stress In The Frozen Wall Of Multi-Turn Tube

As the need of coal is increasing, a huge number of large and super coal mine are established, and most of the shaft have to cross deep topsoil. As a result, using freezing method to sink the shaft appeared, which made a series of engineering problems, such as the increasing of freezing depth and the thickness of frozen wall, and the number of turns by freezing pipes has also raised. The increasing freezing stress in frozen wall has caused a number of project accidents. For example, sidewall would be broken by the freezing stress, and the frozen wall would be deformed during excavation of shaft, ect.By the inquiries of many documents inside and outside the country, the laws of the development of freezing stress inside the frozen wall and on the sidewall are researched during the artificial multi-freezing-tube cycles,combined with the engineering conditions.Model testing, numerical simulating and field measurement are used to study the law of freezing stress inside the frozen wall and on the sidewall in this article. The biggest freezing stress is about 0.54Mpa, which located on the inner side of middle cycle, while the one by the outer flank is much smaller, just about 0.3Mpa,and the rising speed is quite low. The freezing stress on the sidewall would speed up quickly by the decreasing of temperature, and can reach the top at 0.35Mpa.By experiments we can draw the conclusion that freezing stress in the frozen wall is related not only with the temperature field, but also with the way of layout and the interval of freezing pipes, while the freezing stress on the sidewall is related with the temperature field, especially the heat of hydration of concrete. On the beginning of the hydration, the freezing temperature decreases rapidly, and then it increases slowly to a relatively stabilized number.The developing of freezing stress variation inside the frozen wall and the one on the sidewall would be obtained by the coupling simulation of temperature field and freezing stress field, integrating the monitoring of field measurement of freezing stress inside the frozen wall and on the sidewall. The stress in the frozen wall is found to be much bigger during the formation, such as field test values, which can be up to 5.8Mpa.So in the engineering the control of deep freezing pressure should be emphasized to ensure the safety of the works.Figure [57] table [14] reference [46]...