Research On Calculation Model Of Artificial Frozen Wall In Saline Strata

Relied on Shanghai Changjiang River Tunnel Project, series experiments have been conducted on artificial frozen soil, aimed at ascertaining the impact of salt content on basic properties of artificial frozen soil in saline strata. Meanwhile, the calculation model of artificial-ground-frozen temperature field considering the influence of the salt content was also established, including the formula of major design parameters of artificial freezing wall.By series experiments, the distribution regularity of salt content, common physical and thermal properties of artificial frozen soil in riverbed strata of estuary area were summarized. The characters of influence of the salt content on the properties mentioned above also were classified. This research provides foundation to the following study on the calculation methods of artificial freezing wall in saline strata.The major impact of salt content on the calculation of artificial-ground-frozen temperature field is the ascertaining on boundary temperature. As salinity of strata grows, the freezing point of strata, scilicet the boundary temperature of temperature field becomes lower. Based on modification of some classical analytic solutions of the artificial-ground-frozen temperature field, such as the solutions for single-pipe freezing, single-row-pipe freezing and the double-row-pipe freezing, presented by the former USSR scholars Trupak and Bakholdin, modified solutions which fully describe the relationship between the frozen wall thickness and the soil freezing point were deduced. Numerical analysis Results show the law that frozen wall thickness decreases due to the depression of freezing point. Meanwhile, it is demonstrated that the soil freezing point could never be neglected in calculating the frozen wall thickness.In addition, considering the freezing point of soil, calculation methods of major parameter of artificial-frozen-wall design, such as temperature in characteristic planes, average temperature and thickness of freezing wall were presented. By analysis of actual records and calculation, modified methods presented in this dissertation were compared with those conventional ones. The results show that due to the press ion of freezing point, the calculated average temperature and thickness of freezing wall decreases; and the modified methods is better in guiding the practice.