Research On The Stress Of The Special Segment During The Construction Of Connected Aisle Using Artificial Freezing Method

Artificial freezing method has been widely used in the construction of connected aisle which between uplink and downlink in the metro. Especially in weak strata, this method can improve the intensity of surrounding rock excavated area and waterproof properties, make its own support ability strong, and increased the safety of the construction. The stress of special segment is complex during the artificial freezing process. Big distinction is existed in the forces of special segment with different forms. This paper relies on a tunnel connected aisle engineering of Suzhou rail transit line 1.Some research is carried out through theoretical analysis, numerical simulation methods. The main contents, methods and the conclusions are as follows:(1)This paper expounds the relevant mechanism of freezing method, analyzes some key issues such as the moisture transfer, phase change and frost heave in freezing process.(2)Using transient analysis to simulate the positive freezing process, through the definition of enthalpy simulates the water phase transition phenomenon. Through the analysis and calculation results, we can see the process that from the freeze began to freeze into circle and frozen curtain wall is formed well at last. It forms the general process of each period of surrounding soils and shows the temperature change and distribution. At last, roughly estimates the thickness of tundra curtain after a completion of the positive frozen.(3)Compare the three different forms of the special segment under the action of frost heave force and analyze their mechanical characteristics, evaluate the safety. A numerical simulation was calculated on three different segments of the special form in the frost heave force using indirect thermal stress analysis method, using different methods and index to analyze and compares their mechanical characteristics. Finally assesses the influence on main tunnel with the frost heave.(4)In view of the special form of segments is new used in Suzhou metro linel, not too much experience can draw lessons from engineering applications, so optimizes the form using the numerical simulation method. Compares the various changes in the force before and after optimization through the optimization calculation results, and evaluates the influence of cost with these optimization methods. Finally puts forward reasonable suggestions on optimization.