Abstract:

It is difficult to solve the problem of water inrush and mud gushing during shield tunneling in waterrich and softweak strata when adopting cement for soil consolidation. As a result, the shield receiving engineering of QinhuaiBinnan 220 kV shield tunnel is taken for example, the liquid nitrogen vertical partial freezing technology is used to carry out secondary consolidation of the shield end soil which has been consolidated by chemical method. And then the necessary conditions that field measurement should meet are proposed during shield receiving; and the temperature development laws are analyzed after field measurement. The results show that: (1) Under the influence of hydration heat, the average speed of development of frozen wall is 81.9 mm/d which is 55%-68% that of liquid nitrogen freezing rate and 3.2 times that of saltwater freezing rate. (2) The average temperature of the frozen wall which is frozen by liquid nitrogen is 3 times that of frozen by saltwater. (3) The freezing period of liquid nitrogen is 1/3-1/2 that of saltwater. (4) During the period of maintain freezing, 1/3 liquid nitrogen consumption of the active frozen period can maintain the frozen wall′s temperature. It is concluded that the water inrush can be sealed by using liquid nitrogen quickfreezing to consolidate secondly, so as to insure the construction period and avoid accidents.

Key words: shield receiving, soil consolidation, liquid nitrogen vertical freezing, temperature measurement, hydration heat