Research On Radical Instability Of Freezing Pipe In Hard Rock

In the construction using freezing method, the safety and stability of freezing pipe has a key impact on the success of construction. In recent years, several freezing pipe radical instability accidents occurred when freezing method was applied in the shaft sinking projects under hard rock condition, resulting in a great impact on the progress and effectiveness. For this phenomenon, this thesis conducted a comprehensive and systematic research on the radical instability of freezing pipe in hard rock through a method combining theoretical analyses, numerical simulation and physical simulation.Firstly, promote the linear elastic mechanical model of multilayer cylinder, including freezing pipe, frozen slurry, unfrozen slurry and hard rock. Then get the theoretical solution of frost force in unfrozen slurry area, the results show how the frost force changes along with the frozen wall thickness and the the relationship between frost force and each factor.Secondly, based on the simulation of temperature field around a single freezing pipe, radical instability of freezing pipe and hard rock crack, conduct numerical simulation research on the freezing pipe radical instability by frost force under ideal condition and obtain the law of annular space frost force and freezing pipe radical instability, as well as the relationship between related factors. It is found that the main influence factors of frost force are, and the formation horizontal stress is the key influence factors of hard rock hoop stress. The annular space frost force increases along with the increasing of the elastic modulus of frozen slurry, the porosity of slurry and formation depth, and the hard rock hoop stress increases along with the decreasing of the formation horizontal stress.Thirdly, conduct the physical simulation test with self-designed experiment device, through freezing pipe buckling tests of different thickness and freezing tests under different conditions, get the law of annular space frost force and freezing pipe radical instability. Experimental results show that the radial instability phenomena of freezing pipe can be classified as pressuring, shrinking, frost heaving and destroy four stages, the results of the radial buckling critical load agree with the results of buckling test and numerical simulation and instability wave number quite accord with eigenvalue buckling calculation mode. In addition, the frost force in unfrozen slurry area under pressure is significantly greater than no pressure condition. When the annular space is eccentric, the frost force is slightly greater than the ideal situation, and the frost force of measuring points in the same monitoring exist certain disparity.Finally, based on the above research results, contrast the radical instability of freezing pipe and hard rock cracking in time, if hard rock cracking prior to radical instability, the freezing pipe is in a safe condition, if radical instability prior to hard rock cracking, the freezing pipe damage.