Abstract:

The study on factors influencing the shear strength of the interface of steel pipefrozen soil composite structure in freezesealing pipe roof method(FSPR) is of great significance. In this paper, based on the construction method applied to the Gongbei Tunnel project of Hong KongZhuhaiMacao Bridge, a test of different shear angles using variable angle shear test method is conducted from the aspects of temperature and roughness; the shear strength envelopes of the shear surface under 5 temperature conditions of -10 ℃,-10 ℃, -15 ℃, -20 ℃ and -25 ℃ and 3 roughness conditions of 0 mm, 0.3 mm and 0.5 mm are fitted. The test results show that: (1) The temperature affects the friction angle of the steel pipefrozen soil composite structure little. (2) The cohesive force increase linearly below -15 ℃ and peaking at -15 ℃, then reaches a minimum at -20 ℃, and the cohesive force is negatively correlated with temperature below -20 ℃. (3) The increase of the roughness of steel pipefrozen soil interface has a positive effect on the shear strength, however, the influence is not linear. Excessive roughness will cause internal structure damage of the frozen soil at the interface (such as ice particles, soil particle gap, etc.), resulting in the decrease of the shear strength. The results provide the proper range of temperature and roughness under the optimum shear strength.

Key words: Gongbei Tunnel of Hong KongZhuhaiMacao Bridge, freezesealing pipe roof method (FSPR), steel pipefrozen soil composite structure, variable angle shear test method, temperature, roughness