Abstract:

In order to find out the longitudinal deformation and development of shield tunnel crossing softhard uneven strata under the action of different sea levels and ground losses, the distribution laws of tunnel settlement and curvature radius under overlying load and underlying ground loss of crossingsea tunnel project of Xiamen Metro Line 2 are analyzed by similar model test and by simulating the overlying sea level with surcharge and the underlying ground loss with sand leakage. The results show that: (1) Under the overlying sea level load, the longitudinal settlement of tunnel is distributed in the form of "spoon"; the range of settlement transition zone is 20 rings, corresponding to the prototype length of 30 m. (2) With the increase of overlying load, the differential settlement in settlement transition zone increases in quadratic function, and the curvature radius decreases in exponential form; when the sea level load is 7.50 kPa, the water pressure of prototype reaches 60 kPa (the highest water level in history is 6 m), the radius of curvature is the smallest and the radius curvature of prototype is 156 450 m, which is far greater than the control value of 15 000 m in a specification. (3) Under the underlying ground loss, the longitudinal settlement of tunnel is in the form of "gauss" distribution; the settlement groove range is 24 rings, corresponding to the prototype length of 36 m. (4) With the increase of the underlying ground loss, the difference settlement value of settlement groove increases in cubic function relation and the curvature radius decreases in cubic function relation; when the ground loss rate is 4.57%, the curvature radius of the prototype settlement groove reaches the control value of 15 000 m specified in a specification.

Key words: shield tunnel, model test, sea level, ground loss, differential settlement, curvature radius