为探明不同海水水位、地层损失作用下穿越软硬不均地层盾构隧道结构纵向变形与发展，依托厦门地铁2号线跨海区间隧道工程，采用相似模型试验，以堆载模拟上覆水位荷载、漏砂法模拟下卧地层损失，分析上覆荷载、下卧地层损失下隧道沉降和曲率半径分布规律。结果表明： 1）上覆海水水位荷载下，隧道纵向沉降呈“勺形”分布，沉降过渡区范围为20环，原型长度为30 m； 2）随上覆荷载增大，沉降过渡区差异沉降呈二次函数增大，曲率半径呈指数形式减小，当上覆海水水位荷载为7.50 kPa时，原型水压为60 kPa（历史最高水位6 m），曲率半径最小，对应原型曲率半径为156 450 m，远大于《规范》控制值（15 000 m）； 3）下卧地层损失下，隧道纵向沉降呈“高斯”分布，沉降槽范围为24环，原型长度为36 m； 4）随下卧地层损失增加，沉降槽差异沉降值呈三次函数关系增大，曲率半径呈三次函数关系减小，当地层损失率为4.57%时，原型沉降槽曲率半径达到《规范》规定控制值（15 000 m）。

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.