螺旋输送机的排土和保压作用的发挥对土压平衡盾构的施工安全与效率有重要影响，对其作用机制及影响其作用发挥的因素进行系统的理论分析，并参考工程实测数据，得出以下结论： 1）盾构施工中的土压平衡包括土仓内外与螺旋输送机内的压力平衡和进、出土量的平衡，其通过螺旋输送机排土量的控制来实现； 2）渣土进入螺旋输送机后，依靠自身重力及与螺杆、叶片和筒壁界面间的摩擦作用来抵抗土仓内的水土压力，保持出渣过程的稳定性； 3）渣土性质对螺旋输送机的排土和保压效果有较大影响，主要通过向刀盘前方和土仓内添加改良材料的方法对渣土状态进行调整； 4）从螺旋输送机结构分析，可通过减小螺距、采用间断式螺杆或双螺旋输送机3个方面进行改造，以增加保压效果。

The earth conveying and pressure maintaining of screw conveyors play an important role in the safe and efficient boring of EPB shields. The working principles and influencing factors of the earth conveying and pressure maintaining of screw conveyors are systematically analyzed. Conclusions drawn are as follows: 1) The earth pressure balance in the boring of EPB shields includes the pressure balance between inside chamber and outside chamber, the pressure balance inside the screw conveyor, and the earth input/output volume balance, which can be realized by controlling the volume of earth conveyed. 2) When the earth enters the screw conveyors, the water/soil pressure in the chamber is resisted by the gravity of the earth and the friction with the screw rod, lamina and the inner side of the conveyor, so as to keep stable earth conveying. 3) The earth behavior, which has great influence on the earth conveying and pressure maintaining of screw conveyors, can be improved by injecting ground conditioning agents into areas ahead of the cutter heads and into the chamber. 4) Regarding the structure of the screw conveyor, the pressure maintaining effect can be improved by means of reducing the pitch, adopting discontinuous screw and double screw conveyors. 