A model test was performed to study the effects of the cutterhead aperture ratio on the main shield driv-ing parameters during shield tunnel construction. Rules of pressure variations induced by different aperture ratios of the shield cutterhead inside and outside of the earth chamber were analyzed based on the monitoring of pressure changes and the transfer and distribution of soil pressures at the panel of the earth chamber under different aperture ratios of the cutterhead. Pressure differences at the work face and earth chamber panel were discussed, correlation formulas were established based on viscous fluid mechanics and a brief analysis of the influential factors of the pres-sure difference inside and outside of the earth chamber is conducted;the influence of the cutterhead aperture ratio on the squeezing effect and torque of the cutterhead was discussed and two kinds of squeezing effect mechanisms were presented. The test results show that the squeezing effect induced only by the cutterhead thrust occupies about 70%of the total squeezing effect, and the squeezing effect induced by cutterhead rotation occupies about 30%of the total squeezing effect. The relationship of the aperture ratio, torque of the cutterhead and the squeezing effect was systematically analyzed.%文章通过模型试验,对盾构开挖过程中刀盘开口率对盾构各参数之间的影响进行了研究,试验监测了不同刀盘开口率条件下盾构土舱面板处压力的变化情况以及土压力的传递和分布状态,研究了盾构刀盘开口率引起的土舱内外压力变化规律,同时对开挖面和土舱面板之间的压差进行了讨论,基于试验研究内容,进一步利用粘性流体力学理论建立了相关公式,可以简要分析土舱内外压差的影响因素;讨论了刀盘开口率对刀盘挤土效应和刀盘扭矩的影响关系,提出了两种不同的挤土效应机制,试验结果显示仅靠刀盘推力引发的挤土效应约占全部挤土效应的70%,刀盘转动引发的挤土效应占30%左右,系统分析了刀盘开口率、刀盘扭矩以及挤土效应之间的内在关联.
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