The cause of the ground surface deformation in front of shield tunneling machine was analyzed and a new method based on the earth pressure of working chamber direct feedback technology was proposed in order to reduce the ground surface deformation in shield tunneling with the conventional method that has great dependence on engineer's construction experience and shows slow response to geological condition change. Mathematical models of two different earth pressure balance (EPB) control modes were given and experiments were conducted on the $1. 8 m EPB test machine in the lab, so as to analyze the cause of disturbance of the earth pressure and verify the new ground surface deformation control method. The test results indicate that the cutting ratio greatly influences on the earth pressure in working chamber; unstable cutting ratio can result in disturbance of earth pressure in working chamber and goes against ground deformation control. By means of earth pressure direct feedback, the new method can precisely control the volume of discharged soil and discharge rate using self-tuning PID controller so that EPB condition can be kept in real time. As a result, the ground surface deformation in front of the shield machine can be controlled between-5mm and +3 mm, which meets the standard of shield tunneling.%为了解决传统地表变形控制方法对施工人员经验的依赖性与控制的滞后性造成施工事故频发的问题,在分析引起盾构前方地表变形原因的基础上,提出密封舱压力直接反馈地表变形控制技术.以土压平衡盾构为对象,建立2种密封舱压力调节模式的数学模型,并在Φ1.8 m土压平衡盾构综合试验台上开展多次实验,分析引起土压力波动的原因和检验新地表变形控制方法的有效性.实验结果表明,切深率变化会引起密封舱压力波动,不利于地表变形控制.采用密封舱压力直接反馈,通过自整定PID控制器控制螺旋输送机转速可以精确控制排土量和出土率,保证密封舱压力实时平衡,并能将盾构前方地表变形控制在-5～+3mm,满足隧道施工标准要求.
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