Ground surface deformation control based on chamber pressure direct feedback

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 Φ1.8 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 -5 mm and +3 mm, which meets the standard of shield tunneling.