Shield is a kind of underground construction machinery used to excavate soil tunnel with efficiency

environmental protection

safety and high quality

and it is employed widely in city metro construction in China. The origin driving of shield is one of the key techniques in shield construction. Through analyzing normal and origin driving shields

the mechanical model of shield driving in the two driving modes is established with reference to fundamental principles of soil mechanics. The calculation formula for resistance moment of the shield is presented

and the composition and effects of resistance moment of normal driving mode of shield are analyzed. It is discovered that in the normal driving mode

the resistance moment from the cave wall is strong enough to countervail the reverse torque resulted from the shield chisels’ cutting rock

and during the origin driving

protective measures should be taken in between shield cushion and its crust to prevent torsion. The formula has been adopted in some earth pressure balance (EPB) shield tunneling construction project with good results achieved. Conclusions can be referenced for the design and application of EPB shield.