Abstract:

In order to study the advancing speed and force characteristics of shield cutterhead in upper soft and lower hard strata, a numerical computational model of shieldrock mass is established based on continuum discontinuum element method (CDEM). By introducing a series of algorithms to CDEM, such as simple FVM, virtual mass method and element erosion algorithm, the 3D simulation of tunneling process of shield cutterhead is realized. Five numerical models for cutterheadrock system with different granite ratios are established, and the cutting depth, advancing speed, average torque and average bending moment are analyzed in detail. The numerical simulation results show that: (1) With the increase of excavation time, the cutting depth increases linearly when boring in a particular composite stratum; but in the footage curve, there is an alternate cycle between smooth and fast rising sections. (2) When the granite ratio increases from 0 to 100%, the tensile failure element near tunnel face increases, while the shear failure element decreases; meanwhile, the advancing speed of the cutterhead shows a trend of exponential decay, and the advancing speed reduces by 88.7%. (3) When the granite ratio increases from 0 to 100%, the average torque increases gradually by 117.5%; the average bending moment firstly increases and then decreases, and the peak occurs when granite ratio is 50%.

Key words: shield, cutterhead, composite strata, advancing speed, force characteristics, CDEM, numerical simulation