Torque fluctuation and penetration analysis of shield tunnel in rock–soil mixed ground

Abstract

Tunnelling in rock–soil interface mixed ground has often been faced with cutterhead torque fluctuation, a reasonable penetration rates to reduce the torque fluctuation and improve tunnelling efficiency is of great significance. In this paper, the cutting torques model was established. Torque changes with the rotation angle of cutterhead has been studied when the cutterhead in rock–soil interface with different hard rock area ratios (Fc). The results show that the average torque of cutterhead increases with the increase of Fc. The torque fluctuation cannot be eliminated, and torque fluctuation reaches its maximum when the Fc is about 10%–20%, which most likely to cause blockage and damage for the cutterhead. Such compound stratum sections should be avoided as far as possible when designing of tunnel lines. In the case of the same average torque, the penetration does not decrease linearly with the increase of Fc because of torque fluctuation. The penetration decreases slightly when the Fc reaches 10%–20%, and decreases obviously when the Fc exceeded 30%. The reason is that the penetration needs to be reduced to decrease the torque as well as torque fluctuation; when Fc reaches 60%, the penetration reaches the lowest; when Fc exceeds 60%, the penetration increases slightly to improve the tunnelling efficiency because torque fluctuation is reduced.