What adjustments can be made to the thrust force of a TBM to improve penetration rate in fractured rock?

In fractured rock, increasing the thrust force alone may not always improve the penetration rate and can even be detrimental. The key is to optimize the thrust force in conjunction with other parameters, focusing on controlled and balanced adjustments. Initially, a slightly lower thrust force might be beneficial to prevent cutter overload and premature wear. Fractured rock is already weakened, so excessive force could lead to the cutters impacting the rock too aggressively, reducing their lifespan. However, the *distributionof the thrust force across the cutterhead becomes more important. Ensuring even pressure on all cutters prevents some from being overloaded while others are underutilized. This can be achieved through sophisticated control systems that monitor cutter loads and adjust hydraulic pressures accordingly. Cutterhead RPM (rotations per minute) also needs adjustment in conjunction with thrust force. Often, a higher RPM with a moderate thrust force proves more effective than a lower RPM with high thrust. This is because the higher RPM allows the cutters to 'search' for weaknesses in the fractured rock. Monitoring cutter wear is crucial when adjusting thrust force in fractured rock. Increased cutter wear indicates that the thrust force is not being applied effectively, or that other parameters need adjustment. It may also suggest the fractured rock contains unexpected hard inclusions. Furthermore, consider the support system behind the cutterhead. Fractured rock is prone to collapse, so immediate and effective ground support is vital. A delay in support can allow the fractured rock to further deteriorate, making excavation more difficult regardless of the thrust force applied. The 'thrust force' is the force applied by the TBM to push the cutterhead against the rock face. 'Penetration rate' is the distance the TBM advances into the rock per unit of time. 'Cutter wear' is the gradual loss of material from the disc cutters due to abrasion and impact.