Rock Breaking Mechanism of Raise Boring Rig Cutters

1. What are raise drilling rig tools?

In coal mine construction, the raise boring rig (raise boring machine, RBM) is a common equipment used for drilling, and the RBM cutters on it are rock-breaking roller cutters inserted with cemented carbides. When the drilling rig is running, the RBM roller cutters are subjected to alternating periodic fatigue loads such as rock impact and wear, and the working conditions are very harsh, which requires very high quality of the raise boring roller cutters. There are many factors that affect the service life of raising boring drilling tools. Now we discuss the rock breaking mechanism and processing technology of the roller cutters to improve the service life of them.

2. Understand the rock-breaking mechanism of the raise boring roller cutters

The raising drilling rig transmits the main drive, that is, the pushing and rotating motion, to the cutters on the reaming cutter head through the power tap, drill pipe, and reaming cutter head, and relies on the rotary mechanism and the pressure mechanism of the drilling rig, exerts pressure on the cutters, and give the cutters a rotational moment and an axial tension to break rocks. When the raise boring drilling rig tool is working, the carbide inserts of the RBM cutters are subjected to periodic normal pressure and shear force. The cemented carbide inserts are subjected to impact loads such as normal pressure and shear force of the rock, when in contact with the rock, and they are in a non-working state when the cutter turns an angle and breaks away from the rock. Therefore, the carbide inserts are subjected to alternating periodic fatigue loads such as repeated positive pressure resistance and shear resistance.

The rock shows brittle and subbrittle grinding and crushing, when crushing hard rock and extremely hard rock formation, due to the high compressive strength and strong cementation of the rock, and the carbide inserts are not easy to wedge into the rock formation. At this time, the damage mechanism of cemented carbide inserts to rock is mainly impact and crushing. Therefore, when breaking the rock, it is necessary to increase the contact stress of the carbide inserts on the rock, and increase the crushing and impact of the inserts on the rock. For this reason, when operating raise drilling rig tools, it is generally used to increase the lifting force, that is, to increase the contact stress on the rock, and to reduce the speed appropriately, that is, to reduce the shear resistance of the rock to the carbide inserts.

The rock breaking of the roller cutters is mainly based on scraping, squeezing and shearing rocks, when encountering medium-soft and medium-hard rock formations. From the above analysis, it can be seen that in order to improve the rock-breaking effect, perforation speed, and prolong the service life of the RBM cutters, it is necessary to fully grasp the physical and mechanical properties of the rock when drilling, so that the cutters can achieve the best rock-breaking effect. Therefore, when designing and using the drilling rig tools, these characteristics should be fully utilized. For rocks with high brittleness and hardness, when determining the movement mode and operation of the hob, the cutters should produce a stronger impact. For rocks with high plasticity and toughness, the cutters should have a stronger scraping effect, so as to improve the rock-breaking effect and perforation speed of the cutters, and effectively increase the service life of the RBM cutters.