A multifunctional testing device for rock fragmentation by combining cut with impact

Abstract

Mechanical rock fragmentation is widely used in the fields of mineral resources exploitation, geological prospecting, tunnel excavating, civil engineering construction and national defence building, etc. At home and abroad researches on loading ways of rock fragmentation were mainly concentrated on the single static pressure or impacting loading, and the optimum loadings as well. Recent studies on brittle fracture showed that stress impulse can effectively improve the propagation of the crack, and the combination of impact and static pressure can increase the effect of breakage. In order to further understand the feasibility and efficiency of the cutting-impact rock fragmentation technology, a multi-function testing device was developed and its major parameters were analyzed by the authors. Principally the method of fragmenting rock by cutting-impact is putting a cutter on the surface of rock, applied with horizontal cutting force, vertical static pressure and impact load, and then the rock is broken under the combined loading. The multi-function testing device was designed on the basis of the above mentioned principle of rock fragmentation. It includes three parts: the static loading mechanism, the impact mechanism and the cutting mechanism. To carry out impact with different energy, the hammer's mass were designed to eight classes: 16.0, 18.5, 21.0, 23.5, 26.0, 28.5, 31.0 and 33.5 kg. According to the whole structure of the test setting, the largest stroke was chosen to be 300 mm. The low frequency which is adjusted by buncher and f=30-50 min-1 were selected. The device can conduct single breaking rock tests including cutting under horizontally static load as well, fragmentation under impact load and indentation under static load, and combined cutting impact test under the dynamic and static load. Not only can it be applied for single cutter test, but also for multi-cutters or roller cutter test. Granite and concrete samples with different strength were tested on the testing machine by PDC (Polycrystalline Diamond Compact) flat cutters and carbide alloy cutters under different loadings. The results show that the testing parameters are adjustable and the data are reliable. The testing device is a suitable and easy to operate one, and has reasonable structure in laboratory for simulating rock drilling or breaking under the combination of dynamic and static load, and has much value in designing and manufacturing of tunnel machine and mechanized excavators. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.