Theoretical Investigations on the Influence of Artificially Altered Rock Mass Properties on Mechanical Excavation

Abstract

guaranteeing the access to mineral deposits and for extracting the valuable minerals from these deposits. Mechanical excavation tools like full-face tunnel boring machines and roadheaders use either discs or conical picks for applying the required forces into the rock mass. The efficiency of the processes is mainly governed by the mechanical properties of the rock type, especially strength and abrasivity. Roadheaders are limited by a uniaxial compressive strength of 150 MPa, TBMs by roughly 300 MPa. In particular, the development of underground mines furthermore requires a high flexibility of the used equipment which is mainly characterised by the turning radius of the machine. The rather simple relationship is the harder the rock, the bigger the machine, the lower the flexibility.In order to improve the performance of their machines, most machine manufacturers on the market have introduced new machine concepts recently. Many of which change the cutting principle and apply the so-called undercutting technology (e.g. Aker Wirth "Mobile Tunnel Miner", Atlas Copco "Mobile Miner", Joy Mining "Oscillating Disc Cutter", Caterpillar "Rock Straight system" and Sandvik "MX650" (Sifferlinger et al. 2017)).In addition to changing the machine concept, the goal of extended research activities all over the world during the last decade is focussed on overcoming the highlighted restrictions. The major focus is set on artificially altering the rock mass properties in order to ease the machines' life by reducing the UCS and rock mass rating. This can be done by introducing cracks and/or slots in the rock mass which help the subsequent cutting process with a conical tool. The technologies under consideration are high-power lasers Parker et al. 2003;Graves and Bailo 2005), microwaves (Toifl et al. 2017; Hartlieb and Grafe 2017), high-pressure water jets (Ciccu and Grosso 2010;Miller 2016) and activated tools (Keller and DrebenstedtAbstract This study presents a theoretical analysis of the influence of the rock mass rating on the cutting performance of roadheaders. Existing performance prediction models are assessed for their suitability for forecasting the influence of pre-damaging the rock mass with alternative methods like lasers or microwaves, prior to the mechanical excavation process. Finally, the RMCR model was chosen because it is the only reported model incorporating a range of rock mass properties into its calculations. The results show that even very tough rocks could be mechanically excavated if the occurrence, orientation and condition of joints are favourable for the cutting process. The calculated improvements in the cutting rate (m 3 /h) are up to 350% for the most favourable cases. In case of microwave irradiation of hard rocks with an UCS of 200 MPa, a reasonable improvement in the performance by 120% can be achieved with as little as an extra 0.7 kWh/m 3 (= 1% more energy) compared to cutting only.

Energy intensity study for soil transportation by inertial rotor

“…1(b)). Thus, the total energy consumption of digging is the sum of the energy consumption of cutting and the energy consumption of transporting the soil along the cut profile with its subsequent unloading onto the conveyor [3].…”

Rock hardness identification based on optimized PNN and multi-source data fusion

“…7 In recent years, many studies, which aimed to increase cutting performance and reduce cutting consumption by using the roadheaders more efficiently, have been conducted by different researchers. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Ramazan comakli et al deeply analyzed the influences of coal and rock properties on roadheader cutting load, and subjected different sandstones with uniaxial compressive strength to cutting tests under different levels of cutting parameters, and the change rule of roadheader cutting load under different coal rock properties is obtained. [8][9][10] K. Fukui et al suggested a method to estimate rock strength from the cutting force exerted by the roadheader, based on the results of laboratory experiments, which offers a basis for selection of cutting head with different geological conditions of coal or rock.…”

Recognition of cutting rock hardness by hydraulic cylinder pressure

“…5 In recent years, many studies, which aimed to increase cutting performance and reduce cutting consumption by using the roadheaders more efficiently, have been conducted by different researchers. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Ramazan Comakli et al deeply analyzed the influences of coal and rock properties on roadheader cutting load and subjected different sandstones with uniaxial compressive strength to cutting tests under different levels of cutting parameters, and the change rule of roadheader cutting load under different coal rock properties is obtained. [6][7][8][9] H. Ergin et al established the mathematical model of the cutting system of longitudinal roadheader, and they obtained the threedimensional force of the cutting head.…”

“…The cutting head parameters are optimized and the cutting efficiency of the roadheader is improved by analyzing dynamic characteristics of roadheader cutting system. 19 Yang et al 20,21 put forward the method of using the shearer motor working parameters or the shearer rocker arm horizontal vibration signal to reflect the hardness of coal and rock. To the best of our knowledge, this method is mainly used to distinguish coal and rock interface of the shearer, and seldom applied in cutting rock hardness identification of roadheader.…”