Abstract Microwave-induced rock fracturing technology is considered as a promising method for rock fragmentation and mineral processing. However, owing to microwaves causing selective heating, different types of rocks show different heating effects. Some rocks are cracked and broken, some other rocks are molten, while some parts undergo no significant change. Based on microwave heating experiments on multiple types of rocks, three typical rocks with different heating effects were investigated. According to X-ray diffraction (XRD) patterns and microscope images, the primary mineral compositions of rocks and microstructures of minerals were determined. By employing an infrared thermal imager, the distribution of surface temperature of samples were measured. Afterwards, according to sensitivity to microwaves and thermal expansion of rock-forming minerals, the mechanism whereby different types of rocks show different heating effects was analysed. The heating capacity of rocks depends on sensitivity of minerals to microwaves while fracturing effect is determined by the thermal expansion of minerals. Chifeng basalt contains both minerals (pyroxene) sensitive to microwaves and minerals (olivine) with a high coefficient of thermal expansion, mainly manifesting itself as rock fracturing during microwave heating. As only minerals (pyroxene) sensitive to microwaves, while no minerals with high coefficients of thermal expansion were found in Anshan gabbro, the rock was mainly molten during microwave heating. Neither minerals sensitive to microwaves, nor minerals with a high coefficient of thermal expansion were contained in the Beishan granite, so these samples underwent no significant change before, or after, microwave irradiation. The uniaxial compressive strength underwent a quasi-linear reduction with duration of microwave irradiation and the strength of rocks containing minerals with high thermal expansion decreased more rapidly.
Last. Xiwei Zhang(NU: Northeastern University)H-Index: 14
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A new, high-efficiency technology for fracturing and breaking rocks is required. Due to various advantages including high efficiency, energy-saving, and having no secondary pollution, the technology of microwave-induced fracturing of hard rock has been considered as a potential method for rock fracturing and breaking. Aiming at the realisation of two engineering applications: microwave-assisted mechanical rock breaking and stress release from rock masses in deep underground engineering works to ...
Last. Xiwei Zhang(NU: Northeastern University)H-Index: 14
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Microwave energy can be used to assist mechanical rock breakage for civil and mining engineering operations. To assess the industrial applicability of this technology, microwave heating of basalt specimens in a multi-mode cavity (a microwave chamber) at different power levels was followed by conventional mechanical strength and fragmentation effect tests in the laboratory. X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray spectroscopy were used to determine the mineral c...
Abstract This study deals with low-power (3.2 kW) microwave irradiation of a range of rocks and provide an indication of the suitability of certain rock types for this treatment method for rock fragmentation and mineral comminution. The influence of microwave irradiation was assessed physically by measuring rock properties and observing cracking phenomena and chemically by analysing the mineralogical and chemical composition before and after microwave irradiation. The results show that the react...
During the railway tunnel excavation of the Beijing Underground Zhijingxian Project, which used a large-diameter slurry shield, excessive wear of the cutterhead and cutting tools was found. Cutterhead modifications as well as frequent maintenance on the cutterhead and cutting tools were necessary for sustained shield tunneling, and creating a reliable working space near the cutterhead remained critical to performing the maintenance operations. The tunnel crossing beneath densely populated areas ...
#1Guozhong Hu(CUMT: China University of Mining and Technology)H-Index: 11
#2Nan Yang(CUMT: China University of Mining and Technology)H-Index: 3
Last. Jialin Xu(CUMT: China University of Mining and Technology)H-Index: 16
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Abstract The gas drainage rate of low-permeability coal seam is generally less than satisfactory. This leads to the gas disaster of coal mine, and largely restricts the extraction of coalbed methane (CBM), and increases the emission of greenhouse gases in the mining area. Consequently, enhancing the gas drainage rate is an urgent challenge. To solve this problem, a new approach of using microwave irradiation (MWR) as a non-contact physical field excitation method to enhance gas drainage has been...
Abstract Mechanical comminution of rocks is an energy intensive process with energy efficiency around 1%. A possible way to enhance the efficiency is the prior application of high-power microwaves. Microwave irradiation of a heterogeneous material introduces inhomogeneous electromagnetic and thermal fields which result in stresses and potentially in damage. In order to assess the industrial applicability, various 3D numerical analyses with either constant microwave power or constant energy were ...
Last. Xiwei Zhang(NU: Northeastern University)H-Index: 14
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Abstract The sample will burst into fragment when the thermal stress induced by thermal expansion greater than the ultimate strength of the rock after microwave irradiation. Microwave-assisted rock fragmentation has been illustrated to be potentially beneficial for mineral processing, mining and geotechnical engineering. In order to have a comprehensive understanding on the influence of microwave on thermo-mechanical properties of rocks, it is necessary to investigate the interaction effect betw...
#1Jamal Rostami(PSU: Pennsylvania State University)H-Index: 17
#1Jamal Rostami(PSU: Pennsylvania State University)H-Index: 17
Abstract Performance prediction of TBMs is an essential part of project scheduling and cost estimation. This process involves a good understanding of the complexities in the site geology, machine specification, and site management. Various approaches have been used over the years to estimate TBM performance in a given ground condition, many of them were successful and within an acceptable range, while some missing the actual machine performance by a notable margin. Experience shows that the best...
Abstract This paper deals with experimental studies regarding the thermo-physical properties of granite, sandstone and basalt in the temperature range of 25–1000 °C. It is shown how phase transitions (e.g. α-β quartz phase transition) influence the texture and stability of these rock types. The results of these measurements and analyses are linked to microwave irradiation tests at 17.5 kW power. The measurements demonstrate the strong variation of effects depending on the parameter rock/mineralo...
Abstract Demand is growing for explosive-free rock breakage systems for civil and mining engineering, and space industry applications. This paper highlights the work being undertaken in the Geomechanics Laboratory of McGill University to make a real application of microwave-assisted mechanical rock breakage to full-face tunneling machines and drilling. Comprehensive laboratory tests investigated the effect of microwave radiation on temperature profiles and strength reduction in hard rocks (norit...
During the construction of nuclear waste storage facilities, deep drilling, and geothermal energy development, high-temperature rocks are inevitably subjected to thermal shock. The physical and mechanical behaviors of granite treated with different thermal shocks were analyzed by non-destructive (P-wave velocity test) and destructive tests (uniaxial compression test and Brazil splitting test). The results show that the P-wave velocity (VP), uniaxial compressive strength (UCS), elastic modulus (E...
Abstract Microwave assisted mechanical rock breaking is a hybrid rock breaking method that combines microwave heating and mechanical rock breaking technologies and is proven to have potential applications in mineral processing, mining, and geotechnical engineering. It is, thus, important to understand the effect of microwave-induced damage on rock fracture characteristics. In this study, granite specimens of the Cracked Straight Through Brazilian Disc (CSTBD) were used to carry out the mode I fr...
Due to the diversity of mineral particle features in rock, including sizes, shapes, arrangements, and structural connections, the color image of the rock sample surface at laboratory scale is quite complex. Thus, unacceptable misjudgement and information loss often occur when the traditional image processing algorithms are adopted. To improve the accuracy of fracture extraction, a method based on image processing algorithms is proposed in this paper to extract fractures from 3D point clouds. Fir...