The limit bearing formulae of a blasting-roof under various boundary conditions are derived based on the principle of virtual work. Second, the external and internal work of the blasting-roof under the plastic limit state are calculated. First, a mechanical analysis model for the plastic limit bearing is built. There are still some parameters that are difficult to determine in practice, including the blasting-roof thickness (final area in the kerf blasting), which directly influences the efficiency and safety of the kerf blasting, making approaches for its rational determination important.Ĭurrently, there is no systematic research available concerning blasting-roof thickness quantification therefore, we propose a method to determine this quantity. However, deep hole mining is extremely complex because of the blast instantaneity. Industrial experiments, theoretical analyses, monitoring, and numerical simulations promote the scientific rational and feasibility of deep hole mining.
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conducted directional focused-energy blasting tests and monitored the blasting process using a high-speed camera and analysed the crack development and stress evolution to verify the feasibility of the approach. applied the ‘small resistance blasting’, ‘hole bottom reversed blasting’, and ‘non electric blasting network’ techniques in a uranium mine and showed improvements to the blasting efficiency. optimized the blasting design based on the spatial distribution of rock factors, which significantly reduced the blasting fragmentation and costs. simulated the blasting process with different charge weights and coupling coefficients and chose an optimized charge structure through simulations. Monjezi & Dehghani established a neural network between the blasting parameters and vibration effect to reasonably select the blasting parameters. For instance, the cave height using the VCR method in the Anqing copper mine has reached 120 m (iv) the application of a visual remote-control scraper transforms the stope bottom structure from a funnel and trench to being flat, which significantly reduces the mining workload and bottom pillar losses.ĭue to its representation and progressiveness, deep hole mining has been a well-studied topic among mining scholars. The kerf full-hole lateral blasting and kerf sectional lateral blasting techniques were subsequently invented to improve the blasting efficiency and have since been frequently used in VCR mining (iii) with the development of mining equipment, the cave height in deep hole mines can often reach 30 m, with some even exceeding 100 m.
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The blasting charge structure evolved from a single-layer globular to a multiple-layer column, which significantly improved the blasting efficiency (ii) down-upside funnel blasting was widely used in early VCR mining approaches, which had a limited free surface and low blasting efficiency. The present status of the VCR method is summarized in four points: (i) ordinary emulsion explosives replace ammonium nitrate explosives to reduce blasting costs. After decades of development, the VCR method has become the epitome of efficient and safe mining. This approach, specifically the Vertical Crater Retreat (VCR) mining method, was introduced in China in the 1980s. In other countries, deep hole mining is widely used due to its high efficiency and safety. The unique environment in deep regions (high stress, high temperature, high water pressure, and strong disturbance) requires mining innovation, with safety and efficiency having been the main targets of mining enterprises. With the gradual depletion of mineral resources in shallow areas, multiple mines have now entered the stage of deep mining.
The plastic bearing calculation method can provide a new method to determine the blasting-roof thickness in deep hole mining.
Variations in the simulated indexes (stress and plastic zone volume) prove that the theoretical calculations are reliable. A numerical model of stope was constructed using the Surpac-Flac3D technique, while the blasting-roof stability was simulated under different thicknesses.
A Vertical Crater Retreat stope was taken as the object, and the safe blasting-roof thickness was determined to be 6 m using the derived formula (considering the safety coefficient). The limit bearing formulae of blasting-roofs under various boundary conditions were derived based on the principle of virtual work.
The external and internal work of the blasting-roof are equal under the plastic limit state through calculation. A mechanical analysis model for the plastic bearing was built for the typical boundary conditions of blasting-roofs. A plastic bearing calculation method for a blasting-roof is proposed to solve the problem of determining the blasting-roof thickness in deep hole mining.
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