Abstract Stress conditions around deep underground mine openings can significantly influence rock fragmentation and stability, and thus the cuttability of the targeted rock. In this study, rock breakage experiments and associated regression analyses indicate nonlinear rock cuttabilities (decreasing followed by increasing) with increases in the differences between biaxial confining stresses and the values of uniaxial confining stresses. Rock breakages were found to be efficient and safe under low and no-stress conditions that require low indentation force and depth, cutting work and specific energy to completely split the rock wtih no rockburst risk. Stress concentration initially impeded rock breakage, although high uniaxial stress improved rock cuttability. Inducing high stress to fracture the rock and produce an excavation damage zone (EDZ) via stress release effectively transformed the stress condition into low confining stress or even the stress-free condition, improving rock cuttability significantly and preventing rockburst. Mining of rock in the EDZ around the pillar could be efficient, cost-effective and safe when using roadheaders, which showed high cutting efficiencies, low pick wear failures, high machine stabilities and no rockbursts. In addition, a binary linear regression model was proposed to determine the thickness variation of the EDZ correlated with the excavation span and a coupled index of rock properties and buried depth of opening. The results indicated that the thickness of the EDZ increases with increases in the buried depth of the opening, which can improve the applicability of non-explosive mechanized mining in deep mines.
Last. Shaofeng Wang(CSU: Central South University)H-Index: 22
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Uniaxial compressive properties of rocks are very important for designing and constructing engineering projects. Based on the available standards for determining these properties, high quality core specimens with proper geometry are needed. In many cases, the standard specimens, especially in clay-bearing, fractured, and weathered rocks, are always not able to be prepared. On the other hand, in some natural conditions, rocks with different size, shape, and cross-section are undergoing uniaxial c...
The exploitation of mineral resources is gradually shifting from shallow to deep targets. However, the corresponding basic theoretical research has not determined the differences in rock-mining engineering at different depths. In this paper, longitudinal wave velocity measurements, uniaxial compression tests, and dynamic impact tests were conducted on granite from various burial depths to reveal the static and dynamic mechanical properties of the rocks. The initial damage variables of the rock s...
Abstract In order to obtain influence laws of crack angles on energy characteristics of sandstones in complex stress environment, this study performed a cyclic loading and unloading test under stress gradients with a constant lower limit of stress on sandstone samples with cracks at different angles. By utilizing the integral method for area, total energy density, elastic energy density and dissipated energy density of the sandstone samples with cracks at different angles were derived. Moreover,...
#1Chendi Min(CSU: Central South University)H-Index: 3
#2Xibing Li(CSU: Central South University)H-Index: 44
Last. Ying Shi(CSU: Central South University)H-Index: 5
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Abstract Mixing time is one of the operational parameters that can affect the rheological and mechanical behaviors of cemented backfill. The objective of this study was to investigate the effect of mixing time on the cemented backfill process. The backfill mixture consisted of a solid waste phosphogypsum (PG), a hydraulic binder, and water. The fresh slurry of backfill was sampled at seven different mixing times (ranging from 5 to 240 min), and its physical properties including apparent viscosit...
Last. Xibing Li(CSU: Central South University)H-Index: 44
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Abstract Recent years have witnessed a clear trend to develop deeper and longer tunnels to meet the growing needs of mining. Micro-seismic events location is vital for predicting and avoiding the traditional mine disasters induced by high stress concentration, such as rock burst, roof caving, water inrush and slope landslide. Deep learning has become a research hotspot within the field of artificial intelligence in recent years, which has achieved significant progresses and applications in the a...
#2Xibing Li(CSU: Central South University)H-Index: 44
Last. Shanyong Wang(University of Newcastle)H-Index: 29
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Abstract This study aims to determine the influences of confining stresses and cutting parameters on hard rock fragmentation using a conical pick. Using a true triaxial testing apparatus, single/double pick forces and static/coupled static-dynamic pick forces were applied to granite rock specimens to break them confined by biaxial, uniaxial and no lateral stress conditions. The corresponding cuttabilities were estimated and compared by the peak pick force, insertion depth and disturbance duratio...
Abstract In order to study the effects of temperature and loading rate on the dynamic fracture behaviour of granite under a given preload, dynamic fracture tests of pure mode-I were carried out on cracked straight-through Brazilian disc (CSTBD) specimens with a dynamic and static coupling test device based on the split Hopkinson pressure bar (SHPB) system. The experiments were performed at different loading rates and specimens were heat-treated at different temperatures. The thermal damage of sp...
#1Xibing Li(CSU: Central South University)H-Index: 24
#2Chongjin Li(CSU: Central South University)H-Index: 2
Last. Ming Tao(CSU: Central South University)H-Index: 21
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Abstract A theoretical formulation was first established to evaluate the dynamic stress concentration factor (DSCF) around a circular opening under conditions of blasting stress wave incidence. A two-dimensional numerical model was then constructed by the particle flow code (PFC) in order to simulate the dynamic responses around an underground tunnel subjected to blasting load. In the simulation, a series of horizontal blasting stress waves were applied to an underground tunnel under various in ...
#1Kun Du(CSU: Central South University)H-Index: 16
#2Xuefeng Li(CSU: Central South University)H-Index: 1
Last. Shaofeng Wang(CSU: Central South University)H-Index: 22
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Abstract null null The surrounding rocks of underground engineering are usually subjected to the coupling of compressive and shear stresses. The variable angle shear tests (VASTs) and direct shear tests (DSTs) are two types of lab tests that can easily achieve different compression-shear stress states. The VASTs and DSTs on cubic rock specimens were conducted to analyze the shear strength parameters and acoustic emission (AE) characteristics during rock failure process. The test results show tha...
Last. Jianchun Li(SEU: Southeast University)H-Index: 23
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Abstract null null null Understanding of indentation rock damage and breakage under confining stress is necessary for underground engineering applications, as both loading rate and in-situ stress can affect the null failure behaviour null null and mechanism. A triaxial apparatus capable of both static lateral confinement and dynamic loading is utilised to experimentally investigate the influence of both loading rate and confinement on rock indentation failure. The force-displacement relationship...
#1Linqi Huang(CSU: Central South University)H-Index: 6
#2Jun Wang(CSU: Central South University)H-Index: 210
Last. Shaofeng Wang(CSU: Central South University)H-Index: 22
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Abstract null null Rocks are likely to undergo spalling failure under dynamic loading. The fracture development and rock failure behaviours were investigated during dynamic tensile loading. Tests were conducted with a split-Hopkinson pressure bar (SHPB) in four different impact loading conditions. Thin sections near failure surfaces were also made to evaluate the growth patterns of fractures observed by polarizing microscope. Scanning electron microscopy (SEM) was used to observe mineral grains ...
User’s choices of conical picks currently involve specifying their material and geometric parameters (functional requirements), incorporating the place and conditions of their work (operational requirements). The selection is usually made based on solely one criterion, which is the price. Thus, at the stage of both purchase and operation, the quality of picks, as well as their matching for a specific machine, are not assessed. The problem of defining whether the producer has fulfilled the user’s...
#2Shaojie Chen(SDUST: Shandong University of Science and Technology)H-Index: 1
Last. Zhonghui Li(CUMT: China University of Mining and Technology)H-Index: 15
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Abstract Rockburst is a complex coal and rock dynamic disaster, which poses a serious threat to safe and efficient mining activities. With the increase in the mining depth and strength, rockburst becomes more and more serious. Coal rock contains different types and sizes of structural surface, and its bucking failure is the result of crack propagation and coalescence. In this paper, based on the elastic-plastic mechanics and damage mechanics, we established the elastic-plastic-brittle mutation r...
Last. Kun Du(CSU: Central South University)H-Index: 2
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Abstract null null The rock indentation tests by a conical pick were conducted to investigate the rock cuttability correlated to confining stress conditions and rock strength. Based on the test results, the regression analyses, support vector machine (SVM) and generalized regression neural network (GRNN) were used to find the relationship among rock cuttability, uniaxial confining stress applied to rock, uniaxial compressive strength (UCS) and tensile strength of rock material. It was found that...
Last. Haojie Lian(TUT: Taiyuan University of Technology)H-Index: 13
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Abstract In this technical paper, large-scale true triaxial tests were conducted with sandstone specimens to investigate several factors that determine whether hydraulic fractures can propagate from the tips of axial prefabricated cracks (pre-cracks). Specifically, we investigated the influence of pre-crack inclination angles on hydraulic fracture initiation locations and how the critical pre-crack angle varies with different confining stresses, fluid viscosities, and leak-off effects. The exper...
#1Qiang Li(CSU: Central South University)H-Index: 3
#2Xibing Li(CSU: Central South University)H-Index: 44
Last. Tubing Yin(CSU: Central South University)H-Index: 14
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Abstract Hard rock breaking is a great challenge for deep drilling and mining engineering, and the microwave-assisted rock breaking technique offers a promising solution. However, the lack of knowledge of the effects of microwave irradiation on hard rocks limits the further development of this technology. Laboratory tests have been conducted to investigate the variations of fracture properties of granite subjected to microwave heating. The semi-circular bend (SCB) specimens were prepared, and mo...