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Zou Y.,Central South University | Zou Y.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | And 5 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

In order to reveal the mechanism of the occurrence of deep engineering catastrophe and the influence of various factors on excavation perturbing effect, the models with different original stress states and different excavation sections are established by using the distinct element numerical simulation software PFC. Through explicit calculation, the kinetic release curves of high-stress rock mass under various circumstances are gained, and the peak and final stable values of the obtained curves are regarded as energy indices, which are used for representing the disturbance intensity and the stability degree of the excavation system respectively. The analysis based on these indices shows that the excavation with a circular cross section will induce the minimum disturbance effect under a nearly hydrostatic pressure stress state. The stress redistribution characteristics of high original stress rock mass excavated by different sections are also studied. Through the inspection of stress redistribution course which is regarded as an unloading process, the influence mechanisms of the original rock mass stress state and the geometry of excavation section on the stress redistribution are revealed ultimately.


Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Yao J.-R.,Central South University | Gong F.-Q.,Central South University | Gong F.-Q.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2011

The energy storage characteristics of hard rock in metal mines under high stress was described from the deep mining environment. And the inevitable trend of continuous mining methods in the future with the increase of exploitation depth of metal mines was also analyzed. For hard rock in metal mines under high stress, the dynamic disturbance caused by continuous mining was conducted on it, which can be considered as a mechanical problem coupled static and dynamic loads. On this basis, three key dynamics problems were analyzed by using the theory of coupled loads as follows: the system disturbance and rock burst in deep metal mines exploitation, mine earthquake and drift instability caused by blasting in deep mines, energy release and orderly regulation in deep metal mines exploitation. Theoretical analysis and engineering practice proved that several dynamics problems in deep metal mines can be explained by using the theory of coupled static and dynamic loads, which will provide some engineering practice guidance for deep exploitation.


Gong F.,Central South University | Gong F.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Lu J.,Central South University
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2014

Mine water inrush is one of the greatest natural disasters in the mining production process. Quick and effective identification of mine water inrush source is an important guarantee of safe production in mining engineering. Seven kinds of water chemical composition having been selected as the sample variables in water bursting source recognition, and a forecast model of water inrush source is built by combining distance discriminant analysis with principal component analysis. This model is tested and applied in the different water layer of Xieyi Coal Mine in Huainan with thirty-three training samples and eleven predicting samples, and it is compared with the gray correlation discrimination model and Bayesian discrimination model. The results show that the model shows 95% of accuracy, and the predicting correct rate is up to 91%, which provides a new method for mine water inrush identification.


Hu Y.-X.,Central South University | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

A Bayes discriminant analysis method to identify the risky of complicated goaf in mines was presented. Nine factors influencing the stability of goaf risky, including uniaxial compressive strength of rock, elastic modulus of rock, rock quality designation (RQD), area ratio of pillar, ratio of width to height of pillar, depth of ore body, volume of goaf, dip of ore body and area of goaf, were selected as discriminant indexes in the stability analysis of goaf. The actual data of 40 goafs were used as training samples to establish a discriminant analysis model to identify the stability of goaf. The results show that this discriminant analysis model has high precision and misdiscriminant ratio is 0.025 in re-substitution process. The instability identification of a metal mine was distinguished by using this model and the identification result is identical with that of practical situation. © 2012 The Nonferrous Metals Society of China.


Gong F.-Q.,Central South University | Gong F.-Q.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | And 2 more authors.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

Dynamic triaxial compression tests of sandstone were conducted with a modified triaxial split Hopkinson pressure bar (SHPB) coupled static and dynamic loads. For the comparison, the quasi-static triaxial compression tests were also conducted with RMT-150C device. The influence of confining pressure on dynamic characteristics of sandstone and its failure model in impact tests were analyzed based on the experimental data. The results showed that the dynamic compression strength of sandstone increases with increase in strain rate when the confining pressure is a constant; when the strain rate is a constant, the dynamic compression strength and the elastic modulus of sandstone increases with increase in confining pressure; the critical incident energy for rock failure increases with increase in the confining pressure; there is a linear increasing relationship between the energy absorption per unit volume of rock and strain rate; under the triaxial dynamic impact, there are some compression-shear breaking surfaces inside rock and rock keeps stable when the strain rate is low, when the strain rate is high, rock failures and breaks into some cone-shaped blocks.


Wang S.-M.,Central South University | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Gong F.-Q.,Central South University | And 2 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2013

In order to understand the mechanical properties of concrete at different ages under dynamic loads systematically, the impact compression tests of 5 early aged concrete were conducted with a 75 mm diameter split Hopkinson pressure bar (SHPB). And static compression tests, for comparison, were also conducted with an INSTRON system. The experimental results show that, although the growth model of concrete strength and elastic modulus under static load are different, both of them increase with the growth of the age, while critical strain decreases with the growth of the age in general; under dynamic loads, the concrete compression strength, critical strain and unit volume absorbed energy increase with the growth of the age, all of them are sensitive to strain rate and the growth trend of concrete dynamic strength with strain rate can be presented with an index function. Under dynamic loads, the concrete is destroyed in a tensile failure mode. And a shear failure mode was presented for concrete under static loads.


Li X.,Central South University | Li X.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Tao M.,Central South University | Tao M.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines
Geomechanics and Engineering | Year: 2015

The governing equations of wave propagation in one dimension of elastic continuum materials are investigated by taking the influence of the initial stress into account. After a short review of the theory of elastic wave propagation in a rock mass with an initial stress, results indicate that the initial stress differentially influences P-wave and S-wave propagation. For example, when the initial stress is homogeneous, for the P-wave, the initial stress only affects the magnitude of the elastic coefficients, but for the S-wave, the initial stress not only influences the elastic coefficients but also changes the governing equation of wave propagation. In addition, the P-wave and S-wave velocities were measured for granite samples at a low initial stress state; the results indicate that the seismic velocities increase with the initial stress. The analysis of the previous data of seismic velocities and elastic coefficients in rocks under ultra-high hydrostatic initial stress are also investigated. © 2015 Techno-Press, Ltd.


Zhu J.-J.,Central South University | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Gong F.-Q.,Central South University | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Experiments on dynamic mechanical performance of granite are carried out under uniaxial cyclic impact loads by using a modified large diameter split Hopkinson pressure bar (SHPB). The dynamic characteristics of the granite specimens and the laws of the energy absorption are analyzed. The cumulative damage of the granite specimens is calculated by use of the dynamic statistics damage model based on the Weibull random distribution. The laws of the cumulative damage of the granite specimens are also analyzed through the stress-strain curves. The results show that, in the cyclic impact compressive tests, with the increase of repeated action times of impact loads, the deformation modulus of granite decreases, the yield strain increases and the yield stress shows a decreasing trend. The value of cumulative specific energy increases with the increase of impact times, which increases slowly before the failure of the specimen and increases rapidly at its failure. The model curves and the test curves have good consistency, which shows that this model can reasonably reflect the relationship of the stress-strain and stress-strain rate. The value of cumulative damage increases with the increase of impact times, and its increasing rate changes from slowly to rapidly. Before the failure of the specimen, the cumulative damage increases smoothly, and the main increment occurs in the last impact when the specimen is broken.


Yin T.-B.,Central South University | Yin T.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | And 6 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

The mechanical properties of sandstone specimens such as density, longitudinal wave velocity, peak dynamic strength are studied under dynamic compression loading after being heated at different temperatures (25°C~800°C). Dynamic fragmentation characteristics of sandstone specimens are analyzed from different aspects of failure mode, fragment distribution and high-speed photography. The testing device of SHPB is adopted to conduct the dynamic experiments of rock specimens experiencing high temperatures. Though the experimental results are discrete, the general law is obvious. The results show that, with the increasing temperature, the specimen density, the longitudinal wave velocity and the peak strength all gradually decrease, and the decreased magnitude of the longitudinal wave velocity increases when the temperature is over 200°C. And the temperature changes from 400°C to 600°C, the peak strength of rock has less decreased magnitude, and decreases sharply when the temperature is over 800°C. The dynamic failure characteristics of sandstone are mainly tensile failure after high temperature, with the increasing temperature, when rock fragmentation degrees increase, rock blocks become smaller. Through high-speed photography, dynamic failure process of rock is expressed. It is obtained that radial cracks are distributed around the specimens along the loading direction, the failure mode of rock is not representative at the initial loading, but the final failure mode of rock is obtained through the stress wave multiple reflection.


Gong F.-Q.,Central South University | Gong F.-Q.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | Li X.-B.,Central South University | Li X.-B.,Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines | And 2 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

Based on the distance discriminant analysis model of rockburst prediction, and combined the characteristics and the principle of Bayes discriminant analysis theory, a Bayes discriminant analysis method to predict rockburst in underground engineering is presented. Some main control factors of rockburst, such as the values of in-situ stresses, the compressive strength and tensile strength of rock, the elastic energy index of rock, are selected as the discriminant factors of the Bayes discriminant analysis model; and the resubstitution method is used to estimate the ratio of mistake-distinguish. The data of a series of underground rock projects at home and abroad are taken as the training and testing samples. Rockburst of three tunnels are used to verify this model. The results show that the Bayes discriminant analysis model of rockburst has excellent performance and high prediction accuracy.

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