工作面矿压显现规律数值模拟研究

根据平岗煤矿地下现场地质资料、顶板岩石力学参数测定、关键层理论分析,以及现场开采条件,应用RFPA2D数值模拟软件对平岗矿1207回采工作面顶板破断形态进行数值模拟,分析回采后工作面顶板下移规律、采空区煤柱应力分布规律,为井下安全回采提供理论依据。

Verification of Numerical Modeling in 2-D Wave Propagation in Rock

Compressional harmonic wave propagation from a cylindrical tunnel or borehole in an intact rock is the basis for investigation of the practical explosion waves in a fractured rock mass. The amplitudes of the radial stress wave obtained from the universal distinct element code (UDEC) were compared with the analytical solutions for two cases with different conditions. Good agreements between the UDEC results and the analytical solutions have been achieved. It indicates that UDEC can model 2-D dynamic problems at a high degree of accuracy.

THE ANALYSIS OF ROCKBURST IN COALMINE

This paper has put forward energy criteria and disturbance-response criteria for rockburst. The coal pillar rockburst or rockburst at roadway and working face have been analyzed. An equation is given to calculate the critical load when a rockburst occurs. The ratio E/A of the elastic modulus E and softening descending modulus A is believed to be an important parameter of rockburst. The concept of resistance zone is put forward and the critical depth of resistance zone can be used in the forecast and prevention of rockburst. The value of dupporting stress of roadway has much effect on the critical load.

Shear stress distribution and characteristics of deformation for shear band-elastic body system at pre-peak and post-peak

The distributed shear stress and the displacement across shear band, the evolution of plastic zones, and the load-carrying capacity of rock specimen were investigated in plane strain direct shear test according to Fast Lagrangian Analysis of Continua （FLAC）. And then the shear displacement distribution in normal direction of system composed of localized shear band and elastic rock was analyzed based on gradient-dependent plasticity. The adopted failure criterion was a composite of Mohr-Coulomb criterion, that is, the relation between tension cut-off and postpeak constitutive of rock was linear strain-softening. Numerical results show that shear stress field approximately undergoes three different stages. At first, shear stress is only concentrated in the middle of top and base of specimen. Next, shear stress in the middle of specimen tends to increase, owing to superposition of shear stresses. Interestingly, two peaks of shear stress appear far from the loading ends of specimen, and the peaks approach with the increase in timestep until elements at the center of specimen yield. Finally, relatively lower shear stress level is reached in large part of specimen except in the regions near the two ends. As flow stress decreases, the analytical shear displacement distribution in shear band based on gradient-dependent plasticity becomes steeps outside the band, it is linear and its slope tends to decrease. These theoretical results qualitatively agree with that of the present numerical predicted results. Main advantage of the analytical solution over the numerical results according to FLAC is that it is continuous, smooth and non-linear （except at elastic stage）.

Mechanical model of roof on stope and its analysis

Based on the engineering background of No.8402 stope face in Silaogou Coal Mine of Datong Mineral Bureau and the theory of plate presented by researchers before, considering surrounding rock structure in the stope and according to mechanical property of rock bodies with various kinds of joint planes, presented an assumption that the key roof was divided into a series of elastic plate group by joint planes, then set up mechanical model of elastic plate group with pin joint. After compared the deflection and the stress in the mechanical model by numerical modeling with data from field engineering, the rule of rock plates’ break in turn and the difference in rock plates’ stress during the roof’s first and periodic weighting along the stope face were found.

Stability assessment of the freeway over the gob of coalmine

The freeway passes over the gob area of the Zaibo coalmine or its neighbor- hood when it is built. It is a noticeable problem that the construction of freeway and the underground coal mining interact, especially the deformation and destruction of the gob area of the coalmine influence the long-term stability of the freeway. In the paper, based on the actual data of the exploration about the gob area of Zaibo coalmine and the built project of the freeway,the variety rule of the coal beds below the freeway was studied by using of FEM during the process of coal mining. The statuses of the stresses and strains,the varieties of the plastic area were simulated in the whole rock mass. The characters of stresses and deformation of the gob area of the coalmine were analyzed and evaluated after the freeway built. The long-term stability of the gob area was pre- dicted. The deformation of the gob area under the freeway has not been finished, and the relative measures must be taken.

Numerical simulation and analysis of underground pressure in the 101 fully-mechanized top coal caving face of the Tingnan Coalmine

The forms of roof break,roof fall,and effects of the region scope in a fully mechanizedtop-coal caving (FMTC) face of the 101 fully-mechanized top coal caving face ofthe Tingnan Coalmine were analyzed by UDEC and FLAC^(3D) software.The analysis resultconfirms the phenomenon of roof falling,roof-off-strata,roof breaking,first weighting,periodicweighting and stress concentration,redistributions of surrounding rock and so on.Itprovides the gist to analyze the law of roof movement,characteristic of confining pressure,and to determine the formative structure forms of the immediate roof and main roof duringthe caving process.These results and the underground pressure observation results are inagreement.

Measurement and numerical analysis of influence of key stratum breakage on mine pressure in top-coal caving face with super great mining height

To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.

Numerical simulation of high voltage electric pulse comminution of phosphate ore

Numerical simulation of the electrical field distribution helps in-depth understanding of the mechanisms behind the responses and the benefits of the high voltage pulse comminution. The COMSOL Multiphysics package was used to numerically simulate the effect of ore compositions in this study. Regarding phosphate ore particles shape and composition, the effects of mineral composition, particle size, particle shape and electrodes distance were investigated on the electrical field intensity and distribution. The results show that the induced electrical field is significantly dependent on the electrical properties of minerals,the feed particle size and the location of conductive minerals in ores. The angle of material contact surface with the discharge electrode is also an important factor in the intensity of electrical field. Moreover,it is found that the specific liberation effect at the disintegration of phosphate ore by electrical pulses is due to the locality of the electrical field at the interface of mineral components of the phosphate ore aggregates with different permittivities. However, the intensity of the electrical field increases with sharpening the contact angle. Besides, the electrical discharge in the samples is converted to the electrohydraulic discharge across the surrounding water by changing the distance between the discharge electrode and sample surface.