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Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the problems of low accuracy and abnormal error in numerical simulation method for stability analysis of large-scale rock mass engineering, a more than 100 million degree-of-freedom（DOF）numerical simulation technique was developed. Taking the surface rock movement engineering of open-pit and underground combined mining at Dahongshan iron mine as an example, this technique is elaborated in detail. Combining the simulated results with the fissure of ground surface range, a method of the fissure of ground surface range inversed by fuzzy surface subsidence value is proposed. Combined with the more than 100 million DOF numerical simulation technique, this method accurately estimates the development of the fissure of ground surface range. The absolute error of position is 1.59～4.71 m with a span error rate of 1.141%, verifing the reliability of the method and improving accuracy compared to the commonly numerical simulation method of millions DOF. At the same time, the fissure of ground surface range is estimated after 5 years. With the mining of underground 300～720 m level ore body five years later, although the waste rock filling of collapse pit can inhibit the deformation of surrounding rock, the surface movement and cracking range will still affect the open-pit, and it is estimated that the crack area will affect the range above 990 m steps at least in the open-pit. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Gold (1001-1277) is the property of Gold Magazine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to clarify the mechanism of driving out gas in the coal seam， the soft coal sample of the No.2 coal seam structure was collected in the Xinggong coalfield of western Henan， and the large-scale tests on CO2 injection was performed to drive out coal seam gas injection in laboratory. Results show that the CO2 injection of driving out the gas in the coal seam is a dynamic process， combined with the knowledge of domestic and foreign experts on the gas injection mechanism of coal seam gas displacement， the definition of replacement effect and displacement effect is given. Based on the change of CH4 concentration in the gas outlet， the gas injection process was divided into three stages to study the conversion process of CO2 promoting CH4 mechanism in coal seam. Before CO2 breaks through the cavity， it mainly shows the replacement effect. The replacement effect of CO2 injection is dominant. After CO2 breaks through the cavity， part of the injected CO2 is replaced with CH4， and part of it and CH4 flow out of the cavity， with a concurrent state of replacement and displacement effect. For the whole experimental process， the CO2 replacement effect is more obvious and plays a leading role. [ABSTRACT FROM AUTHOR]

Aiming at the problems of complex engineering geology, long service life and stability of large-span chamber (exposure area up to 2 000 m² or more) of Beishan cross-country ski resort rebuilt by Jilin Beishan Civil Air Defense Project, refinement investigation of rock mass structure was carried out. The indoor rock mechanics experiment and wave velocity test in borehole were conducted. Structural surfaces investigation based on photogrammetry method combined with the method based on in borehole radar and television was adopted to study the surface joints, fractured zones and spatial distribution of loosening zone of surrounding rock mass. The quality of surrounding rock was classified and zoned, the mechanical parameters were determined, and the stability of surrounding rock was studied. Through numerical simulation analysis and calculation of large-span tunnel, the tension stress zone of roof was delineated, the reinforcement scheme was proposed. This study has reference significance for similar tunnel expansion and reconstruction projects. [ABSTRACT FROM AUTHOR]

Acoustic emission(AE) monitoring technique has been widely applied in the area of geotechnical engineering. Automated arrival time picking of P-wave is the fundament and key in the further rock mechanical AE study. In order to get the more accurate arrival time of AE single, an improved Pphase-Picker P-wave arrival time picking algorithm was proposed and its principle was described in detail. Several automatic arrival time picking algorithm were compared in 1 000 typical AE wave, the result indicated that the improved algorithm can not only get a more accurate P-wave arrival time rapidly, but also can get an error estimation of P-wave arrival time. [ABSTRACT FROM AUTHOR]

Taking the Yuheng mine in Northern Shaanxi as an example，aeolian-sand incipience experiment and water-sand inrush experiment were expansion by high-velocity seepage and entire visual equipment of water-sand two-phase flow. The experiment results indicated that， the loss of fine particles is the precondition of water-sand inrush and creates expansive space for the coarse particle migration. The process of water-sand inrush is a physical process， when the aeolian-sand size between 0.3~0.6mm， the energy transmits mainly in the form of particles collision.But it is different for the aeolian-sand size between 0.15~0.3mm， because the friction and squeeze are in the dominant role， that will lose less energy compared with collision. So the variation mass of aeolian-sand inrush is inversely proportional to the particle size. The critical velocity of aeolian-sand inrush is becoming higher with the increasing of axial stress. When the aeolian-sand begins to move， the seepage state is linear laminar flow and the critical velocity is 0.03~0.4cm/s for the aeolian-sand size d<0.6mm.The mass of sand inrush is proportional to the hydraulic gradient in unit time. It can be deduced from this result that water pressure of aquifer is the key factor， which greatly decisive the disaster degree of water-sand inrush. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Social Science) / Dongbei Daxue Xuebao (Shehui Kexue Ban) is the property of Dongbei Daxue and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Uniaxial compression experiments were carried out for granite specimen with pre-existing cracks. Variation laws of rock strength and elastic modulus under different crack angles were obtained， and the crack propagation process was recorded. The calculation model for rock particle flow under different flaw inclinations was established and the micro-parameters of calculation model were calibrated based on the laboratory testing results. Crack information during the crack propagation process was extracted by FISH language and was also analyzed in detail. The results show that with the increase of crack inclination， both the crack initiation stress and initiation angle increase continuously. The crack propagation types change from wing-crack-dominated to secondary-crack-dominated. Through the analysis of crack aggregation coefficient， it is found that with the increase of crack angle， the curve of crack aggregation coefficient changes from smooth to tortuous， and the crack propagation path is under the transition from concentrated to decentralized. [ABSTRACT FROM AUTHOR]

The Xiadian gold mine has already experienced the deep mining， the stope by the caving method and filling method is affected by multiple disturbance stress. It is very important to determine the reasonable stope size and the stability of surrounding rock for the safety operation of the mine. The parameters of discontinuities around the experimental stope were obtained by using the advanced photogrammetry technique， and the stability of surrounding rock mass of the experimental stope was evaluated by multi-method. On the basis of this， the parameters of the stope are optimized by using the Mathews method and the span experience formula. Finally， through the numerical simulation， the rationality of the obtained experimental stope size is analyzed and verified. The successful application of the optimized stope size in the mine designed by Mathews method， verified the feasibility of the graphic method in the design of the stope size under complex stress. [ABSTRACT FROM AUTHOR]

Considering the characteristics of short diagenetic age and high intensity mining of Jurassic weak cemented sandstone in western China， the conventional triaxial compression tests， different unloading rates of confining pressure in triaxial compression tests and multi-stage triaxial tests were conducted to study the effects of confining pressure path on the strength and deformation. The results show that: the peak strength， residual strength， peak strain， elastic modulus and Poisson ratio depend on the confining pressure strongly， and the cohesion and internal friction angle of the sandstones in western China are lower than those of other sandstones. As the confining pressure increases， the failure mode transits from single plane fracture to complex multi-fracture. During the loading process， the change of confining pressure can remarkably affect the strength and the deformation characteristic by restricting lateral dilatation and increasing the angle of internal friction. The effect of unloading and loading confining pressure path on the mechanical parameters can provide references for the optimization of mining velocity and the support design of the surrounding rock masses. [ABSTRACT FROM AUTHOR]

A case of water inrush through fault induced by mining in Zhongguan iron mine was studied by the finite element simulation. The fault stress and damage zones were analyzed to study the mechanism of fault reactivation-induced water inrush. The simulation results illustrate that the excavating process is the cause of damage zones initiation， accumulation， extension and coalescence. The fault shear stress concentration moves from the top downward to roof gradually. The compression-shear damage zone in the fault changes to tension-shear damage zone and grows gradually. When the fault is fully exposed， the connected damage zone provides a channel for the groundwater outburst and finally causes the inrush incident. Therefore， the conductivity of the natural waterproof fault cannot be completely confirmed by horizontal cover hole before excavations. To be safe， more acclivitous cover holes should be drilled to probe the conductivity of the fault in the higher positions for the further confirmation. [ABSTRACT FROM AUTHOR]

Aiming at a landslide appeared during the creep deformation in the south slope of an open-pit mine， the surface morphology of the west boundary of the landslide was determined by using the on-site measurement and the INSAR technique when the east and south boundary shape were already known. Meanwhile， the underground sliding surface was determined by micro-seismic monitoring technique and the west boundary shape was determined according to the surface morphology and the underground sliding surface. Both the geological horizons in the main researching area and the bottom sliding surface of the landslide body were established by the 3D modeling technique. The west boundary shape provides a theoretical basis for the following determination of the landslide shape in the south slope. This collaborative monitoring programme can be a reference for mine slope monitoring under the similar condition. [ABSTRACT FROM AUTHOR]

In order to make clearly the process and features of gas emission by injecting N2， N2 displacement coal seam CH4 tests were performed by using coal bed gas injection displacement experiment device. The results show that N2 displacement coal bed CH4 is a time-dependent process with a gradual decay of drained CH4 concentration， and CH4 flow increases at first and then decreases. Gas injection pressure has significant impact on the displacement effect， the higher the injection pressure， the faster the drained CH4 concentration decay， the larger injection gas flow， the more significant the flow rate increases. During the same time， the higher gas injection displacement pressure is， the larger the drained CH4 volume. According to the theoretical analysis， the mechanisms of injecting N2 displacement coal bed CH4 include the gas displacement， the air carrying and the dilution and diffusion of gas flow. [ABSTRACT FROM AUTHOR]

IMS microseismic monitoring system was employed in Xiaojihan coal mine， a typical high-intensity mining mine in Western China. The spatial monitoring of the whole monitoring area was realized and more comprehensive information of surrounding rock failure was captured. The mine pressure behavior， strata movement， and the stress and deformation around the surrounding rock mass were analyzed based on microseismic monitoring. The results showed that the microseismic events evolved periodically with the continuous mining of 11203 working face， which is closely related to the mining pressure behavior in the working face， and the average periodic weighting length is 23m. The height of “three zones” and the influence range of mining disturbance in the working face could provide help for support design and disaster prevention. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the western mines，the deformation，movement and breakage of overlying strata induced by high intensity mining are the root causes of geological hazards (e.g.large area roof falling，water and sand inrush) and environment damage (e.g.water and soil loss). Incorporated with numerical simulation，in-site micro-seismic monitoring and theoretical analysis，the paper study on influence factors of overlying coal strata falling and mine pressure behaviours. Taking Xiaojihan Coal Mine as an example，the deformation，breakage，falling and “three zones” formation are well discussed，the ground pressure behaviours at different mining speed are also investigated in detail，and the influence rules of different mining height and excavation speed on failure of coal strata are finally clarified. Results of in-site micro seismic monitoring show that，different mining rates of working face causes different range and completion degree of ground stress adjustment. Through comprehensive analysis，the caving characteristics of overlying coal strata and the law of “three zones” origination and evolution are systematically revealed，which will provide scientific basis for establishing failure law and stability criterion of overlying strata in high intensity mining. [ABSTRACT FROM AUTHOR]

Water inrush through karst collapse pillar is one of the great disasters which threaten coal mine safety production.In this paper，a three field coupled non-linear flow model was built based on the essentially flow translation，from laminar flow in aquifer to turbulence flow in tunnel，in the process of collapse pillar water inrush. And then，the model that couples the Darcy laminar，Forchheimer flow and N-S turbulence flow was applied in the numerical simulation analysis of Luotuoshan Coal Mine “3·1” collapse pillar water inrush incident from coal seam floor. The results show that，with the increase of water inrush flow，the Forchheimer flow in karst collapse pillar is firstly controlled by viscous resistance，and then affected by both viscous resistance and inertial resistance，and finally controlled by inertial resistance. Therefore，collapse pillar water inrush is the dynamic process of flow transition gradual to mutation. It further indicates that Forchheimer equation applied to describe the high non-linear laminar flow can reflect the intermediate state of the flow translation from the laminar flow in aquifer to turbulence flow in tunnel，and also can reveal the essence of the three flow translation of the water inrush through karst collapse pillar. [ABSTRACT FROM AUTHOR]

Uniaxial cyclic loading/unloading experiments were conducted on dry and saturated sandstones from Xiaojihan coal mine in Shaanxi province to study the deformation and strength characteristics, acoustic emission (AE) and load/unload response ration (LURR) in the failure process of sandstones. The results show that water has a significant influence on the properties mentioned above. The compressive strength and plastic hysteresis loops number of water-saturated specimens are less than that of dry specimens, and the axial strain in the compaction stage of water-saturated specimens is 18. 9% larger than that of dry specimens, but the axial strain prior to peak strength of water-saturated specimens is 17. 4% less than that of dry specimens. The elastic moduli of dry and saturated specimens both tend to increase during the cyclic loading/unloading process. AE cumulative energy of dry and saturated specimens is 3. 87 × 10 -11 J and 2. 58 × 10 -11 J respectively,and the latter is reduced by 33. 3% . Furthermore,the LURR of dry and saturated specimens shows similar changing laws, but the characteristic peak time of saturated specimens appears earlier, which means the macroscopic crack generates earlier in saturated specimens. [ABSTRACT FROM AUTHOR]

The state of the art of nonlinear seepage theories，non-Darcy flow tests and nonlinear flow numerical models of water-inrush induced by nonlinear flow in fractured rock mass are summarized according to the available data. It is found that both three flow fields，i.e.，Darcy flow，the high-velocity non-Darcy flow and the turbulent flow，and three principal factors，i.e.，Darcy flow of the water resource，the high-velocity non-Darcy flow in water-inrush channel and the influence of mining disturbances，exist together in the process of mining induced water inrush. This paper holds that non-Darcy flow in water-inrush channel，the unity of three dynamic flow fields and the stress disturbance characteristics of the three principal factors are quite important to the flow in fractured rock mass. Based on the above views，the trends of water-inrush in fractured rock mass have been put forward. Considering the three principal factors of mining-induced water inrush，the laws of the seepage in fractured rocks under different confining pressures，hydraulic gradients and flow rates will be researched according to the experiment and the field investigation.The aim is to establish a coupled model of Darcy equation，Forchheimer equation and Navier-Stokes equation with the effect of mining stress. The corresponding model will be studied by numerical method，which is proposed on the basis of coupling integral equations of the weak form of the finite element and the finite volume technique. In the model，both the flow and the pressure boundaries of the Forchheimer flow zone are dynamic as time changes. In this way，the problems of the nonlinear seepage models in fractured rock mass can be solved effectively，and the complete flowing process of mining induced water-inrush can also be simulated reasonably. [ABSTRACT FROM AUTHOR]

There are eighty unprocessed mined-out areas in Hongling lead-zinc ore for years of mining.In order to evaluate the stability of the goafs， several kinds of indexes representing the engineering quality of rock mass in mines were acquired by the survey of engineering geology and the ore-bearing rock mechanics experiments. According to the acquired ore and rock mechanics index， the stability number and radius of hydraulic in testing goaf were calculated using the Mathews stability graph method.And stability and probability of the testing goaf were evaluated by rendering synthetic map including the isoprobability contours and the Mathews stability graph. The testing goaf was simulated with FLAC3D， and the results agreed well with the results by using the Mathews stability graph method. The parameters for unstable goaf were optimized， and some supporting measures for the unstable goaf were proposed. This method can be used to evaluate all goafs in Hongling ore and provide reference for the similar mines. [ABSTRACT FROM AUTHOR]

The transversely isotropic rock samples with different dip angles were studied under uniaxial compression using the bonded particle model (BPM) of PFC2D. The strength and failure patterns were explored and compared with the experimental results. The results showed that the mechanical properties are affected significantly when the ratio of joint contact bond strength (both shear and normal) to rock contact bond strength is below 15%. The failure pattern is similar to the experimental result when the ratio falls into the range of approxiamtely 2%~4%. The uniaxial compressive strength decreases firstly at a certain value with the increase of joint angles and increases subsequently with a U-shape. The results can provide a reference for jointed rock mass with PFC2D code. [ABSTRACT FROM AUTHOR]

The variations of plastic strain energy and plastic deformation of weak cemented sandstone in different particle sizes were analyzed in triaxial cyclic loading experiments. The sandstone was taken from a coal mine in Western China. The results show that the cyclic loading paths have a notable effect on the deformation properties and plastic strain energy. The plastic strain energy and its growth rate of sandstone decrease with the decrease of sandstone particle sizes，moreover，the plastic strain energy increases exponentially with the increase of loading. The plastic strain energy stored in each loading and unloading cycles changes in the form of “U” with the increase of number of cycles and stress，namely，at the initial stage，the void and cracks are consolidated，so the plastic strain energy is stored，and during the elastic stage，the deformation stemmed from lattice elastic compression can recover when the loading is released，so the plastic strain energy is less，and during the yield stage，the plastic strain energy stemmed from fracture slipping grows rapidly. Furthermore，during the cyclic loading，the axial residual deformation and lateral residual deformation increase exponentially with the increase of loading，and the lateral residual deformation grows faster than the axial residual deformation. The plastic strain energy is more reliable than the residual deformation in reflecting the change of state in the process of loading. [ABSTRACT FROM AUTHOR]

The mesozoic medium particle sandstone slices of northeastern and western coal mines were observed under microscope，and the mineral particles，cementing composition and crystallization degree were analyzed for the following triaxial cell loading and cyclic loading acoustic emission (AE) experiments. The variation laws of strength criterion，dissipated energy，Kaiser effect and load/unload response ratio (LURR) were discussed. The results show that the northeastern calcareous cemented sandstones show a higher strength than that of the western calcareous argillaceous cemented specimens by the Mohr-Coulomb criterion. At the equal stress level the northeastern sandstone elastic energy is higher and the dissipated energy is lower comparing with western sandstone. During the cyclic loading，the Kaiser effect usually occurs at the elastic stage within low stress level，and the northeastern specimens contains more Kaiser points than that of western specimens. As the stress increases，the LURR decreases sharply at low stress stage，then declines steadily，and reaches minimum at the peak strength，moreover the northeastern sandstone LURR is lower than that of the western specimens.The differences of the mechanics and energy dissipation can be ascribed to the diversity of cementing composition and crystallization lithogenesis degree. [ABSTRACT FROM AUTHOR]

On the basis of the acoustic emission under uniaxial compression on granite，the meso-mechanical properties and influence of damage on elastic modulus of intact rock were simulated using particle flow code.Results from numerical simulations using DEM code were presented，and compared with experimental results. The relationship between the accumulated number of AE events and uniaxial stress was also studied. Moreover，the variation of secant modulus was analyzed before the pre-peak strength stage. The study results indicate that shear crack initiated before tensile cracks with the increase of uniaxial loading stress. Four stages of AE events existed during the complete compression process and the accumulated number of AE events after peak strength was much larger than that of the number before peak strength. The larger the time-step in the numerical test was，the smaller of the variation of elastic modulus in pre-peak loading stage became. All the elastic moduli tended to fluctuantly stabilize to a certain value. The results can be utilized as a new approach in AE test. [ABSTRACT FROM AUTHOR]