查看更多>>摘要：Rock mass dynamics disasters caused by excavations and mining occur frequently in deep mines.In order to establish a theoretical system and control technologies for such disasters,we first classify and define dynamic disasters,such as rock bursts,coal bursts,mine pressure bumps,and mine earthquakes.According to the occurrence mechanism of different types of dynamic disasters,we establish a compen-sation control theory based on excavation and mining effects.On the basis,we propose three key tech-nologies:high prestress compensation technology for the roadway,pressure relief technology using directional roof cutting,and the goaf filling technology using broken rock dilation.These three technolo-gies constitute the compensation control method for dynamic disasters in deep mines.Finally,this method was successfully applied in a deep coal mine with high stress,with monitored results suggesting its rationality.This work provides a new concept and control method for the prevention of rock dynamic disasters in deep mines.
查看更多>>摘要：The review covers the development and the state of the art in deep-sea mining rock mechanics,equip-ment and challenges.It begins by introducing the significance of deep-sea mining,the types and geo-graphical distribution of deep-sea resources.Section 2 reviews the mechanical properties and fracture mechanism of seabed and related continental rocks,which contributes to the advancement of relevant technologies and theories.Deep-sea mining systems developed by coastal countries are presented in Section 3.Seabed mineral collection systems are critically assessed in Section 4.Subsea mining vehicle is reviewed by walking mechanism and controlling system in Section 5.In Section 6,the development of subsea lifting system is detailed by dividing it into hydraulic and pneumatic lifting modes,and some technical problems in the lifting system are described.An in-depth description of surface support sys-tems is presented in Section 7,which includes the deep-sea mining ship,dynamic positioning system,heave compensation system,launch and retrieval system,mineral disposing system as well as the storage and transferring systems.Section 8 discusses the challenges in the deep-sea mining,in terms of natural occurrence conditions,international legal framework and cooperative mining,environmental protection and economic benefits,etc.Finally,a brief summary and some aspects of prospective research are pre-sented in Section 9.
查看更多>>摘要：Users of the digital image correlation method are faced with the problem of poor operability,low repeata-bility,and lack of standardized specifications for spraying speckles.To solve the problem,the research proposed a rock deformation measurement method that obviates the need to spray speckles.A local bin-ary model was established by using the local binary pattern(LBP)operator based on deep texture features on rock surfaces.The resulting LBP digital speckle pattern can substitute artificial speckle patterns and demonstrates high quality and strong applicability.Based on the LBP digital speckle pattern,the target tracking algorithm was employed to achieve non-contact measurement of the dynamic displacements of rocks.The feasibility and effectiveness of the algorithm in practical application were verified by con-ducting shear tests on granite and siltstone.Test results show that the deformation characteristics in the displacement nephograms are in line with the measured data pertaining to rock fracturing and conform to the basic characteristics of the shear failure of rocks.The deformation measurement method based on surface texture information can realize non-contact displacement measurement of rocks under condi-tions without speckles:this obviates the influence of the quality of sprayed speckles on the accuracy of the measurement of deformation.
查看更多>>摘要：To investigate the dynamic damage evolution characteristics of bank slopes with serrated structural planes,the shaking table model test and the numerical simulation were utilized.The main findings indi-cate that under continuous seismic loads,the deformation of the bank slope increased,particularly around the hydro-fluctuation belt,accompanying by the pore water pressure rising.The soil pressure increased and then decreased showed dynamic variation characteristics.As the undulation angle of the serrated structural planes increased(30°,45°,and 60°),the failure modes were climbing,climbing-gnawing,and gnawing respectively.The first-order natural frequency was used to calculate the damage degree(Dd)of the bank slope.During microseisms and small earthquakes,it was discovered that the evo-lution of Dd followed the"S"shape,which was fitted by a logic function.Additionally,the quadratic func-tion was used to fit the Dd during moderately strong earthquakes.Through the numerical simulation,the variation characteristics of safety factors(Sf)for slopes with serrated structural planes and slopes with straight structural planes were compared.Under continuous seismic loads,the Sf of slopes with straight structural planes reduce stalely,whereas the Sf for slopes with serrated structural planes was greater than the former and the reduction rate was increasing.
查看更多>>摘要：The significant difference between the mechanical properties of soft rock and hard rock results in the complexity of the failure mode of the anti-dip layered slope with soft and hard rock interbedding.In order to reveal the landslide mechanism,taking the north slope of Fushun West Open-pit Mine as an example,this paper analyzed the failure mechanism of different landslides with monitoring and field sur-veys,and simulated the evolution of landslides.The study indicated that when the green mudstone(hard rock)of the anti-dip slope contains siltized intercalations(soft rock),the existence of weak layers not only aggravates the toppling deformation of anti-dip layered slope with high dip,but also causes the shear failure of anti-dip layered slope with stable low dip.The shear failure including subsidence induced sliding and wedge failure mainly exists in the unloading zone of the slope.Its failure depth and failure time were far less than that of toppling failure.In terms of the development characteristics of deforma-tion,toppling deformation has the long-term and progressive characteristics,but shear failure deforma-tion has the abrupt and transient characteristics.This study has deepened the understanding of such slope landslide mechanism,and can provide reference for similar engineering.
查看更多>>摘要：To enhance gas drainage in the soft and hard interbedded(SHI)coal seam,it's necessary to unload the in-situ stress and improve its gas migration performance.In this research,a directional hydraulic flushing(DHF)technology was carried out.The stress-unloading and gas migration improvement mechanism was analyzed through numerical simulation,and systematic engineering tests were conducted to verify the gas drainage effect.The results show that the improvement of gas migration performance in the SHI coal seam is caused by a combined effect of seepage-improving and diffusion-improving.After DHF,stress-unloading and plastic failure could be achieved both in the soft coal(SC)sublayer and in the hard coal(HC)sublayer.However,the gas diffusion capacity improves significantly in the SC sublayer,while the gas seepage capacity improves notably in the HC sublayer.Meanwhile,the stress-unloading and gas migration improvement effect improves with the flushing radius and the thickness of the SC sublayer.Besides,after adopting the DHF technology,the gas drainage effect improved markedly.The borehole number dropped by 49％,the gas drainage ratio increased from 26.0％to 48.2％,and the average coal road-way excavation speed increased from 2.4 to 5.6 m/d.
查看更多>>摘要：An important index to evaluate the process efficiency of coal preparation is the mineral liberation degree of pulverized coal,which is greatly influenced by the particle size and shape distribution acquired by image segmentation.However,the agglomeration effect of fine powders and the edge effect of granular images caused by scanning electron microscopy greatly affect the precision of particle image segmenta-tion.In this study,we propose a novel image segmentation method derived from mask regional convo-lutional neural network based on deep learning for recognizing fine coal powders.Firstly,an atrous convolution is introduced into our network to learn the image feature of multi-sized powders,which can reduce the missing segmentation of small-sized agglomerated particles.Then,a new mask loss func-tion combing focal loss and dice coefficient is used to overcome the false segmentation caused by the edge effect.The final comparative experimental results show that our method achieves the best results of 94.43％and 91.44％on AP50 and AP75 respectively among the comparison algorithms.In addition,in order to provide an effective method for particle size analysis of coal particles,we study the particle size distribution of coal powders based on the proposed image segmentation method and obtain a good curve relationship between cumulative mass fraction and particle size.
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