Modelling erosion of a single rock block using a coupled CFD-DEM approach

Rock block removal is the prevalent physical mechanism for rock erosion and could affect the stability of dam foundations and spillways.Despite this,understanding of block removal is still inadequate because of the complex interactions among block characteristics,hydraulic forces,and erosive processes acting on the block.Herein,based on a previously conducted physical experiment of erosion of a single rock block,the removal processes of two different protruding blocks are represented by a coupled computational fluid dynamics-discrete element model(CFD-DEM)approach under varied flow conditions.Additionally,the blocks could be rotated with respect to the flow direction to consider the effect of the discontinuity orientation on the block removal process.Simulation results visualize the entire block removal process.The simulations reproduce the effects of the discontinuity orientation on the critical flow velocity inducing block incipient motion and the trajectory of the block motion observed in the physical experiments.The numerical results present a similar tendency of the critical velocities at different discontinuity orientations but have slightly lower values.The trajectory of the block in the simulations fits well with the experimental measurements.The relationship between the dimensionless critical shear stress and discontinuity orientation observed from the simulations shows that the effect of block protrusion becomes more dominant on the block incipient motion with the increase of relative protrusion height.To our knowledge,this present study is the first attempt to use the coupled finite volume method(FVM)-DEM approach for modelling the interaction behavior between the block and the flowing water so that the block removal process can be reproduced and analyzed.

A state‑of‑the‑art review on rock seepage mechanism of water inrush disaster in coal mines

Water inrush is one of the most dangerous disasters in coal mining.Due to the large-scale mining and complicated hydrogeological conditions,thousands of deaths and huge economic losses have been caused by water inrush disasters in China.There are two main factors determining the occurrence of water inrush:water source and water-conducting pathway.Research on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush,and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush mechanism.This paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects,i.e.,mechanisms of stress-seepage coupling,fow regime transformation and rock erosion.Through numerical methods and experimental analysis,the evolution law of stress and seepage felds in the process of water inrush is fully studied;the fuid movement characteristics under diferent fow regimes are clearly summarized;the law of particle initiation and migration in the process of water inrush is explored,and the efect of rock erosion on hydraulic and mechanical properties of the rock media is also studied.Finally,some limitations of current research are analyzed,and the suggestions for future research on water inrush are proposed in this review.

论川西南地区地震反射波特征与二叠、三叠系气藏中气水分布关系

根据川西南地区346条地震测线反射波特征,结合实钻资料对该区中下三叠统侵蚀面和二叠系阳新统顶界两个碳酸盐岩反射层的气水分布进行研究后,发现地震可疑+无反射井之和与可靠反射井相比,不仅孔缝发育率前二者之和是后者的1.3—1.6倍,而且高、中产井也较后者多,其中嘉陵江组甚至高达4.7倍。笔者认为这可能是地腹岩层孔缝发育程度在地震反射记录上的反映,从而为预测二叠、三叠系碳酸盐岩储层地腹孔缝发育,拓宽勘探领域,增加储产量提供了重要依据。

黔中隆起及周缘下组合主要不整合分布特征及其对盖层的影响

以沉积盆地沉积波动过程分析方法为理论指导,对黔中隆起及其周缘地区7个典型野外地质观测剖面震旦—石炭系沉积-剥蚀过程进行了系统分析和预测,对地层因不整合所造成的剥蚀厚度进行恢复,研究表明区内不同构造单元的沉积-剥蚀过程35Ma,20Ma的高频波动周期,定量恢复了下中奥陶统顶部、下中志留统顶部不整合剥蚀量分别为100m^540m和100m^390m。黔中隆起及周缘地区2个主要不整合呈现近西向-近北东方向和近南北向的剥蚀叠加,再现了关键时期沉降沉积区和隆起剥蚀区区域分布规律。综合分析认为不整合对盖层的影响是该区油气成藏的主要控制因素,预测盖层有利区域主要分布于黔中隆起西北部和滇黔北部坳陷。