共查询到20条相似文献，搜索用时 31 毫秒
1.
A. Refahi J. Aghazadeh Mohandesi B. Rezai 《International Journal of Mineral Processing》2010,94(1-2):83-91
In the present study, Discrete Element Method (DEM) technique was applied to model the fracture behavior of a single spherical and cubic rock in a laboratory jaw crusher. The rocks studied were modeled as granular assemblies located between two jaws, and their fracture mechanism was studied. To verify the obtained results, the spherical and cubic specimens produced from Dokoohak Limestone and Dehbeed Granite were studied and the energy applied by the jaws was compared to those of the fracture energy estimated by the single particle breakage analysis. There is fairly good agreement between the energy acquired from the DEM model and the single particle fracture energy of the spherical rocks. It appears that DEM is a suitable method for predicting the crushing energy of the spherical rocks in the jaw crusher. The fracture behavior of the crushed rocks was examined and compared by the results obtained from the DEM model. The tensile mode of fracture occurring in the spherical rocks is well presented by the discrete element modeling. However, the DEM technique is not capable of modeling the delamination mode occurring in the cubic rocks. 相似文献
2.
岩石颗粒破碎是影响粒状材料剪切强度和变形的最主要因素, 岩石颗粒破碎并不是想象的那么难, 像花岗岩颗粒有时在很小的压应力作用下就可以破碎。岩石单颗粒破碎的物理试验结果常常很离散, 完成大量单颗粒破碎的物理试验费时费力不现实, 采用离散单元法(Discrete element method, DEM)PFC软件模拟单颗粒压缩破碎试验, 既能克服单颗粒破碎物理试验的缺陷, 又能解决单颗粒破碎物理试验工作量大的难题, 是研究单颗粒破碎的理想选择。基于DEM的软件PFC2D, 将粒径为0.075～0.1245mm的基本粒子捆绑成不同粒径的单颗粒, 模拟岩石单颗粒压缩破碎试验, 观察颗粒破碎演化过程, 统计单颗粒破碎强度。计算单颗粒压缩破碎后颗粒分布的分维, 验证单颗粒破碎强度的分形模型和单颗粒破碎强度的尺寸效应。文中引用玄武岩单颗粒破碎试验结果, 与单颗粒破碎的离散单元模拟结果进行比较, 验证单颗粒破碎强度的尺寸效应和修正的Weibull理论的离散单元模拟结果。 相似文献
3.
Yang Xiao Chandrakant SDesai Ali Daouadji Armin WStuedlein Hanlong Liu Hossam Abuel-Naga 《地学前缘(英文版)》2020,(2):363-374
Grain crushing is commonly encountered in deep foundation engineering,high rockfill dam engineering,railway engineering,mining engineering,coastal engineering,petroleum engineering,and other geoscience application.Grain crushing is affected by fundamental soil characteristics,such as their mineral strength,grain size and distribution,grain shape,density and specimen size,and also by external factors including stress magnitude and path,loading rate and duration,degree of saturation,temperature and geochemical environment.Crushable material becomes a series of different materials with the change in its grading during grain crushing,resulting in a decrease in strength and dilatancy and an increase in compressibility.Effects of grain crushing on strength,dilatancy,deformation and failure mechanisms have been extensively investigated through laboratory testing,discrete element method(DEM)modelling,Weibull statistics,and constitutive modelling within the framework of the extended crushing-dependent critical state theory or the energy-based theory.Eleven papers summarized in this review article for this special issue addressed the above issues in grain crushing through the advanced testing and modelling. 相似文献
4.
This study proposed a novel approach for generating crushable agglomerates with realistic particle shapes in discrete element modeling (DEM). The morphologies of sand particles were obtained by X-ray micro-computed tomography scanning and image processing. Based on the particle surface reconstructed by spherical harmonic analysis, the crushable agglomerates with realistic particle shapes can be generated in DEM simulations. The results of single particle crushing tests showed that particle shapes significantly influence the fracture patterns and crushing strengths of sand particles. Furthermore, two one-dimensional compression tests were conducted to investigate the particle shape effect on micro- and macro-mechanical behaviors of crushable sands. 相似文献
5.
This paper presents a combined method to model grain crushing effects with discrete element method.This method combines the two most commonly used concepts to model grain crushing in DEM,i.e.the replacement method and the agglomerate method,so that it is both accurate and efficient.The method can be easily implemented.The performance is shown by several DEM simulations of biaxial tests.Particles with different crush-abilities are modeled.DEM simulation results with and without grain crushing are compared and discussed.The change of grain size distribution due to grain crushing is also investigated. 相似文献
6.
7.
围绕堆石料单粒强度尺寸效应的颗粒流模拟方法展开研究。首先,基于FISH二次开发建立了堆石料的随机不规则单粒模型,充分考虑堆石料的形状特征和破碎现象;然后,建立了堆石料单粒强度尺寸效应的等效模拟方法,以单粒强度随其粒径的变化规律为基础,推导了堆石料模型中细观黏结强度与堆石料等效粒径的负指数经验公式;其次,基于建立的数值模型对堆石料的室内单粒压缩试验进行仿真模拟,验证数值模型的正确性和合理性,并对较大粒径堆石料的单粒强度进行模拟预测,突出数值试验的优势;最后,基于建立的数值模型对相同粒径不同形状特征堆石料的单粒强度分布特征进行模拟研究。研究结果表明：（1）堆石料内部缺陷含量和尺寸随粒径增加对其单粒强度所产生的尺寸效应,可通过堆石料模型中细观强度参数随粒径折减进行等效模拟;（2）形状特征对堆石料的破裂机制具有重要影响,方形颗粒为压剪破裂,单粒强度较高,而随机不规则颗粒和圆形颗粒为拉剪或劈裂,单粒强度相对较低;（3）拉剪或劈裂条件下,堆石料形状越不规则,其单粒强度的离散程度越高,反之则离散程度越低。相关研究成果可为进一步研究荷载作用下堆石体内各粒径段堆石料的破碎量奠定基础,从而更加真实地反映堆石体的级配演化规律。 相似文献
8.
岩石破碎过程涉及到多个变量（应力、应变和孔隙率等）变化和裂纹的产生、拓展和聚集,是研究岩石破碎机制的重要途径。为了克服现有研究中岩石颗粒模型未考虑岩石内部特征问题,针对岩石内部颗粒非均匀分布、聚集的特点,开展了岩石轴压破碎试验和岩石岩相分析试验,并在此基础上,构建符合真实岩石内部特征的多尺度内聚颗粒模型。根据离散元的颗粒黏结模型（BPM）理论,求解了多尺度内聚颗粒模型不同粒级颗粒间黏结键的力学关系,发现与二级颗粒形成的黏结键断裂判据为 ≥ 2 GPa,三级颗粒之间形成的黏结键断裂判据为 ≥ 6 GPa,并基于该判据建立了用于模拟颗粒模型破碎的演化模型。通过模拟轴压破碎试验,破碎演化模型可以从细观角度得到颗粒模型各颗粒间黏结键承受力的实时变化和岩石破碎过程中黏结键从外而内的断裂顺序;从宏观角度得到岩石内部裂纹呈V形从上表面两端延伸并相交于岩石中部。通过与岩石轴压破碎试验结果对比发现,模拟试验得到的岩石裂纹特征与岩石轴压破碎试验结果相似,验证模型的可靠性,实现了从细观和宏观角度分析岩石破碎过程。 相似文献
9.
Haiying Zhang Alexander Chudnovsky George Wong John W. Dudley 《Rock Mechanics and Rock Engineering》2013,46(3):499-514
Rocks and other geomaterials are heterogeneous materials, with a well-recognized hierarchy of defects from micro-heterogeneities on the grain level to a large-scale network of cracks and layering structures. Their nature create a challenge for determining macroscopic properties, particularly for properties that are scale dependent, complicating both the property measurement and its appropriate application in modeling. This paper discusses the concept of a “representative volume”, which is commonly used in modeling microheterogeneous but statistically homogeneous material by an effective homogeneous continuum. The foundation of this concept is presented, along with its limitations in dealing with properties like strength and fracture toughness that exhibit a scale effect. This limitation is illustrated with a study of brittle fracture of a concrete where it is considered a model for statistically homogeneous rock. The study includes determining a scaling rule for the scale effect in fracture toughness, and shows that the fracture of brittle materials like rocks and concrete appears in the form of highly tortuous, stochastic paths. This reflects a complex interaction between a crack and pre-existing as well as newly formed micro-defects controlled by chance, and results in a large scatter of all fracture-related parameters. This behavior suggests a synthesis of fracture mechanics with probability and statistics, and so a brief exposition of statistical fracture mechanics (SFM) that addresses the statistical aspects of fracture is also presented. SFM is a formalism that combines fracture mechanics methods with probability theory and serves as the basis for an adequate modeling of brittle fracture. 相似文献
10.
Certain rock properties that depend on intergranular fracture and frictional sliding appear to be independent of rock type. This relationship is true for the rock-on-rock frictional sliding coefficient. The generalization has been widely applied to geomechanical modelling of upper crustal strength. Porous sandstones can be relatively weak and poorly cohesive, hence susceptible to deformation involving grain fragmentation and pore collapse. The critical state theory is commonly applied to describe such behaviour. Previous work showed that the yield surface is substantially independent of rock type when mean stress and differential stress are normalized by the grain crushing pressure, implying that the critical state line is rock type-independent and equivalent to the frictional sliding criterion. We test these hypotheses using previously published data for a range of porous sandstones augmented by new experimental results on Hollington and Berea sandstones deformed to large strains to define the critical state line over a wide range of pressures for each rock type. Results confirm the rock type-independence of the critical state line and show that it is nearly equivalent to frictional sliding. These relationships point to a simple procedure for estimating approximately the mechanical properties of sandstones based only on petrographic characteristics. 相似文献
11.
Using field data from Agnico-Eagle’s Meliadine gold project located in Nunavut Territory in northern Canada, a coupled DFN–DEM approach was used to evaluate the rock mass mechanical properties at REV. Variability in the structural data gathered on site and the variability associated with the stochastic modeling process have an impact on discrete fracture model (DFN) properties. Through a sensitivity analysis, this paper assesses the influence of a variation in the DFN model input parameters’ values on the rock mass peak properties – uniaxial compressive strength, Young modulus and Poisson ratio. The results not only highlight the possibilities associated with DFN–DEM modeling in characterizing rock mass properties at the engineering scale, they also provide a systematic way to assess the critical structural parameters controlling the rock mass properties. 相似文献
12.
为研究裂隙岩体结构效应对其等效力学参数的影响,引入基于离散元的合成岩体技术,通过可控的改变三维岩体结构网络中的结构参数,制作相应的合成岩体试件,开展计算机模拟试验研究。结果表明：随岩体中裂隙体积密度增大,裂隙的变形参数和强度参数随裂隙密度增加而减少,其中等效弹性模量对结构面密度变化最为敏感;随岩体中裂隙倾角增加,岩体等效弹性模量随之单调增加,且等效弹性模量的离散程度（标准差）随倾角增加而减小,而各强度参数指标则先减少而后增加,形成一个U形变化规律;岩体等效力学参数均随结构面尺寸增加而减小,同时等效力学参数的离散程度（标准差）随结构面直径增加而增加,其中单轴抗压强度指标变化最为敏感;岩体等效力学参数对裂隙尺寸和产状的离散程度不敏感。该研究结论可为其他结构效应研究提供一种新思路。 相似文献
13.
岩爆破坏过程能量释放的数值模拟 总被引：1，自引：0，他引：1
岩爆是地下岩石开挖中的一种工程灾害现象,是岩体结构发生破坏时,由于内部储存的弹性能释放并转换为动能而造成动力形式的破坏。岩爆破坏过程中的能量释放与岩体在应力峰值前后的应力-应变特性紧密相关。另外,施工中开挖速度引起的加载速率的变化也会对岩爆的产生有明显影响。以岩体全过程应力-应变曲线试验为基础分析岩爆破坏过程。分析中采用的模型考虑了岩石峰值后应力-应变特性及加载速率的影响。运用数值方法对岩石洞室的开挖过程进行了模拟,在模拟中对岩体破坏的发生及弹性能释放过程进行了分析。数值分析结果显示,岩体洞室开挖过程中岩石破坏由岩体表面向岩体内部发展,岩石的弹性能释放率也随着破坏的发展而不断增加。分析结果还显示,岩体破坏时的弹性能释放速率会随着开挖速率的提高而明显增加。 相似文献
14.
Numerical Analysis of Block Caving-Induced Instability in Large Open Pit Slopes: A Finite Element/Discrete Element Approach 总被引：3，自引：2，他引：1
This paper addresses one of the most challenging problems in mining rock engineering—the interaction between block cave mining
and a large overlying open pit. The finite element modeling/discrete element modeling (FEM/DEM) approach was utilized in the
analysis of block caving-induced step-path failure development in a large open pit slope. The analysis indicated that there
is a threshold percentage of critical intact rock bridges along a step-path failure plane that may ensure the stability of
an open pit throughout caving operations. Transition from open pit to underground mining at Palabora mine presents an important
example of a pit wall instability triggered by caving. Using combined FEM/DEM-DFN (discrete fracture network) modeling, it
was possible to investigate the formation of a basal failure surface within an open pit slope as a direct result of cave mining.
The modeling of Palabora highlighted the importance of rock mass tensile strength and its influence on caving-induced slope
response. 相似文献
15.
The grains of lunar regolith are characterized with rough surfaces, angular shapes and mutual adhesions due to short-range interactions. These features control the macroscopic mechanical behavior of lunar regolith but have not been completely captured by contact models in previous Discrete Element Method (DEM) analyses. In this paper, a simplified two-dimensional microscopic contact model is proposed for high efficiency DEM analyses of lunar regolith. The model consists of three components in the normal, tangential and rolling directions respectively, plus two new parameters. A shape parameter is used to control the rolling resistance ability at the contact area between two particles to capture the features of grain shape and interlocking. The second parameter, micro-separation, which denotes the nominal minimum distance between the molecules of the two contacting particles, is introduced to account for van der Waals force as the major component of the short-range interactions that contribute to the adhesion of regolith grains in lunar environment conditions. The novel model has been implemented in a two-dimensional DEM code for numerical simulations of biaxial compression tests on lunar regolith. The effects of interparticle friction, grain shape, lunar environment conditions and void ratio on the strength of lunar regolith were numerically investigated. The results show that soils in the simulated lunar environment exhibit greater strength and more apparent strain-softening and shear dilatancy than on the Earth. The proposed model can capture the main features of the mechanical behavior of lunar regolith (apparent cohesion and high peak friction angle) and a wide range of strength indices can be obtained by the contact model. 相似文献
16.
用数值方法对岩质高边坡进行稳定性分析时,描述岩体结构对的精细程度会影响分析结果,但常见的有限单元法程序仍难以对复杂节理岩体进行精细建模。为解决这一问题,将结构面网络模拟与离散单元法相结合,在UDEC软件中,利用FISH语言编写网络模拟程序,依据结构面统计资料和结构面分级,实现对复杂岩体结构的精细描述。以某大型水电工程边坡为例,在对岩体结构进行精细描述的基础上,采用离散元强度折减法对边坡进行稳定性分析。通过与极限平衡法和一般离散元结果的对比,表明基于复杂岩体结构精细描述确定的边坡潜在滑动面和安全系数是合理的,为复杂岩质边坡破坏模式和稳定性的分析提供了新的途径。 相似文献
17.
Quantitative assessment of rock texture and correlation with drillability and strength properties 总被引：10，自引：1，他引：10
Summary A dimensionless quantitative measure of rock texture, describing grain: —shape, orientation, degree of grain interlocking and relative proportions of grains and matrix (packing density) has been developed. Data required for the model are obtained by image analysis of thin sections and concerns percentage areas of grains and matrix, length, breadth, perimeter, orientation and area of each grain in the viewing window. The results of rock strength, diamond and percussion drillability tests in eleven sandstones, marbles and igneous rocks are reported, and correlated with the developed texture coefficient. The texture coefficient returns highly statistically significant correlations with rock strength and drillability data. Sandstones have low texture coefficients and high drillability whereas igneous rocks have high texture coefficients and low drillability. With particular reference to percussive drillability it is suggested that extensional crack propagation in the sandstones in an energy efficient process since fracture paths propagate through the weak phyllosilicate matrix. Extensional crack propagation in the igneous rocks is an energy intensive process since a significant proportion of the available drilling energy is consumed in the formation of intra-granular fracture paths. Observational and correlated data are supportive of the suggestion that the texture coefficient is a measure of the resistance of the microstructure of a rock to crack propagation, whether it be inter-or intra-granular. The texture coefficient can be used as a predictive tool for the assessment of drillability and rock strength properties. The technique offers a useful approach in understanding fracture initiation and growth as controlled by the texture of intact rock samples. 相似文献
18.
珊瑚单颗粒破碎特性与珊瑚砂高压缩性、剪缩性及良好蠕变性等宏观力学行为密切相关。珊瑚颗粒的应变率效应对于不同形式荷载作用下珊瑚砂强度与变形特性研究具有重要意义。对约300颗珊瑚颗粒进行0.1～50 mm/min位移速率下的单颗粒破碎试验,探讨加载应变速率对颗粒破碎强度、破碎模式、破碎能量及破碎分形的影响。结果表明,珊瑚颗粒破碎强度服从Weibull分布规律,且特征破碎强度随应变率的提高非线性增大;随着加载速率的增大,颗粒主劈裂破坏往往先于棱角的局部碎裂和表面研磨,相应的荷载?位移曲线呈现出由峰前“多峰”向峰后“多峰”现象转变;珊瑚颗粒破碎能量密度和破碎分形维数同样具有明显的应变率效应,且均与对数应变率呈线性正相关关系,表征能量耗散和破碎程度均随加载应变率的增大而增大。 相似文献
19.
Morched Zeghal 《Geotechnical and Geological Engineering》2009,27(4):549-558
This paper presents the results of a study of grain crushing in road construction and its effect on road behaviour. Sieve
analyses of field samples confirmed that grain crushing occurs during compaction of the base layer despite the good quality
of aggregates used. Laboratory testing indicated that grain crushing reduces the resilient modulus of the aggregate material
by half and increases the permanent deformations by onefold to threefold depending on the state of density and stresses considered.
Road design and analyses undertaken to delineate the effect of grain crushing on performance showed that particle breakage
yields a significant increase in rutting and longitudinal and alligator cracking of roads. 相似文献
20.
Yang Xiao Zengchun Sun Armin WStuedlein Chenggui Wang Zhijun Wu Zhichao Zhang 《地学前缘(英文版)》2020,(2):495-510
Crushing of grains can greatly influence the strength,dilatancy,and stress-strain relationship of rockfill materials.The critical state line(CSL)in the void ratio versus mean effective stress plane was extended to the breakage critical state plane(BCSP).A state void-ratio-pressure index that incorporated the effect of grain crushing was proposed according to the BCSP.Rowe’s stress-dilatancy equation was modified by adding the breakage voidratio-pressure index,which was also incorporated into the formulations of the bounding stress ratio and plastic modulus.A BCSP-based bounding surface plasticity model was proposed to describe the state-dependent stressstrain behaviors and the evolution of grain crushing during shearing process of rockfill materials,and was shown to sufficiently capture the breakage phenomenon. 相似文献