Application of Weibull Statistics to the Tensile Strength of Rock Aggregates

Rock aggregates forming part of engineering structures such as embankments, rock fills, pile foundations, and pavements are subjected to static and dynamic loads. As a result of these loads crushing occurs in two different forms: abrasion and particle fragmentation. Particle fragmentation takes place when a particle is subjected to a tensile stress greater than its tensile strength. This tensile strength is a highly variable parameter. The work presented in this study shows that Weibull statistics can be used to characterize the variability in tensile strength of rock aggregates by only using one constant called the Weibull modulus. This parameter can be used not only to describe variability in tensile strength but also to describe the effect of size specimen in tensile strength. The higher the modulus, the lower is the influence of the variability of tensile strength and sample size. More than 390 different specimens coming from a red Biotite Gneiss and a grey Quartzite were tested to validate the use of Weibull statistics. The Weibull modulus was found to be equal to 2.75 and 4.23 for the red Biotite Gneiss and the grey Quartzsite respectively.     

应用低温等离子体破碎岩石

一般地,破岩方法可分为机械能破岩和热能破岩两种,随着科学技术的发展,热能破岩的方法和技术已在很多领域应用,特别是利用火钻焰流开采石材在很多矿山广泛得到了应用.从实际应用出发,重点介绍了低温等离子体破岩、凿岩的原理和方法,等离子装置的结构及其特点.     

Effect of Rock Strength Criterion on the Predicted Onset of Sand Production

The variation of sanding onset prediction results with the selection of one or another rock strength criterion is investigated. In this paper, four commonly used rock strength criteria in sanding onset prediction and wellbore stability studies are presented. There are Mohr–Coulomb, Hoek–Brown, Drucker–Prager, and modified Lade criteria. In each of the criterion, there are two or more parameters involved. In the literature, a two-step procedure is applied to determine the parameters in the rock strength criterion. First, the Mohr–Coulomb parameters like cohesion So and internal friction angle ?f, are regressed from the laboratory test data. Then, the parameters in other criteria are calculated using the regressed Mohr–Coulomb parameters. It is proposed that the best way to evaluate the parameters in a specific rock strength criterion is to perform direct regression of the laboratory test data using that criterion. Using this methodology, it is demonstrated that the effect of various rock strength criteria on sanding onset prediction is less dramatic than using the commonly used method. With this methodology, the uncertainties of the effect of rock strength criterion on sanding onset prediction are also reduced. Through this study, it is also demonstrated that a sanding onset prediction problem cannot be properly solved by adopting strength criteria that are not influenced by the intermediate principal stress if laboratory test data indicate rock failure is dependent on intermediate principal stress.     

The Kaiser effect in rocks: principles and stress estimation techniques

Irreversible deformation of rocks is accompanied by the Kaiser effect involving acoustic emission (AE). AE activity increases dramatically as soon as the largest previously experienced stress level is exceeded, similar to strain hardening in ductile materials. The Kaiser effect can be considered as a basis for stress measurements in rocks. This phenomenon is characterized by complexity which is the reason for disputable data interpretation procedures. A review of experimentally established features of the Kaiser effect, including those under a triaxial state of stress, is given. Mechanisms and theoretical models of the phenomenon are discussed. Stress measurement techniques based on the Kaiser effect in core specimens and in rocks around a borehole are explained; their strengths and weaknesses are analyzed. The necessity and the directions for future research are outlined. The analysis given should facilitate future applications of the Kaiser effect and improve the correctness of data interpretation.     

Poisson's ratio values for rocks

Compared to other basic mechanical properties of rocks, Poisson's ratio is an elastic constant of which the significance is generally underrated. Yet, in rock mechanics, there is a considerable number of diverse areas which require a prior knowledge or estimation of the value of Poisson's ratio. This paper examines the values and applications of Poisson's ratio in rock mechanics. Following an historical account of the initial controversy, whether it was a material constant or not, the effects of Poisson's ratio in the elastic deformation of materials, intact rocks, and rock masses are briefly reviewed. Also, the reported values of Poisson's ratio for some elements, materials, and minerals are compiled while typical ranges of values are presented for some rocks and granular soils. Finally, Poisson's ratio classifications are recommended for isotropic intact rocks.     

岭南园林石景

岭南园林石景有其独特之处,叠石假山多与池水、建筑、植物共同组成园林景观。论文分析了造园石景特点及常用景观石材,并总结了岭南园林叠石的几种造景手法。     

Modeling Triaxial Test on Intact Rock Using Discrete Element Method with Membrane Boundary

A new membrane boundary that applies realistic fluid confining pressure has been developed for modeling triaxial tests on intact rock by using the discrete element method. To realistically simulate the confining pressure, the new approach applies updated boundary force rather than a “wall” boundary. The applied forces only act on the boundary particles, which are identified and updated periodically. Comparisons between rigid-wall boundary and membrane boundary show that rigid-wall boundary can significantly alter the material response especially the material strength. The effect of confining pressures on the simulated results of triaxial tests is also investigated.     

普光气田碳酸盐岩储层测井解释方法

普光气田目的层段飞仙关组-长兴组海相碳酸盐岩地层发育气层,储层类型以孔隙-孔洞型为主,局部发育裂缝。针对这些储层特征,参考地质资料、微电阻率扫描成像资料,总结出了利用常规测井资料识别储层储集空间类型的方法;并在碳酸盐岩储层孔隙度参数求取中,采用光电吸收截面指数(Pe值),准确确定储层中岩性成分,为求取孔隙度参数提供了保障;在识别储层流体性质方面,通过实践经验总结出了交会图法、纵横波速度比值法等多种识别流体的方法,同时在核磁共振资料识别流体性质方面也做了大量的工作,在实际生产中显示出了很好的应用效果。     

鄂尔多斯盆地吴定地区烃源岩的油源对比

为了研究鄂尔多斯盆地吴定地区烃源岩油源对比,通过萜烷、甾烷生物标志化合物特征,厘定油源关系。原油和源岩的分析表明,长8储集层原油与长7烃源岩有密切的亲缘关系,而与长9烃源岩可比性差。因此,长8的原油来源于长7烃源岩。     

Roughness and Unit Side Resistances of Drilled Shafts Socketed in Clay Shale and Limestone

Rock socketed drilled shafts are being used increasingly to support heavily loaded structures. Rock sockets provide resistance to the load through a combination of side and base resistances. In this study, the effect of drilling tools such as an auger and a core barrel on the unit side resistance was investigated. A total of four field studies were performed on clay shale (compressive strength of 1–2?MPa) and limestone (compressive strength of 10?MPa). Borehole roughnesses produced by the different types of drilling tools in clay shale and limestone were measured using a laser borehole roughness profiler developed in this study to measure roughness to 0.5?mm in the boreholes. Based on the results of this study, it was observed that the drilling tools developed different socket roughnesses, which in turn affected the side resistances of the rock socketed drilled shafts.