Quantitative Parameters for Rock Joint Surface Roughness

Summary The morphologies of two artificial granite joints (sanded and hammered surfaces), one artificial regularly undulated joint and one natural schist joint, were studied. The sanded and hammered granite joints underwent 5 cycles of direct shear under 3 normal stress levels ranging between 0.3–4 MPa. The regularly undulated joint underwent 10 cycles of shear under 6 normal stress levels ranging between 0.5–5 MPa and the natural schist replicas underwent a monotonous shear under 5 normal stress levels ranging between 0.4–2.4 MPa. In order to characterize the morphology of the sheared joints, a laser sensor profilometer was used to perform surface data measurements prior to and after each shear test. Rather than describing the morphology of the joints from the single profiles, our characterization is based on a simultaneous analysis of all the surface profiles. Roughness was viewed as a combination of a primary roughness and a secondary roughness. The surface angularity was quantified by defining its three-dimensional mean angle, θ_s, and the parameter Z2_s. The surface anisotropy and the secondary roughness were respectively quantified by the degree of apparent anisotropy, k _a, and the surface relative roughness coefficient, R _s. The surface sinuosity was quantified by the surface tortuosity coefficient, T _s.  Comparison between the means of the classical linear parameters and those proposed shows that linear parameters underestimate the morphological characteristics of the joint surfaces. As a result, the proposed bi-dimensional and tri-dimensional parameters better describe the evolution of the joints initial roughness during the course of shearing.     

Laboratory Estimation of Rock Joint Stiffness and Frictional Parameters

Numerical modeling of complex rock engineering problems involves the use of various input parameters which control usefulness of the output results. Hence, it is of utmost importance to select the right range of input physical and mechanical parameters based on laboratory or field estimation, and engineering judgment. Joint normal and shear stiffnesses are two popular input parameters to describe discontinuities in rock, which do not have specific guidelines for their estimation in literature. This study attempts to provide simple methods to estimate joint normal and shear stiffnesses in the laboratory using the uniaxial compression and small-scale direct shear tests. Samples have been prepared using rocks procured from different depths, geographical locations and formations. The study uses a mixture of relatively smooth natural joints and saw-cut joints in the various rock samples tested. The results indicate acceptable levels of uncertainty in the calculation of the stiffness parameters and provide a database of good first estimates and empirical relations which can be used for calculating values for joint stiffnesses when laboratory estimation is not possible. Joint basic friction angles have also been estimated as by-products in the small scale direct shear tests.     

An Investigation of Discontinuity Roughness Scale Dependency Using High-Resolution Surface Measurements

The influence of roughness on the hydro-mechanical behavior of rock discontinuities has long been recognized. As a result, several definitions and measures of roughness have been developed. According to the ISRM (Int J Rock Mech Min Sci Geomech Abstr 15(6):319–368, 1978), discontinuity roughness comprises large-scale (waviness) and small-scale (unevenness) components. However, the division between these scales is not clear and most investigations of surface roughness have been restricted to small fracture surfaces (<1 m²). Hence, the large-scale components of roughness are often neglected. Furthermore, these investigations typically define roughness using two-dimensional profiles rather than three-dimensional surfaces, which can lead to biased estimates of roughness. These limitations have led to some contradictory findings regarding roughness scale dependency (scale effects). This paper aims to provide some explanation of these contradictory findings. Through the in situ digitization and analysis of two adjacent large-scale (~2 × 3 m² and ~2 × 2 m²) migmatitic-gneiss fracture surfaces, the influence of sample size on roughness estimates are investigated. In addition, the influence of measurement resolution on roughness estimates is investigated by digitizing small-scale (100 × 100 mm²) samples from the same fracture with varying resolution. The findings show roughness to increase as a function of the sampling window size, in contrast to what is commonly assumed. That is, the combined waviness and unevenness of a discontinuity relative to its mean plane increases with scale. Compared to the sampling window size, the resolution of surface measurements is shown to have a far greater influence on roughness estimates. This influence of measurement resolution may explain some of the contradictory roughness scale relationships that have been published previously. It is important to note that the observed decrease in shear strength with increasing scale, as observed in many prior studies, is not being questioned; rather, a clarification of the role of roughness in this phenomenon is sought.     

An Anisotropic Modelling for the Determination of Regional Attenuation Coefficients

The anisotropic attenuation of macroseismic intensity for a seismogenetic zone is dealt with using a new modelling of intensity distribution. The analysis, carried out starting from the intensity maps of the earthquakes of different seismogenetic zones of Central and Southern Italy, allows the determination of the attenuation coefficients for each seismogenetic zone by an anisotropic attenuation law. The obtained results show the reliability of the proposed modelling within seismic hazard evaluation studies.     

水文地质参数计算方法探讨

阐述了水文地质参数的重要性,及其发展和尚需完善的方面。推出可以解决基岩裂隙、溶隙含水层坐标距离与水力距离不一致问题的导水系数计算方法。该方法的特点是简捷,能较直观地判别含水层主要水文地质参数的大小,具有很高的可靠性。     

A Constitutive Model for Shear Behavior of Rock Joints Based on Three-Dimensional Quantification of Joint Roughness

A new constitutive model to describe the shear behavior of rock joints under constant normal stiffness (CNS) and constant normal load (CNL) conditions is proposed. The model was developed using an empirical approach based on the results of a total of 362 direct shear tests on tensile fractured rock joints and replicas of tensile joints and on a new quantitative roughness parameter. This parameter, the active roughness coefficient C _r, is derived from the features of the effective roughness mobilized at the contact areas during shearing. The model involves a shear strength criterion and the relations between stresses and displacements in the normal and shear directions, where the effects of the boundary conditions and joint properties are considered by the shape indices C _d and C _f. The model can be used to predict the shear behavior under CNS as well as CNL conditions. The shear behavior obtained from the experimental results is generally in good agreement with that estimated by the proposed model, and the effects of joint roughness, initial normal stress, and normal stiffness are reasonably reflected in the model.     

Influence of Internal Friction Angle and Interface Roughness on Shear Behavior of Mortar-Rock Binary Medium Joint

Geotechnical and Geological Engineering - The damage of the interface between mortar and rock often occurs in engineering projects. The stability of the binary medium joint is the key factor in...     

榴辉岩部分熔融过程中钒分配系数的实验测定

钒(V)是常见的变价元素,其在矿物-熔体间的分配行为主要受氧逸度控制。近年来, V的分配行为与氧逸度之间的关系常被用于揭示地幔的氧化还原状态。板块俯冲过程中, V能否迁移是理解俯冲带V地球化学行为的关键环节,也是探讨俯冲带地幔楔氧逸度的重要前提。本文使用活塞圆筒装置模拟含水榴辉岩部分熔融过程,测定石榴子石、单斜辉石和金红石与熔体之间V的分配系数。实验压力为2.5GPa、温度介于900～1125℃之间,实验产物计算的氧逸度ΔFMQ介于-5.24～+0.74之间,实验结果表明V在石榴子石、单斜辉石和金红石中为相容元素(矿物/熔体分配系数D>1.0),并且DV(金红石)>DV(单斜辉石)>DV(石榴子石); V的分配系数也是氧逸度、温度和熔体聚合度的函数,随氧逸度和温度的增加,石榴子石、单斜辉石和金红石的V分配系数都减小,而随着熔体聚合程度的增加, V分配系数增大。模拟结果表明在榴辉岩部分熔融过程中熔体将显著亏损V,因此, V在榴辉岩(俯冲带洋中脊玄武岩)部分熔融过程中是不运移的;而板块俯冲过程中,榴辉岩部分熔融产生的熔体交代地幔楔不能明显改变地幔的V含量, V在地幔矿物和...     

An Algorithmic 3D Rock Roughness Measure Using Local Depth Measurement Clusters

Summary. A computational algorithm which uses depth data from a reference plane to a rock fracture surface in calculating a new three-dimensional joint roughness coefficient is presented. Two independent sets of fracture data are investigated. The new coefficient is compared to Barton’s 2D joint roughness coefficient JRC. A measure indicating corrupt data is discussed. The algorithm is also used to show that, in general, rock roughness is only a local variable, not a directional one.     

Blast Design Using Measurement While Drilling Parameters

Measurement while drilling (MWD) techniques can provide a useful tool to aid drill and blast engineers in open cut mining. By avoiding time consuming tasks such as scan-lines and rock sample collection for laboratory tests, MWD techniques can not only save time but also improve the reliability of the blast design by providing the drill and blast engineer with the information specially tailored for use. While most mines use a standard blast pattern and charge per blasthole, based on a single rock factor for the entire bench or blast region, information derived from the MWD parameters can improve the blast design by providing more accurate rock properties for each individual blasthole. From this, decisions can be made on the most appropriate type and amount of explosive charge to place in a per blasthole or to optimise the inter-hole timing detonation time of different decks and blastholes. Where real-time calculations are feasible, the system could extend the present blast design even be used to determine the placement of subsequent holes towards a more appropriate blasthole pattern design like asymmetrical blasting.     

模型区定量估算参数确定

预测模型是将当代成矿理论与现代高新综合勘查技术结合,并将传统的定量数值科学方法与计算机信息技术结合的桥梁。目前全国正在开展的矿产资源潜力评价工作中,资源量估算采用的是矿床模型综合地质信息体积法,该方法基于模型区含矿地质体的体积及其赋含的资源储量来获得模型区含矿系数,再通过类比估算其他预测区潜在资源量。以红石山镍矿为例,详细讲述了模型区的圈定以及含矿地质体定量参数确定的原则及方法。研究认为,国内外目前选用的许多定量预测模型一般都缺少对矿床成因等因素的考虑,该方法则通过对成矿有利的含矿建造的限定来确定成矿系统的范围,从而较好地将矿床成因与定量模型结合起来,提高了预测资源量的可信度。     

Open Stope Stability Using 3D Joint Networks

Summary The most popular exploitation method used in Canadian hard rock mines is open stope mining. Geomechanical design of open stopes relies on a range of analytical, numerical and empirical tools. This paper presents an engineering approach for the analysis and the design of reinforcement for open stopes in jointed rock. The proposed methodology, illustrated by three case studies, relies on developing 3D joint network models from field data. The 3D joint networks have been successfully linked to a 3D limit equilibrium software package. The models account for the finite length of joints as well as the influence of random joints. The integrated approach facilitates comparative analyses of different reinforcement strategies under different degrees of jointing in the hard rock environment. Received February 23, 2001; accepted October 11, 2002; Published online January 21, 2003 Acknowledgments The financial support of the National Science and Engineering Council of Canada and the Institut de Recherche en Santé et Sécurité au Travail of Quebec and Noranda Inc. is greatly appreciated. Authors' address: Prof. John Hadjigeorgiou, Université Laval, Department of Mining, Metallurgy and Materials Engineering, G1K 7P4 Quebec City, Quebec, Canada; e-mail: john.hadjigeorgiou@gmn.ulaval.ca