基于三维裂隙网络RQD的确定及最佳测线数量的研究

作为评价岩体质量好坏的重要指标,RQD的应用已十分广泛,其在工程地质与岩土工程的分析中发挥着重要的作用。而通过钻孔的方法进行RQD的获取具有明显缺点。真实岩体不同方向的RQD并不一致,而以垂直于地表的钻孔获取的RQD并不能完全代表整体岩体的好坏程度。引入三维裂隙网络的方法进行RQD的计算,在三维裂隙网络内设立测线,以测线的形式来模拟钻孔,获取指定方向的RQD值。岩体不同于其他人工材料,其具有明显的非均质性,即在不同位置获取的RQD值并不一致,现今RQD的研究则鲜有考虑。对岩体内的最佳测线数量进行了研究。结果表明：当沿x,y与z轴分别存在25,80与55条测线时,可获取岩体各方向的真实RQD值,且最大限度的节省计算时间以实施进一步的研究。     

窗口测线法获取岩体RQD

岩石质量指标RQD是评价岩体质量的一个重要指标，但这一传统的RQD完全取决于钻孔布置数量和方向。若钻孔数量有限，则误差较大，工程实际使用中受到限制。而采用在测量窗口中借助计算机布置测线的方法来计算RQD，可以减少误差，可综合反映岩体的各向异性特征，且可方便地获取大量的RQD，方法简便易行，适合于实际工程应用。     

分形理论在岩体质量评价中的应用研究

简要地回顾了岩体质量评价体系,提出了一种利用分形分布与概率的联系来评价岩体质量的方法,并给出了相应的岩体质量评价的标准。研究表明,分维数D能够弥补岩石质量指标RQD在评价岩体质量中的某些不足,可以作为评价岩体质量的一个定量指标。     

基于V.RQD值与Hoek-Brown准则的破碎岩体强度研究

被多组贯通结构面切割后产生的大体积破碎岩体在不同围压下仍具有一定的强度,但通过Hoek-Brown准则对其进行强度评价时,因对岩体结构划分缺乏定量描述,使得参数m与s的取值很难准确确定。在传统RQD值不足的基础上,引入不同阈值下的三维体积V.RQD值概念,建立破碎岩体质量指标V.RQD值计算机模拟方法,结合RMR评分标准和Hoek-Brown强度准则,通过探讨三维体积V.RQD值的取值范围,得到不同阈值时岩体质量参数m,s值与Hoek-Brown强度包络线以及岩体变形模量E0等之间的一些变化规律,定量化表述V.RQD值对破碎岩体强度的影响。结果表明,V.RQD值作为岩体质量指标之一,可为破碎岩体的强度估计提供新的实用途径。     

基于三维裂隙网络的RQD尺寸效应与空间效应的研究

 岩石质量指标(RQD)是岩土工程与地质工程中的重要概念,在岩体性质分析中起到了重要作用,但RQD存在着明显的尺寸效应与空间效应,这在以后岩体工程设计计算中并没有引起充分的重视。为研究RQD的空间效应,采用三维裂隙网络模拟方法模拟现场真实岩体,并在模型中设立大量测线获取岩体中不同位置的RQD值。结果表明,岩体中不同位置的RQD值并不相同,存在明显的空间效应。为获取可整体代表岩体好坏程度的RQD值,需在大量RQD样本的基础上进行分析。另外,为更好地体现岩体的非均质性,研究不同阈值下的RQD范围,最终确定可充分反映待分析岩体的最佳阈值,为4 m。尺寸效应是RQD参数的重要性质,通过改变测线长度的方法探讨RQD在不同尺度下的变化情况。总结、提出RQD的计算模型与公式,即：A-A模型、T-T模型、A-A-S模型、Priest-Hudson公式与Senz-Kazi公式。分别研究与对比不同模型下RQD的尺寸效应,结果表明,采用A-A-S模型可充分减少尺寸效应带来的RQD的计算误差;当阈值较大时,Priest-Hudson公式与Senz-Kazi公式存在一定的误差,基于三维裂隙网络模拟的方法进行RQD的计算将会更为准确。     

岩体结构面网络模拟在滑坡中的应用

通过结构面网络模拟研究滑坡的岩体结构特征 ,进而利用岩体质量指标 (RQD)进行岩体分类、估计岩体强度。此方法在赵树岭滑坡的研究中得到了很好的应用。     

三维节理岩体分形维数与RQD相关性研究

 应用三维随机不连续面网络模拟技术对岩体结构统计均质区内的不连续面进行计算机模拟,再现岩体结构,并应用分形理论计算三维节理岩体的分形维数。平行于三维节理岩体网络模型的x,y,z轴布置测线,计算不同阈值下三维岩体的岩石质量指标(RQD)。对获取的分形维数与RQD分析表明,三维岩体RQD随分形维数增大而减小,二者具有良好的线性关系。最后,推导三维节理岩体的分形维数与若干个阈值下RQD的关系式,并根据不同阈值下RQD与分形维数关系曲线的斜率确定合理阈值。     

边坡岩体质量评价及其应用

本文应用RMR体系和Q体系对宣钢近北庄铁矿边坡岩体质量进行了评价，在此基础上估算了岩体强度和变形参数，为探索边坡岩体的变形、破坏规律提供了依据，该方法简单易行，能较好地反映岩体的实际状态，是解决岩体稳定问题的重要途径。     

钻孔电视技术在高边坡勘察中的基础效用分析

以某核电边坡工程为例,介绍了钻孔电视技术的工作原理。重点分析了其在岩体结构面产状统计分析、岩石质量指标(RQD)评价、岩体完整性评价、脉岩与围岩的接触关系评价等方面的基础效用,得出了一些有意义的结论。     

柏叶口水库坝址基岩风化的综合判定

通过勘察研究,阐述了工程场区岩体风化类型及岩体强风化带、弱风化带、微风化带在空间上的分布及其规律,分析了岩体风化波速比Kw、岩体完整性系数KV和RQD值之间的相关性,确定了综合划分工程场区岩体风化带的定性和定量指标。     

Using multivariate adaptive regression splines to develop relationship between rock quality designation and permeability

The assessment of in situ permeability of rock mass is challenging for large-scale projects such as reservoirs created by dams, where water tightness issues are of prime importance. The in situ permeability is strongly related to the frequency and distribution of discontinuities in the rock mass and quantified by rock quality designation (RQD). This paper analyzes the data of hydraulic conductivity and discontinuities sampled at different depths during the borehole investigations in the limestone and sandstone formations for the construction of hydraulic structures in Oman. Cores recovered from boreholes provide RQD data, and in situ Lugeon tests elucidate the permeability. A modern technique of multivariate adaptive regression splines (MARS) assisted in correlating permeability and RQD along with the depth. In situ permeability shows a declining trend with increasing RQD, and the depth of investigation is within 50 m. This type of relationship can be developed based on detailed initial investigations at the site where the hydraulic conductivity of discontinuous rocks is required to be delineated. The relationship can approximate the permeability by only measuring the RQD in later investigations on the same site, thus saving the time and cost of the site investigations. The applicability of the relationship developed in this study to another location requires a lithological similarity of the rock mass that can be verified through preliminary investigation at the site.     

Determination and applications of rock quality designation(RQD)

Characterization of rock masses and evaluation of their mechanical properties are important and challenging tasks in rock mechanics and rock engineering.Since in many cases rock quality designation(RQD)is the only rock mass classification index available,this paper outlines the key aspects on determination of RQD and evaluates the empirical methods based on RQD for determining the deformation modulus and unconfined compressive strength of rock masses.First,various methods for determining RQD are presented and the effects of different factors on determination of RQD are highlighted.Then,the empirical methods based on RQD for determining the deformation modulus and unconfined compressive strength of rock masses are briefly reviewed.Finally,the empirical methods based on RQD are used to determine the deformation modulus and unconfined compressive strength of rock masses at five different sites including 13 cases,and the results are compared with those obtained by other empirical methods based on rock mass classification indices such as rock mass rating(RMR),Q-system(Q) and geological strength index(GSI).It is shown that the empirical methods based on RQD tend to give deformation modulus values close to the lower bound(conservative) and unconfined compressive strength values in the middle of the corresponding values from different empirical methods based on RMR,Q and GSI.The empirical methods based on RQD provide a convenient way for estimating the mechanical properties of rock masses but,whenever possible,they should be used together with other empirical methods based on RMR,Q and GSI.     

Variation of rock quality designation (RQD) with scanline orientation and length: a case study in Korea

Rock quality designation (RQD) has been widely used to evaluate the degree of fracturing of rock masses. Although it has been frequently pointed out that RQD is dependent on the orientation of measurement and on the scanline length, these effects have not been considered in site investigation for tunneling in Korea. Therefore, a series of practical examinations using in situ data collected from recent tunneling sites in Korea has been conducted. Variation of RQD with scanline orientation was observed to be as high as 24% in the sub-horizontal tunneling where the design was based on the results of RQD from vertical drill core logging. In addition, the range of possible variation of RQD with scanline length was analyzed with four different models, including two new models introduced in this case study for the first time. It is shown that at least 4 m of scanline length is required to maintain a reliable value for the RQD in the three models. The simulation from the so-called A–A–S model showed that it is possible to maintain the same reliability of the RQD in a situation where only a much smaller extent (i.e. 0.4 m) of rock exposure is available in the field. It is hoped that the results of this case study will provide the tunnel engineer with an enhanced understanding of the variation of RQD with measurement method.     

Correlations between jointing and seismic velocities in highly fractured rock masses

The paper presents the results of a study of heavily fractured calcareous rock masses outcropping in southern Italy based on both the unidimensional joint frequency (Nl) and rock quality designation (RQD) of rock cores and seismic velocity data from laboratory and down-hole tests. The in situ longitudinal wave velocities (v) were always very low and were correlated with both Nl and RQD. Between 1 and 2 km/s, small increases in velocity were associated with a considerable decrease in Nl and significant increase in RQD value. A velocity of 1.22 km/s corresponded to an RQD value of 0. The study indicated that the simple correlation proposed by the International Society for Rock Mechanics to evaluate the RQD from the unidimensional joint frequency can underestimate the results for heavily fractured rock masses, but that good correlations can be obtained between RQD and seismic velocity. Electronic Publication     

Estimation of rock mass deformation modulus using variations in transmissivity and RQD with depth

Discontinuity normal stiffness and deformation modulus of large scale rock masses are very difficult to determine. A method for estimation of discontinuity normal stiffness based on the decrease in transmissivity with depth has been proposed by the authors in a former paper. In the current study, the method is further developed by accounting for the changes in both discontinuity aperture and frequency with depth, which are key factors that cause the transmissivity to decrease with depth. The discontinuity frequency can be estimated from RQD measurements, which are readily available in most geotechnical investigations. The transmissivity data from packer tests are usually available in geotechnical investigations for hydropower plants. For a rock mass in a dam site mainly controlled by lithostatic stress, based on transmissivity and RQD data at different depths, the change in discontinuity aperture with depth can be linked to the change in aperture with stress, which defines the normal stiffness of discontinuities. In the case study, the discontinuity normal stiffness is successfully estimated by using transmissivity and RQD data, and the result shows that the normal stiffness increases with stress (depth) and the rate of normal stiffness versus stress (depth) decreases with stress (depth), which is consistent with experimental studies. The estimated normal stiffness has been utilized to calculate the rock mass deformation modulus using an equivalent model. The result of deformation modulus by the proposed method is close to that obtained by using in situ measurements, as well as by using empirical models relating RQD to deformation modulus.     

灰色关联分析法在围岩分类中的应用

采用灰色关联分析法,对影响围岩质量的5项指标:岩石质量指标RQD,湿抗压强度Rw,完整性系数Kv,结构面强度系数Kf,地下水渗水量W/L等进行了关联分析,提出了一种进行围岩分类的新方法,具有一定的工程实用价值。