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, Qand GSI.

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.

A novel approach to structural anisotropy classification for jointed rock masses using theoretical rock quality designation formulation adjusted to joint spacing

Rock quality designation(RQD)has been considered as a one-dimensional jointing degree property since it should be determined by measuring the core lengths obtained from drilling.Anisotropy index of jointing degree(AI_(jd))was formulated by Zheng et al.(2018)by considering maximum and minimum values of RQD for a jointed rock medium in three-dimensional space.In accordance with spacing terminology by ISRM(1981),defining the jointing degree for the rock masses composed of extremely closely spaced joints as well as for the rock masses including widely to extremely widely spaced joints is practically impossible because of the use of 10 cm as a threshold value in the conventional form of RQD.To overcome this limitation,theoretical RQD(TRQD_(t))introduced by Priest and Hudson(1976)can be taken into consideration only when the statistical distribution of discontinuity spacing has a negative exponential distribution.Anisotropy index of the jointing degree was improved using TRQD_(t) which was adjusted to wider joint spacing by considering Priest(1993)’s recommendation on the use of variable threshold value(t)in TRQD_(t) formulation.After applications of the improved anisotropy index of a jointing degree(AI'_(jd))to hypothetical jointed rock mass cases,the effect of persistency of joints on structural anisotropy of rock mass was introduced to the improved AI'_(jd) formulation by considering the ratings of persistency of joints as proposed by Bieniawski(1989)’s rock mass rating(RMR)classification.Two real cases were assessed in the stratified marl and the columnar basalt using the weighted anisotropy index of jointing degree(W_AI'_(jd)).A structural anisotropy classification was developed using the RQD classification proposed by Deere(1963).The proposed methodology is capable of defining the structural anisotropy of a rock mass including joint pattern from extremely closely to extremely widely spaced joints.

Computing in-situ strength of rock masses based upon RQD and modified joint factor: Using pressure and damage sensitive constitutive relationship

In th is study, a n e w m odel w as p re se n te d for com p u tin g stre n g th o f rock m asses based u p o n in -situo bservations o f RQD p o pularly kno w n as rock quality d esignation. This m odel links u p th e rock m assp aram eters from in -situ investigations w ith th e stre n g th p a ram eters o f jo in ted rocks obtain ed fromlaboratory scale ex p erim en tal observations. Using th e co n stitu tiv e relation, th e a u th o r derived a p ressu reand d am age sensitive plastic p a ra m e te r to d ete rm in e stre n g th o f rock m asses for varied ex te n ts ofd isco n tin u ity an d p ressu re induced dam age. The te s t results show th a t plasticity characterized byhard en in g an d softening inclusive o f dam ag e invariably d e p en d s u p o n m ean p ressu re an d e x te n t ofdefo rm atio n s alread y experien ced by rock m asses. The p re se n t w ork explores th e te s t d a ta th a t revealth e d ep en d en c e o f in -situ stren g th on increm ental jo in t p ara m e te rs o b tain ed from th e jo in t num ber,jo in t orien tatio n , jo in t roughness, gouge p a ram eters an d w a te r pressure. S ubstituting th e relationshipb e tw e e n th e RQD and m odified jo in t factor w ith th a t b e tw e e n m odulus ratio an d stren g th ratio, th em odel show s successfully th a t using d am age inclusive plastic p a ra m e te r an d RQD provides a relationshipfor estim atin g th e stre n g th o f rock m asses. One o f th e m ain objectives o f this w ork is to illustrate th a t th ep re se n t m odel is sensitive to p la s tic ity a n d dam ag e to g e th e r in estim atin g in -situ stre n g th o f rock m assesin foundations, u n d e rg ro u n d excavation an d tunnels.

结构面三维网络模拟计算RQD及精度对比研究

以汶川映秀镇百花大桥边坡岩体为实例,运用结构面三维网络模拟法计算RQD值,具体步骤为:在概率统计结构面各项参数获取结构面模拟参数的基础上,利用Monte-Carlo法生成岩体节理三维网络,在边坡震时主滑平面、主滑横剖面、水平面上各方向布置测线模拟钻孔,获取54个钻孔岩石质量指标RQD值,以其期望值作为最终RQD。以结构面测量统计得到的等效钻探RQD为真值,对比体积RQD法和网络模拟法的相对误差(体积RQD法为24.6%;结构面三维网络模拟法仅为3.3%),证实结构面三维网络模拟法相对误差要小得多,精度显著提高。结构面三维网络模拟法是计算RQD的好方法,具有广泛的应用前景。

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。

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。

岩石质量指标（RQD）的各向异性分析

各向异性是工程岩体的重要工程特性，岩石质量指标ＲＱＤ具明显的各向异性。本文运用结构面网络模拟技术，通过结构面间距、倾角、相对夹角以及结构面组数的敏感性分析，探讨了ＲＱＤ的各向异性规律。结合实际工程应用，提出正确引用ＲＱＤ指标的建议。

补充RQD值的几类岩体质量评价图

针对ＲＱＤ值不能全面反映裂隙间距、块体大小以及随机表象的多重尺度等问题，介绍了三种岩体质量评价图，即基于裂隙岩体分数维结构之上的分维岩体质量图、考虑裂隙长度的累积长度图、建立在不同岩块频度基础上的岩块累积频度图。根据不同图解对岩体质量进行了评价，并对岩体完整性作了划分。三种图解能较全面地反映岩体质量的特点。

基于三维激光扫描技术的岩体RQD获取方法与程序

在西南地区岩质边坡高陡的特殊地形条件下,常规的地面地质调查方法难以开展。引入三维激光扫描技术获取边坡体出露的结构面各项几何参数(产状、间距、迹长),然后以这些地质资料为基础,结合结构面网络模拟技术生成不同走向网络图,通过在网络图上布置人工虚拟钻孔来计算得到岩体质量指标(RQD)。结果表明:提出的方法适用性较强,方便可靠,不仅解决了常规地质调查方法在高陡边坡地段难以开展的问题,而且还克服了以往钻孔岩芯获取岩体RQD指标数据少、误差大的缺点,获得岩体RQD指标经过修正后能满足工程实际需求。

基于分形的岩体质量评价及广义RQD阈值确定

基于三维结构面网络模拟技术,对采样区岩体优势结构面进行仿真模拟,在建立的模型中分别沿垂直于X,Y,Z轴方向切取剖面,得到各剖面的结构面二维网络图,运用分形理论分别计算其结构面分布的分形维数,进而对岩体质量进行评价。在上述网络剖面图中模拟钻孔,不断改变广义RQD的阈值,得到不同阈值下的RQD值。将各剖面的分形维数与广义RQD值对比分析,可以为准确选取广义RQD的最佳阈值提供依据。以某段公路边坡为例,当阈值在0.2~0.3时,广义RQD值与结构面分形维数吻合较好,故选取的RQD阈值应在0.2~0.3之间较为合理。

RQD研究的几个理论问题

岩石质量指标ＲＱＤ是岩体工程分类和稳定性评价中最常用的定量描述参数。３０多年来，ＲＱＤ的概念和理论研究有了重大进展。本文对源于工程应用的几个ＲＱＤ理论问题进行了评述，同时提出了一些新的研究思路。

保山西邑铅锌矿采选工程RQD与RBI对比研究

用岩石质量指标和岩体块度指数的理论,对钻孔岩心实测资料进行分析和对比研究,对钻孔周围岩体进行分级。结果表明:岩体块度指数在岩石质量评价中能更准确地反映其优越性,具有更为显著的工程意义。

煤矿床工程地质勘查中岩石质量指标(RQD)存在问题的探讨

岩石质量指标(RQD)是评价岩体完整性及质量分级的一个重要指标。针对矿区工程地质勘查规范中推荐的岩体质量评价方法,详细分析了岩石质量指标(RQD)在用于岩体分类与评价中存在的岩心长度的计算、采取率、硬度和结构对其赋值大小的影响,以及对规范理解的差异,提出了解决这些问题的有效方法与途径,为岩石质量指标(RQD)的正确应用及煤矿床岩体质量合理评价做了有益的探讨。

利用RQD对岩体完整质量评价的操作方法

岩石质量指标(RQD)是表示岩石完整性的一种指标。也是评价岩石质量的一个重要指标,利用RQD指标能达到客观准确的评价岩石质量的目的。

Determination of blast-induced ground vibration equations for rocks using mechanical and geological properties

In the recent decades, effects of blast loads on natural and man-made structures have gained considerable attention due to increase in threat from various man-made activities. Site-specific empirical relationships for calculation of blast-induced vibration parameters like peak particle velocity （PPV） and peak particle displacement （PPD） are commonly used for estimation of blast loads in design. However, these relation- ships are not able to consider the variation in rock parameters and uncertainty of in situ conditions. In this paper, a total of 1089 published blast data of various researchers in different rock sites have been collected and used to propose generalized empirical model for PPV by considering the effects of rock parameters like unit weight, rock quality designation （ROD）, geological strength index （GSI）, and uniaxial compressive strength （UCS）. The proposed PPV model has a good correlation coefficient and hence it can be directly used in prediction of blast-induced vibrations in rocks. Standard errors and coefficient of correlations of the predicted blast-induced vibration parameters are obtained with respect to the observed field data. The proposed empirical model for PPV has also been compared with the empirical models available for blast vibrations predictions given by other researchers and found to be in good agreement with specific cases.

基于数字图像处理功能的RQD分级方法的应用

RQD分级被广泛地应用于评价岩体的完整性。传统的RQD分级方法采用手工测量进行作业,工人劳动强度大,工作效率低,针对该问题,本文以巨龙铜矿为工程背景,提出了一种基于Image J图像分析功能的RQD分级方法。该方法首先通过拍摄钻孔岩心图像获取钻孔岩芯信息,然后通过Image J软件对钻孔岩芯图像中不同长度岩芯进行编号,通过测量分析功能得出不同编号的岩芯长度,进而计算RQD值,即可快速完成钻孔岩芯编录工作。计算结果与传统RQD分级方法所得结果误差仅在0.5%~1.0%,一致性较好,准确性较高。该方法便捷高效,适用于实际工程应用,尤其在高原地区以及工作环境恶劣地区值得推广。

钻爆法隧道智能建造技术研究综述与展望

首先,概述智能建造的基本内涵,即采用新一代信息技术、人工智能技术和机器人技术,构建智能超前地质预报、智能围岩质量评价、智能设计、智能施工、工程智能管理的多系统协同控制的隧道建造新模式。其次,从智能超前地质预报、智能围岩质量评价(钻进参数、数字图像、三维激光扫描点云等)、智能设计(信息化和数字化支护参数设计、智能化生成式设计方法等)、智能施工(施工工法工艺、施工装备等)、智能建造协同管理平台5个方面总结钻爆法隧道智能建造技术的研究现状。最后,从以下方面对智能建造今后的发展前景和方向进行展望:需构建与钻爆法隧道智能建造相适应的智能算法和模型;探索智能建造条件下隧道围岩响应规律和支护力学特性;发展考虑时间效应的隧道围岩整体稳定性评价方法和支护体系一体化设计方法;研制自感知、自适应、自决策的谱系化、多功能智能装备;形成更为安全、高效、经济的隧道智能建造标准化工法工艺;开发覆盖面更广、功能更强大、智能化水平更高的协同管理平台。

开放式微波致裂模拟节理岩体试验及辅助破岩评估

为研究开放式微波作用下节理岩体的破裂特征,并评估微波辅助悬臂掘进机的破岩效率,开展微波致裂模拟节理岩体试验。首先,利用9块尺寸为0.5 m×0.5 m×0.3 m(长×宽×厚)的闪长岩岩样垒成1.5 m×1.5 m×0.3 m(长×宽×厚)的人造节理岩体,以模拟节理间距为0.5 m的岩石开挖面;然后,利用6 kW的工业微波系统及缩径介质填充天线对该节理岩体进行微波照射加热致裂试验,研究不同微波照射点间距(15 cm和20 cm)下岩体的破裂特征,分析节理与照射点间距对微波致裂的影响,测量微波处理后岩体的等效岩石质量指标(RQD)和磨蚀性指数(CAI);最后,基于Bilgin经验模型评估微波照射前后刀盘功率为200 kW的悬臂掘进机的破岩效率和刀具磨损变化。结果表明:1)2种照射点间距下,岩体的等效RQD从100降低到62和50,微波预处理可使悬臂掘进机在该闪长岩岩体中的破岩效率提高170%~280%;2)照射点间距为20 cm时,CAI从4.0减少到3.4,可使刀具损耗降低11%。

梅山铁矿破碎区稳定性分析及支护研究

近年来随着矿山开采进入深部,局部区段节理裂隙发育,采动地压增大,矿岩稳定性急剧变化。目前梅山铁矿采用喷射混凝土支护,部分破碎区域采用喷锚联合支护和喷锚网联合支护,但部分主要生产联络道和穿脉巷道依旧存在巷道顶板楔形体大面积冒落的现象,矿山现有的支护方式不能满足安全生产要求。为解决以上生产技术难题,本研究从现场工程地质调查、室内岩石力学试验、岩体质量分级、岩体力学参数估算等出发,利用Unwedge对破碎区楔形体进行稳定性分析,总结巷道失稳破坏类型,提出了“树脂锚杆+金属网+喷射混凝土+长锚索”联合支护方式,并利用数值模拟软件Phase2对-330 m水平8LS7的巷道进行了数值模拟分析,根据对支护前后巷道总位移和塑性区范围的对比,初步验证了所选支护方式对维持围岩稳固的有效性。