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Zekai Sen - One of the best experts on this subject based on the ideXlab platform.
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Rock Quality Designation-fracture intensity index method for geomechanical classification
Arabian Journal of Geosciences, 2014Co-Authors: Zekai SenAbstract:Rock Quality Designation (RQD) is a simple and effective way of Rock mass classification from surface scanlines or preferably borehole measurements. A major drawback in its classical use is that only one representative RQD value is obtained from the field measurements per core run. However, it is shown in this paper that the field measurements along a scanline provide detailed information about the Rock Quality and the fracture intensity (FI) for a given number of joints. In order to be able to extract the complete information concealed within the field data, the RQD-fracture index diagram concept is proposed and applied to actual field scanline measurements from England. The basis of the suggested procedure is to obtain a series of all possible RQD and FI values from given intact length measurements. This procedure provides additional information as to the local zones of heterogeneities within the Rock mass and a new way of Rock classification on the basis of the combined effects of RQD and FI. It is also possible to calculate percentages of different Rock qualities within the same Rock mass.
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Rock Quality Designation Model Formulation and Simulation for Correlated Fracture Intact Lengths
Mathematical Geology, 2000Co-Authors: Zekai SenAbstract:An important factor in the Rock Quality assessment analysis from discontinuity measurements along a scanline is the correlation of intact lengths. The autorun model and first order autorun coefficient are proposed as a method for objectively quantifying intact length correlation structure and discontinuity occurrences along any scanline. Necessary definitions for the methodology are presented on a quantitative basis such as the alternative intact length percentages and experimental autorun coefficient. An expression is proposed for the number of discontinuity occurrences along a scanline depending on the scanline length, alternate intact length percentages, and the autorun coefficient. Monte Carlo simulation technique is used with a suitable autorun model to verify this expression. A mathematical expression is derived for the expected Rock Quality Designation (RQD) value by taking into account the correlation of the intact lengths. Additional simulations show the validity of the new RQD expression. With the methodology proposed much less engineering experience and judgment are required in estimating the RQD value from scanline measurements. The application of the methodology has been presented for some field data.
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Naturally fractured Rock mass Quality zonation in Saudi Arabia
Quarterly Journal of Engineering Geology and Hydrogeology, 1996Co-Authors: Bahaaeldin H Sadagah, Zekai SenAbstract:Abstract The intensity of joints varies spatially throughout any Rock mass, therefore the description of the whole Rock mass Quality by a single conventional Rock Quality Designation(RQD) value is rather insufficient.In practice, the Rock mass Quality changes along any line through a Rock mass depending on the direction of measurement. A new statistical method is proposed for expressing Rock Quality data which involves deriving an empirical RQD distribution from scanline data. The method is demonstrated with reference to three different Quality Rock masses in Saudi Arabia. The distribution can be used in the assessment of the level of risk entailed in adopting a particular single design value of RQD.
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Block Size Distribution and Quality Classification in Naturally Fractured Rocks
Environmental & Engineering Geoscience, 1992Co-Authors: Bahaaeldin H Sadagah, Zekai SenAbstract:A refined Rock mass classification is proposed which exposes percentages of different quantities as solid, massive, blocky, fractured, and crushed. It is shown that some of the classical Rock Quality Designation indices with a single value of classification fail to provide detailed information. In fact, different Rock mass compositions might lead to the same single values, but they may be entirely different in the overall Rock mass behavior. The basis of the methodology presented in this paper is the cumulative frequency distribution of intact lengths which is drawn on a specially developed semi-logarithmic paper so as to identify different Quality regions. Additionally, an empirical relationship is proposed which relates the classical Rock Quality Designation (RQD) value to descriptive values of these graphs. Besides the Quality, percentages obtained in this manner might give some clues about the tectonic activities especially in the igneous Rock environments. Application of the methodology has been presented for two regions in the Kingdom of Saudi Arabia.
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Fracture Simulation and Multi-Directional Rock Quality Designation
Environmental & Engineering Geoscience, 1991Co-Authors: Elsayed A. Eissa, Zekai SenAbstract:A simple fracture network model is proposed based on the negative exponential distribution of the discontinuities in all directions. In the fracture generating procedure the midpoint coordinates of each fracture is generated by a uniform distribution function; the fracture directions are simulated by normal probability distributions and the fracture lengths are derived from a logarithmic-normal distribution. Three different sets of fractures are presented on a planar surface with different random seeds. The main purpose of this paper is to asses the Rock Quality Designation, (RQD), on the basis of one, two and three directional fracture sets. However, all of the previous studies up to date theoretically or practically were confined to one direction only. A graphical procedure is presented for depicting the population estimate of the average number of discontinuities along a scanline. The substitution of this estimate into the relevant RQD equation provides the Rock Quality estimation in a better representative manner than the classical estimates.
Tingchang Yin - One of the best experts on this subject based on the ideXlab platform.
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Selection of Optimal Threshold of Generalised Rock Quality Designation Based on Modified Blockiness Index
Advances in Civil Engineering, 2019Co-Authors: Qingfa Chen, Tingchang Yin, Hangyu JiaAbstract:Rock Quality Designation (RQD) is a critical index for quantifying the degree of Rock mass jointing; it is widely used for evaluating the qualities and stabilities of engineering Rock masses. However, the use of traditional RQD may yield inaccurate assessments because only core pieces longer than 100 mm are counted. To enhance the utility of RQD, generalised RQD was introduced. Based on the modified blockiness index (MBi), the determination of the optimal threshold of generalised RQD was performed. In this work, 35 types of hypothetical three-dimensional joint network models were constructed, and their generalised RQD values (with different thresholds) and MBi values were measured. The correlation between the standard ratings of MBi and RQD was assessed; based on this correlation, the theoretical RQD values of the 35 models were derived. The reasonable thresholds of the generalised RQD were determined according to the theoretical RQD values, and the optimal threshold of generalised RQD was obtained using the variation coefficient and anisotropy index of the jointing degree. The discrepancy between the results produced using traditional and generalised RQDs was discussed. Finally, an actual case study was conducted, and the results indicate that the generalised RQD associated with the optimal threshold determined in this study can properly quantify the degree of jointing of a given Rock mass.
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Should the Use of Rock Quality Designation Be Discontinued in the Rock Mass Rating System
Rock Mechanics and Rock Engineering, 2018Co-Authors: Qingfa Chen, Tingchang YinAbstract:In 2013, an updated Rock mass rating system (RMR13) was introduced, in which the combined use of Rock Quality Designation (RQD) and fracture spacing (FS) in the commonly used version (known as RMR89) was replaced with the fracture frequency (FF). Multiple studies have suggested that the incorporation of RQD into the RMR system is no longer necessary, and this stance is extremely controversial. In this study, to investigate whether the use of RQD should be discontinued in the RMR system, both RMR89 and RMR13 were applied to a large number of cases involving artificial and real data sets, and comparisons of RMR89 and RMR13 were conducted. The artificial data sets were constructed through developing theoretical discrete fracture network (DFN) models, and the real data sets were collected from 187 actual cases worldwide. The comparison between RMR89 and RMR13 was based on the following steps. (1) The combined ratings of RQD and FS in RMR89 (RRQD+FS) and the rating of FF in RMR13 (RFF) were used to determine the fracturing degrees of the theoretical DFN models. Additionally, the classification abilities of the two subsystems were analysed and compared, and the correlation coefficient (r) and included angle cosine value of two vectors (λij) were calculated. (2) Two specific case studies were performed, and an analysis of variability between RMR89 and RMR13 was conducted. (3) In comparative analyses of 187 real cases, RRQD+FS, RFF, RMR89 and RMR13 were adopted to assess the structures and basic qualities of Rock masses. Moreover, their results and classification abilities were compared, and r and λij were calculated. The conclusions of the study were as follows: (1) the assessment results of theoretical DFN models show that RRQD+FS and RFF exhibit a similar ability to distinguish Rock mass structures; (2) the two specific case studies performed suggest that the discrepancy between RMR89 and RMR13 truly exists; (3) the real case studies indicate that RMR89 and RMR13 differ in their sensitivities to Rock mass fracturing and basic Quality, and RMR89 is superior, but the application potential of RMR13 cannot be denied; and (4) the introduction of RMR13 is not a sufficient reason to cease the use of RMR89, which remains highly practical. In real cases, individuals should select a proper classification system by considering the geological conditions and their experiences and preferences.
S.j. Bauer - One of the best experts on this subject based on the ideXlab platform.
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Fracture analysis and Rock Quality Designation estimation for the Yucca Mountain Site Characterization Project; Yucca Mountain Site Characterization Project
1993Co-Authors: M. Lin, M.p. Hardy, S.j. BauerAbstract:Within the Yucca Mountain Site Characterization Project, the design of drifts and ramps and evaluation of the impacts of thermomechanical loading of the host Rock requires definition of the Rock mass mechanical properties. Ramps and exploratory drifts will intersect both welded and nonwelded tuffs with varying abundance of fractures. The Rock mass mechanical properties are dependent on the intact Rock properties and the fracture joint characteristics. An understanding of the effects of fractures on the mechanical properties of the Rock mass begins with a detailed description of the fracture spatial location and abundance, and includes a description of their physical characteristics. This report presents a description of the abundance, orientation, and physical characteristics of fractures and the Rock Quality Designation in the thermomechanical stratigraphic units at the Yucca Mountain site. Data was reviewed from existing sources and used to develop descriptions for each unit. The product of this report is a data set of the best available information on the fracture characteristics.
Ali Bouafia - One of the best experts on this subject based on the ideXlab platform.
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Load-settlement behaviour of socketed piles in sandstone
Geotechnical & Geological Engineering, 2003Co-Authors: Ali BouafiaAbstract:Nine Static vertical pile loading tests were carried out in Abu-Dhabi, the United Arab Emirates in order to assess the end bearing capacity and settlement of piles bored in slightly silty sands overlying soft Rocky horizons like sandstone and calcarenite. The paper is aimed at presenting the results of interpretation of the pile tests in order to estimate the end bearing capacity in correlation with the unconfined compressive strength R _ c and the Rock Quality Designation (RQD). Load-settlement behaviour is also studied through an analysis by the elastic methods commonly used in pile design.
Qingfa Chen - One of the best experts on this subject based on the ideXlab platform.
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Selection of Optimal Threshold of Generalised Rock Quality Designation Based on Modified Blockiness Index
Advances in Civil Engineering, 2019Co-Authors: Qingfa Chen, Tingchang Yin, Hangyu JiaAbstract:Rock Quality Designation (RQD) is a critical index for quantifying the degree of Rock mass jointing; it is widely used for evaluating the qualities and stabilities of engineering Rock masses. However, the use of traditional RQD may yield inaccurate assessments because only core pieces longer than 100 mm are counted. To enhance the utility of RQD, generalised RQD was introduced. Based on the modified blockiness index (MBi), the determination of the optimal threshold of generalised RQD was performed. In this work, 35 types of hypothetical three-dimensional joint network models were constructed, and their generalised RQD values (with different thresholds) and MBi values were measured. The correlation between the standard ratings of MBi and RQD was assessed; based on this correlation, the theoretical RQD values of the 35 models were derived. The reasonable thresholds of the generalised RQD were determined according to the theoretical RQD values, and the optimal threshold of generalised RQD was obtained using the variation coefficient and anisotropy index of the jointing degree. The discrepancy between the results produced using traditional and generalised RQDs was discussed. Finally, an actual case study was conducted, and the results indicate that the generalised RQD associated with the optimal threshold determined in this study can properly quantify the degree of jointing of a given Rock mass.
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Should the Use of Rock Quality Designation Be Discontinued in the Rock Mass Rating System
Rock Mechanics and Rock Engineering, 2018Co-Authors: Qingfa Chen, Tingchang YinAbstract:In 2013, an updated Rock mass rating system (RMR13) was introduced, in which the combined use of Rock Quality Designation (RQD) and fracture spacing (FS) in the commonly used version (known as RMR89) was replaced with the fracture frequency (FF). Multiple studies have suggested that the incorporation of RQD into the RMR system is no longer necessary, and this stance is extremely controversial. In this study, to investigate whether the use of RQD should be discontinued in the RMR system, both RMR89 and RMR13 were applied to a large number of cases involving artificial and real data sets, and comparisons of RMR89 and RMR13 were conducted. The artificial data sets were constructed through developing theoretical discrete fracture network (DFN) models, and the real data sets were collected from 187 actual cases worldwide. The comparison between RMR89 and RMR13 was based on the following steps. (1) The combined ratings of RQD and FS in RMR89 (RRQD+FS) and the rating of FF in RMR13 (RFF) were used to determine the fracturing degrees of the theoretical DFN models. Additionally, the classification abilities of the two subsystems were analysed and compared, and the correlation coefficient (r) and included angle cosine value of two vectors (λij) were calculated. (2) Two specific case studies were performed, and an analysis of variability between RMR89 and RMR13 was conducted. (3) In comparative analyses of 187 real cases, RRQD+FS, RFF, RMR89 and RMR13 were adopted to assess the structures and basic qualities of Rock masses. Moreover, their results and classification abilities were compared, and r and λij were calculated. The conclusions of the study were as follows: (1) the assessment results of theoretical DFN models show that RRQD+FS and RFF exhibit a similar ability to distinguish Rock mass structures; (2) the two specific case studies performed suggest that the discrepancy between RMR89 and RMR13 truly exists; (3) the real case studies indicate that RMR89 and RMR13 differ in their sensitivities to Rock mass fracturing and basic Quality, and RMR89 is superior, but the application potential of RMR13 cannot be denied; and (4) the introduction of RMR13 is not a sufficient reason to cease the use of RMR89, which remains highly practical. In real cases, individuals should select a proper classification system by considering the geological conditions and their experiences and preferences.
