• Title/Summary/Keyword: rock mass classification

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A Suggestion of Rock Mass Classification Systems for Stability of Underground Limestone Mines - A Case Study (석회석 광산의 지하갱도 안정성평가를 위한 암반분류법 개발)

  • Karanam U. M. Rao;Choon Sunwoo;Chuug, So-Keul;Park, Sung-Oong;Jeon, Yang-Soo
    • Tunnel and Underground Space
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    • v.13 no.6
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    • pp.421-433
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    • 2003
  • Demand for limestone production from both the underground and opencast mines in Korea is gradually increasing. Increase in productivity with safe mining operations is the emphasis laid on the mining industry. KIGAM has undertaken a detailed investigation to apply RMR and Q classification system for the design of underground limestone mining operations. The field investigations were confined to the underground mines of Daesung Mining Development Co. Ltd. and Pyunghae Mines of Korean Airport Service. Modification to the standard RMR and Q for limestone mines in Korea along with the correlation between these two systems are discussed while attempts were also made to calculate the width of a safe unsupported span.

A Study on the Quantification of Assessment Category of Roughness of Discontinuity of Rock Mass Classification Using Delphi method (델파이방법을 이용한 암반분류법의 불연속면 거칠기 평가분류 정량화에 관한 연구)

  • Kim, Byung-Ryeol;Lee, Seung-Joong;Choi, Sung-Oong
    • Tunnel and Underground Space
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    • v.25 no.2
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    • pp.210-219
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    • 2015
  • This paper describes a new quantitative process for evaluating the roughness of discontinuity, which is suggested as a qualitative criteria in RMR or Q-system. For this purpose, the Delphi method which is one of the surveying methods was introduced. The selected panels were asked to evaluate the roughness of discontinuities on the Web which was hosted by authors in advance. A total of 3 surveys were performed using JRCs suggested by Barton and Choubey as well as Ai generated by the Monte Carlo simulations. After each survey, the results were provided to all panels for comparing their decisions to others. As surveys proceeded, better consensus and convergence were achieved. With a good agreement of panels on roughness classification, the quantitative criteria for roughness of discontinuity in RMR and Q-system was established in this study.

Probabilistic rock mass classification using electrical resistivity - Theoretical approach of relationship between RMR and electrical resistivity- (전기비저항을 이용한 확률론적 암반분류 - RMR과 전기비저항 관계 이론 중심으로-)

  • Ryu, Hee-Hwan;Joo, Gun-Wook;Cho, Gye-Chun;Kim, Kyoung-Yul;Lim, Young-Duck
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.2
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    • pp.97-111
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    • 2013
  • It is very important to understand the condition of the surround rock for the successful construction of underground space. Representative methods of estimating the rock mass condition are RMR method and Q-system, and they are applied on design, construction, and maintenance. However, many problems with the accuracy of the measurement method and the subjective viewpoint are questioned continuously, so many researchers have been studied for estimating rock condition from various methods. Most of them show only the local relation and a tendency between site investigation data and rock conditions. In this paper, the relationship between RMR method and electrical resistivity is deducted using the analytical equation derived theoretically from electric field analysis on jointed rock mass. And also, probabilistic relationship between RMR method and electrical resistivity is deducted for the increase of accuracy. If a suggested method is applied with the conventional method for estimating the rock condition, it will be helpful to estimate RMR values on the field.

Shield TBM disc cutter replacement and wear rate prediction using machine learning techniques

  • Kim, Yunhee;Hong, Jiyeon;Shin, Jaewoo;Kim, Bumjoo
    • Geomechanics and Engineering
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    • v.29 no.3
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    • pp.249-258
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    • 2022
  • A disc cutter is an excavation tool on a tunnel boring machine (TBM) cutterhead; it crushes and cuts rock mass while the machine excavates using the cutterhead's rotational movement. Disc cutter wear occurs naturally. Thus, along with the management of downtime and excavation efficiency, abrasioned disc cutters need to be replaced at the proper time; otherwise, the construction period could be delayed and the cost could increase. The most common prediction models for TBM performance and for the disc cutter lifetime have been proposed by the Colorado School of Mines and Norwegian University of Science and Technology. However, design parameters of existing models do not well correspond to the field values when a TBM encounters complex and difficult ground conditions in the field. Thus, this study proposes a series of machine learning models to predict the disc cutter lifetime of a shield TBM using the excavation (machine) data during operation which is response to the rock mass. This study utilizes five different machine learning techniques: four types of classification models (i.e., K-Nearest Neighbors (KNN), Support Vector Machine, Decision Tree, and Staking Ensemble Model) and one artificial neural network (ANN) model. The KNN model was found to be the best model among the four classification models, affording the highest recall of 81%. The ANN model also predicted the wear rate of disc cutters reasonably well.

Assessment of elastic-wave propagation characteristics in grouting-improved rock mass around subsea tunnels (해저터널 주변 그라우팅 보강암반의 탄성파 전달특성 평가)

  • Kim, Ji-Won;Hong, Eun-Soo;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.2
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    • pp.235-244
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    • 2016
  • Grouting is frequently used before the construction of subsea tunnels to mitigate problems that can occur in weak ground zones such as joints, faults or unconsolidated settlements during construction. The grout material injected into rock mass often flows through the discontinuities present in the host rock and hence, joint properties such as its distribution, roughness and thickness greatly affect the properties of grouting-improved rocks. The grouting-improved zones near subsea tunnels are also subjected to high water pressures that can cause long-term weathering in the form of changes in grout microstructure and crack formation and lead to subsequent changes in ground properties. Therefore, an assessment method is needed to accurately measure changes in the grouting-improved zones near subsea tunnels. In this study, the elastic wave propagation characteristics in grouting-improved rocks were tested for various axial stress levels, curing time, joint roughness and thickness conditions under laboratory conditions and the results were compared with wave velocity standards in different Korean rock mass classification systems to provide a basis for inferring improvement in grouted rock-mass.

A study on analysis of tunnel behaviors considering the characteristics of in-situ stress distribution in rock mass (암반응력의 분포특성을 고려한 터널거동 분석에 관한 연구)

  • Part, Do-Hyun;Kim, Young-Geun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.9 no.3
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    • pp.275-286
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    • 2007
  • In construction of a structure in underground space, in-situ stress in rock mass has great effect on the stability of the structure. Especially, the direction and magnitude of rock stress have influence on the excavation method, the choice of support and reinforcement method for establishing the stability of tunnel. Therefore, it is very important to consider the characteristics of in-situ stress in rock mass for tunnel stability analysis. In this study, a reasonable design method for underground structure was reviewed through the case study for tunnel design considering in-situ rock stress. For this purpose, the estimation for SRF (Stress Reduction Factor) as input parameter in rock classification using Q-System and the assesment for tunnel support were studied. Also, considering the characteristics of in-situ rock stress such as the magnitude of K and the direction of principal stress, the parameter studies for tunnel stability analysis were carried out. An improved method was proposed for obtaining the better results in the tunnel stability analysis.

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A study on correlation between electrical resistivity obtained from electrical resistivity logging and rock mass rating in-situ tunnelling site (전기비저항 검층으로 얻은 전기비저항과 터널 현장 암반등급의 상관관계에 관한 연구)

  • Lee, Kang-Hyun;Seo, Hyung-Joon;Park, Jin-Ho;Ahn, Hee-Yoon;Kim, Ki-Seog;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.14 no.5
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    • pp.503-516
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    • 2012
  • Rock mass rating (RMR) is the key factor when designing the appropriate support pattern of tunnel projects. Borehole drilling is usually performed along the tunnel route in order to determine the rock mass rating to be used for tunnel design. The rock mass rating at the non-boring region between boreholes is usually assessed through geophysical surveys such as electrical prospecting, seismic prospecting, etc. Many studies were carried out to find out the correlation between electrical resistivity and rock mass rating. However, most researches were aimed at obtaining the relationship between the two parameters utilizing experimental results obtained from laboratory tests or electrical prospectings. In this paper, efforts were made to analyze and obtain relationships between the electrical resistivity obtained from in-situ electrical resistivity logging data and the rock mass rating. Correlation studies using field data showed that the electrical resistivity is highly correlated with the rock mass rating with the determination coefficient more than 90%. The correlation analysis was also carried out between RMR classification parameters and the electrical resistivity. It was shown that the correlation between the condition of discontinuities and the electrical resistivity was very high with the determination coefficient more than 80%; that between the groundwater condition and the electrical resistivity was very low with the determination coefficient less than 57%.

Empirical correlation for in-situ deformation modulus of sedimentary rock slope mass and support system recommendation using the Qslope method

  • Yimin Mao;Mohammad Azarafza;Masoud Hajialilue Bonab;Marc Bascompta;Yaser A. Nanehkaran
    • Geomechanics and Engineering
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    • v.35 no.5
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    • pp.539-554
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    • 2023
  • This article is dedicated to the pursuit of establishing a robust empirical relationship that allows for the estimation of in-situ modulus of deformations (Em and Gm) within sedimentary rock slope masses through the utilization of Qslope values. To achieve this significant objective, an expansive and thorough methodology is employed, encompassing a comprehensive field survey, meticulous sample collection, and rigorous laboratory testing. The study sources a total of 26 specimens from five distinct locations within the South Pars (known as Assalouyeh) region, ensuring a representative dataset for robust correlations. The results of this extensive analysis reveal compelling empirical connections between Em, geomechanical characteristics of the rock mass, and the calculated Qslope values. Specifically, these relationships are expressed as follows: Em = 2.859 Qslope + 4.628 (R2 = 0.554), and Gm = 1.856 Qslope + 3.008 (R2 = 0.524). Moreover, the study unravels intriguing insights into the interplay between in-situ deformation moduli and the widely utilized Rock Mass Rating (RMR) computations, leading to the formulation of equations that facilitate predictions: RMR = 18.12 Em0.460 (R2 = 0.798) and RMR = 22.09 Gm0.460 (R2 = 0.766). Beyond these correlations, the study delves into the intricate relationship between RMR and Rock Quality Designation (RQD) with Qslope values. The findings elucidate the following relationships: RMR = 34.05e0.33Qslope (R2 = 0.712) and RQD = 31.42e0.549Qslope (R2 = 0.902). Furthermore, leveraging the insights garnered from this comprehensive analysis, the study offers an empirically derived support system tailored to the distinct characteristics of discontinuous rock slopes, grounded firmly within the framework of the Qslope methodology. This holistic approach contributes significantly to advancing the understanding of sedimentary rock slope stability and provides valuable tools for informed engineering decisions.

Rock Mass Stability of the Buddha Statue on a Rock Cliff using Fracture Characteristics and Geological Face-Mapping (마애불 암반의 단열특성과 지질맵핑을 이용한 안정성 해석)

  • Ihm, Myeong Hyeok
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.1
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    • pp.539-544
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    • 2023
  • The subject of this study is the Maae Buddha statue in granodiorite of the Mesozoic Cretaceous period, which is concerned about stability as a standing stone cultural property located in ◯◯-dong, Gyeongsangbuk-do. For stability analysis, three-dimensional face mapping, geological properties of joints, three-dimensional scanning, ultrasonic velocity, polarization microscopy, electron microscopy analysis and XRD analysis were performed. In addition, the safety factor of the Maaebul was calculated by analyzing the damage status investigation, stereographic projection analysis, rock classification, and limit equilibrium analysis. The types and scales of damage and possible collapse by section depend on the degree of weathering of the rock and the orientation and characteristics of the joints, but wedge-failure and toppling-failure are expected to be small-scale. The safety factor of Maaebul in dry and wet conditions is less than 1.2, so stability is concerned. The types of damage were mainly observed, such as exfoliation, cracking, granular decomposition, and vegetation growth. The Maaebul rock is granodiorite, and the surface discoloration materials are K, Fe, and Mg. The 4 sets of joints are developed, J1 is tensile joint and the others are shear joint. The uniaxial compressive strength estimated by ultrasonic exploration is 514kgf/cm2, which corresponds to most soft rocks and some weathered rocks. Rock classification(RMR) is estimated to be grade 5, very poor rock mass. These technique along with the existing methods of safety diagnosis of cultural properties are expected to be a reasonable tool for objective interpretation and stability review of stone cultural properties.

A Case Study for the Support Pattern Appropriateness in Rock Tunneling Designs (지하철 설계시의 지보형식 적정성에 관한 연구)

  • 김수정;장태우
    • The Journal of Engineering Geology
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    • v.5 no.2
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    • pp.167-179
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    • 1995
  • The only three elements such as RQD, N -value and Es were used as a quantitative standard for the design of supporr pattern determidetion on subway line 8th in Seoul. Because the support pattern that was obtained by these elements could not he determined on the basis of the quantitative of geology and the orientations and properties of discontinuity planes, there have been some problems in determining the economic support pattern and tunnel stability. Therefore, in an attempt to determine the stable and economic support pattern with more quantitative elements, more flerrible rock mass classification with geologic conditions was performed by using RMR at 1745 sections and Q-system at 374 sections within Seongnam block on subway line 8th. Then, rusults by these two methods were compared with standard support pattern of the subway line 8th. Moreover, relationships between geology, geologic structures and topography to rock mass grades were studied. According to the rusult of this study, it is judged that the standard support pattern designed with PD-4 or PS - 4 should have been subdivided into 4~6 support patterns. Some sections where geologic structures such as faults and joints are developed tend to have rock mass grades. And they also have low rock mass grades near valley. On thr other hand, they show intermediate grades at piedmont area and the greatest ones at high mountains.

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