Rock Mass Classification Research Articles

Analisis Kelas Massa Batuan Terhadap kestabilan Lereng Bendungan Lolak Menggunakan Metode Rock Mass Rating

The process of displacement or movement of slope stability constituent materials followed by the sedimentation process of the deposited material is a landslide event. The negative impact of the landslide if it occurs in residential areas, can cause material and infrastructure losses, or economic losses in the affected area if the landslide products can cover the road access. The purpose of this study was to determine the level of rock mass and its effect on slope stability, and to determine the rock mass quality of the study area. The research area is located in Lolak Dam. Based on the results of the analysis carried out, the conclusion is that the observations starting from station 1, station 2, station 3, and station 4 show moderate-good rock strength. The condition of the discontinuity shows continuity of less than 1 meter, the aperture of discontinuity are open to a bit wide, with varying roughness, namely coarse, and slightly coarse, with the infilling material calcite veins. The level of weathering starts from weathered to very weathered. Groundwater conditions are dominated by discontinuities that have a dry level. Based on the discontinuity characteristic, station 1 has good rock mass class, station 2 has medium rock mass class, station 3 has medium rock mass class, and station 4 has good rock mass class. this value can be used as a reference value for the next stage of decision making regarding the strengthening of the slopes in the study area.

A real-time intelligent classification model using machine learning for tunnel surrounding rock and its application

ABSTRACT Real-time and accurate prediction of surrounding rock grade is crucial for tunnel dynamic construction and design. However, the internationally accepted semi-quantitative methods (e.g. rock mass rating (RMR), Q, and basic quality (BQ)) cannot provide fast and accurate classification in construction. This study proposed an intelligent surrounding rock classification method and a tunnel information management system, which can predict the surrounding rock grade in real-time and accurately. A database is collected with 286 cases in China, including seven geological parameters and surrounding rock grades. Based on different training parameters, 12 classification models are established using VGGNet, ResNet, and support vector machine (SVM) algorithms. The accuracy of the SVM classifier is 93.02%, which performs better than the VGGNet and ResNet classifiers. Moreover, precision, recall, F-measure, receiver operating characteristic (ROC), and 20-case verification show that the SVM classification model has greater robustness in learning and generalising for small and imbalanced samples. Additionally, a tunnel information management system is developed with cloud technology, which can accurately predict the surrounding rock grade within 10 s. Overall, the achievements of this study can provide valuable references for real-time rock mass classification in traffic tunnels and underground powerhouses.

Multi-Rock Mass Classification Systems for the Assessment of Excavation Method and Support Design of Spillway Tunnel, Sidan Dam, Bali, Indonesia

This paper presents the implementation of rock mass classification systems to determine the excavation method and the support design of the Spillway Tunnel, Sidan Dam, Bali, Indonesia. In order to mitigate the uncertainty associated with using single rock mass classification during designing tunnels, this study provides an evaluation by applying multiple rock mass classifications. Rock Mass Rating (RMR), QSystem, Geological Strength Index (GSI), Japan Society of Civil Engineering (JSCE), and Rock Mass Index (RMi) were among the rock mass classification systems used for comprehensive analysis. Rock mass parameters were determined based on engineering geological mapping and rock & soil core analysis. The rock mass quality of pyroclastic rock along the tunnel is generally poor to fair. Based on the GSI rating, digging and ripping excavation were recommended. The top heading with benching (1-3 m advance in top heading) was the proposed excavation method by RMR and JSCE. Each classification system advised the combination of reinforced shotcrete and rock bolt for the primary tunnel support with varying shotcrete thickness (30-400 mm), rock bolt length (2.6-6 m), and rock bolt spacing (1-2.5 m). However, field investigations during excavation and numerical stability analysis were recommended to eliminate risks and ensure safe construction.

Geotechnical Investigation and Monitoring of Underground Excavation of Tunnel-2 in Srisailam Left Bank Canal Tunnel Project (AMRP), Nalgonda District, Telangana, India

Construction stage geotechnical investigation for tunnels within rocks includes detailed engineering geological mapping of excavated strata and its subsequent rock mass classification for the purpose of selection and installation of suitable supports. Monitoring of ground deformations during excavation of rock tunnels serves as the principal means of verifying the design of tunnel supports and stability of the excavation. Geology of the area comprises of Archean gneissic complex with basic intrusives overlain unconformably by the Srisailam Quartzites. The contact of basic intrusives with granite reaches was expected to be fractured and sheared and identified as adverse geological conditions and may warrant instrumental monitoring. In this work, the underground excavation of Srisailam Left Bank Canal (SLBC) Tunnel2, excavated in the Archean gneisses and granites was mapped by face mapping and 3D geological logging on 1:250 scale during construction stage, for the entire length of 7121Mresulting in identification of Chainages 2776M, 3200M and 4170M for field monitoring. Field instrumentation comprising of MPBX/SPBX, Load cells were installed at the adverse locations. The ground deformations were found to have attained stability with the installation of primary supports comprising shotcrete 50MM thick and pattern rock bolts 4M long full grouted for Rock Mass Class III (Fair Rock), shotcrete 100MM thick and pattern rock bolts)/ Steel Ribs with back fill concrete for Rock Mass Class IV and V(Poor Rock and Very Poor Rock). Keywords: Geological Investigation, Rock Mass Classification, Excavation Monitoring, Ground Deformation, Tunnels, Nalgonda District

ASSESSMENT OF ROCK SLOPE STABILITY IN A HUMID TROPICAL REGION: CASE STUDY OF A COAL MINE IN SOUTH KALIMANTAN, INDONESIA

PT.X, a coal mining company in South Kalimantan, Indonesia, plans to use the highwall mining method to excavate marginal reserves on the final slope to maintain production. However, the stability of the slope and determination of the highwall mining dimensions are major concerns due to unfavourable rock mass conditions caused by intensive weathering and tectonics. This paper aims to evaluate the feasibility of highwall mining in the study area using empirical, analytical and numerical methods. The innovation of this research is the integration of these methods, which include rock mass classification, analytical calculation of load and rock support strength, 2D and 3D numerical modelling, and estimation of recovered coal from the highwall design. The initial condition assessment using rock mass classification and analytics calculation of the mining geometry model determined mine openings and pillar dimensions. Numerical modelling re-evaluated the geometry models to obtain an optimal design. The suggested optimal thickness, mine opening, web pillars, and barrier pillars are 3.20, 3.00, 3.50, and 4.00 m, respectively, with four web pillars in one panel at Seam-C and 2.50, 3.00, 3.50, and 4.00 m with four web pillars in one panel at Seam-D. The recovery of coal for Seam-C and Seam-D is estimated to be 40.54%. Deformation was found to have the closest relationship with the dimensions of the mine opening, and the safety factor is most sensitive to changes in the depth of the mine opening. This study provides a reference for future highwall mining in Indonesia and other regions with similar conditions.

Estimating the Hydraulic Conductivity of jointed rock mass using Genetic Programming

Ground engineering through injection of cementitious grouts or polymer resins is an integral part of fractured rock mass stabilisation by improving its maximum load carrying capacity, stiffness, cohesiveness and reduction in permeability. To optimise product delivery and achieve a high penetrability of product into the rock mass, it is imperative to understand the permeability characteristics or hydraulic conductivity of the rock mass. The hydraulic conductivity of the rock mass also dictates the type of polyurethane (PU) or cement-based products to be injected. For this purpose, a Packer test has to be conducted to measure the hydraulic conductivity of a rock formation which is an expensive and time-consuming process. Alternatively, a number of empirical methods that use rock mass classifications and rock joint properties Rock Quality Designation (RQD), Q-system (Q), Geological Strength Index (GSI), Joint Spacing (JS), Joint Aperture (a) proposed by a number of researchers that are capable of predicting hydraulic conductivity (HC). In this research, a predictive model between rock mass properties and HC is proposed using new approach - genetic programming (GP). For this purpose, a database of rock mass parameters including RQD, Q, GSI, JS, Joint Aperture (a), Second Permeability Index (SPI) and Packer test results available in the literature is established. The database is split into randomly selected training and testing sets. To assess the fitting quality, the sum of the absolute difference is used, while maximum depth on trees is set to control the bloat of the model. The performance is assessed with four statistical criteria and three GP models using different input combinations are proposed. These models have been converted into simple mathematical equations to calculate HC based on collected input data. In summary, two out of three models have successfully predicted HC with high correlation to the actual HC (R2 of testing sets ≈ 0.92). Therefore, this study has shown the feasibility of applying GP models into future prediction of HC for the initial phase of rock grouting design.

Rock Mass Characterizations and Kinematic Analysis for Construction Design Method of Diversion Tunnel of Dolok Dam, Central Java

Investigation of slope stability in the design of the tunnel portal is important to minimize slope failure. This research aims to describe the rock mass characterizations and classifications using Geological Strength Index (GSI) and Rock Mass Rating (RMR), along with the kinematic analysis and Slope Mass Rating (SMR) to define the risk of slope failure and the recommended support at the tunnel portal. Geological mapping and core evaluation were conducted to analyse the slope stability. The results show that the rock masses consist of intercalated rudstone with mudstone, typically have disintegrated, moderately disturbed, and blocky structures with slightly to highly weathered. The discontinuities have 3 – 4 sets consisting of bedding and joint, have medium to high persistence, close spacing, and dominantly have no infillings. These rock masses are classified as poor-fair rock in the upper part of the sequence, and good rock in the bottom part of the sequence. The kinematic analysis predicts the risk of toppling failure both in the inlet and outlet portal. The recommended support in the inlet portal is the combination of shotcrete, beams, and bolts, whilst in the outlet portal is the combination of surface drainage, shotcrete, dental concrete, beams, and bolts.

THE SIZE CORRECTION AND CORRELATION OF POINT LOAD INDEX WITH COMPRESSIVE STRENGTH OF SOME DIMENSION STONES OF TECTONIC ZONES, NORTH PAKISTAN

The Uniaxial compressive strength (UCS) is an important geotechnical property of rock used in tunnel design, rock mass classification and other surface and underground mining projects. It is the Key parameter of rock mass rating (RMR) and the RMR is the basic of all the slope stability analyses methods. This key parameter of slope stability analyses and tunneling can be determine easily by axial and diametral point load test (PLI/Is50). In the past irregular lumps PLI is also correlated with UCS but the data is limited particularly the rocks along Karakoram High Way (KKH), North Pakistan. In this study the diametral, axial and the irregular lumps PLI is correlated with UCS using dimension stones of tectonic regions along KKH. A methodology of size correction of irregular lumps have been set. Using regression analyses the PLI of cores and lumps have been correlated with UCS. The significance of the correlation were developed by correlations coefficients. It is found that the Is(50) of irregular lump of white marble is 1.8MPa. For pink and white granite the Is(50) value is recorded as 3.2MPa and 2.4MPa respectively. In the size correction factor (F) the power n for irregular lump is corrected as 0.8 for marble lumps and the n value for pink and white granite is 0.9 and 1.4 respectively. For diametral and axial PLI the power n is used as 0.45. The correction factor F=(De/50)0.8 is suggested for marble irregular lumps while for axial and diametral specimens of marble the correction factor is F=(De/50)0.45 is recommended. In the case of pink and white granite the correction factors are F=(De/50)0.9 and F=(De/50)1.4 respectively.

The technique for extrapolation of rock mass initial parameters during the construction of the tunnel

It is important to perform research to the degree that it is adequate to identify the features of the terrain composition, before, during, and after the building of facilities since predicting the behaviour of rock mass during tunnel construction is a complicated engineering challenge. Engineering research works in laboratories and in the field are of different scope and methodology during testing. In this paper, the established interdependencies of some of the basic parameters obtained during the testing of rock mass are presented: Edyn = f(Vp), Edyn = f(RMR) i Edyn = f(Q). Also, the relations between the engineering systems of rock mass classification and seismic primary waves are derived. RMR = f(Vp), Q = f(Vp). The relations were based on the examination of the rock mass for the construction needs of the tunnel on the Nis-Merdare highway. The results obtained in this study can be applied in environments that have similar lithological and structural characteristics.

SLOPE STABILITY TECHNICAL STUDY USING SLOPE MASS RATING (SMR) METHOD AT PT. KARYA SUMBER ALAM PERKASA, SANGGAU REGENCY, KALIMANTAN BARAT

Soil (topsoil and overburden) above the granite quarry in pit 2 (two) PT. Karya Sumber Alam Perkasa has experienced a landslide. It is probably caused by the condition of pit 2 (two) slopes at PT. Karya Sumber Alam Perkasa, which is currently being mined, is quite steep. External factors that can trigger the movement of rock masses are vibrations due to breakers. This condition has the potential to increase the risk of slope stability. Slope stability is influenced by geological conditions, joints, slope geometry, water conditions below the soil surface, physical and mechanical properties, and vibrations due to blasting and mechanical equipment. Therefore, it is necessary to conduct a technical study of slope stability. The research aims to study rock mass class, potential type of landslide, and potential slope stability. The technical study of slope stability uses the Slope Mass Rating (SMR) method. Data processing using software Rocscience Dips 7.016. Analysis of potential types of landslides based on stereographic projections. The result of the RMR calculation is 78, so the rock mass class is number II, which is included in the excellent category. The results analysis of the potential for the type of failure indicates t tends to lead to the toppling failure, but after the study, there is no failure because it does not meet the landslide requirements. The result of the analysis of potential slope stability is that the slope in pit 2 (two) is safe or stable because the SMR value is 78 and the safety factor value is 2,458.

SLOPE STABILITY TECHNICAL STUDY USING SLOPE MASS RATING (SMR) METHOD AT PT. KARYA SUMBER ALAM PERKASA, SANGGAU REGENCY, KALIMANTAN BARAT

Soil (topsoil and overburden) above the granite quarry in pit 2 (two) PT. Karya Sumber Alam Perkasa has experienced a landslide. It is probably caused by the condition of pit 2 (two) slopes at PT. Karya Sumber Alam Perkasa, which is currently being mined, is quite steep. External factors that can trigger the movement of rock masses are vibrations due to breakers. This condition has the potential to increase the risk of slope stability. Slope stability is influenced by geological conditions, joints, slope geometry, water conditions below the soil surface, physical and mechanical properties, and vibrations due to blasting and mechanical equipment. Therefore, it is necessary to conduct a technical study of slope stability. The research aims to study rock mass class, potential type of landslide, and potential slope stability. The technical study of slope stability uses the Slope Mass Rating (SMR) method. Data processing using software Rocscience Dips 7.016. Analysis of potential types of landslides based on stereographic projections. The result of the RMR calculation is 78, so the rock mass class is number II, which is included in the excellent category. The results analysis of the potential for the type of failure indicates t tends to lead to the toppling failure, but after the study, there is no failure because it does not meet the landslide requirements. The result of the analysis of potential slope stability is that the slope in pit 2 (two) is safe or stable because the SMR value is 78 and the safety factor value is 2,458.

A comprehensive investigation of engineering geological characteristics of interlayer shear weakness zones embedded within Baihetan hydropower station

The interlayer shear weakness zones (ISWZs), which are a kind of large-scale infilled discontinuity, are frequently considered the most hazardous potential slip surface in the rock masses. Based on laboratory and field investigations, the engineering characteristics of ISWZs (i.e., genesis, fabric, structure, mineral composition, water-physical properties, shear strength properties, and engineering classification) embedded in and around the Baihetan hydropower station area are systematically examined.The results of the laboratory and field show that ISWZs have complex occurrence features, undulating and spatial inconsistency in thickness, and variation in mineral composition, fabrics, and structures. Moreover, based on variabilities in various features and extend, ISWZs are categorized into single-layer structures (Type-A) and multilayer structures (Type-B). An engineering geological classification approach for large-scale ISWZs is developed based on the two essential index such as clay proportion and infilled ratio. This classification method not only involves the influence of the undulating state of ISWZs on their shear properties but also considers the physical and mechanical properties of weak interlayer materials. The results of this investigation contribute to a proper understanding of mechanical properties and rock mass classification, especially for large-scale ISWZs.

Load-bearing Behavior of Offshore Rock Socketed Monopile Foundation Regarding Different Rock Mass Classification

With the increasing electricity demand in China, wind power has been heavily developed in recent years. It is important to stabilize the wind turbine foundations in rock bedded near the sea area while installation. Based on different rock classification standards (GB 50218 and GSI), this paper numerically analyzed the load capacity of rock socketed monopile. When the rock class is high (class III and above), under effective socketed depth, the rock-socket effect is important, and the pile tip deflection is nearly 0, which could be considered as a clamping constraint. In this case, even if the rock quality around the pile tip decreases a little or becomes a little weakened, the pile deformation and internal force will not change a lot. However, when the rock mass class is lower than IV, the pile tip load capacity will largely decrease. The definition of rock mass parameters is also important when analyzing rock socketed monopile. In conclusion, it is suggested to take GB 50218 as a reference. BQ engineering rock mass classification and its corresponding rock mass parameters could be applied. Also, the M-C model is suggested to be used for some related work.

A comparison of slope stability assessment techniques using different rock mass classification systems and finite element method (FEM): A case study from the Garhwal Himalayas, India

A comparison of slope stability assessment techniques using different rock mass classification systems and finite element method (FEM): A case study from the Garhwal Himalayas, India

Modified RMR Rock Mass Classification System for Preliminary Selection of Potential Sites of High-Level Radioactive Waste Disposal Engineering

This paper proposed a modified Rock Mass Rating (RMR) system, the RMRHLW system, for evaluating the rock quality of High-level Radioactive Waste (HLW) geological disposal engineering. Some salient factors, including the weakening of groundwater and temperature on the uniaxial compressive strength, the continuity of index values, the geostress, the rock permeability, and the groundwater chemical properties, were further incorporated based on the widely used RMR system. The proposed RMRHLW system was then verified by the case study of selection of nine candidate sites for HLW disposal engineering in China. The results indicated that the rock quality of the Xinchang site was the best and ranked as the most appropriate site, while the Jiujing site ranked the worst. Compared with the traditional RMR system, the proposed RMRHLW system can further consider crucial factors related to the long-term safety of HLW disposal and better reflect the differences between the potential sites. It can facilitate engineers to preliminarily evaluate the rock quality of the potential sites for High-level Radioactive Waste geological disposal engineering.

Prediction of geology condition for slurry pressure balanced shield tunnel with super-large diameter by machine learning algorithms

Real-time and precise prediction of geological conditions is extremely beneficial to the safe and efficient construction of slurry pressure balanced shield machines (SPBMs), especially for super-large diameter tunnels. Machine learning algorithms provide an effective way to predict geological conditions and have been successful in hard-rock tunnel boring machine (hard-rock TBM) tunnels or earth pressure balance shield machine (EPBM) tunnels. However, the effectiveness of machine learning in predicting geological conditions for super-large diameter SPBM tunnels is still unknown. This study systematically demonstrated the application of machine learning algorithms to the prediction of geological conditions in super-large diameter SPBM tunnels based on field data from the Heyan Road crossing river tunnel. The relationship between SPBM parameters and geological conditions was first evaluated, and subsequently, an adaptive model was proposed to determine the number of input variables. The performance of three algorithms, random forest (RF), AdaBoost, and support vector machine (SVM), in rock mass classification, and seven algorithms, multi-objective random forest (MORF), single-target-RF, regressor chain-RF, single-target-AdaBoost, regressor chain-AdaBoost, single-target-SVM, and regressor chain-SVM, in formation percentage prediction, were compared. The results showed that machine learning algorithms can effectively predict the geological conditions in super-large diameter SPBM tunnels. Specifically, RF had the best performance in rock classification compared with AdaBoost and SVM. MORF outperforms the other six algorithms in terms of formation percentage prediction. Additionally, sensitivity analysis indicates that the newly proposed parameters, including slurry system parameters and cutter type, have a clear positive effect on the performance of geological condition prediction.

Why Engineers Should Not Attempt to Quantify GSI

In the past decade, there has been an increasing trend of digitalizing rock engineering processes. However, this process has not been accompanied by a critical analysis of the very same empirical methods that many complex numerical and digital methods are founded upon. As engineers, we are taught to use and trust numbers. Indeed, we would not be able to define the factor of the safety of a structure without numbers. However, what happens when those numbers are nothing but numerical descriptions of qualitative assessments? In this paper we present a critical review of the many attempts presented in the literature to quantify GSI (geological strength index). To the authors’ knowledge, this paper represents the first time that all the different GSI tables and quantification methods that have been proposed over the past two decades are collated and compared critically. In our critique, we argue against the paradigm whereby the quantification process adds the experience factor for inexperienced engineers. Furthermore, we discuss the limitations of the notion that GSI quantification methods could transform subjectivity into objectivity since the parameters under considerations are not quantitative measurements. Relying on empirically defined quantitative equivalences raises important questions, particularly when these quantitative equivalences are being used to define so-called accurate rock mass classification input for design purposes.

Mixture distribution model for three-dimensional geometric attributes of multiple discontinuity sets based on trace data of rock mass

The geometric attributes of discontinuities are critical to an accurate discrete fracture network (DFN) model of rock mass. It is difficult to estimate three-dimensional (3D) geometric parameters of multiple groups of discontinuities by observation data. The study proposes a mixture distribution model for the 3D geometric attributes of multiple discontinuity sets. The method of estimating the mixture distributions of 3D geometric attributes of all discontinuity sets from the two-dimensional (2D) trace data in a sampling window is established and modified, including discontinuity diameter distribution estimation, volume density estimation, orientation distribution estimation, and distribution mixing. Discontinuities are assumed to be thin disks uniformly distributed in space, and their roughness and aperture are ignored. Discontinuity diameter and orientation follow lognormal distribution and bivariate normal distribution, respectively. Orientation distributions defined on the definitional domain of the geological coordinate system are derived to represent the real frequency distributions of orientation measurements in 3D rock mass space. The mixture distribution model is verified by using Monte Carlo method to generate DFNs with different volume densities, and distribution parameters of orientation and diameter. The maximum error of volume density is <0.5 m−3. The estimated distributions of diameter and orientation are in good agreement with the true distributions, while there are limited symmetry estimation errors of the discontinuity sets with orientation samples covering both sides of the 0° or 180° polar axis. The model is applied to Sejilashan tunnel, and the result indicates that the surrounding rock of two excavation faces have a high probability to be rated as the V classification according to the engineering classification of rock mass in China, which is in good agreement with the reality according to the geological survey and field observation.

Application of the NATM Methodology for the Excavation of Rail Tunnel in Difficult Geological Conditions: A Case from Garhwal Himalaya, Uttarakhand

Abstract The documentation of excavation method and support design based on rock mass classification systems i.e. rock mass rating (RMR), Q-system and New Austrian tunneling method (NATM) for adit-7 tunnel being constructed in Garhwal Himalaya, India is discussed in this paper. The New Austrian tunneling method classes of rock units have been developed by using correlations with the RMR and Q systems, according to the ONORM B 2203. NATM principles were used because the geological conditions were continually changing. The study indicated that the RMR-based rock mass estimation was overstated, but the qualitative assessment was right. The NATM technique is more adaptable for Garhwal Himalayan rocks having various uncertainties in rock mass evaluation. The current adit investigations indicate that there are numerous unanswered concerns, concerning rock mass quality evaluation, tunnel behavior during construction and usability. Results of the analysis are considered to be useful for the design of the new tunnels constructed in the similar type of the terrain.

Obtaining initial data for forecast engineering geological model construction

Objective and relevance. Technologies in mining and geology are intensely developing making the present research particularly relevant. The research considers the problems of obtaining reliable and high-quality data on the degree and nature of rock mass fracturing in a solid mineral deposit. These are fundamental data required to construct a forecast engineering geological model of a deposit. The engineering geological model is usually based on a structural geological model with the addition of various geomechanical parameters used in generally accepted international classifications for rock stability analysis, in particular, RMR (Bieniawski), MRMR (Laubscher), and Q-system (Barton). Methods of research. The authors describe the procedure for obtaining classification geomechanical parameters of a rock mass according to the data from oriented and non-oriented core drilling of special engineering geological (geomechanical) boreholes. Research results. The main factors and conditions for reliable data acquisition are given. Among the most important ones are: economic feasibility and validity of geomechanical boreholes drilling as well as their number; features of the geological and structural composition of a deposit as a condition for borehole location selection; proper organization of the drilling process aimed at obtaining high-quality core material; characteristics of geomechanical description of the core, depending on the rating system of rock mass classification applied. Scope of results. By way of example, deposits with different geological and structural conditions are listed where the described procedure was applied. High-quality and reliable information about the structural and tectonic features of the rock mass allows to create and fill the engineering geological model with data and solve the problems of stability analysis for almost any area of the future mine working.