Maintaining geological reality in application of GSI for design of engineering structures in rock

Marinos, V.; Carter, Trevor G.

doi:10.1016/j.enggeo.2018.03.022

Cited by 67 publications

(17 citation statements)

References 14 publications

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“…In areas where rockmasses are particularly heterogeneous with multiple layers or zones of materials that exhibit distinct mechanical properties, successful variations of GSI to address these types of rockmass structure have been developed on a case by case basis. Examples of heterogeneous rockmasses for which GSI has been modified include tectonically disturbed interbedded sediments (Marinos and Hoek 2001;Marinos 2019), transition zones between fresh granite to residual soils (Babendererde et al 2004), ophiolite complexes with serpentinization (Marinos et al 2006), and other variability arising from tectonism, weathering, and alteration (Marinos and Carter 2018). This demonstrates the flexibility of GSI and supports the introduction of modifications to GSI for application to hydrothermally altered rockmasses with stockwork veins and other healed rockmass structures that are presented in this study.…”

Section: Applications Of Gsi To Heterogeneous Rockmassessupporting

confidence: 53%

Composite Geological Strength Index Approach with Application to Hydrothermal Vein Networks and Other Intrablock Structures in Complex Rockmasses

2019

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Conventional rockmass characterization and analysis methods for geotechnical assessment in mining, civil tunnelling, and other excavations consider only the intact rock properties and the discrete fractures that are present and form blocks within rockmasses. As modern underground excavations go deeper and enter into more high stress environments with complex excavation geometries and associated stress paths, healed structures within initially intact rock blocks such as hydrothermal veins, veinlets and stockwork (termed intrablock structures) are having an increasing influence on rockmass behaviour and should be included in modern geotechnical engineering design. Field observations indicate the conventional Geological Strength Index (GSI) does not accurately estimate rockmass strength and behaviour of complex rockmasses. A modified GSI chart to include intrablock structures and a new Composite Geological Strength Index (CGSI) methodology to combine multiple suites of rockmass structure using a weighted harmonic average are presented as tools to evaluate complex rockmasses that contain multiple suites of structure for application to geomechanical numerical models. CGSI is introduced and numerically validated using implicit and explicit finite element method numerical simulations of an underground excavation and a case study of field observations in an adit at the El Teniente mine in Chile. In both cases, the CGSI approach using the modified GSI chart results in an improved estimate of rockmass behaviour in implicit equivalent continuum numerical models when compared to a conventional GSI approach. Keywords Rockmass characterization Á Complex rockmasses Á Healed intrablock structures Á Geological Strength Index Á Finite element method numerical models Á Composite Geological Strength Index

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Section: Applications Of Gsi To Heterogeneous Rockmassessupporting

confidence: 53%

Composite Geological Strength Index Approach with Application to Hydrothermal Vein Networks and Other Intrablock Structures in Complex Rockmasses

2019

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“…Based on the H-B criterion, a series of estimation results of MPs corresponding to the IPs in the fluctuation ranges are obtainable, and then the sensitivity analyses of MPs to IPs can be carried out. e sensitivity function (S) and sensitivity factor (s i ) [22] used to describe the sensitivity relationships between IPs, MPs, and the predicted results of displacement and EDZ are defined as in (6) and (7)). To illustrate the physical meaning of s i , (7) is transformed into the expression, as shown in (8).…”

Section: Sensitivity Of the Mps Estimated By The H-b Criterion To Thementioning

confidence: 99%

“…Many methods have been proposed to solve the aforementioned difficulties. e method of converting rock parameters obtained by laboratory tests into engineering rock mass parameters, based on a rock mass classification system, has been increasingly recognized by specialists in the geotechnical engineering [6][7][8][9]. is method fully considers the integrated influence of joints and fissures in rock mass, groundwater, and size effects.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity Analysis in the Estimation of Mechanical Parameters of Engineering Rock Mass Based on the Hoek–Brown Criterion

Liu

Duan

et al. 2020

Mathematical Problems in Engineering

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Geological strength index GSI, disturbance factor (D), material constant mi, and uniaxial compressive strength σci of the intact rock are essential input parameters IPs of the Hoek–Brown H−B criterion. Mechanical parameters MPs of the engineering rock mass, including elastic modulus E, cohesion c, and internal friction angle φ estimated by the H–B criterion, and the predicted excavation response of surrounding rock, including the displacement and excavation damage zone EDZ based on the MPs, are of high relevance with the four IPs of the H–B criterion. In this paper, the deep and huge underground cavern excavated in basalt from a hydropower station under construction in the southwest of China is used to analyse the sensitivity of the IPs on the MPs, the displacement, and EDZ of the surrounding rock mass. Firstly, the H–B criterion is applied to estimate the MPs, among which the IPs are obtained from a series of in situ and laboratory tests, including borehole camera observation, wave velocity test, uniaxial and triaxial compression tests, and so on. Secondly, the sensitivity relationships between IPs, MPs, and prediction results of displacement and EDZ are established and described quantitatively by the sensitivity factor (si). Results show that the MPs of the rock mass are more sensitive to GSI and D⋅GSI and σci are high-sensitivity parameters affecting the displacement and EDZ. Finally, the variations in the estimated MPs and associated prediction results concerning excavation response, which are caused by the uncertainties in the determination of the IPs, are further quantified. This study provides a straightforward assessment for the variability of the rock mass parameters estimated by the H–B criterion. It also gives a valuable reference to similar geotechnical engineering for the determination of rock mass parameters in the preliminary design.

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“…clearly characterised favoured failure surface or discontinuities. The appropriate use of rock mass characterisation systems, notably the GSI (for details, see [14,24]), allowed the quantification of difficult ground for the evaluation of the geotechnical properties and the selection of the design parameters. An extension of the original GSI application charts for heterogeneous and structurally complex rock masses, such as flysch, was initially introduced by Marinos and Hoek [10] and recently updated and extended by Marinos [11].…”

Section: Introductionmentioning

confidence: 99%

“…An extension of the original GSI application charts for heterogeneous and structurally complex rock masses, such as flysch, was initially introduced by Marinos and Hoek [10] and recently updated and extended by Marinos [11]. Specific GSI charts for molassic formations [12], ophiolites [13], gneiss in its disturbed form [14,15] and particular cases of limestones [15] and under particularly difficult geological conditions have been developed from experience gained during excavation of 62 tunnels as part of the Egnatia project in Northern Greece, along Alpine mountain belts.…”

Section: Introductionmentioning

confidence: 99%

Engineering Geology and Tunnels

Marinos¹

2020

Tunnel Engineering - Selected Topics

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Currently, knowledge and understanding of the role of geological material and its implication in tunnel design is reinforced with advances in site investigation methods, the development of geotechnical classification systems and the consequent quantification of rock masses. However, the contribution of engineering geological information in tunnelling cannot be simply presented solely by a rock mass classification value. What is presented in this chapter is that the first step is not to start performing numerous calculations but to define the potential failure mechanisms. After defining the failure mechanism that is most critical, selection of the suitable design parameters is undertaken. This is then followed by the analysis and performance of the temporary support system based on a more realistic model. The specific failure mechanism is controlled and contained by the support system. A tunnel engineer must early assess all the critical engineering geological characteristics of the rock mass and the relevant mode of failure, for the specific factors of influence, and then decide either he or she will rely on a rock mass classification value to characterise all the site-specific conditions. Experiences from the tunnel behaviour of rock masses in different geological environments in Alpine mountain ridges are presented in this chapter.

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Maintaining geological reality in application of GSI for design of engineering structures in rock

Cited by 67 publications

References 14 publications

Composite Geological Strength Index Approach with Application to Hydrothermal Vein Networks and Other Intrablock Structures in Complex Rockmasses

Composite Geological Strength Index Approach with Application to Hydrothermal Vein Networks and Other Intrablock Structures in Complex Rockmasses

Sensitivity Analysis in the Estimation of Mechanical Parameters of Engineering Rock Mass Based on the Hoek–Brown Criterion

Engineering Geology and Tunnels

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