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Review of predictive capabilities of JRC-JCS model in engineering practice

Authors:
  • Nick Barton & Associates

Abstract

The database used in developing the Barton-Bandis joint model is reviewed. It is shown how tilt testing to obtain JRC is extrapolated both in terms of stress and sample size. Field measurement of JRC is demonstrated, and relationships with Jr in the Q-system are developed. Constitutive modelling of shear stress-displacement, dilation and shear reversal are also described.
... Following Amadei (1996), Amadei and Stephansson (1997), Zang and Stephansson (2010), and Basnet and Panthi a Measurement of JRC 0 using a 100 mm profiler comb and based on Barton and Bandis (1990) b Measurement of JCS 0 using a Schmidt L-hammer and based on ISRM (1978) and Barton and Bandis (1990) Joint set Dipdir / dip ( (2019), both the magnitude and the orientation of horizontal stresses can be influenced by the rock mass structure, the geology, the degree of jointing, and the topography. Considering that the main direction of the regional lineaments in the area of the project are oriented NNW-SSE, NNE-SSW and E-W directions ( Fig. 2b), some degree of rotation may be expected in H to likely align from its tectonic NW-SE orientation to that of the more pervasive NNW-SSE structures. ...
... Following Amadei (1996), Amadei and Stephansson (1997), Zang and Stephansson (2010), and Basnet and Panthi a Measurement of JRC 0 using a 100 mm profiler comb and based on Barton and Bandis (1990) b Measurement of JCS 0 using a Schmidt L-hammer and based on ISRM (1978) and Barton and Bandis (1990) Joint set Dipdir / dip ( (2019), both the magnitude and the orientation of horizontal stresses can be influenced by the rock mass structure, the geology, the degree of jointing, and the topography. Considering that the main direction of the regional lineaments in the area of the project are oriented NNW-SSE, NNE-SSW and E-W directions ( Fig. 2b), some degree of rotation may be expected in H to likely align from its tectonic NW-SE orientation to that of the more pervasive NNW-SSE structures. ...
... The rock material was modelled with the Generalized Hoek-Brown failure criterion (Hoek et al. 2002) and an elasto-plastic material function. Rock joints were modelled with the non-linear Barton-Bandis criterion (Barton and Bandis 1990). The modelling with such combination of material and joint constitutive laws is deemed to be representative of the studied in-situ rock mass conditions with hard and jointed rock exposed to low rock overburden. ...
Article
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Engineering rock mass classifications are used to describe rock masses and to assist in the design of rock support in hard rock tunneling. In most of the encountered geological- and rock mechanical conditions, from hard and competent rock to poor and fractured rock masses, the application of classification systems has normally resulted in successful and economic designs. However, complex ground conditions as these derived from tunneling in low rock overburden pose several challenges to rock mass classification and support design. In the present study, an analysis of the ground behavior and tunnel stability in a portion with very low rock overburden during the construction of the Hestnes railway tunnel (Norway) was conducted to investigate the performance of the current classification practice for tunnel rock support design. The results have revealed several challenges, which are related to conservative rock mass and rock support assessments due to the lack of consideration of the important stabilizing effect that rock arching has on tunnel stability. It was also found that with the application of an integrated methodology able to combine classification methods with numerical simulations and detailed information of the ground properties and behavior, more optimal designs in the form of rock reinforcement with bolts and shotcrete can be achieved when rock mass quality Q < 1. On this basis, a set of design recommendations was developed for the integration of classification systems with more elaborated engineering design analyses to provide guidance in design optimization for hard rock tunnels subject to low overburden.
... For each scenario, support measures, such as rock bolting, were applied to ensure stability, aiming for a factor of safety (F.S.) greater than 1.5. The Barton and Bandis failure criterion [23] was used to evaluate the shear strength of the discontinuities, considering both mechanical and geometric characteristics (JRC, JCS, φ), with safety factors calculated according to Eurocode 7 (EC-7) standards. After the assessments conducted within the VR system, data from the 3D models were exported for numerical stability analysis using Rocscience software, including Unwedge and RS2. ...
... For each scenario, support measures, such as rock bolting, were applied to ensure stability, aiming for a factor of safety (F.S.) greater than 1.5. The Barton and Bandis failure criterion [23] Once the wedge stability analysis was completed, a 2D finite element modeling (FEM) analysis was conducted using RS2 v11 software from Rocscience Inc. to further assess the stability of critical sections in the Nymphs' and Pan's quarries, particularly in areas showing potential roof collapse or pillar failure (Figures 25-27). Four cycles of FEM analysis were carried out on sections exhibiting significant instability. ...
Article
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Underground monument preservation is tightly linked to geological risk. The geological risk management of underground structures typically relies on a preliminary site investigation phase. Engineering geological mapping—as a key site investigation element—is largely based on manual in situ work, often in harsh and dangerous environments. However, although new technologies can, in many cases, decrease the on-field time as well as eliminate inaccessibility issues, the example presented in this study demonstrates a special challenge that had to be addressed. The ancient underground marble quarries of Paros Island in Greece constitute a gallery complex of a total length of 7 km and only two portals, resulting in total darkness throughout almost the full length of the unsurveyed galleries. As such, the entire survey and engineering geological mapping solely relied on a virtual reality application that was developed based on a digital replica of the quarries using laser scanning. The study identifies several critical locations with potentially unstable geologic structures and computes their geometrical properties. Further numerical analyses based on data extracted directly from the digital replica of the rock mass led to the definition of appropriate risk mitigation measures along the underground marble quarries.
... Barton-Badis Strength Criterion is used for the analysis. The model incorporates key parameters from the Barton-Badis Strength Criterion, including joint wall compressive strength (JCS), joint roughness coefficient (JRC), and joint friction angle [22]. The values of JRC range from 8 to 10 which is measured from the roughness profiles corresponding to the joint surface as given by Barton and Choubey [23]. ...
Article
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Geological and geotechnical evaluation for the 7–9 m diameter and 100 m length, 10 numbers of parallel draft tube tunnels were carried out. The draft tubes are constructed to connect the underground pump house and surge pool for lifting the water. Due to adverse geological conditions and the complex geometry of the structure, a sequential excavation method and controlled blasting were adopted, which minimized the risk of instability during the excavation of the draft tubes. To classify the rock masses and recommendation of support, detailed engineering geological investigations were done. The rocks encountered during the excavation of these tunnels are granites/granitic gneiss which are traversed by mafic dykes of Dharwar Craton. Prominent three to four joint sets were recorded during geological mapping and rock mass shows W-I to W-II weathering grade. For the determination of principal stresses, an in-situ hydrofracturing test was conducted in the borehole. Q-values were determined based on the rock joints and their characteristics, 3D mapping of geological units and stress measurement conducted inside the borehole. The Q-system provides a quantitative assessment of rock mass stability in jointed rock for underground tunnel design and construction. Good stability is indicated by high Q-values, while poor stability is shown by low values. Based on the “Q” system, the entire lengths of the tunnels were characterised as poor to fair rock mass categories. Wedge analysis was conducted along the tunnel alignments using RocScience Unwedge software and accordingly, stability was checked. Engineering geological investigations identified potential geotechnical issues, and corresponding engineering solutions were recommended. A support system was designed based on the Q-system and site-specific geological conditions.
... O programa permite o dimensionamento dos espaçamentos de chumbadores em função da resistência e deformabilidade da tela, para que os fatores de segurança desejados sejam atendidos. O software adota o critério de ruptura de juntas deBarton-Bandis (Barton & Bandis, 1990) e permite a caracterização específica das fraturas críticas por meio do ângulo de mergulho, coeficiente de rugosidade de junta e resistência à compressão da parede da junta. ...
Conference Paper
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... Para complementar el análisis anterior, la definición de la presión de rotura admisible de cada una de las bases ha sido identificada en función de la disposición del sistema de discontinuidades menos favorable en el sitio de emplazamiento. En tal condición, el modelo de análisis aplicado, se base en el esquema indicado en la Figura 12. Dentro de este modelo la resistencia última al deslizamiento () en el plano de disconti nuidad ha sido valorada según el modelo de Barton y Bandis (1982, 1990, indicado en la ecuación (2). La misma depende de la presión normal sobre el plano de deslizamiento ( n ), del ángulo de fricción de base de los bloques en contacto ( b ), y de los pa rámetros de ondulación de la superficie (JRC) y de resistencia a compresión simple de la junta (JCS). ...
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Chapter
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Technical research from the National Institute for Occupational Safety and Health (DHHS (NIOSH) Publication No. 2015-107) about Shotcrete Design and Installation Compliance Testing: Early Strength, Load Capacity, Toughness, Adhesion Strength, and Applied Quality.
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