scholarly journals Empirical Evaluation of Rock Mass Rating and Tunneling Quality Index System for Tunnel Support Design

2018 ◽  
Vol 8 (5) ◽  
pp. 782 ◽  
Author(s):  
Hafeezur Rehman ◽  
Abdul Naji ◽  
Jung-joo Kim ◽  
Han-Kyu Yoo
Keyword(s):  
Rock Mass ◽  
Index System ◽  
Quality Index ◽  
Empirical Evaluation ◽  
Rock Mass Rating ◽  
Support Design ◽  
Tunnel Support

scholarly journals Weightage Effect during Back-Calculation of Rock-Mass Quality from the Installed Tunnel Support in Rock-Mass Rating and Tunneling Quality Index System

2019 ◽  
Vol 9 (10) ◽  
pp. 2065 ◽  
Author(s):  
Jonguk Kim ◽  
Hafeezur Rehman ◽  
Wahid Ali ◽  
Abdul Muntaqim Naji ◽  
Hankyu Yoo
Keyword(s):  
Rock Mass ◽  
Quality Index ◽  
Rock Bolt ◽  
Rock Mass Rating ◽  
Rock Mass Quality ◽  
Back Calculation ◽  
The Difference ◽  
Bolt Spacing ◽  
Q System ◽  
Selection Of

In extensively used empirical rock-mass classification systems, the rock-mass rating (RMR) and tunneling quality index (Q) system, rock-mass quality, and tunnel span are used for the selection of rock bolt length and spacing and shotcrete thickness. In both systems, the rock bolt spacing and shotcrete thickness selection are based on the same principle, which is used for the back-calculation of the rock-mass quality. For back-calculation, there is no criterion for the selection of rock-bolt-spacing-based rock-mass quality weightage and shotcrete thickness along with tunnel-span-based rock-mass quality weightage. To determine this weightage effect during the back-calculation, five weightage cases are selected, explained through example, and applied using published data. In the RMR system, the weightage effect is expressed in terms of the difference between the calculated and back-calculated rock-mass quality in the two versions of RMR. In the Q system, the weightage effect is presented in plots of stress reduction factor versus relative block size. The results show that the weightage effect during back-calculation not only depends on the difference in rock-bolt-spacing-based rock-mass quality and shotcrete along with tunnel-span-based rock-mass quality, but also on their corresponding values.

scholarly journals Tunnel support design by comparison of empirical and finite element analysis of the Nahakki tunnel in mohmand agency, pakistan

2016 ◽  
Vol 38 (1) ◽  
pp. 75-84
Author(s):  
Asif Riaz ◽  
Syed Muhammad Jamil ◽  
Muhammad Asif ◽  
Kamran Akhtar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Rock Mass ◽  
Support Systems ◽  
Classification Systems ◽  
Geological Strength Index ◽  
Support Design ◽  
Element Analysis ◽  
Tunnel Support ◽  
Geological Conditions

Abstract The paper analyses the geological conditions of study area, rock mass strength parameters with suitable support structure propositions for the under construction Nahakki tunnel in Mohmand Agency. Geology of study area varies from mica schist to graphitic marble/phyllite to schist. The tunnel ground is classified and divided by the empisical classification systems like Rock mass rating (RMR), Q system (Q), and Geological strength index (GSI). Tunnel support measures are selected based on RMR and Q classification systems. Computer based finite element analysis (FEM) has given yet another dimension to design approach. FEM software Phase2 version 7.017 is used to calculate and compare deformations and stress concentrations around the tunnel, analyze interaction of support systems with excavated rock masses and verify and check the validity of empirically determined excavation and support systems.

scholarly journals Review of Rock-Mass Rating and Tunneling Quality Index Systems for Tunnel Design: Development, Refinement, Application and Limitation

2018 ◽  
Vol 8 (8) ◽  
pp. 1250 ◽  
Author(s):  
Hafeezur Rehman ◽  
Wahid Ali ◽  
Abdul Naji ◽  
Jung-joo Kim ◽  
Rini Abdullah ◽  
...  
Keyword(s):  
Rock Mass ◽  
Quality Index ◽  
Classification Systems ◽  
Design Tools ◽  
Rock Mass Rating ◽  
Rock Mass Properties ◽  
Rock Engineering ◽  
Mass Properties ◽  
Tunnel Design ◽  
Empirical Design

Although rock-mass rating (RMR) and tunneling quality index (Q) systems are used in different rock engineering projects as empirical design tools, their application in tunnel design is widely accepted as these systems were developed and updated for this purpose specifically. This paper reviews the work conducted by various researchers since the development of these two systems with respect to tunneling only. Compared to other empirical classification systems, these systems received international acceptance and are still used as empirical design tools in tunneling due to their continuous updates in the form of characterization and support. As the primary output of these systems is the initial support design for tunnel, however, their use in the calculation for rock-mass properties is an essential contribution of these systems in rock engineering design. Essential for the tunnel design, these rock-mass properties include the modulus of deformation, strength, Poisson’s ratio, Mohr-Coulomb parameters and Hoek-Brown constants. Other application for tunneling include the stand-up time and rock load. The uses and limitations of these systems as empirical tunnel design tools are also included in this review article for better results. Research to date indicates that if the ground behavior is also taken into account, the application of these empirical systems will be more beneficial to the preliminary design of tunnels.

scholarly journals Rock support in hydropower projects of Nepal: case studies

2006 ◽  
Vol 34 ◽  
pp. 29-38
Author(s):  
Subas Chandra Sunuwar
Keyword(s):  
Rock Mass ◽  
Large Diameter ◽  
Design Guidelines ◽  
Rock Mass Classification ◽  
Classification Systems ◽  
Rating Systems ◽  
Rock Support ◽  
Support Design ◽  
Tunnel Support ◽  
Mass Classification

The principal objective of rock support is to assist the rock mass to support itself. One common example is where the rock support system (e.g. rock bolts and shotcrete) actually becomes integrated with the rock mass. Rock support strengthens the rock mass surrounding an excavation by creating a reinforced zone, which maintains the integrity of the excavated surface, possesses sufficient flexibility to allow for the redistribution of stresses around the excavation, and has enough stiffness to minimise the dilation (opening) of discontinuities. Rock mass classification systems are used worldwide as a basis for tunnel support design. The Q and Rock Mass Rating systems have been extensively applied in rock support design on most of the hydropower projects in Nepal. Generic design guidelines based on rock mass classification systems cannot provide suitable rock support for every site. Therefore some modifications are necessary to suite the site-specific ground conditions including local rock mass and geological hazards. There are relatively few tunnels excavated in the tectonically active Nepal Himalaya. Large diameter tunnels in Nepal are commonly lined with concrete whereas recently smaller-diameter tunnels are either shotcrete-lined or left unsupported. "Leaky" lining has been used in most of the projects to avoid the heavy reinforcement needed to withstand the occasional very high external water pressures.

scholarly journals Engineering geological characteristics based on rock mass rating (RMR) and geological strength index (GSI) in Tunnel Number 1 of the Sigli-Aceh toll road

2021 ◽  
Vol 325 ◽  
pp. 01014
Author(s):  
Jabnes Satria ◽  
I Gde Budi Indrawan ◽  
Nugroho Imam Setiawan
Keyword(s):  
Rock Mass ◽  
Poor Quality ◽  
Geological Mapping ◽  
Geological Strength Index ◽  
Rock Mass Rating ◽  
Strength Index ◽  
Geological Investigation ◽  
Tunnel Support ◽  
Toll Road ◽  
Tunnel Number

This paper presents engineering geological investigation results in the form of rock mass characteristics for tunnel number 1 of the Sigli-Aceh toll road. The investigation was carried out through geological mapping, core drill evaluation, and laboratory tests. In this research, the rock mass rating (RMR) and Geological Strength Index (GSI) were applied for the rock mass classifications. The measurement of rock mass quality is then used to determine the excavation method and tunnel support system on the SigliAceh toll road. The results showed that the research location consisted of calcareous sandstone with poor to good-quality (GSI (21.7 - 85.5), RMR (32.0 - 67.6)), and sandstone with good quality (GSI (86.3 - 86.9), RMR (64.0 - 65.0)). The poor quality rock masses were mainly caused by weathering effect. In addition, this research also analyzes the relationship between RMR and GSI based on the type and quality of rocks in the research location so that this correlation can be used in other areas with similar rock type and quality to this research location.

scholarly journals Construction of a tunnel under thin rock overburden in Middle Marsyangdi Hydroelectric Project, Central Nepal

2004 ◽  
Vol 29 ◽  
Author(s):  
Kaustubh Mani Nepal
Keyword(s):  
Rock Mass ◽  
Support System ◽  
Deformation Monitoring ◽  
Actual Condition ◽  
Support Design ◽  
Tunnel Support ◽  
Hydroelectric Project ◽  
Central Nepal ◽  
Rock Overburden ◽  
Smooth Blasting

This paper deals with an application of New Australian Tunnelling Method (NATM) in low cover tunnelling in Lesser Himalaya of Nepal. The length of the tunnel is 365.8 m with a 8.2 m finished diameter. The average thickness of the rock overburden is 16- 18 m with a maximum of 30 m, whereas average side cover is 40 m. Top heading and multiple benching methods were applied for tunnelling work. The rational support design techniques were conceived together with Bieniawski's Support Guideline for each standard support classes. Standard initial support system was designed according to NATM, to provide complete stabilization of excavation. It consisted of a combination of systematic rock bolts and shotcrete.  The smooth blasting technique was adopted for the tunnel excavation. The specific charge was 1.39-1.47 kg/m3 A special emphasis was given in the collection of discontinuity data so that the rock mass could be evaluated effectively. Geomechanics classification for rock mass was used for the rock mass evaluation. The rock mass was also back evaluated by using Q and GSI classification on the basis of installed support. After the careful assessment of the data, the rock mass in the tunnel was classified into fair to poor according to RMR and Q and blocky / disturbed to very blocky / fair according to GSI. The rock mass parameters collected during the construction stage agree with the data collected at surface during feasibility and tendering stages. The rock mass classification based on the surface outcrop survey and drillings was a considerable success and found to be very close to the actual condition. The effectiveness of revised support system with steel rib was found to be negligible or minimum for tunnel support. Rock support deformation monitoring in the tunnel was regularly carried out to determine the efficiency and adequacy of the installed support.

scholarly journals Engineering Geological Characteristics Based on Rock Mass Rating (RMR) and Geological Strength Index (GSI) in Jlantah Dam Intake Tunnel, Karanganyar District, Central Java Province

2021 ◽  
Vol 325 ◽  
pp. 08003
Author(s):  
Doni Apriadi Putera ◽  
Heru Hendrayana ◽  
I Gde Budi Indrawan
Keyword(s):  
Rock Mass ◽  
Research Area ◽  
Geological Mapping ◽  
Geological Strength Index ◽  
Rock Mass Rating ◽  
Strength Index ◽  
Tunnel Support ◽  
Weak Rocks ◽  
Rock Mass Characterization ◽  
Central Java

This paper presents the results of a geological engineering investigation in the form of rock mass characterization at the Jlantah Dam Intake Tunnel. The study was carried out through technical geological mapping, core drill evaluation and supported by laboratory test data. The determination of rock mass classification at the research site has been carried out using the Rock Mass Rating (RMR) method, but it is necessary to use another method that is more suitable based on rock mass for weak rocks, namely using the Geological Strength Index (GSI) method.The rock mass quality will be used as a parameter in determining the excavation method and tunnel support system that will be used in the Jlantah Dam intake tunnel. The results showed that the research area consisted of lithology in volcanic breccias and tuff lapilli. GSI rock mass value at the research location ranged from 15 - 65, while the RMR value ranged from 24 - 70. The correlation between RMR and GSI in the study area is different when compared to Hoek and Brown (1997) but has similarities with Zhang et al (2019).

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