scholarly journals Empirical Support Design for Proposed Diversion Tunnels at Dasu Dam Site Pakistan

2021 ◽  
Vol 64 (2) ◽  
pp. 131-136
Author(s):  
Muhammad Bilal ◽  
Muhammad Zaka Emad ◽  
Fawad Ul Hassan ◽  
Zaheer Ahmed
Keyword(s):  
Rock Mass ◽  
Support System ◽  
Research Work ◽  
Empirical Support ◽  
Left Bank ◽  
Hydroelectric Power ◽  
Support Design ◽  
Tunnel Support ◽  
Dam Site ◽  
Q Index

  This research work presents the rock mass characteristics and tunnel support system recommendations for hydroelectric power tunnels at Dasu dam site Pakistan. Two inverted U-shaped tunnels are proposed at the left bank of Indus river. The tunnels have inlet portals at an elevation of 773.00 m and outlet portals at an elevation of 758.00 m. The thickness of rock cover above the tunnels is between 100 and 200 m. Three types of rock are encountered at project site including Granulite, Amphibolite and Gabbronorite. Granulite rocks are encountered along the alignment of tunnels. Rock mass is classified using Rock mass rating (RMR) and Tunneling quality index (Q system). Support system is suggested based on values of Q and RMR. Correlation between Q-index and RMR is also derived.    

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 Support System for Tunnelling in Squeezing Ground of Qingling-Daba Mountainous Area: A Case Study from Soft Rock Tunnels

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Xiuling Wang ◽  
Jinxing Lai ◽  
Rodney Sheldon Garnes ◽  
Yanbin Luo
Keyword(s):  
Support System ◽  
Strong Support ◽  
Mountainous Area ◽  
Squeezing Ground ◽  
Tunnel Face ◽  
Support Design ◽  
Tunnel Support ◽  
Geological Conditions ◽  
Rock Tunnels

Tunnelling or undertaking below-ground construction in squeezing ground can always present many engineering surprises, in which this complicated geology bring a series of tunnelling difficulties. Obviously, if the major affecting factors and mechanism of the structure damage in these complicated geological conditions are determined accurately, fewer problems will be faced during the tunnel excavation. For this study, reference is made to four tunnel cases located in the Qingling-Daba mountainous squeezing area that are dominated by a strong tectonic uplift and diversified geological structures. This paper establishes a strong support system suitable for a squeezing tunnel for the purpose of addressing problems exhibited in the extreme deformation of rock mass, structure crack, or even failure during excavation phase. This support system contains a number of temporary support measures used for ensuring the stability of tunnel face during tunnelling. The final support system was constructed, including some key techniques such as the employment of the foot reinforcement bolt (FRB), an overall strong support measure, and more reserved deformation. Results in this case study showed significant effectiveness of the support systems along with a safe and efficient construction process. The tunnel support system proposed in this paper can be helpful to support design and provide sufficient support and arrangement before tunnel construction in squeezing ground.

scholarly journals Analysis of Support Design in Weak Rock Drift Using a Systematic Approach

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Xingdong Zhao ◽  
Shujing Zhang ◽  
Huaibin Li ◽  
Guoju Chen ◽  
Pengqiang Zhang
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Rock Mechanics ◽  
Support System ◽  
Systematic Approach ◽  
Wire Mesh ◽  
Weak Rock ◽  
Support Design ◽  
Cable Bolt ◽  
Q System

The aim of this study is to develop a systematic approach for support design of weak rock drift based on empirical, analytical, and numerical method, which is employed to estimate weak rock support demand and design support system. Detailed engineering geological investigations and rock mechanics test have been carried out in weak rock drift. The Q-system and GSI-system were used to determine the primary support design and rock mass properties, respectively. The numerical model of RS2 finite element program has been calibrated by analyzing the relation of falling height observed in the field to the frictional angles obtained from empirical method, rock mechanics test, and calculated rock mass parameters, respectively. In an attempt to check the validity of sophisticated support, support suggested by Q-system, and the combination support system proposed by analytical approach, the RS2 program was employed to analyze the depth of plastic zone and total displacement surrounding the weak rock drift. Numerical results show that the depths of plastic zone and total deformation surrounding the weak rock drift supported by the combination support system significantly descended 87% and 90% of those of sophisticated support. In particular, the rock bolt and cable bolt provide enough frictional and interlocked forces to resist weak rock falling which change the weak rock mechanicals properties and the surface holding function reinforced by the shotcrete, wire mesh, and steel strap. The factor of safety (FOS) of 8.28 of the combination support system is much more than the FOS of 1.5 for permanent drift. The combination support system with rock bolts, cable bolt, shotcrete, wire mesh, and steel straps has been applied to stabilize the weak rock drift and found to be successful to prevent further deformations surrounding the drift.

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.

Blast Induced Damage Due to Repeated Vibrations in Jointed Gneiss Rock Formation

2010 ◽  
Vol 1 (1) ◽  
pp. 110-134 ◽  
Author(s):  
M. Ramulu ◽  
T. G. Sitharam
Keyword(s):  
Rock Mass ◽  
Dynamic Loading ◽  
Seismic Waves ◽  
Damage Zone ◽  
Research Work ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Rock Blasting ◽  
Hydroelectric Power ◽  
Blast Vibrations

Blasting is the most common method of rock excavation technique in mining and civil construction and infrastructure projects. Rock blasting produces seismic waves similar to those produced by earthquakes, but with relatively high frequency and low amplitude. General blast induced damage was extensively studied by researchers globally, but the studies on damage due to repeated blast vibrations is not yet reported, quantitatively, on underground openings. This paper deals with the research work carried on the effect of repeated dynamic loading imparted on the jointed rock mass from subsequent blasts in the vicinity, on the jointed rock mass at Lohari Nag Pala Hydroelectric Power Construction Project. The blast induced damage was monitored by borehole extensometers, borehole camera inspection surveys and triaxial geophones installed at three test sites of different joint orientations at the Main Access Tunnel of power house. The study reveals that there was extra damage of 60%, exclusively due to repeated blast vibrations. The results of the study indicate that repeated dynamic loading, resulted in damage even at 33% of the conventional damage threshold vibrations (Vc) in case of favorable joint orientations and 23% of Vc in case of unfavorable joints. The paper concludes in quantification of effect of repeated blast loading and the orientation of joints on the extension of damage zone in jointed rock mass of underground excavations.

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 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 mapping for empirical design evaluation of Tunnel 10 of Jakarta - Bandung high-speed railway, Indonesia

2021 ◽  
Vol 325 ◽  
pp. 01006
Author(s):  
Hanifah Hilda Herdiana ◽  
I Gde Budi Indrawan ◽  
Hendy Setiawan
Keyword(s):  
Rock Mass ◽  
Support System ◽  
High Speed ◽  
Geological Mapping ◽  
Construction Site ◽  
Engineering Geological Mapping ◽  
High Speed Railway ◽  
Tunnel Support ◽  
Geological Conditions ◽  
Empirical Design

An engineering geological mapping was carried out at the construction site of the Tunnel 10 of Jakarta Bandung High-Speed Railway to obtain data and information of the engineering geological conditions, particularly the rock masses. This research aims to determine the rock mass classes at the tunnel construction site and recommend the tunnel support system based on the Rock Mass Rating (RMR) and the Japan Society of Civil Engineers (JSCE) systems. This research is expected to better understand the rock mass classes, which were previously determined based on the newly applied Basic Quality (BQ) system for the tunnel support empirical design. The results showed that the research area consisted of young volcanic products, namely moderate to highly weathered tuff breccia and andesitic breccia. The uniaxial Compressive Strength (UCS) of rock mass varies between 1-25 MPa. The RMR value ranges from 21 to 40, indicating disintegrated and poor rock mass quality. The proposed tunnel support system is the combination of shotcrete, steel support for top heading and bench support, arch sidewall, and invert concrete.

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