scholarly journals Probabilistic Approach for Assessing Rock Mass Quality in the Tunnel

2012 ◽  
Vol 11 ◽  
pp. 6-11
Author(s):  
Krishna Kanta Panthi
Keyword(s):  
Rock Mass ◽  
Heterogeneous Media ◽  
Probabilistic Approach ◽  
Cost Effective ◽  
Quality Data ◽  
Rock Mass Quality ◽  
Headrace Tunnel ◽  
Key Issues ◽  
Tunnel Alignment

Rock mass is a heterogeneous media and the quality of the rock mass may change within a very short distance. As a result, on many occasions considerable discrepancies (variations) have been found between the predicted and actual rock mass conditions along the tunnel alignment, resulting in signifi cant cost and time overruns. Finding innovative solutions for quantifying the quality of rock mass and assessing the risk of discrepancies are, therefore, key issues for cost effective and optimum tunneling solutions in the Himalayan region.In this paper, a probabilistic approach of uncertainty analysis has been proposed to evaluate the quality of rock mass based on the Q-system of rock mass classifi cation. Mapped rock mass quality data from the Modi headrace tunnel from Nepal have been used as a case study. The degree of correlation between the simulated results achieved by a probabilistic assessment using @Risk and values actually measured in the tunnel have been discussed. It is concluded that the probabilistic approach can be used as a tool in predicting rock mass quality and assessing risk in tunneling projects.DOI: http://dx.doi.org/10.3126/hn.v11i0.7154 Hydro Nepal Vol.11 2011 pp.6-11

scholarly journals Analysis of engineering geology conditions based on the quality of rock mass in the Tiga Dihaji Dam’s diversion tunnel, South Sumatera, Indonesia

2021 ◽  
Vol 325 ◽  
pp. 05001
Author(s):  
Zekrinaldi ◽  
Ferian Anggara ◽  
Hendy Setiawan
Keyword(s):  
Rock Mass ◽  
Geological Strength Index ◽  
Strength Index ◽  
Diversion Tunnel ◽  
Rock Mass Quality ◽  
Geological Conditions ◽  
Q System

This research has examined the rock mass quality case study in the Tiga Dihaji Dam’s diversion tunnel. Observations of geological conditions were carried out on the surface and subsurface of the study site and show that the study area consists of tuffaceous sandstone and carbonate interbeds. The method of this study is based on the classification of the Geological Strength Index (GSI), Rock Mass Rating (RMR), and the Q-system. The results indicate that tuffaceous sandstone has a GSI value of 15 - 87.5 (very poor - very good), RMR 48 - 82 (fair - very good), and Q-system 0.01 – 60.0 (exceptionally poor - very good). Meanwhile, carbonate interbeds have a low value, with a GSI value of 10.5 - 77.5 (very poor to very good), RMR 17.0 – 56.0 (very - poor fair), and Q-system 0 - 35.2 (exceptionally poor - good). Moreover, a correlation was made between rock mass quality for conditions in the study area. The correlation between GSI and RMR was obtained by the equation GSI = 2.2885RMR 82.567 (R2 = 0.6653), RMR and Q-system RMR = 2.0175ln(Q) + 63.061 (R2 = 0.4987), and GSI and Q-system GSI = 7.2119ln(Q) 54.578 (R2 = 0.8095).

scholarly journals The Use of Self Supporting Capacity of Rock Mass for Sustainable Hydropower: An Analysis of the Middle Marsyangdi Headrace Tunnel, Nepal

1970 ◽  
Vol 6 ◽  
pp. 18-26
Author(s):  
Kiran K. Shrestha ◽  
Krishna K Panthi
Keyword(s):  
Rock Mass ◽  
Stability Analysis ◽  
Concrete Lining ◽  
Rock Support ◽  
Hydroelectric Project ◽  
Tunnel Section ◽  
Geological Conditions ◽  
Headrace Tunnel ◽  
Support Principle

The history of hydropower development in the Himalaya indicates that many tunnels have suffered from cost over- runs and delays. These issues are directly dependent on the quality of rock mass and the permanent rock support applied in underground excavation. Right judgment and proper evaluation of the self supporting capability of the rock mass and the use of optimum rock support systems help considerably in reducing construction cost and delays. This paper examines such issues as geological conditions in the Himalayas and varying approaches and costs in tunnel construction. An assessment is made regarding the exclusion of permanent concrete lining in the headrace tunnel of the 72MW Middle Marsyangdi Hydroelectric Project in Nepal. The project has 5.2 km fully concrete lined headrace tunnel that passes through fair to poor rock mass. The evaluation is based on the use of actually recorded rock mass quality of the headrace tunnel during construction and rock support principle used at the comparable Khimti Hydro Project headrace tunnel. The evaluation includes calculation of equivalent tunnel section for similar headloss, stability analysis, assessment of possible water leakage, and required injection grouting measures. We conclude that the headrace tunnel without permanent concrete lining was possible and would have been equally stable, at considerable fnancial savings.Key words: Equivalent tunnel section; Squeezing; Tunnel lining; Stability analysis; Leakage control; Hydropower; NepalDOI: 10.3126/hn.v6i0.4188Hydro Nepal Vol 6, January 2010Page : 18-26Uploaded Date: 23 January, 2011

scholarly journals Evaluation on the TBM Performance at a Hydropower Project in Ecuador

2019 ◽  
Vol 24 ◽  
pp. 10-16
Author(s):  
Krishna Kanta Panthi ◽  
Jhonny Encalada
Keyword(s):  
Rock Mass ◽  
San Francisco ◽  
Penetration Rate ◽  
Tunnel Boring Machine ◽  
Quality Parameters ◽  
Hydropower Project ◽  
Tbm Performance ◽  
Rock Mass Quality ◽  
Geological Conditions ◽  
Headrace Tunnel

The aim of this manuscript is to discuss the Tunnel Boring Machine (TBM) performance along the recently constructed headrace tunnel of Minas-San Francisco Hydropower Project in Ecuador. Firstly, the manuscript briefly describes the importance of TBM tunneling and about the Minas-San HPP. Further, discussions are made on the engineering geological conditions along the headrace tunnel. Detailed evaluations are made on the performance of TBM tunneling considering influence of rock mass quality on the TBM penetration rate. The manuscript emphasizes that the knowledge of the rock mass quality parameters and cutter technology available at present are among the key factors that influence the estimation of the net penetration rate of the TBM. It has been demonstrated that the hard to very hard rock masses of high abrasivity that were encountered along the headrace tunnel alignment caused very low penetration giving slow progress, which was not predicted during planning phase design. The authors investigated a fairly good link between TBM penetration and the mechanical strength of the rock mass.

On the influence of rock mass quality on the quality of blasting work in tunnel driving

1998 ◽  
Vol 13 (1) ◽  
pp. 81-89 ◽  
Author(s):  
N. Innaurato ◽  
R. Mancini ◽  
M. Cardu
Keyword(s):  
Rock Mass ◽  
Rock Mass Quality

Multi-source data driven method for assessing the rock mass quality of a NATM tunnel face via hybrid ensemble learning models

2021 ◽  
Vol 147 ◽  
pp. 104914
Author(s):  
Mingliang Zhou ◽  
Jiayao Chen ◽  
Hongwei Huang ◽  
Dongming Zhang ◽  
Shuai Zhao ◽  
...  
Keyword(s):  
Rock Mass ◽  
Ensemble Learning ◽  
Data Driven ◽  
Learning Models ◽  
Tunnel Face ◽  
Rock Mass Quality ◽  
Source Data ◽  
Natm Tunnel

scholarly journals Engineering geology of Kankai Hydroelectric tunnel alignment

2006 ◽  
Vol 31 ◽  
pp. 67-74
Author(s):  
Sunil Kumar Dwivedi ◽  
Prakash Chandra Adhikary
Keyword(s):  
Rock Mass ◽  
Poor Quality ◽  
Project Area ◽  
Hydroelectric Project ◽  
Headrace Tunnel ◽  
Quality Category ◽  
Tunnel Alignment ◽  
The Stability ◽  
Quality Categories ◽  
Intake Portal

This paper describes the engineering geological characteristics of rock mass in the headrace tunnel, powerhouse, and intake portal of the Kankai Hydroelectric Project. The project area lies in the Lower Siwaliks of east Nepal and consists of alternating sandstone and mudstone beds with frequent siltstone intercalations. The rock mass of the project area was classified according to rock mass rating (RMR) and rock mass quality index (Q) systems. It is of very poor, poor, to fair quality (categories V, IV, and III) in the headrace tunnel; of very poor quality (category V) in the powerhouse; and of fair quality (category III) in the intake portal. The stability analysis of irregularly jointed and fractured rocks of the area was carried out using SWEDGE and UNWEDGE. The analysis gave the safety factor of 0.45, 0.64, and 0.45, respectively for the powerhouse, intake portal, and headrace tunnel. The final safety factors obtained after the installation of support for powerhouse, intake portal, and headrace tunnel were 1.14, 3.33, and 4.53, respectively.

scholarly journals Fluid Flow and Leakage Assessment Through an Unlined/Shotcrete Lined Pressure Tunnel: A Case from Nepal Himalaya

2021 ◽  
Author(s):  
Krishna Kanta Panthi ◽  
Chhatra Bahadur Basnet
Keyword(s):  
Fluid Flow ◽  
Rock Mass ◽  
Cost Effective ◽  
Hydropower Plant ◽  
Water Leakage ◽  
Hydroelectric Project ◽  
Water Head ◽  
Headrace Tunnel ◽  
Hydraulic Jacking ◽  
Leakage Assessment

AbstractThe use of unlined/shotcrete lined pressure tunnels and shafts are cost-effective solutions for a hydropower project and are being implemented worldwide. To implement this concept, the ground conditions at the area of concern should be favorable regarding minimum principal stress magnitude, which should be higher than hydrostatic water head acting on the tunnel periphery. In addition, the rock mass should be relatively unjointed or joints in the rock mass should be relatively tight. Among the most important issues in the design of unlined/shotcrete lined pressure tunnels is the extent of hydraulic jacking and water leakage out of the tunnel during operation. This manuscript first presents fluid flow and potential hydraulic jacking assessment of two selected locations of the headrace tunnel of Upper Tamakoshi Hydroelectric Project (UTHP) in Nepal using the UDEC. It is noted here that the 7960 m long headrace tunnel will experience a hydrostatic water head that will vary from 2.9 to 11.5 bars (0.29–1.15 MPa). The headrace tunnel is supported by sprayed concrete (shotcrete) in combination with systematic rock bolts in the tunnel walls and crown. The invert of the tunnel and few hundred meters downstream end (at surge shaft area) of the headrace tunnel is being concrete lined after the completion of all other works. The qualitative fluid flow assessment carried out using UDEC indicated considerable pressure built-up in the joint systems suggesting potential hydraulic jacking. This was especially the case at the downstream segment (downstream from chainage 7100 m) of the headrace tunnel. The manuscript further presents the quantitative results of water leakage estimation from the headrace tunnel carried out using Panthi (Panthi KK (2006) Analysis of engineering geological uncertainties related to tunnelling in Himalayan rock mass conditions. PhD Thesis, NTNU, Trondheim, Norway;Panthi, Note on estimating specific leakage using Panthi’s approach, NTNU, Trondheim, 2010;) approach. The leakage assessment carried out indicated an average specific leakage of about 2.5 l/min/m tunnel, which may result in over 210 l/s leakage from the headrace tunnel. The evaluation also indicated that the outer reach (860 m downstream segment) of the headrace tunnel after chainage 7100 m seems extremely vulnerable and over 80 l/s water leakage may occur only from this headrace tunnel segment during operation of the hydropower plant.

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