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 Engineering geological study of the Kali Gandaki 'A' hydroelectric project area, western Nepal Lesser Himalaya

1996 ◽  
Vol 13 ◽  
Author(s):  
K. N. Kafle
Keyword(s):  
Shear Zones ◽  
Acute Angle ◽  
Lesser Himalaya ◽  
Project Area ◽  
Hydroelectric Project ◽  
The North ◽  
Headrace Tunnel ◽  
Dam Site ◽  
Tunnel Alignment ◽  
Intake Portal

The Kali Gandaki 'A' hydroelectric project area lies in the Lesser Himalayan Zone of the Syangja district of western Nepal. The rocks are characterised by highly deformed, thick sequences of the elastic rocks belonging to the Andhi Khola Formation and the carbonates of Darsing Dolomite, both belonging to the Kali Gandaki Supergroup. The dark bluish grey, brecciated and highly fractured dolomite is exposed on the abutments of the proposed diversion dam site area. It also forms steep cliffs to the north of the dam site. The contact between the dolomite and the overlying phyllite is a tectonized zone. This contact exposed along the exploratory audit and test trenches gives evidence of a fault dipping steeply towards the east. The phyllites exposed along the proposed headrace tunnel alignment and in the powerhouse site are variable in composition and rock strength. At the powerhouse area thin bands of limestone are intercalated in phyllites with sheared contacts. The headrace tunnel alignment makes acute angle with the foliation along most of the length and some sections passes parallel to the foliation. An inferred fault at about 1 km chainage, shear zones with varying thickness and a syncline at about 4 km from the intake portal are the main geological structures along the tunnel alignment which have to be carefully dealt with during the design and construction phase of the project.

scholarly journals Engineering Gology Model of Bener Dam Diversion Tunnels in Geological Risk Disaster Mitigation

2020 ◽  
Vol 6 (3) ◽  
pp. 205-215
Author(s):  
Daru Jaka Sasangka ◽  
Dian Insani ◽  
I Gde Budi Indrawan
Keyword(s):  
Rock Mass ◽  
Laboratory Data ◽  
Poor Quality ◽  
Disaster Mitigation ◽  
Primary Data ◽  
Diversion Tunnel ◽  
Rock Mass Quality ◽  
The Difference ◽  
The Stability ◽  
Quality Type

The Bener Dam Diversion Tunnel Plan is located in Bener District, Purworejo Regency. Engineering geology mapping data, drillimg data and laboratory data used as primary data. Surface and subsurface analysis show that each rock unit has different index and mechanical properties. Generally, the rock mass quality conditions in the dam belonged to good Rock (80%) in the Rock Mass Rating (RMR) system (Bieniawski, 1989).  The other rock mass quality type also found among them fair rock (5%), poor rock (5%), and very poor rock (10%). Poor rock mass quality conditions were controlled by geological structures, especially faults that partially cut through the tunnel geometry. The very poor quality of rock mass was in the volcanic lens (loose sand material) did not cut through the tunnel path. The difference stand-up time of the rock on the tunnel requires proper mitigation (Nguyen Nguyen, 2015). The stand-up time belonged to the dangerous condition was in the fault zone with poor rock mass quality, while the lens with very bad rock mass quality did not affect the stability of the excavation of the tunnel.

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 Engineering geological study of the Mai Khola Hyroelectric Project, Ilam, eastern Nepal

2018 ◽  
Vol 56 (1) ◽  
pp. 55-63
Author(s):  
Pusker Raj Joshi ◽  
Kamal Kant Acharya ◽  
Rabindra Dhakal
Keyword(s):  
Rock Mass ◽  
Surge Tank ◽  
Surface Mapping ◽  
Concrete Dam ◽  
Hydroelectric Project ◽  
Hill Slope ◽  
Headrace Tunnel ◽  
Middle Siwalik ◽  
The Hill ◽  
Poor Relation

The Mai Khola Hydroelectric Project, a run-of-river scheme, has a capacity 15.6 MW. It has design discharge of 16 m3/s, design net head of 112.71 m and includes 2192 m long inverted-D shaped headrace tunnel with 4.3 m diameter, concrete dam of 10.6 m height and semi-surface powerhouse. The project area consists of rocks of the Middle Siwalik Subgroup, comprising of sandstone, siltstone and mudstone, inter bedded frequently. Sandstone is predominant in head works area, headrace tunnel and is completely absent in a surge tank, and penstock alignment. Siltstone alternating with thin layer of mudstone is predominant in powerhouse area. The headrace tunnel outlet portal and surge shaft lie on the hill slope characterized by colluvial deposits. The penstock alignment passes through highly weathered siltstone and mudstone. The semi-surface powerhouse and the tailrace canal lie on the lower alluvial terrace. The Main Boundary Thrust (MBT) is the major structure observed at about 90 m upstream from the weir axis. The average Q-value of rock mass along the headrace tunnel surface mapping was 0.062–1.33 and after excavation the value was 0.004–0.23. An extremely poor to poor relation was observed between the rock mass class on surface mapping and exceptionally poor to very poor on excavation. Analysing the results of the surface and underground study of the rock mass, the excess support is required during construction.  

scholarly journals Stability and stress analyses of headrace tunnel, Upper Seti Storage Hydroelectric Project, Western Nepal

1970 ◽  
Vol 10 ◽  
pp. 45-54
Author(s):  
Niraj Kumar Regmi ◽  
Prakash Chandra Adhikary ◽  
Jayandra Man Tamrakar ◽  
Rabindra Prasad Dhakal
Keyword(s):  
Concrete Gravity Dam ◽  
Tunnel Support ◽  
Underground Powerhouse ◽  
Hydroelectric Project ◽  
Rock Bolting ◽  
Headrace Tunnel ◽  
Mass Classification ◽  
Intake Portal ◽  
Storage Type

The Upper Seti (Damauli) Storage Hydroelectric Project has a capacity of 128 MW, the storage type scheme, and includes 1000 m long horse shoe headrace tunnel, 140 m high concrete gravity dam, two diversion tunnels of lengths 712 m and 881 m and an underground powerhouse. The study was carried out to identify stability and stress conditions for the headrace tunnel to suggest the required tunnel support. The project area extensively covers dolomite and minorly covers slate. The rock mass classification showed fair to good quality of dolomite and poor to fair quality of slate. The surface wedges would form in intake portal and powerhouse site. In the headrace tunnel, structural wedges would be formed due to underground excavation and would be stabilized with the help of shotcrete and rock bolting.   doi: 10.3126/bdg.v10i0.1419 Bulletin of the Department of Geology, Tribhuvan University, Kathmandu, Nepal, Vol. 10, 2007, pp. 45-54

scholarly journals Analysis of Squeezing Phenomenon in the Headrace Tunnel of Chameliya Project, Nepal

2014 ◽  
Vol 13 ◽  
pp. 44-51 ◽  
Author(s):  
Pawan Kumar Shrestha ◽  
Krishna Kanta Panthi ◽  
Chhatra Bahadur Basnet
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Cross Section ◽  
Support Pressure ◽  
Rock Mass Properties ◽  
Tunnel Wall ◽  
Hydroelectric Project ◽  
Mass Properties ◽  
Headrace Tunnel ◽  
Tunnel Cross Section

The headrace tunnel of Chameliya Hydroelectric Project, Nepal has faced severe squeezing problems from chainage 3+100m to 3+900m. Due to the severe squeezing and deformation, the tunnel cross section has narrowed considerably along this 800m long tunnel stretch. The tunnel wall closure (deformation) is mostly well over 1 m and the maximum recorded closure exceeds 2m. This paper assesses the squeezing phenomenon along this tunnel stretch through evaluation of rock mass properties and support pressure. Three different methods (two analytical and one 2D finite element numerical modeling program) are used in this analysis. The finding is that it is possible to predict extent of squeezing in tunnel if more than one method is used to verify rock mass mechanical properties. DOI: http://dx.doi.org/10.3126/hn.v13i0.10039HYDRO NEPAL Journal of Water, Energy and EnvironmentIssue No. 13, July 2013Page: 44-51Uploaded date: 3/13/2014

scholarly journals Back calculation of in-situ rock stresses for a tunnel project in Himachal, India

2011 ◽  
Vol 42 ◽  
pp. 117-124
Author(s):  
Krishna Kanta Panthi
Keyword(s):  
Rock Mass ◽  
Element Model ◽  
The State ◽  
Stability Assessment ◽  
Rock Support ◽  
Hydroelectric Project ◽  
State Of Stress ◽  
Headrace Tunnel ◽  
Tunnel Instability

Determination of in-situ stresses in the rock mass is necessary for stability assessment and proper design of underground openings. It is important to know the state of stress surrounding the opening so that right and optimum rock support is assigned as preliminary and permanent rock support. However, the majority of long tunnels with high rock cove r face severe tunnel instability problems related to rock stresses. The headrace tunnel of Parbati II hydroelectric project is one of such tunnels, especially the tunnel segment passing through Manikaran quartzite. It is known fact that the extent and type of stress induced instability vary greatly upon rock type, deformability properties, jointing and inter-bedding characteristics in the rock mass. This paper back calculates the state of stress using Phase 2  finite element model  in a TBM  bored segment of  the tunnel and  also briefly reviews mechanical properties of the  intact rock that may have direct link on the  nature of stress induced  instability. It is believed that back calculated stress magnitude may be useful for the stability assessment in other segment of headrace tunnel.

scholarly journals Linear combination of chi-squares for multinomial process monitoring

2021 ◽  
Vol 28 (3) ◽  
Author(s):  
Ramzi Talmoudi ◽  
Ali Achouri ◽  
Hassen Taleb
Keyword(s):  
Linear Combination ◽  
Control Chart ◽  
Process Monitoring ◽  
Goodness Of Fit ◽  
Average Run Length ◽  
Poor Quality ◽  
Chi Square ◽  
Control Signals ◽  
Quality Category ◽  
Quality Categories

Abstract: Marcucci (1985) proposed a chi square goodness of fit statistic based generalized p-chart for multinomial process monitoring. A chi square distribution quantile was considered as a control chart limit. A weighted chi square goodness of fit statistic-based control chart is proposed for multinomial process monitoring in this paper, where more important weights are advocated to poor quality categories. The statistic distribution is approximated by a well-known linear combination of chi squares distribution. The approximation is assessed through a simulation, an extreme percentile of the approximated distribution is used as an upper control chart limit and a comparison is carried out with a chi square goodness of fit statistic-based control chart. The average run length is used as a benchmark and the comparison is performed using simulations considering two process shifts scenarios. Under some restrictions, the weighted statistic-based control chart allows an earlier detection of process shift in case of deterioration and postpones out of control signals in case of improvement. This benefit is clearer when the process is improved by a decrease in the poor quality probability category and an increase in the best quality category probability.

scholarly journals Engineering Geological Design of Underground Works for Upper Madi Hydroelectric Project

2012 ◽  
Vol 9 ◽  
pp. 27-34
Author(s):  
Prem Krishna K.C. ◽  
Krishna Kanta Panthi
Keyword(s):  
Rock Mass ◽  
Complex Geometry ◽  
Empirical Method ◽  
Underground Structures ◽  
Hydroelectric Project ◽  
Headrace Tunnel ◽  
Himalayan Geology ◽  
Rock Mass Condition ◽  
Complex Geology ◽  
Actual Rock

Himalayan geology is termed as one of the youngest tectonic formations in the world. Tunneling in this region is hence complex in nature. The very complex geology in the region offers challenges in stability of even the best located underground structures. Tunneling in weak rock is more challenging in terms of stability and application of support. Moreover, in many occasion, prediction of the rock mass has been done optimistically in most of the underground projects in Nepal. In this paper, predicted versus actual rock mass condition has been compared for two already completed projects. Based on this needed support is calculated by empirical method for the project under investigation and later on verified by numerical analysis using the software Phase2. Stability analysis is also done for both high pressure headrace tunnel and underground surge shaft. Numerical method of analysis has an added advantage over empirical and analytical methods, particularly in complex geometry. The Phase2 code and the Hoek-Brown Failure criterion have been used to determine the state of stress, strength factor and deformations around the periphery and in the tunnel walls.DOI: http://dx.doi.org/10.3126/hn.v9i0.7069 Hydro Nepal Vol.9 July 2011 27-34

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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