scholarly journals Engineering geological and geotechnical investigations of dam of the Bunakha Hydroelectric Project (180 MW), Chukha Dzong, Bhutan Himalaya

2014 ◽  
Vol 47 (1) ◽  
pp. 77-94 ◽  
Author(s):  
A. K. Naithani ◽  
P. C. Nawani ◽  
L. G. Singh ◽  
D. S. Rawat
Keyword(s):  
Rock Mass ◽  
Shear Zones ◽  
Geological Mapping ◽  
Engineering Properties ◽  
Concrete Gravity Dam ◽  
Hydroelectric Project ◽  
Laboratory Test Results ◽  
Geotechnical Investigations ◽  
Tehri Dam

A 197 m high roller compacted concrete gravity dam is proposed across river Wang Chhu in Chukha Dzong of the Bhutan Himalaya. Bunakha Dam will be the third highest dam constructed by India after the Tehri Dam and Bhakra Dam. The Bunakha Dam site area is located in the Thimpu Formation of the Himalayan crystalline complex. This litho-units at site is characterized by heterogeneous lithology consisting of viz.  banded gneisses, foliated gneisses, with large boudins and bands of quartzite and calc-silicate gneisses with large porphyroblasts of garnet measuring up to 4 mm. These litho units form the foundation of proposed dam. In this paper attempt has been made to bring out the rock mass condition of the foundation of dam of the proposed scheme on the basis of detailed engineering geological mapping, geological logging of drill holes, rock mass permeability values, 3D mapping of exploratory drifts, geophysical profiling, in-situ and laboratory test results. Rock mass classification using Rock Mass Rating (RMR) system and Q-system was done. The basic purpose of these investigations was to identify/map different rocks and structures like joints, shear zones, faults, fracture zones etc. and to determine engineering properties of rock and rock mass by lab and in-situ testing and to provide basic data for economic and fail-safe design of the dam. On the basis of these investigations suitable recommendations have been made which will be helpful during the construction of the dam. 

Research on the Spacing of Structural Plane Used in Rock Mass Structure Classification

2012 ◽  
Vol 446-449 ◽  
pp. 2011-2014
Author(s):  
Ai Guo Han ◽  
Min You ◽  
De Xin Nie
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Structure Type ◽  
Engineering Properties ◽  
Rock Mass Structure ◽  
Structural Plane ◽  
Hydroelectric Project ◽  
Quality Classification ◽  
Structure Research ◽  
Made In

Great achievements have been made in rock mass structure research to evaluate engineering properties of rock mass in the engineering geology field. In fact, rock mass structure can not only indicate the quantity of structural planes (discontinuities) and size of rock blocks, but also indicate the integrity and mechanical properties of the rock mass. More and more attention has been paid to rock mass quality classification by using rock mass structure. During the past 40 years, rock mass structure research has been carried out by many scholars, and various standards of rock mass structure classification have been proposed in different industries of different countries. In these standards, the most widely used index was the spacing of structural plane. However, it is a pity that the method of determining the spacing value is not unified in different standards, therefore, the structure type of a rock mass may be different according to different standard. But which kind of method to determine the spacing value is most reasonable? It becomes an important problem to be solved. In this paper, rational method of determining the spacing of structural planes is demonstrated based on lots of statistical data in dam abutment rock mass of one large-scale hydroelectric project in Southwest China.

scholarly journals The engineering geological behaviour of disturbed and weatherd gneiss in slopes. The case of the "vertical axis" of Egnatia motorway, Komotini - Nymfea, Northern Greece.

2013 ◽  
Vol 47 (4) ◽  
pp. 1749
Author(s):  
V. Marinos ◽  
A. Goricki
Keyword(s):  
Rock Mass ◽  
Case Studies ◽  
Back Analysis ◽  
Vertical Axis ◽  
Shear Zones ◽  
Slope Instability ◽  
Rock Masses ◽  
Northern Greece ◽  
Tectonic Disturbance ◽  
Laboratory Test Results

Sound gneiss forms evidently very competent rock masses with minor problems in geotechnical works. However, poor rock masses and problematic behaviour can be encountered in engineering projects in a geological environment characterized by intensive and sequent tectonic disturbance, where, weathering may be strongly favoured. Case studies with slope instability problems are analysed from the Egnatia Motorway along the vertical axis from Komotini to Nymfea, in Northern Greece. The basic engineering geological consideration focuses on the weathering degree, the tectonic disturbance, the foliated structure and the presence of shear zones. In the paper the gneissic rock masses are categorized in a number of specific rock mass types according to key engineering geological characteristics that define the rock mass behaviour in slopes. Subsequently, the slope behaviour of each rock mass type is discussed. The geotechnical properties of such failure surfaces are very difficult to be estimated due to the heterogeneous nature of these planes and back analysis is the best method to obtain reliable parameters. Back analysis results from two case studies showed significant differences to the laboratory test results. Finally, the concepts of the appropriate support measures based on the mechanism of failure of two case studies are presented in the paper.

Geotechnical appraisal of the foundation rock mass behaviour of Narmada Sagar Dam project, central India: a case study

1991 ◽  
Vol 28 (1) ◽  
pp. 148-159
Author(s):  
Vishnu D. Choubey ◽  
Shailendra Chaudhari
Keyword(s):  
Rock Mass ◽  
Central India ◽  
Maximum Height ◽  
Concrete Gravity Dam ◽  
Dam Foundation ◽  
Core Recovery ◽  
Geotechnical Investigations ◽  
Modulus Of Deformation ◽  
Under Construction ◽  
Crest Length

The Narmada Sagar Dam, a concrete gravity structure under construction across the Narmada River in central India, will have a crest length of 653 m and a maximum height of 92 m. The present paper discusses the results of geotechnical investigations undertaken for evaluating the rock mass strength parameters, applying the modern concepts of rock mechanics, especially the rock mass rating, modulus of deformation, shear parameters, and strength and permeability of the dam foundation rocks. The joint systems observed are used to interpret and explain the occasional zones of poor core recovery and to explain the location and orientation of the drilling programme. It is suggested that the estimate of spacing and opening of water-conducting joints may lead to useful estimates of the groutable volume of voids in the rock mass, and inclined drill holes are preferable for optimum grouting. The values of different parameters have been obtained and correlated. The studies have led to the conclusion that the foundation rocks of Narmada Sagar Dam are competent and suitable for designing the proposed concrete gravity dam. Key words: dam, strength, elastic modulus, deformability, rock discontinuity, rock quality designation, rock mass classification.

scholarly journals Estimating the rock mass modulus of Missouri shale using pressuremeter tests

2017 ◽  
Author(s):  
◽  
Cassidy Mathews
Keyword(s):  
Rock Mass ◽  
Field Tests ◽  
In Situ Stress ◽  
Triaxial Tests ◽  
Strain Response ◽  
Stress Strain ◽  
Intact Specimen ◽  
Laboratory Test Results ◽  
Rock Mass Modulus

Rock mass modulus can be a useful property in the design of foundations. Rock mass modulus is defined as the stress strain response of a rock mass in-situ. The stress strain response of the rock mass can be estimated by directly measuring the stress strain relationship via in-situ field tests, such as the pressuremeter, or it can be estimated from the results of laboratory intact specimen tests. Intact laboratory test results are often reduced to account for imperfections or discontinuities and other properties of the rock mass that may be present in the entire system, but are not easily replicated in the lab. The rock mass modulus can be used to design piles, drilled shafts and shallow foundations that are typically employed on Missouri Department of Transportation projects. Most current methods of estimating this modulus requires coring and sampling the material, transporting samples back to a lab with appropriate equipment, extruding and preparing samples and finally performing triaxial tests and estimating the modulus from the resulting stress strain curves. Shale formations found in Missouri are typically sensitive to changes in moisture content and disturbance from sampling and sample preparation. Generally lab tests are only performed on samples that can withstand the disturbances associated with sampling and preparation. Therefore lab tests generally yield values of intact modulus and the insitu rock mass modulus must be estimated or implied from these results. The pressuremeter test (PMT) offers a potentially better method to assess the in-situ rock mass modulus. The PMT allows testing of difficult to sample materials, e.g., shale, under in-situ stress and structure conditions resulting in a modulus more representative of the shale mass. Pressuremeter tests were performed at five sites in Missouri and the results were reduced to yield rock mass modulus. Intact samples of shale recovered from each site and returned to the laboratory for unconsolidated undrained and unconfined triaxial tests to yield intact modulus values. In general, the modulii from the intact specimens were equal to or less than the in-situ modulii measured using the pressuremeter. In these practical cases, the modulii from the intact specimens did not require any reduction to provide rock mass modulus. Rather, the modulii from the intact specimens could be used directly as the rock mass modulii. This result is surprising, but not unheard of.

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 Comparison between deformation modulus of rock mass measured by plate jacking and dilatometer tests

2017 ◽  
Vol 26 (3) ◽  
pp. 317-325
Author(s):  
Mohsen Rezaei ◽  
Rasoul Ajalloeian ◽  
Mohammad Ghafoori
Keyword(s):  
Rock Mass ◽  
Deformation Modulus ◽  
Rock Masses ◽  
Sarvak Formation ◽  
In Situ Data ◽  
Geotechnical Investigations ◽  
Two Samples ◽  
Dam Site

For determination of the in-situ deformation modulus of rock mass at Bakhtiari Dam site, located in south-west of Iran, plate jacking tests (PJT) and dilatometer tests (DLT) carried out during the geotechnical investigations. In this study, the results of PJTs and DLTs were compared. This comparison involves 89 vertical and horizontal PJTs and 83 DLTs carried out in 6 rock units of Sarvak formation. Although, both PJTs and DLTs in the Bakhtiari Dam site were performed in same geological and geotechnical conditions, but there are not sufficient side by side data to make a paired two samples correlation. Therefore, the mean of in-situ data was compared at each rock unit. Besides Mann–Whitney U tests were performed to compare in-situ test results. The comparison shows that the deformation modulus measured by both methods has no significant differences. However, in low quality rock masses the moduli measured by the use of DLTs were greater than the modulus measured by PJTs. Conversely, in high quality rock masses the results of PJTs were greater than DLT’s.

scholarly journals A dynamic analysis of in-situ stress state at the Upper Tamakoshi Hydroelectric Project area, Nepal

2018 ◽  
Vol 23 ◽  
pp. 42-47
Author(s):  
Krishna Kanta Panthi ◽  
Chhatra Bahadur Basnet
Keyword(s):  
Rock Mass ◽  
Stress State ◽  
Large Scale ◽  
Three Dimensional ◽  
In Situ Stress ◽  
Energy And Environment ◽  
Hydroelectric Project ◽  
Detailed Assessment ◽  
Local Shear

 The in-situ stress condition in the rock mass is influenced by both tectonic and geological environment, such as faulting and shearing in the rock mass. This influence is of considerable magnitude in the Himalayan region where the tectonic movement is active, resulting periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy instigating changes in the in-situ stress environment in the rock mass. This paper evaluates the influence of local shear fault on the in-situ stress state along the shot crete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project, 456 MW in Nepal. A detailed assessment of the in-situ stress state is carried out by using both; measured data and three-dimensional numerical analysis using FLAC3D. The analysis includes evaluation on the possible changes in the in-situ stress state in the rock mass caused by seismic activities (dynamic loading). HYDRO Nepal JournalJournal of Water, Energy and Environment Issue: 23Year: 2018

scholarly journals Geotechnical Assessment of the Foundation of Housing Chamber of Yaragol Gravity Dam, Karnataka State, India

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Ajay Kumar Naithani ◽  
L. G. Singh, ◽  
Prasnna Jain ◽  
D. S. Rawat
Keyword(s):  
Rock Mass ◽  
Geological Mapping ◽  
Gravity Dam ◽  
Rock Mass Rating ◽  
Engineering Geological Mapping ◽  
Data Set ◽  
Floor Area ◽  
Geotechnical Assessment ◽  
Laboratory Test Results ◽  
Karnataka State

Geotechnical assessment of the foundation including engineering geological investigations are essential for important civil structures to provide permanent data set for geological interpretations and for recommendations of suitable engineering measures for the improvement of the foundation. Yaragol Gravity Dam for drinking water is being constructed across Markandaya river in Karnataka State of India. Engineering geological mapping on 1:200 scale was carried out for Housing Chamber of Yaragol Gravity Dam to evaluate the design basis foundation parameters. 2 m x 2 m grids were prepared for mapping of the floor. Based on the field observations and evidences, it was found that the floor area consists of foliated gneiss and granite. No evidence of faulting or shearing was observed on the surface of the floor area. Geotechnical assessment of the foundations was done on the basis of detailed engineering geological mapping and laboratory test results. Classification of rock mass using Rock Mass Rating (RMR) of Bieniawski (1989) has been attempted and based on investigations recommendations for the treatment of foundation were given. Rock type and Rock Mass Rating (RMR) methods were used for assessing the safe bearing pressure of the foundation. Consolidation grouting up to 6 m depth in the foundation using primary at 6 m spacing and secondary holes at 3 m spacing was recommended. After detailed investigations it was found that, the foundation is suitable to locate a housing chamber.

scholarly journals Geotechnical Assessment of the Foundation of Housing Chamber of Yaragol Gravity Dam, Karnataka State, India

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Ajay Kumar Naithani ◽  
L. G. Singh, ◽  
Prasnna Jain ◽  
D. S. Rawat
Keyword(s):  
Rock Mass ◽  
Geological Mapping ◽  
Gravity Dam ◽  
Rock Mass Rating ◽  
Engineering Geological Mapping ◽  
Data Set ◽  
Floor Area ◽  
Geotechnical Assessment ◽  
Laboratory Test Results ◽  
Karnataka State

Geotechnical assessment of the foundation including engineering geological investigations are essential for important civil structures to provide permanent data set for geological interpretations and for recommendations of suitable engineering measures for the improvement of the foundation. Yaragol Gravity Dam for drinking water is being constructed across Markandaya river in Karnataka State of India. Engineering geological mapping on 1:200 scale was carried out for Housing Chamber of Yaragol Gravity Dam to evaluate the design basis foundation parameters. 2 m x 2 m grids were prepared for mapping of the floor. Based on the field observations and evidences, it was found that the floor area consists of foliated gneiss and granite. No evidence of faulting or shearing was observed on the surface of the floor area. Geotechnical assessment of the foundations was done on the basis of detailed engineering geological mapping and laboratory test results. Classification of rock mass using Rock Mass Rating (RMR) of Bieniawski (1989) has been attempted and based on investigations recommendations for the treatment of foundation were given. Rock type and Rock Mass Rating (RMR) methods were used for assessing the safe bearing pressure of the foundation. Consolidation grouting up to 6 m depth in the foundation using primary at 6 m spacing and secondary holes at 3 m spacing was recommended. After detailed investigations it was found that, the foundation is suitable to locate a housing chamber.

scholarly journals Excavation Method Implemented in Atal (Rohtang) Tunnel: Case Study

2021 ◽  
Vol 9 (VII) ◽  
pp. 1065-1068
Author(s):  
Verma Aakash
Keyword(s):  
Rock Mass ◽  
Shear Zones ◽  
Himachal Pradesh ◽  
Steel Pipe ◽  
Mechanical Methods ◽  
Geotechnical Investigations ◽  
Excavation Support

Structurally dynamic, youthful collapsed mountains; The Himalayas are loaded with full of geological surprises, involving issues, folds, shear zones and so forth that shows their quality because of progressing structural exercises in the Himalayas. In feature of Atal tunnel, these issues increments multifold due to high overburden of the material and also careful topographical and geotechnical investigations at different scales. This makes vulnerability in planning a specific emotionally supportive network and requests for "structure as you go" approach for whole passage length (8.8km). DRESS (Drainage-Reinforcement-Excavation-Support-Solution) philosophy of excavation is very powerful in water bearing issue zones of delicate Himalayan district. DRESS includes pre-seepage of ground in front of face with long waste gaps and adjustment of the crown in front of passage face by steel pipe umbrella curve, up to a foreordained length, trailed by exhuming in little strides by mechanical methods and backing thereof. Numerous troublesome issues have been experienced during construction which was unpredicted initially. One such issue is an experience of Seri Nala. Due to differing conduct of rock mass, continuous update of rock mass is constantly required. NATM is dependent on disfigurement observing information to assess amount and nature of emotionally supportive network, has end up being a fitting apparatus for tunneling in the youthful Himalayas. This paper depicts the consolidation of NATM as well as DRESS method in the unearthing of Atal Tunnel, Himachal Pradesh, India

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