DIPLOM- / MASTER-OPPGAVER 1994-2004, Veileder Bjørn Nilsen

2004:

Pawan Kumar Shrestha: Engineering geological analysis of underground structures at Middle Marsyangdi Hydroelectric Project, Nepal.
Construction work for the Middle Marsyangdi project started in 2002 and is expected to be completed in 2006. Among the main underground excavations for the project are 3 large settling basins, each with width ~15 m, height ~30 m and length ~ 150 m, and a 5 km long headrace tunnel (the powerhouse is located on the surface). The bedrock in the area mainly consists of foliated quartzite, and the rock cover of the underground structures is relatively small. The purpose of this thesis has been to analyse the engineering geological aspects of the underground excavations of the project, with main emphasis on the large settling basins. Stability, cavern design and rock support requirement have be analysed with main emphasis on empirical analysis and numerical analysis based on the Phase2 FEM code.

Halgeir Dahle: Slope stability analysis for Oppstadhornet.
(in co-operation with NGU and International Centre for Geohazards)
Oppstadhornet, a steep mountain on the Oterøya Island West of Molde, shows signs of partly collapse with initial sliding and formation of wide, open joints. As a following-up of earlier, detailed engineering geological mapping and testing, stability analysis of the steep Oppstadhornet slope has been carried out in this thesis work. Several alternatives for analyses have been discussed, and introductory empirical analyses have been done. Main emphasis has, however, been placed on numerical analysis based on UDEC-BB. Back calculation of the situation prior to initial sliding has been done as well as analysis of today’s stability situation. As an important part of the study, extensive parameter studies have been done. A main conclusion based on this work is that the mountain appears to be more stable today than prior to initial sliding.

2003:

Chinh, Nguyen Huu: Engineering geological analysis of Sesan 3 Hydropower project, Vietnam.
The purpose of this thesis has been to carry out engineering geological analyses of the planned underground excavations for the SeSan3 Hydropower Project in Vietnam. Feasibility studies for SeSan3 have recently been carried out by the Swedish consultant SWECO in co-operation with Vietnamese consultant PECC1. The planned project includes two approximately 80 m long and diameter 7 m lined headrace tunnels, an underground power house and 2 approximately 90 m long and diameter 7 m tailrace tunnels. Main emphasis have been placed on analysing the proposed tunnel alignments and power house cavern location and orientation, the power house design and geometry and the requirement/design of support and lining. Numerical modelling based on FLAC-3D represents a major part of the analyses. Based on the analyses, recommendations have been made concerning design and further studies.

Gjerde, Arild: The Rogfast tunnel, engineering geological analysis of alignment and geometry.
(in co-operation with the Public Roads Administration)
For the Rogfast tunnel, a planned 24 km long subsea road tunnel under the Boknafjord in Southwest Norway, engineering geological analyses of the alignment and geometry have been carried out. If built, this tunnel, going down to a maximum depth below the sea level of approximately 360 meters, will be the longest and deepest subsea road tunnel in the world. The rock mass, consisting of Paleozoic phyllite and greenstone and Precambrian granitic gneiss, has been characterized based on available background material, site visits and laboratory testing. As part of the analyses, numerical modelling based on Phase2 has been carried out. It is concluded that the planned tunnel project is feasible with a minimum rock cover of 40-50 meters. For final design of alignment and geometry, more ground investigations are required.

Gudmundsson, Hlynur: Analysis of grouting carried out in the Skaugum tunnel
(in co-operation with Mika AS)
For the 104 m2/3.6 km long Skaugum railway tunnel, presently under excavation between Sandvika and Asker near Oslo, engineering geological aspects of grouting have been analysed. The extent of grouting in the tunnel has been mapped and described, and as-built results have been compared with pre-construction prognoses. Main emphasis has been placed on discussing the extent and effect of grouting versus the engineering geological conditions. Correlations between grouting results and classification parameters such as RQD and Q have also been discussed, and the usefulness of measurement while drilling (MWD) has been evaluated. Due to the very strict leakage criteria (maximum permissible inflow 4-16 l / min x 100 m), systematic grouting has been performed in the entire tunnel. It is concluded that the grouting has been mainly successful. To a great extent, this is believed to be result of the fact that grouting has been highly prioritized.

Hagen, Kjersti Fuglseth: Analysis of grouting in the Lunner tunnel
(in co-operation with the Public Roads Administration)
For the 3.8 km long Lunner road tunnel, excavated as part of new Rv. 35 in Oppland (Southeastern Norway), and completed in October 2002, the effect of grouting has been analysed. Particular emphasis has been placed on discussing correlations between engineering geological conditions and extent /effect of grouting, the significance of grouting technique on grouting result, and the potential correlation between inflow in probe drillholes and the grout requirement. The extent of grouting carried out it the tunnel turned out to be considerably higher than originally estimated. It is concluded that to a great extent this is believed to be due to the fact that the joints in the rock mass were more open than expected. Finally, a comparison has been made between the grout requirement in the Lunner tunnel and the nearby Hagan road tunnel, which was excavated with a considerable smaller rock cover than the Lunner tunnel.

Knudsmoen, Hanne: Analysis of the usefulness of engineering geological investigations for the Jong-Asker tunnels
(in co-operation with the National Rail Administration)
For the 104 m2 and 3.6/2.7 km long Jong-Asker railway tunnels, presently under excavation just West of Oslo, the usefulness of engineering geological investigations has been analysed. The pre-construction investigations for this tunnel project have been extensive, and during excavation, thorough mapping is carried out by engineering geologists. The correlations between investigation results and as-built geological conditions are discussed, as well as the practical use of pre-investigations results and the value of supplementary investigation during excavation. Due to the very strict leakage criteria of these tunnels (maximum permissible inflow 4-16 l / min x 100 m), particular emphasis in this thesis has been placed on investigations for prognosticating water inflow. It is concluded that the prognoses based on pre-investigations have correlated mainly quite well with the actual conditions.

2002:

Kassana, Leonard B.: Analysis of water leakages at the Lower Kihansi Hydropower Project, Tanzania.
In Tanzania, the Lower Kihansi Hydropower project, utilising a head of about 850 m in an unlined tunnel system, was put in operation in year 2000. The entire system of tunnels and power plant is located underground in Precambrian rock mass. During water filling, leakage from the headrace tunnel was experienced, and also some minor leakage into the powerhouse.
The main purpose of this thesis has been to analyse the water leakages during water filling in relation to the engineering geological and rock mechanical characteristics of the project site. The work is focused primarily on the rock engineering aspects of the project, with main emphasis on:
& Correlations between water leakage and the engineering geological conditions.
& Possible future development of the water leakage.
The study has found that the major two aspects correlating and linking water leakages and engineering geological characteristics are weathering and jointing/faulting in the project area.

Livik, Steinar: Rock engineering analysis of the Korgfjell tunnel.
For the Korgfjell tunnel, a 8.5 km long road tunnel under excavation in Nordland, analysis of the rock engineering conditions has been carried out. Various geological maps and reports have been available as background material, and as part of the present work field mapping, sampling and laboratory analyses of rock samples have been carried out. The predominant rock types in the project area are micaschist/-gneiss and marble. Based on evaluation of the engineering geological characteristics such as rock types, weakness zones/faults, groundwater conditions and rock stresses, the tunnel project is considered to be of medium geotechnical complexity.

2001:

Tilahun, Daniel: Engineering Geological Analysis of Tunnels, Shafts and Caverns at Gilgel Gibe Hydropower Project.
The 180 MW Gilbel Gibe Hydroelectric Project in Ethiopia is situated some 260 km South-West of Addis Ababa. The project includes about 9 kilometres of tunnels, several shafts and caverns, including a 25 meter wide powerhouse cavern. In this thesis, a detailed engineering geological analysis of tunnels, shafts and caverns has been carried out, with the following engineering geological aspects in main focus:
& The feasibility of unlined headrace tunnel as alternative to the selected lined alternative.
& Design and planned rock support of the powerhouse cavern.
& Selected rock engineering design of caverns and tunnels as compared to standard designs.
Numerical modelling (Phase2) is included in the analysis, and comparisons have been made between deformations calculated by Phase2 and deformations measured in the powerehouse cavern.

2000:

Eggen, Bjørn Erling: Analyse av metoder for driving gjennom svakhetssoner i Frøyatunnelen.
The Frøya subsea tunnel - Analysis of tunnelling methods through weakness zones.
(/Statens Vegvesen Sør-Trøndelag)
Based on available background material, interview with site staff members, field investigations and laboratory testing, methods used for tunnelling through weakness zones at the Frøya subsea tunnel have been evaluated. Field investigations were focused mainly on the remaining 100 meters of the tunnel, but also covered other sections. Laboratory testing mainly covered properties of gouge material and the adhesion of shotcrete used for rock support. A combination of conventional rock bolting and shotcreting, spiling and shotcrete arches was often used as final support, and proved to be succesful.

Sanjeev Kumar Thakur: Excavation and stability of pressure shaft - A case study based on Khimti Khola Hydropower Project, Nepal.
(/Statkraft Anlegg)
Inclined shafts are key elements of hydropower projects, and major problems will be the result of any shaft failure. The intentions of this thesis have been to evaluate excavation methods, rock support and potential stability problems of pressure shafts first on a general basis, and then to discuss in detail the incidents during excavation of the pressure shaft at Khimti Khola hydropower project in Nepal. It is discussed what could possibly have been done to prevent the shaft failure at Khimti, and what should be done in the future in Himalayan rock conditions to avoid such incidents. The main conclusion is that thorough investigation in preconstruction phase as well as construction phase investigations are the key issues for obtaining a good result.

Bhuban Prasad Dhakal: Engineering geological analysis of Nyadi Hydropower project, Nepal.
For the proposed 15 MW Nyadi Hydropower Project West of Kathmandu in Nepal, a feasibility study has been carried out by Butwal Power Company. The plans include about 5 kilometres of tunnels, pressure shaft with about 350 meters static head and underground powerhouse cavern. This thesis represents a detailed engineering geological analysis of the proposed project, including all aspects of design, stability and rock support. The work is focused on the engineering geological aspects of the planned project, such as: location of the pressure shaft and the feasibility of the unlined shaft alternative, location and design of the powerhouse cavern, stability of the headrace tunnel, and the rock support requirement of the powerhouse cavern and the various tunnels.

Rødseth, Stein Vegar: Numerisk analyse av bergsikring.
Numerical modelling of rock support.
Numerical analyses of the effects of various types of rock support in tunnels have been carried out. Main emphasis has been placed on analyzing the effect of reinforced shotcrete ribs as alternative to cast in place concrete lining. The Frøya subsea tunnel, where both these support alternatives have been used, and comprehensive convergence measurements have been carried out, has been used as relevant case and calculation example. Only small differences in deformation was found between the two alternatives. It is concluded that the biggest difference between the two support alternatives is the greater flexibility of the alternative with reinforced shotcrete ribs.

Anthi, Aina Katharina: Stabilitetsanalyse av vegskjæringer i Oslo-området
Stability of road cuts in the Oslo area.
(/Statens Vegvesen Oslo)
Along main highways in the Oslo area, such as E18 Mossevegen and E6, there are several large road cuts. In this thesis a selection of the most relevant cuts have been analysed regarding stability condition, existing rock support, history of earlier sliding/rock fall activity and risk of future instability. The requirement for new/additional rock support has been evaluated, and alternative technical solutions and cost of new/additional support have been discussed. A considerable number of locations have been found where additional support is recommended, and list of priority for the recommended measures is proposed.

Einarsson, Eirikur: Siglufjörður-Ólafsfjörður vegtunneler, ingeniørgeologisk og anleggsteknisk analyse
Siglufjörður-Ólafsfjörður Road Tunnels, Rock engineering analysis
(/Vegegerðin/BAH)
At Siglufjörður-Ólafsfjörður in Iceland, two road tunnels of lengths approximately 4.0 km and 6.0 km are planned. This thesis evaluates engineering geological and construction engineering factors, such as rock mass conditions, earthquake activity, requirement of rock support and lining and cost/scheduling of the planned project. As basis for the evaluation, geological reports and relevant documents from pre-investigations have been available, and additional field work and sampling have been carried out by the candidate. Particular emphasis has been placed on groundwater conditions and methods for solving potential problems caused by water. Uncertainty analysis and a comparison between Icelandic and Norwegian cost levels are included in the cost analysis. The main challenges of the project are believed to be represented by geothermal areas/groundwater and strong seismic events.

Steingrímsson, Jón Haukur: Kárahnjúkar kraftverk, ingeniørgeologisk og anleggsteknisk analyse.
Kárahnjúkar hydropower project, rock engineering analysis
(/Landsvirkjun)
As part of Kárahnjúkar hydropower project in Iceland, about 40 km of diameter 7.2 m TBM tunnels are planned. In this work, detailed analyses of the feasibility, technical complexity, scheduling and cost of the TBM tunnels have been carried out. Particular emphasis has been placed on analysing the significance of so-called "mixed-face conditions" for performance prediction. In the discussion of mixed face conditions, relevant data from other projects in similar geology are also included. As basis for the evaluation of Kárahnjúkar, geological information and reports from pre-investigations have been available from Landsvirkjun, and field survey, sampling and laboratory boreability testing have been carried out by the candidate. Predicted net penetration according to the NTNU prognosis model is 3.2 m/h, corresponding to a gross advance rate of approximately 130 m/week.

1999:

Karlsen, Lars Christian: Miniatyrtester for borbarhetsundersøkelser.
The feasibility of miniature testing for boreability estimation has been studied. As background for the study, a review of relevant methods for boreability testing has been made based on available literature. A representative selection of rock samples have then been collected, and boreability testing has been carried out according to "traditional NTNU procedure" and based on miniature testing. Promising correlation between standard and modified boreability testing has been found, although further correlation study is required for the miniature testing to become fully reliable.

Kjørmo, Gro Røst: Skråningsstabilitet i Tellnes dagbrudd.
(/Titania AS)
Based on review of available background material, field mapping and theoretical analyses, rock slope stability at Tellnes open pit mine in Southern Norway has been evaluated. During field mapping, main emphasis has been placed on character and orientation of discontinuities relatively to the slope face. Field and laboratory testing has been carried out for estimation of joint friction. The open pit mine has been divided into design sectors, and maximum slope angles have been proposed for each sector. Stabilizing measures, such as drainage, have been proposed, and also a system for monitoring/stability control.

1998:

Hermanstad, Elin & Hovelsen, Morten: Khimti Hydropower Project, Nepal - Analysis of engineering geology, tunnelling methods and rock support.
(/Statkraft Anlegg)
The diploma represents a follow up of an earlier project in engineering geology with purpose to make a first evaluation of the rock engineering conditions of the Khimti Hydropower Project in Nepal. As basis for the diploma, comprehensive field and tunnel mapping were carried out during the summer months and at the initial stage of the diploma work. The project has an underground powerhouse cavern and about 10 km of tunnels. It is planned to be opened in 2000, with a total output of 60 MW. Very difficult ground conditions have been encountered during tunnelling. Based on the mapping results, rock support and excavation methods at the hydropower tunnels, and the extent of rock support, have been analyzed. Among key issues have been integration of rock support with tunnel excavation and optimisation of methods according to local conditions.

Huang Ziping: Ertan Hydroelectric Project - Analyses of Rock Slope Stability.
For the Ertan hydroelectric project, presently under construction in Sichuan, P.R. China, rock slopes with heights in excess of 100 meters have been excavated. Difficult rock conditions have been encountered on several occasions, and considerable effort has been put on careful excavation and rock support. In this thesis the stability of the high rock slopes at Ertan is analysed with particular emphasis on the power intake and spillway intake slopes. Analyses based on UDEC distinct element and SARMA limit equilibrium analyses show that the slopes are satisfactory stable after excavation, provided that rock support and drainage are carried out.

Krishna Panthi,: Direct link between Hetauda and Kathmandu, Nepal - Evaluation of proposed road tunnels.
The proposed road link between Hetauda and Kathmandu in Nepal includes several long tunnels. Pre-feasibility study of the project was carried out in 1993. This thesis evaluates the engineering geological conditions of the proposed tunnels, analyses the geotechnical complexity and risk, and contains preliminary time and cost estimates. The project area is located in the lesser Himalayan crystalline rocks, typically represented by quartzite, marble, mica schist and limestone. All three of the proposed alignment alternatives are found to be technically feasible, with alternative 1 as the best. Conventional drill and blast tunnelling is recommended for excavation. Further engineering geological investigations are recommended.

Sagar Raj Goutam: Khimti Khola II Hydropower Project - Evaluation of pressure tunnel system.
(/Statkraft Anlegg)
For the planned Khimti Khola hydropower project in Nepal, various designs of the pressure tunnel system, with and without shaft, have been proposed. This thesis is discussing the alternative designs based on evaluation of the engineering geological conditions, excavation aspects, stability/rock support and operation of the unlined waterways. A simulation model (FLAC-3D) is used to simulate the topography and calculate the minimum principle stress at the critical points of the tunnels. Based on this, the originally planned power house cavern is recommended to be relocated, and two new tunnel alignments are proposed.

Shubh Pathak: Khimti Khola II Hydropower Project - Stability and support of tunnel portals.
(/Statkraft Anlegg)
For underground hydropower projects in steep topography, the stability of tunnel portal areas is of major concern. This thesis is evaluating the engineering geological conditions and analysing in detail the tunnel portal situation of the planned Khimti Khola II hydropower project in Nepal. Analyses based on stereographic projection techniques and limit equilibrium methods show that the portal slope of the access tunnel to the power house is stable, while for the adit portal slope supplementary rock support and drainage are recommended.

1997:

Bhatti, Tariq Javed: Foundation stability analyses of intake dam, Neelum-Jhelum hydroelectric project, Pakistan.
(/Norconsult)
The engineering geological conditions of the planned intake dam at the Neelum-Jhelum hydroelectric project are analysed based on review of available background material. Foundation stability is analysed by stereographic analyses and limit equilibrium methods, and the foundation quality by bearing capacity analyses. It is concluded that except minor concern connected to differential settlement, there is no significant stability problem.

Bysheim, Njål: Khimti II, Nepal - Ingeniørgeologisk og anleggsteknisk analyse.
(/Statkraft Anlegg)
Based on study of available background material, field mapping and laboratory testing, a feasibilty study of the proposed Khimti II Hydropower Project in Nepal has been carried out. The Khimti II project includes underground powerhouse cavern and 5 km of tunnels. Planned installation is 27.2 MW. Main emphasis has been on evaluating planned design, stability and rock support requirement of the planned underground excavations. The estimated rock support requirement is relatively high, reflecting rather difficult rock conditions. Alternative, apparently more favourable tunnel allignments are also discussed.

Jensen, Jann Atle: Tunnel til Horsøy - Ingeniørgeologisk analyse.
(/Statens Vegvesen Hordaland)
Based on available background material, field mapping and laboratory testing, engineering geological evaluation and planning of a road tunnel system at Horsøy, including underground roundabout, have been carried out. The tunnel system has a total length of about 1.5 km. Stability, rock support requirement and cost are in focus in the evaluations. Potential use of the tunnel muck as well as additional use of the tunnel for public shelter, water pipes etc. are also discussed. It is concluded that this project is feasible technically as well as economically.

Shrestha, Manohar: Cavern stability analysis in Khimti underground powerhouse, Nepal.
(/Statkraft Anlegg)
The design of the powerhouse cavern at Khimti I hydropower project is discussed based on review of available background material, empirical methods and numerical modelling (including UDEC analyses). Two possible powerhouse cavern geometries are considered: ordinary horseshoe shaped and an alternative with the lower portion for tail water. It is concluded that in this case numerical modelling is a good tool for analysing the mechanism of potential stability problems.

Sinh, Tran Dinh: Support requirement and stability analysis of the tunnel system at Neelum-Jhelum Project in Pakistan.
(/Norconsult)
Stability and rock support requirement of the tunnels at Neelum-Jhelum hydroelectric project in Pakistan are analysed based on available background material. Particular emphasis is put on the applicability of shotcrete in the high water speed (approx. 3.5 m/s) headrace tunnel. It is concluded that for economical as well as technical reasons, a combination of rock bolting and shotcreting represent the optimum support alternative.

Vikane, Kjetil: Deponi for lavt- og middelsaktivt atomavfall, Himdalen - Analyse av bergmassekvalitet og sikringsbehov.
(/AF Spesialprosjekt)
A facility for storage and disposal of low- and intermediate level nuclear waste is built at Himdalen in Aurskog-Høland. The facility is planned to be completed by March 1988, and will consist of 4 parallel caverns, each 50 meters long. Based on available background materials, and detailed field mapping, including rock mass classification according to the Q-method engineering geological analysis and evaluation have been carried out. Particular emphasis has been put on rock support requirement, and the distribution between preliminary and permanent support. Safety during construction and design principles are also key words.

1996:

Aryal, Krishna: Stability and rock support of tunnel portals - Khimti Hydropower Project, Nepal.
(/Statkraft Anlegg)
For the underground powerhouse and the 12 km of tunnels at the Khimti Hydropower Project, several adits and access tunnels are excavated. As a result of the difficult topographical and geological conditions at the site, the stability of the portals is a major concern. The stability is analysed based on review of geological data, stereographical analyses and limit equilibrium methods.

Christensen, Morten: Blast vibrations - Romeriksporten tunnel
Comprehensive review and analysis of recorded blast vibration data have been carried out for the Romeriksporten railroad tunnel. Main emphasis is put on potential correlations between vibration magnitude and engineering geological conditions, including foundation conditions. It is found that to a great extent geological structures like foliation, filled joints and dykes may influence on the magnitude and characteristics of the vibrations.

Djuvsland, Jan Olav: The Folgefonn tunnel - Definite plan study
(/Statens Vegvesen Hordaland)
Detailed engineering geological investigation and planning have been carried out for the planned Folgefonn road tunnel. In the field all relevant factors likely to affect stability and tunnelling conditions have been recorded. Laboratory testing to find the most relevant mechanical properties is also carried out. Detailed prognoses for tunnelling cost and time consumption are presented. The high rock stresses most likely represent the main challenge for this project.

Tyssekvam, Ingvar Ove: Weakness zones in Romeriksporten tunnel - Probing and characterisation of swelling material.
(/NSB Gardermobanen)
Faults and weakness zones intersecting the Romeriksporten railway tunnel are described. For some selected zones swelling pressure and other relevant parameters are analysed in the laboratory according to standard procedures. Particularly, representativity and repeatability are studied and discussed in this connection. As a part of the work, an oedometer for testing intact material has been developed. The initial test results based on this new equipment are promising.

Wang, Hui: Long-term deformation of the permanent ship lock of the Three Gorges Project in China.
(/AGN)
For the Three Gorges Project a double lane, five-stage permanent ship lock with slope height up to 170 m is under excavation. Due to the operation of the gates, only very small convergence of the rock slopes can be tolerated. The convergence is analysed based on empirical and numerical (UDEC) methods. Based on these analyses, the maximum creep convergence of the ship lock wall is approximately 10 mm.

Wiig, Torgeir: The North Cape tunnel - Engineering geological conditions.
(/Veidekke)
Based on own field mapping and available background material, a comparison is made between engineering geological conditions and rock quality as seen on the surface and as experienced in the tunnel. Generally high degree of jointing combined with chlorite and clay filling of the joints are found to be the main reasons of the stability problems. A prognosis of rock mass quality of the remaining part of the tunnel is presented.

1995:

Parida, Sanjay Kumar: Evaluation of unlined high pressure tunnels, Ormsetfoss hydroelectric project, Norway - a case study.
(/NTE)
Following a thorough review of the engineering geological conditions, the design of the unlined pressure shaft at Ormsetfoss are analysed based on 1) Empirical methods (literature review), 2) Rules of thumb (modified equilibrium methods) and 3) Numerical modelling. It is concluded that according to all analyses carried out, the design of the pressure shaft is well on the safe side.

Schönborn, Thomas: Stability analysis of the Gausdal open pit mine.
(Nilsen/Myrvang, in cooperation with RWTH Aachen & A/S Olivin)
A stability analysis for the Gausdal open pit peridotite mine in Western Norway has been carried out. Based on comprehensive joint mapping, three main joint sets were identified. The most distinct is represented by steep foliation joints, striking parallell to the main slope. The main risk of slope failure is represented by undercutting of these foliation joints. The factor of safety may be increased by as much 40 % by draining the slope.

Øverland, Jan Håvard: Railway tunnels in Trøndelag - Engineering geological analysis of portal areas.
(NSB Baneregion Nord)
Engineering geological mapping and stability evaluation of about 30 portal areas of railway tunnels in Trøndelag have been carried out. The need of rock support has been discussed, and technical solutions evaluated. Only in two cases, potential instability has been identified. For these cases, a system for continuous monitoring is suggested.

1994:

Broch, Hanna Rachel: Optimisation of alignment of Drøbak sub-sea tunnel.
(/Statens Vegvesen, Anleggskontoret)
A key issue in the planning of sub-sea tunnels is to optimise the alignment according to the actual engineering geological conditions. This thesis particularly emphasises on engineering geological optimisation regarding rock cover. The effect of increase/reduction of rock cover on cost is also discussed. Based on engineering geological evaluation it is concluded that in this case 30 m rock cover is satisfactory.

Sivertsen, Svein Arne: Durability of rock support in Maursund and Kvalsund sub-sea tunnels.
(/Statens Vegvesen, Troms)
Because of the particularly aggressive environment of sub-sea tunnels, durability of rock support is a key issue. Visual inspection, sampling and laboratory testing of support elements, with main emphasis on rock bolts and shotcrete have been carried out. Indications of initial wash out of cement have been identified, but no corrosion of rock bolts.