1. GEOLOGICAL AND ENVIRONMENTAL INVESTIGATIONS OF TUNNEL PROJECTS

2. Geological and environmental investigation of tunnel projects
Purpose of construction of tunnel project
Geological impact of construction of tunnel project
Environmental impact of construction of tunnel projects
Measures to reduce the impact of construction of proposed tunnel projects

3. Tunnels
Tunnel is a nearly horizontal underground passage which is open at both ends.
Tunnels are of different types according to their uses like traffic tunnel, hydropower headrace tunnel and public utility tunnels etc. • Tunnels can be driven or holed through a rock or earth mass by method used in mining, including blasting. •  In soft ground tunnels may be excavated by boring machines with the walls being supported by liner plates.

5. PURPOSE OF TUNNELS
Transportation - Reduce distance between two locations , reduce the travelling time (bus, rail)
Supply of water for irrigation, industry, agriculture
Supply of water for hydropower generation
Underground mining
Transportation of materials in underground mines
Public utility purpose – drainage, gas pipe line, diesel/ petrol/ crude oil pipe line, cables
Bunkers for safety .
Strategic storage of materials ( HPCL crude oil storage at Visakhapatnam)

6. Pilot tunnel(subsurface investigation)
A small tunnel or shaft excavated in advance of the main drivage in mining and tunnel building to gain information about the ground, create a free face, and thus simplify the blasting operations
Geology is the most important factor that determines the nature, form and cost of a tunnel.

7. Geological profile
This profile should show the different type of rocks and soils along the tunnel line, boundaries between them (contacts) and geological defects such as fault.
Water tables needed to be located before the alignment of tunnels
Tunnelling in hard rocks  is more favourable than into the soft rocks as shale, slate.
Tunnelling in soft soil and rock create problem of support as well as squeezing and swelling.

8. Tunnelling in horizontal bed is more favourable as pressure is distributed in all direction in case of horizontal bed unlike the inclined bed where the pressure concentration is at one side.
Location of tunnel in an anticline is not recommended due to the stressed condition of rock in the hinge area.
If water bearing strata is encountered in the syncline then the water tends to flow into the tunnel.

9. How the impact is different from a hazard
A proposed tunnel project may have various impacts. All these can be predicted well in advance at the time of preparation of Environmental Impact Assessment (EIA) report.
Various Impacts of the tunnel project are
Impact on Environment
Impact on Economy
Impact on Culture
Impact on Society.

10. Geological impact of construction of tunnel projects
Any lapse in selection of proper alignment will lead more distance to travel
Lapses in identification of fractured/ jointed rocks at roof may leads to collapse of tunnel
If tunnel axis below the groundwater table, there will be heavy seepage of water in to tunnel
If weak rocks are occurring in the proposed tunnel route, it requires support.

11. Geological impact of construction of highway projects
If faults are not identified before, further displacement of blocks may take place.
If folds are not identified properly , the tunnel will not be safe

12. ENVIRONMENTAL IMPACT OF TUNNEL PROJECT
Construction of tunnel projects will also have negative impact on environment
Loss of forest land if proposed to pass through forest
Problem of dumping of excavated debris

13. Loss of forest land Loss of Green Cover/tress, shrubs wooden material
Loss of tribal culture/ forces migration of tribals to remote areas
Loss of forest produce
- nuts, leaves , spices, gum, fruits, honey, plant based medicines, fiber, timber, fire wood etc.
Impact on climate, rain fall,/ micro climatic changes
Loss of carbon absorption capacity
Loss of bio diversity
Reduction in cleaning capacity of pollutants

14. Loss of forest land
Loss of educational benefits Loss of tourism Loss of aesthetic effect Forest reduces run off and increases infiltration Reduction in infiltration will leads to reduction in availability of groundwater Contributes to floods Loss of ecological benefits In accessible areas in forest will have access to human beings

15. Loss of forest produce nuts leaves spices gum fruits honey
plant based medicines
fiber, timber, fire wood etc.

16. Impact on climate and rain fall
Loss of forest cover results in reduction in CO2 absorption capacity in turn capacity to give O2 also comes down
Increase in temperature in adjoining areas

17. Loss of forest land

18. Loss of wild life
Loss of shelter to wild life will lead to migration of wild animals
Loss of bio diversity
Species may become extinct
Livelihood of tribals will get effected

19. Loss of wildlife

20. Geological and environmental investigations
The purpose of geological and environmental investigation is to identify a suitable site for construction of tunnel projects
- tunnel should be safe
- cost of construction should be economic
- cause less damage to the natural and man
made environment
- tunnel alignment - least distance between the destinations, less excavation, less lining
We need to identify at least two or more routes, evaluate and finally select the route having minimum damage to the environment , safe and economic.

21. Geological investigations
Utilize remote sensing, geological, topographical maps and hydrological maps for alignment of tunnel route
We need to look for shortest possible route
Avoid the locations where soft rocks are occurring. Soft require lining with concrete for stability, results increase in cost
Identify the geological structures – folds, faults and assess stability of rocks by carrying out drilling/ digging shaft along the proposed route

24. 1.main tunnel
2.Service tunnel
3.pilot tunnel
4.connecting gallery

27. Geological investigations
Strong squeezing and high plastic deformation in rocks
Spalling and rock burst in hard rocks associated with high in-situ stresses
Swelling and creep in argillaceous rocks
High water pressure and/or large water inflows

28. Geological investigations
Syncline (the strata slopes upwards)areas are highly unsafe for tunnel when there is water flow in that area
Fault areas are unsafe for tunnel
Identify the rocks occurring along the proposed route and locations of occurrence of soft rocks. Soft rocks require concrete lining.
Identify the position of the proposed tunnel along the proposed route with respect to ground water.

30. Geological investigations
If tunnel passes below the groundwater , it requires lining to prevent seepage.
Map the inclination of the rocks. Thin horizontal rocks are unsafe and require concrete lining
Excavation is done from both the sides. If any failure/ deviation in route will leads to waste of huge investment

31. Environmental investigations
Detailed investigations are essential to assess the impact of the proposed high projects on natural and man made environment
Impact on forestland
Wild life
Economy
Ecological
Aesthetic
Social
Cultural

32. Measures to reduce the impact of tunnel projects
Utilize latest technologies available such as remote sensing geological, topographical maps and hydrological maps to arrive the tunnel alignment
Select the route that cause minimum damage
Preferably avoid passing the route through forests to the possible extent
If required the tunnel to pass through forest , go for compensatory afforestation
Prefer the route that requires less lining, less excavation

33. Measures to reduce the impact of tunnel projects
resettlement and compensation in a appreciable manner
We need to identify at least two or more routes, evaluate and finally select the route having minimum damage to the environment , safe and economic.