Geological investigation.....

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28. Importance of engineering geology in building
construction
• Site investigation provides crucial information about the geotechnical and
geological characteristics of the site, including soil and rock type,
stratigraphy, groundwater conditions, and shear strength parameters.
• Identifying potential hazards, such as landslides, slope instability,
liquefaction, and settlement, is an essential part of the site investigation
process.
• Site investigation helps assess the soil and rock conditions to determine
the appropriate foundation design and construction methods, ensuring the
stability and safety of the building.
• Proper site investigation assists in selecting the site for construction by
evaluating factors such as accessibility, geotechnical and geological
setting, environmental considerations, and previous land use.
• Recommendations for necessary mitigation measures based on site
investigation findings help ensure safe and effective building construction.
• Ultimately, proper site investigation is crucial for minimizing the potential
for construction-related hazards and risks while ensuring the safe and
efficient design and construction of buildings.
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29. Factors considered when selecting the
building construction site for investigation
1. Accessibility: The site should be easily accessible by road, rail, and other
transportation methods to facilitate the movement of materials and workers.
2. Geotechnical and geological setting: The site's geotechnical and geological
characteristics, such as soil and rock type, stratigraphy, and groundwater
conditions, should be considered to determine the site's suitability for
construction.
3. Environmental considerations: The site's environmental characteristics, such
as land use history, potential contamination, and proximity to environmentally
sensitive areas, should be assessed to identify any potential environmental
risks.
4. Regulatory compliance: The site must comply with relevant regulatory
requirements, including zoning regulations, building codes, and environmental
regulations.
5. Construction cost: The cost of construction is an important consideration when
selecting a site, as it affects the overall project budget.
6. Future development potential: The site's potential for future development
should be considered to ensure that the project aligns with long-term goals.
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30. findings of a site investigation related to the
soil and rock conditions
1. Soil and rock types: The type of soil or rock present at the site can affect
foundation design and construction methods. The site investigation may reveal
whether the soil is cohesive or non-cohesive, whether it is composed of clay,
silt, sand, or gravel, and whether the rock is igneous, sedimentary, or
metamorphic.
2. Stratigraphy: The site investigation may reveal the stratigraphic sequence of
the soil and rock layers, including their thickness, depth, and orientation. This
information can help identify potential hazards such as landslides, soil
liquefaction, and slope instability.
3. Groundwater conditions: The investigation can also identify the groundwater
conditions at the site, including the depth of the water table and the
permeability of the soil or rock. This information is crucial for designing and
constructing effective drainage systems.
4. Shear strength parameters: The investigation may also determine the shear
strength parameters of the soil and rock, such as the angle of internal friction,
cohesion, and shear modulus. These parameters are important for foundation
design and construction methods.
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31. Equipment used in site
investigation
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Source:google

32. identifying potential hazards that may affect
the safety and stability of a building during
construction
1. Landslides: The investigation may reveal the presence of unstable slopes or soil
conditions that can cause landslides. These hazards can be particularly significant if the
site is located on a steep slope, in an area with high rainfall or seismic activity, or in an
area with a history of landslides.
2. Soil liquefaction: Soil liquefaction occurs when saturated soil loses strength and stiffness
during an earthquake, resulting in ground settlement and damage to the foundation. The
investigation may reveal the presence of soil types that are susceptible to liquefaction,
such as loose, sandy, or silty soils.
3. Soil settlement: Soil settlement occurs when soil beneath a foundation compresses,
causing the foundation to sink. The investigation can identify soil types that are prone to
settlement, such as loose, saturated, or organic soils.
4. Groundwater: The investigation may reveal the presence of high groundwater levels or
water flow that can cause instability or affect the performance of foundation structures.
5. Soil contamination: The investigation may identify the presence of hazardous materials or
chemicals in the soil, which can pose a risk to human health and the environment.
6. Seismic hazards: The investigation may identify potential seismic hazards, such as
liquefaction, ground shaking, or fault rupture.
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33. Engineering geological investigation of
road and canal
 It deals with the application of geology for a safe,stable and
economical design and construction of civil engineering projects.
 Road:-It is traveled way on which people,animals and vehicles move.
 This subject involves the planning, design, construction, operation, and
maintenance of roads, bridges, and tunnels to ensure safe and effective
transportation of people and goods.
 Grade:-it is the magnitude of its incline or slope. There are different type of
gradient which are rulling gradint,limiting gradient,exceptional gradient
and minimum gradient.
 Level terrain: Any combination of grades and horizontal and vertical
alignment permitting heavy vehicles to maintain approximately the same
speed as passenger car.
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34. General considerations of road design
Source:-Google
Rainfall
Temperature
Atmospheric
pressure
Geological
condition
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35. CANAL
 It is an artificial channel constructed on the ground to carry water to the
field either from a reservoir, tank or river.
 The canal is an artificial channel, usually trapezoidal in section.
 It is construct on the surface of the ground.
 It is use to convey water from the river, lake, reservoir, etc., to fields for
irrigation, for water supply schemes, for power generating units, etc.
 Classification of canals
o Based on financial output
o Based upon the nature of source supoply
o Based upon the purpose of canal
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36. Design of canal
 In the design of a canal one has to find out bed width (B) depth (D), longitudinal slope
(S), and velocity of flow (V).
 In order to obtain the most economical section, it is necessary to adopt the best
discharging section.
 Following data should be known before design of the canal can be carried out:
• Discharge of the channel (Q)
• Rugosity coefficient (N).
• Slope of banks.
• Permissible velocity of flow
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37. Cross section of canal
Source:-Google
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38. Tunnels
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Fig:1

39. Significance of Tunneling in Nepal
 It helps nation to easily transport and manage traffic without hampering the human
settlement.
 For a mountainous country like Nepal, it plays an important role in connecting two places .
 It allows rapid and unobstructed transport facilities in big congested cities.
 To reduce the impact of surface transit operations faced in sensitive areas.
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Fig:2

40. 1.Traffic Tunnels
2.The hydropower Tunnels
3.The public utility tunnels
Types of tunnel
Fig 3: Traffic tunnel Fig 4: Hydropower Tunnel
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Fig 5: Traffic Tunnel

41. In addition, road tunnels or viable means to minimize potential environment
impact such as traffic congestion ,pedestrian n movement ,air quality ,noise
pollution ,visual intrusion ;to protect areas of special culture or historical value
such as conservation of districts, buildings or private properties ;or for other
sustainability reason such as to avoid the impact on natural habit or reduce
disturbance to surface land
Fig:7
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42. 2.The hydropower tunnels
Due to steep terrain and fast flowing rivers in the Lesser Himalayan region of
Nepal, medium to mega size hydropower projects are constructing day-by–
day. The availability of high head for hydropower generation the tunnel cross
sections are relatively small, up to 6 m diameter in size. Excessive tunnel
deformation and support failure were encountered in this region during the
construction as it passes through very weak rock masses with high overburden
pressure. The selection of tunnel supports is carried out by empirical methods,
basically rock mass classification approaches. Among them, Rock Mass Rating
(RMR) by Bieniawski (1984) and Q-system rock classification proposed by
Barton et al. (1974) are mostly used in the Himalayan region to prescribe
tunnel support. Drill and blast is a common method for construction of the
tunnel in this region.
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43. . During blasting, the surrounding rock mass gets disturbed
which is not considered in rock mass classification approach.
This paper focuses on the analysis and design of tunnel
support by using empirical, analytical and numerical
methods. In this study, Middle Bhotekoshi Hydropower tunnel
was selected for the case study, which is an under
construction project located in the Lesser Himalayan region
of Nepal.
Fig:7
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44. 3.The public utility tunnels
Utility tunnels are underground passages created to transport various types of
utility services such as electricity, water, and sewage. They are also used to
hold communication lines like cable television and telephone cables. These
tunnels are also known as service tunnels, trenches, vaults or cable vaults.
For smaller cables, they are often placed in cable ducts or underground
conduits. An alternative to using these tunnels is to bury the cables directly
in the ground.
Fig:8
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45. Geological Investigations for Tunnels:
Objects:
Geological investigations are very essential in tunnelling projects.
These determine to a large extent solutions to following engineering
problems connected with tunnelling:
(a) Selection of Tunnel Route (Alignment):
There might be available many alternate alignments that could connect two
points through a tunnel. However, the final choice would be greatly
dependent on the geological constitution along and around different
alternatives: the alignment having least geologically negative factors
would be the obvious choice.
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46. (b) Selection of Excavation Method:
Tunnelling is a complicated process in any situation and involves huge
costs which would multiply manifolds if proper planning is not
exercised before starting the actual excavation. And the excavation
methods are intimately linked with the type of rocks to be excavated.
excavated. Choice of the right method will, therefore, be possible
only when the nature of the rocks and the ground all along the
alignment is fully known. This is one of the most important aim and
object of geological investigations.
Fig:9
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47. (c) Selection of Design for the Tunnel:
The ultimate dimensions and design parameters of a proposed tunnel are controlled, besides
other factors, by geological constitution of the area along the alignment. Whether the
tunnel is to be circular, D-Shaped, horse-shoe shaped or rectangular or combination of
one or more of these outlines, is more often dictated by the geology of the alignment
than by any other single factor.
Thus, in self-supporting and strong rocks, either, D-shape or horse-shoe shape may be
conveniently adopted but these shapes would be practically unsuitable in soft ground or
even in weak rocks with unequal lateral pressure. In those cases circular outline may be
the first choice.
Fig:10
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48. (d) Assessment of Cost and Stability:
These aspects of the tunnelling projects are also closely interlinked with
the first three considerations. Since geological investigations will
determine the line of actual excavation, the method of excavation
and the dimensions of excavation as also the supporting system
(lining) of the excavation, all estimates about the cost of the project
would depend on the geological details.
Similarly tunnels passing through hard and massive rocks even when
left unsupported may be regarded as stable. However, those passing
through difficult grounds, although these might have been
massively strengthened by secondary support system, might still
collapse or bulge at places or even completely fail, if geological
situation is not perceived properly.
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49. (e) Assessment of Environmental Hazards:
The process of tunelling, whether through rocks or through soft ground, and
for whatsoever purpose, involves disturbing the environment of an area in
more than one way. The tunelling methods might involve vibrations
induced through blasting or ground cutting and drilling, producing
abnormal quantities of dust and last but not the least, interference with
water supply system of the nearby areas.
A correct appreciation of geological set up of the area, especially where
tunnel alignment happens to be close to the populated zones, would
enable the engineer for planning and implementing plans aimed at
minimizing the environmental hazards in a successful manner.
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50. Methods:
The geological information required for tunelling projects may not always be
similar to that required for other civil engineering projects. As a matter of
practice, the desired geological details for a tunnel project are obtained in
three stages using specific methods in each stage. These stages are –
preliminary surveys, conducted well before the actual planning of the
project; detailed surveys which are conducted almost simultaneously with
planning and concurrent explorations which are undertaken during the
construction.
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51. A. Preliminary Surveys:
These are conducted by the routine geological,
geophysical and geochemical methods. In
modern practice and for major tunnelling
projects such fast techniques as aerial
photography and seismic surveying are
commonly adopted in combination with the
routine surface methods.
Fig:11
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52.  Following geological characters are broadly established for the entire area in
which the tunnel project is to be located as a result of preliminary surveys:
 (a) The general topography of the area marking the highest and the lowest
points, occurrence of valleys, depressions, bare and covered slopes, slide areas,
and in hilly regions and cold climates, the snow-line.
 (b) The lithology of the area, meaning thereby, the composition, attitude and
thickness of rock formations which constitute the area.
 (c) The hydrological conditions in the area, such as depth of water table,
possibility of occurrence of major and minor aquifers of simple type and of
artesian type and the likely hydrostatic heads along different possible routes or
alignments.
 (d) The structural condition of the rock, that is, extent and attitude of major
structural features such as folding, faulting, unconformities, jointing and shearing
shearing planes, if developed. Existence of buried valleys is also established
during the preliminary surveys.
 In addition, such surveys would also reveal occurrence of reserves of rocks that
could be beneficially used for construction programmes (lining etc.) in the tunnel
project.
 It is obvious that with the help of above information, the engineers could
propose a number of alternative tunnel routes to connect the two places, and in
most cases, even decide about the general run of the tunnel.
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53.  B. Detailed Surveys:
 Once the general run of the tunnel has been decided, planning for its
construction begins. Such plans require fairly accurate data about the
rocks or the ground to be excavated for passing through.
 Such data are obtained by:
 (i) Bore-hole drilling, along proposed alignments and up to desired
depths; the number of bore-holes may run into dozens, scores or
even hundreds, depending upon the length of the tunnel; rock
samples obtained from bore holes are analysed for their mechanical
and geochemical properties in the laboratories;
 (ii) Drilling exploratory shafts and adits, which allow direct approach
to the desired tunnel for visual inspection in addition to the usual
advantages of drilling;
 (iii) Driving pilot tunnels, which are essentially exploratory in nature
but could better be used as a main route if found suitable by
subsequent enlargement.
 The actual number of bore holes and shafts and adits and their depth
depth and length are decided by the length and location of the
proposed tunnel. For tunnels with little overburden, these may be
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