This document provides an overview of site investigation procedures for tunneling projects. It discusses the objectives of site investigations which include developing a conceptual model of ground conditions and behaviors. It outlines various investigation techniques such as desk studies, site reconnaissance, subsurface investigations including borings and sampling, in-situ testing, geophysical testing, and environmental studies. The document also discusses preliminary studies of tunnel type and shape, route selection factors, and groundwater control methods.

1. Site Investigation for
Tunneling
TUN TUN NAING | 2.6.2022

2. Objective
•To develop a conceptual model to estimate
the range of ground conditions and behaviors
for excavation, support and groundwater
control

3. • Feasible alternative to cross a water body or traverse through
physical barriers
• Minimizing the potential environmental impact, traffic congestion,
pedestrian movement, air quality, noise pollution
• Conservation of special cultural or historical value
• Avoiding the impact on natural habit or reduce disturbance to land
surface

4. • Three main shapes: circular, rectangular, and horseshoe or curvilinear
Shape and Internal Elements
Two Cell RectangularTunnel

5. • Three main shapes: circular, rectangular, and horseshoe or curvilinear
Shape and Internal Elements
CircularTunnel Horseshoe and Curvilinear Tunnel

6. Route Studies
• Subsurface, geological, geo-hydraulic condition
• Long- term environmental impact
• Seismicity
• Land use restriction
• Sustainability: the opportunities that tunnels provide for
environmental improvement and real estate development over them

7. Geotechnical Investigations
• Critical for proper planning of a tunnel
• Selection of alignment, cross section and construction methodology
• Avoiding location of potential ground movement: settlement,
landslide
• Avoid crossing of a fault zone is recommend in planning phase: a
proper measures for crossing should be implement if avoidance of a
fault cannot be achieved
• Seismic consideration
• Geotechnical issues; such as soil and rock properties, ground water,
the ground over the tunnel, the presence of contaminants and
utilities

8. Sustainability
• Longer life expectancy than a surface facility
• Opportunities for land development for residential commercial, or
recreational facilities
• Enhance the area potentially increase property values
• Enhance communities connections and adhesion protect residents
from traffic pollutants and noise

9. Tunnel Type Studies
• Cut and cover tunnels: by excavating a trench, constructed in place by
using precast sections
• Bored or mined tunnel: without excavating the ground surface,
usually labeled according to the type of material being excavated
• Rock tunnel: by drilled and blasting, tunnel boring machines (TBM),
Sequential Excavation method (SEM)
• Soft ground tunnels: excavated in soil by using a shield or pressurized
faceTBM, SEM
• Immersed tunnels: built with very large precast concrete or concrete
filled steel elements
• Jacked box tunnels: prefabricated box structures jacked horizontally
through the soil; to avoid disturbing the surface utilities in shallow
excavation

10. Preliminary RoadTunnelType Selection Process

12. Groundwater control
• No dripping or visible leakage from a single location shall be
permitted

13. • Two basic types of water proofing systems: undrained and drained
• Open system: an umbrella like protection that drains the water
seeping toward the cavity around the arch into a drainage system
located at the bottom of the tunnel sidewalls and in tunnel invert;
commonly used in rock tunnel
• Closed system: refer as tanked system, water proofing membranes
encapsulating the structure, applied in permeable soil esp. at
discharge area
Groundwater control

15. Geotechnical Investigation
• Desk study
• Site Reconnaissance and Survey
• Geologic Mapping
• Subsurface Investigation
• FieldTestingTechnique
• Environment Studies

16. • To obtain necessary characteristics and properties for design and
construction
• To be consistent with the project scope (i.e., location, size and
budget), the project objectives (i.e., risk tolerance, long-term
performance), the project constraints (i.e., geometry,
constructability, third-party impacts, aesthetics, and environmental
impact)
• To be aware of inevitable risk

17. Phased Geotechnical Investigation with Project Development Process

18. Desk Study
• An overall understanding of the site conditions and constraints
• Collection of published topographical, hydrological, geological,
environmental zoning, and other information
• Historical seismic records, USGS
• Case histories of underground work s in the region
• University publications
• Plan subsurface investigation program
• Preliminary mapping (aerial photo, topographic map, route plan)

19. Sources of Information Data
(After FHWA, 2002a)

20. Site Reconnaissance
• A preliminary survey to expand existing topographical data
• A careful reconnaissance over the tunnel alignment, potential portal
and shaft locations
• Feature identified on map and air photo should be verified
• Rock outcrops provide fracturing and discontinuities’ orientation
• Features should be photographed, documented with location
• A preliminary horizontal and vertical control survey to obtain general
site data for route selection and for design

21. Site Survey
• To establish primary control for final design and construction
• to support surface geology mapping and the layout of exploratory borings,
whether existing or performed for the project
• To mark centerline of tunnel
• For transfer of line and grade from surface to tunnel monuments, alignment
control, locating and monitoring geotechnical instrumentation
• Principle survey techniques-
 Global positioning system (GPS)
 EDM withTotal stations (displacement and settlement monitoring)
 Remote Sensing (terrain condition, geologic formation, faults, soil- rock formation)
 Laser Scanning (3D digital imaging at 0.25 inch/150 feet)
3D laser Scanning Tunnel Survey

22. Hydrographical Surveys
• For subaqueous tunnels including immersed tunnel
• To determine bottom topography of the water body, flow direction
and velocity, range in water level
• To determine the existence and location of submarine pipelines,
cables, natural obstructions

23. Utility Surveys
• Esp. in urban areas, to determine type and extent of utility
protection, relocation or reconstruction needed
• The requirement varies with tunneling methods and site conditions
• Cut and cover tunnel
• Gas, steam water, sewerage, electrical, fiber optic

24. Geologic Mapping
• surface geologic mapping of available rock outcrops should be
performed by an experienced engineering geologist to obtain detailed,
site-specific information on rock quality and structure
• Rock mass classification
Discontinuity type
Discontinuity orientation
Discontinuity infilling
Discontinuity spacing
Discontinuity persistence
Weathering

25. Source: JICA project)
• To observed during the geologic mapping
program
Slide
Fault
Sink holes and karstic terrain
Groundwater springs
Volcanic activity
Presence of boulders

26. Subsurface Investigation
• Defining the subsurface profile (i.e. stratigraphy, structure, and
principal soil and rock ty pes)
• Determining soil and rock material properties and mass
characteristics
• Identify geological anomalies, fault zones and other hazards
(squeezing soils, methane gas, etc.)
• Defining hydrogeological conditions (groundwater levels, aquifers,
hydrostatic pressures, etc.)
• Identifying potential construction risks (boulders, etc.)

27. Subsurface Investigation
• consist of borings, sampling, in situ testing, geophysical
investigations, and laboratory material testing
• Boring to identify the subsurface stratigraphy, to obtain disturbed
and undisturbed samples
• In Situ test- to obtain engineering and index properties
• Geophysical tests, to obtain subsurface information over a large area
• Laboratory testing from representative soil samples and rock core
• A more thorough subsurface investigation program would likely have
fewer problems and lower final cost

29. Vertical and Inclined Test Boring
• The location, depth, sample types and
sampling intervals for each test boring
must be selected to match specific
project requirements, topographic
setting and anticipated geological
conditions

30. Horizontal and Directional Boring
• provide a continuous record of ground conditions
and information which is directly relevant to the
tunnel alignment
• horizontal borings can be more economical,
especially for investigating a deep mountainous
alignment
• horizontal borings can be more economical,
especially for investigating a deep mountainous
alignment
• horizontal borings can be more economical,
especially for investigating a deep mountainous
alignment

31. Sampling
• Disturbed soil sample typically at interval not greater than 5 ft and at
change in strata
• Undisturbed sample from each cohesive soil stratum encountered in
boring, an interval not exceeding 15 ft where a thick stratum of
cohesive soil is present
• Rock coring
Depth of core run
Core recovery in inches and percent
RQD
Rock type, including color texture, degree of weathering and hardness
Character of discontinuities, spacing, orientation, roughness and alteration
Nature of joint filling material

32. • In situ tests
• Geophysical testing
Field Testing Techniques

33. • to directly obtain field measurements of useful soil and rock
engineering properties
• in situ testing include both index type tests, such as the Standard
PenetrationTest (SPT) and tests that determine the physical
properties of the ground, such as shear strength from cone
penetrationTests (CPT) and ground deformation properties from
pressure meter tests (PMT)
In situ tests

34. • provide an expeditious and economical means of supplementing
information obtained by direct exploratory methods, such as borings,
test pits and in situ testing; Identifying local anomalies
• determination of the top of bedrock, the ripability of rock, the depth
to groundwater, the limits of organic deposits, the presence of voids,
the location and depth of utilities, the location and depth of existing
foundations, and the location and depth of other obstruction
• Geophysical testing can be performed on the surface, in boreholes
(down or cross hole), or in front of theTBM during construction
Geophysical testing

35. Environment Studies
• Land ownership and uses
• Ecosystem habitat impact
• Impacts to groundwater levels, aquifers and water quality
• Access to residential and commercial properties
• Pest control during construction
• Long term community impacts
• Sites for disposal

36. ThankYou