Rock mechanics for engineering geology (part 2)

DEEP FOUNDTION
Jyoti Khatiwada Anischit
This part is also useful for site investigation

DEFINITION
 If the depth of a foundation is greater than its
width, the foundation is known as deep
foundation.
 In deep foundation the depth to width ratio is
usually greater than 4 to 5.
 Deep foundations as compare to Shallow
foundations distribute the load of the super structure
vertically rather than laterally.
 Deep foundations are provided when the expected
loads from superstructure cannot be supported on
shallow foundations.

Examples of Deep Foundations
 Pile foundations
 Pier foundations
 Wells or
Caissons foundations.

WHEN IT IS USED?
 In cases where
 The strata of good bearing capacity is not available near the ground
 The space is restricted to allow for spread footings
 In these cases the foundation of the structure has to be taken
deep with the purpose of attaining a bearing stratum which is
suitable and which ensures stability and durability of a structure.
 The bearing stratum is not the only case. There may be many
other cases. For example, the foundation for a bridge pier must
be placed below the scour depth, although suitable bearing
stratum may exist at a higher level.

TYPES OF DEEP FOUNDATION
Deep foundation is classified into following types:
• Pile foundation
• Well foundation
• Caisson foundation

Pile Foundations
 Pile foundations are the part of a structure used to
carry and transfer the load of the structure to the
bearing ground located at some depth below ground
surface.
 The main components of the foundation
1. The piles 2. The pile caps

CONT’D
 Piles are long and slender
members which transfer
the load to deeper soil or
rock of high bearing
capacity avoiding
shallow soil of low
bearing capacity.
 Pile caps are thick slabs
used to tie a group of
piles together to support
and transmit column
loads to the piles.

Pile Foundations
 Where Used :
 stratum of required bearing capacity is at greater depth
 steep slopes are encountered
 Compressible soil or water-logged soil or soil of made-up type
 Examples: Piles are used for foundation for buildings, trestle-bridges
and water front installations (piers, docks etc ).

Types of Piles Based on Function
Classification based on Function or Use
1. End Bearing Piles
2. Skin Friction Piles
3. Compaction Piles
4. Driven Piles
5. Auger cast Piles

Types of Piles (cont’d)
End Bearing Piles
 Driven into the ground until a
hard stratum is reached.
 Acts as pillars supporting the
super-structure and transmitting
the load to the ground.
 Piles, by themselves do not
support the load, rather acts as
a medium to transmit the load
from the foundation to the
resisting sub-stratum.

Skin Friction Piles (Floating Piles)
 Piles are driven at a site where soil is
weak or soft to a considerable depth
and it is not economical or rather
possible to rest the bottom end of the
pile on the hard stratum,
 Load is carried by the friction developed
between the sides of the pile and the
surrounding ground ( skin friction).
 The piles are driven up to such a depth
that skin friction developed at the sides
of the piles equals the load coming on
the piles.
 The load carrying capacity of friction pile
can be increased by-
 increasing diameter of the pile
 driving the pile for larger depth
 grouping of piles
 making surface of the pile rough

Anchor Piles
 Piles are used to provide anchorage against horizontal pull from sheet
piling wall or other pulling forces.
Compaction piles:
 When piles are driven in granular soil with the aim of increasing the
bearing capacity of the soil, the piles are termed as compaction piles.

Driven piles:
 Driven piles are deep foundation
elements driven to a design
depth. If penetration of dense soil
is required, pre drilling may be
required for the pile to penetrate
to the design depth. Types
include timber, pre-cast concrete,
steel H-piles, and pipe piles.

Types of Piles (cont’d)• Auger cast piles
Auger cast piles, are deep foundation
elements that are cast-in-place, using
a hollow stem auger with continuous
flights. The auger is then slowly
extracted, removing the drilled
soil/rock.. Reinforcing steel is then
lowered into the wet concrete or
grout. The auger is drilled into the
soil or rock to design depth. The
technique has been used to support
buildings, tanks, towers and bridges.

Well foundations
 Well foundations are
being used in India
from very early days.
Taj Mahal was built on
such foundations. Wells
are also type of deep
foundations. The main
difference between a
well and a pile
foundation is that,
while a pile is flexible
like a beam under
horizontal loads, the
well undergoes rigid
body movement under
such loads.

Types of Well Foundation
Wells have different
shapes and accordingly
they are named as
• Circular Wells
• Dumb bell
• Double-D Wells
• Double Octagonal Wells
• Single and Double
Rectangular Wells
• Multiple Dredged Holed
Wells

LOADS FOR WELL FOUNDATION DESIGN
The following loads are considered for the
analysis and design of well foundation:
1.Dead load
2.Live load
3.Buoyancy
4.Wind load
5.Horizontal force due to water current
6.Centrifugal forces
7.Longitudinal forces
8.Seismic forces
9.Horizontal shear forces at bearings due
to longitudinal forces and seismic forces
10.Forces due to tilt and shift.

TYPES OF FOUNDATION
Caissons
Caisson foundation is also known as
pier foundation.
Caisson is a cylinder or hollow box
that is sunk into the ground to a
specified depth by auguring a deep
hole into the strata. The cylinder or
box is then back filled with
concrete, thus creating the
foundation.
This type of foundation is most
often used when constructing
bridge piers and other such
foundations that will be beneath
bodies of water since the caissons
can be floated to the correct
locations and then sunk in place
using concrete.

Why To Use a Caisson Foundation
• This type of foundation will keep the soils
underneath the building or structure from moving
vertically. Since soil will settle over time, the
building or structure on top of the soil will also
settle. This can cause major structural damage.
Since a caisson foundation is drilled into the earth
and large concrete t filled cylinders are placed
within the ground rather than on top, the
settlement of the soil will not cause many
difficulties for the building or structure.

Types of Caissons
• Box caissons are watertight
boxes that are constructed
of heavy timbers and open
at the top. They are
generally floated to the
appropriate location and
then sunk into place with a
masonry pier within it.
• Excavated caissons are just
as the name suggests,
caissons that are placed
within an excavated site.
These are usually cylindrical
in shape and then back filled
with concrete.

Types of Caissons (cont’d)
• Floating caissons are also
known as floating docks and
are prefabricated boxes that
have cylindrical cavities.
• Open caissons are small
cofferdams that are placed
and then pumped dry and
filled with concrete. These
are generally used in the
formation of a pier.
• Pneumatic caissons are
large watertight boxes or
cylinders that are mainly
used for under water
construction.

Careful study of loads to be transmitted from
columns of super structure and soil profile.
Objective :
oTo identify type of pile
oTo determine load carrying capacity of
individual pile
Only one type of pile below different columns
For large projects two or three sizes may be
adopted

1. IDENTIFYING STRONG BEARING
LAYER FOR LOCATING THE PILE TIP
• Study soil profile
• Look for strong bearing layer
IF STRONG BEARING LAYER IS FOUND
• Locate pile tip, a few meters, in
• Pile becomes ‘end bearing pile’
• Easy to conduct settlement analysis

IF NO STRONG BEARING LAYER IS FOUND
• Pile should be friction pile.
• Pile derives its capacity from both, end
bearing & friction.
• Select two pile lengths as deep as possible.

2. SELECTION OF PILE
Choice of pile depends on
Length
Width
Material ( concrete, steel, wood)
Cross-section (square, circular, tubular)
Installation procedure (driven, bored)
Feasibility of construction
Feasibility of noise and vibration

3. RANGE OF PILE LENGTH &
DIAMETERS
LENGTH :
• Usually 10 – 30 m
• Offshore application 70 – 100 m
WIDTH/DIAMETERS :
• Usually 0.3 – 0.75 m
• Drilled piles 1 – 2.5 m
• Micropiles 0.15 m

4. AXIAL CAPACITY ANALYSIS
Pile type – selected
Range of dimensions – chosen
Estimate the axial capacity
One of the procedures is ‘Pile Load Test’

5. SETTLEMENT ANALYSIS
• For piles, not resting on strong bearing
capacity, settlement analysis is conducted.

6. RESULTS & RECOMMENDATIONS
Presented in tabular form.
In selecting from the options available, two factors
are given :
Large sized but fewer number of piles, hence
installation time is less.
3 piles (min. number) can support only lightly
loaded columns, for heavier loads, increase the
pile group.

ADVANTAGES OF DIFFERENT METHODS
OF DEEP FOUNDATION
DRILLED PIER FOUNDATIONS
Advantages
1.Pier of any length and size can be constructed
at the site
2. Construction equipment is normally mobile and
construction can proceed rapidly
3. Inspection of drilled holes is possible because of
the larger diameter of the shafts
4.The drilled pier is applicable to a wide variety of
soil conditions
5.Changes can be made in the design criteria
during the progress of a job
7.Ground vibration that is normally associated with
driven piles is absent in drilled pier construction
8.Bearing capacity can be increased.

Disadvantages
1. Installation of drilled piers needs a
careful supervision and quality control of all
the materials used in the construction
2. The method is cumbersome. It needs
sufficient storage space for all the
materials used in the construction.

Augered Piles
Advantages……
1.Limited risk of damage to adjacent foundations or underground
utilities from ground displacement or densification of loose sands, as
can occur with displacement piles.
2.CFA piles can be installed with little vibrations or noise.
3.Should problems occur during pile construction, it is relatively simple
to re–drill and install the pile at the same location, thereby eliminating
the need to redesign the pile group or the pile caps.
4.A reliable flow meter can be used to monitor and record penetration /
uplift per revolution, auger depth, concrete supply per increment of
auger uplift during placing, and injection pressure at the auger head.
.

Disadvantage
1.If the appropriate installation procedures are not followed exactly the
pile formed may be of poor and/or inconsistent quality and load
carrying capacity.
2.The most critical factor for the CFA system is still its reliance on
operator performance, which may result in a pile of poor quality and
reduced load carrying capacity. Thus, it is vitally important that
experienced personnel install the piles.
3.To ensure success it is vital to give due care to every stage of the field
installation procedure, including drilling of the hole, casting of the shaft,
extraction of the auger and the placement of the reinforcement.

Driven concrete pile
ADVANTAGES……..
1.Driven concrete pile foundations are applicable under most
ground conditions.
2.Concrete piles are usually inexpensive compared with other
types of deep foundations.
3.The procedure of pile installation is straightforward; piles can
be produced in mass production either on site or in a
manufacture factory, and the cost for materials is usually much
less than steel piles.
4.Proxy coating can be applied to reduce negative skin friction
along the pile.
5.Pile driving can densify loose sand and reduce liquefaction
potential within a range of up to three diameters surrounding
the pile.

DISADVANTAGES……
1.Pile driving produces noise pollution and causes disturbance
to the adjacent structures.
2. Driving of concrete piles also requires large overhead
space.
3.Piles may break during driving and impose a safety hazard.
4.Piles that break underground cannot take their design
loads, and will cause damage to the structures if the broken
pile is not detected and replaced.
5. End-bearing capacity of a pile is not reliable if the end of a
pile is smashed.

DRIVEN WOODEN PILE
ADVANTAGES……
1.The piles are easy to handle
2.Relatively inexpensive where
timber is plentiful.
3.Sections can be joined together
and excess length easily removed.

1.The piles will rot above the ground water level. Have a limited
bearing capacity.
2.Can easily be damaged during driving by stones and boulders.
3.The piles are difficult to splice and are attacked by marine borers in
salt water.
DISADVANTAGES

DRILLED SHAFT METHOD
ADVANTAGES…….
1.The length and size of the foundations can be
tailored easily.
2. Disturbance to the nearby structures is small
compared with other types of deep foundations.
3.Drilled shafts can be constructed very close to
existing structures and can be constructed under
low overhead conditions. Therefore,
4. drilled shafts are often used in many seismic
retrofit projects.

DISADVANTAGES
1. Drilled shafts may be difficult to install under
certain ground conditions such as soft soil, loose
sand, sand under water, and soils with boulders.
2. Drilled shafts will generate a large volume of soil
cuttings and fluid and can be a mess. Disposal of
the cuttings is usually a concern for sites with
contaminated soils.
3. Drilled shaft foundations are usually comparable
with or more expensive than driven piles.

APPLICTION OF DEEP FOUNDATION
A
deep foundation installation for
a bridge in Napa,
California, United States.

Pile driving operations in the
Port ofTampa, Florida, United
States.

Sheet piles are used to restrain
soft soil above the bedrock in
this excavation

Adfreeze Piles supporting a
building in Barrow, Alaska,
United States

Sheet piling, by a bridge, was
used to block a canal in New
Orleans, United States
after Hurricane Katrinadamaged
it

Cutaway illustration. Deep
inclined (battered) pipe piles
support a precast segmented
skyway where upper soil layers
are weak muds.

• DEFORMABILITY MODULUS OF JOINTED
ROCKS, LIMITATION OF EMPIRICAL
METHODS, AND INTRODUCING A NEW
ANALYTICAL APPROACH

• Introduction
• The commission of Terminology, symbols and graphic
representation of the International Society for Rock
Mechanics ISRM ) ISRM, 1975 )
• Modulus of elasticity or Young’s modulus (E) : The ratio of
stress to corresponding strain below the proportionality
limit of a material.
• Modulus of deformation of a rock mass (Em) : The ratio of
stress (p) to corresponding strain during loading of a rock
mass, including elastic and inelastic behavior
• Modulus of elasticity of a rock mass (Eem) : The ratio of
stress (p) to corresponding strain during loading of a rock
mass, including only the elastic behavior

Conclusion On Deformability
• Deformability modulus is a stress dependent
parameter and increases as applied stress
increases.
• All well-known empirical formulations do not
consider this property of deformability modulus.
• A new procedure is proposed to quantify the
stress dependency of deformability modulus.

Plane of weakness
• Discontinuity Orientation
• Dip - Angle of Steepest Inclination of Plane,
Measured Below Horizontal (two digits 00 to 90)
• Dip Direction (Dip Azimuth) - Azimuth of the Line
of Dip (three digits 000 to 360)
• Strike - Azimuth of a Horizontal Line (90 Degrees
to Dip Direction) - Unsuitable for Rock Slope
Engineering

Discontinuity Spacing
• Measure True Spacing in Surface Mapping
• Range:
• Extremely close spacing (<20 mm)
• Extremely wide spacing (>6000 mm)
• Line Mapping or Coreholes: Use Terzaghi
Correction for True Spacing

Persistence
• Document Visible or Inferred Length
• -Range:
• Very low (<1 m)
• Very high (>20 m)
• Document Termination of Joints (0, 1, 2)
• Statistical Estimates of Length Distribution
Persistence cannot be Measured in Core

IMPORTANCE OF JOINTS IN
TERMS OF ROCK MECHNICS
JYOTI KHATIWADA

INTRODUCTION
• In geology, a joint is a fracture dividing rock into two sections that have
not moved away from each other. A joint sees little or no displacement.
• As Earth crust is full of joints, therefore their study and importance is very
significance.
• joints are important not only in understanding the local and
regional geology and geomorphology, but also are important in
development of natural resources, the safe design of structures, and
environmental protection. Joints have a profound control on weathering
and erosion of bedrock. As a result, they exert a strong control on how
topography and morphology of landscapes develop.

• Importance of joints in engineering and geological
applications include:
1. In rock mass classification
2. foundation strength
3. Geohydrology/ Natural circulation of fluids
4. Petroleum and mineral deposition
5. Studying mechanical properties of rock masses
6. Mining and quarry operational feasibility
7. Toxic waste/ risk

1. IN ROCK MASS
CLASSIFICATION
a. In determination of RQD (Rock Quality
Designation)
b. In determination of block size.
c. In determination of RMR (Rock Mass Rating)
d. In determination of rock quality ( Q system)

• In determination of RQD (Rock Quality
Designation):
In many cases the degree of jointing is the most important
factor for the stability of rock masses. The volumetric joint
count (Jv) is a simple measure of the degree of jointing. It
takes into account all the occurring joints and fractures and is
easily calculated from standard joint descriptions. The (Jv) has
been used by engineering geologists in Norway for several
years and it has been a useful tool in the description and
classification of rock masses. The paper describes the
procedure for the calculation of the (Jv) and it shows how the
joint spacings are included in the measure.
RQD = 115 - 3.3 Jv.
Jv = Joint volumetric count

• In determination of block size:
Block size =
If 𝐽 𝑛 = 0, block size tends to infinite, it represents
continuity i.e. ground is made up of rock.
If 𝐽 𝑛 is more, ground is moving towards fractured
ground.
Hence joints are very important parameter affecting
geotechnical behavior of ground.
𝑅𝑄𝐷
𝐽 𝑛

• In determination of RMR (Rock Mass Rating):
RMR is determined as an algebraic sum of six
parameters given below:
1. Rock quality designation
2. Joint spacing
3. Joint condition
4. Joint orientation
5. Ground water condition
6. UCS of rock material.
RMR = RRQD + RJOINT SPACING + RJOINT CONDITION + RORIENTATION + RGROUND
WATER CONDITION + RUCS
RMR
Rock
quality
0 - 20 Very Poor
21 - 40 Poor
41 - 60 Fair
61 - 80 Good
81 - 100 Very good

• In determination of rock quality ( Q system):
• The Q-system for rock mass classification is developed by
Barton, Lien, and Lunde. It expresses the quality of the rock mass
in the so-called Q-value, on which are based design and support
recommendations for underground excavations.
• The Q-value is determined with
𝑹𝑸𝑫
𝑱 𝒏
represents block size
𝑱 𝒓
𝑱 𝒂
represents shear strength
𝑱 𝒓
𝑱 𝒂
represents condition or nature of rock
• Jw is the measure of water pressure which has an adverse effect
on the shear strength of joint due to reduction in effective normal
stress.
𝑸 =
𝑹𝑸𝑫
𝑱 𝒏
×
𝑱 𝒓
𝑱 𝒂
×
𝑱 𝒘
𝑺𝑹𝑭

OTHER IMPORTANCE :
• Joints often impart a well-develop fracture-induced
permeability to bedrock. As a result, joints strongly
influence, even control, the natural circulation
(geohydrology) of fluids.
• groundwater and pollutants within aquifers, petroleum in
reservoirs, and hydrothermal circulation at depth, within
bedrock. Thus, joints are important to the economic and
safe development of petroleum, hydrothermal, and
groundwater resources and the subject of intensive
research relative to the development of these resources.

• Also, regional and local joint systems exert a very strong control on
how ore-forming (hydrothermal) fluids, consisting largely of H2O, CO2,
and NaCl, that formed most of Earth's ore deposits circulated within the
Earth crust. As a result, understanding their genesis, structure,
chronology, and distribution is an important part of finding and
profitably developing ore deposits of various types.
• Finally, joints often form discontinuities that may have a large influence
on the mechanical behavior (strength, deformation, etc.) of soil and rock
masses in, for example, tunnel, foundation, or slope construction.
• As a result, joints are an important part of geotechnical engineering in
practice and research

Footing
Definition
Footings are structural members used to support
columns and walls and to transmit and distribute
their loads to the soil in such a way that the load
bearing capacity of the soil is not exceeded,
excessive settlement, differential settlement,or
rotation are prevented and adequate safety
against overturning or sliding is maintained.

Types of Footing
Wall footings are used to
support structural walls that
carry loads for other floors
or to support nonstructural
walls.

Types of Footing
Isolated or single footings
are used to support single
columns. This is one of the
most economical types of
footings and is used when
columns are spaced at
relatively long distances.

Types of Footing
Combined footings usually
support two columns, or
three columns not in a row.
Combined footings are used
when tow columns are so
close that single footings
cannot be used or when one
column is located at or near
a property line.

Types of Footing
Cantilever or strap footings
consist of two single
footings connected with a
beam or a strap and support
two single columns. This
type replaces a combined
footing and is more
economical.

Types of Footing
Continuous footings
support a row of three or
more columns. They have
limited width and continue
under all columns.

Types of Footing
Rafted or mat foundation
consists of one footing
usually placed under the
entire building area. They
are used, when soil bearing
capacity is low, column
loads are heavy single
footings cannot be used,
piles are not used and
differential settlement must
be reduced.

Types of Footing
Pile caps are thick slabs
used to tie a group of piles
together to support and
transmit column loads to the
piles.

Distribution of Soil Pressure
When the column load P is
applied on the centroid of the
footing, a uniform pressure is
assumed to develop on the soil
surface below the footing area.
However the actual distribution of
the soil is not uniform, but
depends on may factors especially
the composition of the soil and
degree of flexibility of the footing.

Distribution of Soil Pressure
Soil pressure distribution in
cohesionless soil.
Soil pressure distribution in
cohesive soil.

Design Considerations
Footings must be designed to carry the column loads
and transmit them to the soil safely while satisfying
code limitations.
The area of the footing based on the allowable
bearing soil capacity
Two-way shear or punching shear.
One-way bearing
Bending moment and steel reinforcement required
*
*
*
*

Design Considerations
Footings must be designed to carry the column loads
and transmit them to the soil safely while satisfying
code limitations.
Bearing capacity of columns at their base
Dowel requirements
Development length of bars
Differential settlement
*
*
*
*

Size of Footing
The area of footing can be determined from the
actual external loads such that the allowable soil
pressure is not exceeded.
 
pressuresoilallowable
weight-selfincludingloadTotal
footingofArea 
footingofarea
u
u
P
q 
Strength design requirements

Two-Way Shear (Punching Shear)
For two-way shear in slabs (& footings) Vc is smallest of
long side/short side of column
concentrated load or reaction area<2
length of critical perimeter around the
column
where, bc =
b0 =
ACI 11-35
dbfV 0c
c
c
4
2









b
When b >2 the allowable Vc is reduced.

Design of two-way shear
Assume d.
Determine b0:
b0 = 4(c+d) for square columns
where one side = c
b0 = 2(c1+d) +2(c2+d) for
rectangular columns of sides c1
and c2.
1
2

The shear force Vu acts at a
section that has a length
b0 = 4(c+d) or 2(c1+d) +2(c2+d)
and a depth d; the section is
subjected to a vertical downward
load Pu and vertical upward
pressure qu.
3
 
   columnsrrectangulafor
columnssquarefor
21uuu
2
uuu
dcdcqPV
dcqPV



Allowable
Let Vu=fVc
4
dbfV 0cc 4ff 
0c
u
4 bf
V
d
f

If d is not close to the assumed d,
revise your assumptions

Design of one-way shear
For footings with bending action
in one direction the critical
section is located a distance d
from face of column
dbfV 0cc 2ff 

The ultimate shearing force at
section m-m can be calculated








 d
cL
bqV
22
uu
If no shear reinforcement is to
be used, then d can be checked

bf
V
d
2 c
u
f

If no shear reinforcement is to
be used, then d can be checked,
assuming Vu = fVc

Flexural Strength and Footing reinforcement
2
y
u
s










a
df
M
A
f
The bending moment in each
direction of the footing must be
checked and the appropriate
reinforcement must be
provided.

bf
Af
a
85.0 c
sy

Another approach is to
calculated Ru = Mu / bd2 and
determine the steel percentage
required r . Determine As then
check if assumed a is close to
calculated a

The minimum steel percentage
required in flexural members is
200/fy with minimum area and
maximum spacing of steel bars
in the direction of bending
shall be as required for
shrinkage temperature
reinforcement.

The reinforcement in one-way
footings and two-way footings
must be distributed across the
entire width of the footing.
1
2
directionshortinentreinforcemTotal
widthbandinentReinforcem


b
footingofsideshort
footingofsidelong
b
where

Bearing Capacity of Column at Base
The loads from the column act on the footing at the base
of the column, on an area equal to area of the column
cross-section. Compressive forces are transferred to the
footing directly by bearing on the concrete. Tensile
forces must be resisted by reinforcement, neglecting any
contribution by concrete.

Force acting on the concrete at the base of the column
must not exceed the bearing strength of the concrete
 1c1 85.0 AfN f
where f = 0.7 and
A1 =bearing area of column

The value of the bearing strength may be multiplied by a
factor for bearing on footing when the
supporting surface is wider on all sides than the loaded
area.
0.2/ 12 AA
The modified bearing
strength
 
 1c2
121c2
85.02
/85.0
AfN
AAAfN
f
f



Dowels in Footings
A minimum steel ratio r = 0.005 of the column section
as compared to r = 0.01 as minimum reinforcement for
the column itself. The number of dowel bars needed is
four these may be placed at the four corners of the
column. The dowel bars are usually extended into the
footing, bent at the ends, and tied to the main footing
reinforcement. The dowel diameter shall not =exceed
the diameter of the longitudinal bars in the column by
more than 0.15 in.

Development length of the Reinforcing Bars
The development length for compression bars was
given
but not less than
Dowel bars must be checked for proper
development length.
cbyd /02.0 fdfl 
in.8003.0 by df

Differential Settlement
Footing usually support the following loads
Dead loads from the substructure and superstructure
Live load resulting from material or occupancy
Weight of material used in backfilling
Wind loads

General Requirements for Footing Design
A site investigation is required to determine the
chemical and physical properties of the soil.
Determine the magnitude and distribution of
loads form the superstructure.
Establish the criteria and the tolerance for the
total and differential settlements of the structure.
1
2
3

Determine the most suitable and economic type
of foundation.
Determine the depth of the footings below the
ground level and the method of excavation.
Establish the allowable bearing pressure to be
used in design.
4
5
6

Determine the pressure distribution beneath the
footing based on its width
Perform a settlement analysis.
7
8

EFFECT OF DISCONTINUTY STRIKE & DIP
ORIENTATION IN EXPLORATION/TUNNELING
STRIKE PERPENDICULAR
TO TUNNEL AXIS
STRIKE PARALLEL TO TUNNEL AXIS
Drive with dip: Dip 45-
90°
Drive with dip: Dip 20-45° Dip 45-90° Dip 20-45°
Very favorable Favorable Very favorable Fair
Drive against dip: Dip
45-90°
Drive against dip: Dip 20-
45°
Dip 0-20° , Irrespective of strike angle
Fair Unfavorable Fair

MAIN FACTORS AFFECTING THE ROCK QUALITY
 Topography of area
 Types Soil/rock on Surface as well as Subsurface.
 Degree of weathering
 Number of Joint sets
 Spacing between joints
 Cavity
 Filling material
 Dewatering/ ground water inflow
 Direction and amount of Dip and strike

METHODS OF STUDY THE ROCK QUALITY
• A number of Geotechnical parameters govern condition of Rock mass and
the nature of its discontinuities. Main two are:-
• (1) RMR (2) Q SYSTEM
• (1) RMR (Rock Mass rating):
• Bieniawski (1973), proposed RMR system, also know as ‘Geomechanics
Classification” for jointed rock masses. Many modifications has undergone time to
time.
• Five basic parameters considered for RMR: STRENGTH OF ROCK, RQD (Rock Quality
Designation), SPACING OF JOINTS, CONDITION OF JOINTS & GROUND WATER
CONDITION.
• Final RMR value related to five classes of rock mass i.e. ‘very good’, ‘good’’, ‘fair’,
‘poor’, ‘very poor’ rock.

METHODS OF STUDY THE ROCK QUALITY
 Q- SYSTEM (ROCK MASS QUALITY)
 Proposed by Basedon in 1974, based on the study of 200 tunnel case histories.
 The rock quality Q is determined by estimating six parameters. These are RQD, JOINT
SET NUMBER (Jn), JOINT ROUGHNESS NUMBER (Jr), JOINT ALTERATION NUMBER (Ja)
AND STRESS REDUCTION FACTOR (SRF).
 Q= (RQD/Jn) x (Jr/Ja) X (Jw/SRF) (Barton et. al. 1974)
 The numerical value Q ranges from 0.001 (for exceptionally poor quality squeezing
ground) to 1000 (for exceptionally good quality rock which is practically unjointed).
 Q-value is divided into 9 categories of rock quality which are related to support
requirement depending upon excavation span and intended use of excavation.

SURFACE/SUBSURFACE INVESTIGATION
INVESTIGATIONS
FIELD INVESTIGATIONS LABOURATURY INVESTIGATIONS
(A) Geotechnical (a) Physical properties of Soil & Rock
(B) Hydrological (b) Geomechanical Properties
(C) Geophysical (c ) Petrological studies of rock & soil
(D) Construction material
Main Field tests are Drilling, Pit excavation, Deformability test (Goodman Jack Test &
Hydro Fracture test), Load bearing capacity test (Plate Load Test), Water Percolation
test (permeability test), Earth resistivity test, Seismic reflection test (know the
subsurface fault/ shear zone), aggregate test , topographical studies etc.
Studies of Satellite imageries is very useful to understand the topography,
geomorphology of area.

• On the basis of RMR and Q Value, geologist
suggest supporting system in excavated
rock/soil.
• On the basis of geotechnical & geologist
report project designer has fixed the structure
design and remedies measures.
RESULTS

CAREER IN ENGINEERING GEOLOGY
• Infrastructure Projects as Hydro Power Plant,
Tunnels for railway/transport, Canal, Dam,
reservoir, highways, bridges, buildings, water
treatment plant, land use, environmental studies
etc.
• For Mine and Quarry excavations, mine
reclamation.
• For coastal engineering, sand replenishment, sea
cliff stability, water front development.
• For offshore drilling platform, sub sea pipeline
and cables etc.

INTRODUCTION
A tunnel is an underground passageway, completely
enclosed except for openings for egress, commonly at each
end.
A tunnel may be for road traffic,road
traffic,canal,hydroelectric station,sewer etc.
The Delaware Aqueduct in New York USA is the longest
tunnel, of any type, in the world at 137 km (85 mi)

REQUIRMENTS OF
TUNNEL
 IT IS VERY USEFUL WHERE BRIDGE FAIL TO FULFILL REQUIRMENTS
LIKE IN SEA ,IN URBAN AREA ,AND IN MOUNTAINS.
 EFFICIENT COPARED TO BRIDGES.

 IN WAR TIME IT IS MUCH DIFFICULT TO DESTROY A TUNNEL BUT
DESTRUCTION OF BRIDGE IS TOO EASY.
 LOTS OF LAND AND TIME IS SAVED.

MAIN PURPOSES
1.IN ROAD TRAFFICS
2.IN SEWERS
3.IN MININGS
4.IN RAIL TRAFFICS
5.IN HYDROELECTRIC
STATIONS etc.

The process for bored tunnelling involves all or some of the
following operations:
• Probe drilling (when needed)
• Grouting (when needed)
• Excavation (or blasting)
• Supporting
• Transportation of muck
• Lining or coating/sealing
• Draining
• Ventilation

PROBE DRILLING
• This type of drilling is done in order to find out
suitable method for drilling .
• It consist of drilling in sample, by various method to
find most suitable .
• It is necessary part of all drilling operation .

GROUTING
• It is the process of providing additional support to
drilled mine.
• It is done by a liquid called grout ,consist of water
,cement ,color tint and sometime fine gravel .
• Good surface is achieved .

EXCAVATION
• Excavation is the digging and recording of
artifacts at an archaeological site.
• It is necessary to know the archaeological
importance of a site before digging .
• This is performed by experts in a scientific way.
• Many governments grants permission for
tunneling after finding a go certificate in
excavation.

SUPPORTING
• After initial mining , tunnel need supports for
further processing .
• For the sake of life a perfect planning is needed
for support.
• In ancient time timber and masonry were the
main methods.
• Today support is provided by injecting final pipe
or building it completely before further
tunneling

Transportation of muck
• In ancient time transportation was done by
steam engine and by Manual transport.
• Today it is done by modern methods and
process is automatic .
• TBMs are also come with proper arrangment for
the transport of muck.

LINING OR COATING
• Lining of proper material is done by modern
methods like polishing ,painting to prevent wear and
tear and corrosion.
• Very necessary part where corrosive metals are being
used.

DRAINING
• Draining is the process to remove the water or other
liquid from working site .
• Very important where water level is very high.
• Pumps and pipes are used for this purpose.

VENTILATION
• Proper ventilation is required for safety of workers.
• This is done by proper checking of oxygen and other
parameters .
• Proper installations for exit of hazardous gasses
coming out from tunneling .

tunnel construction methods:
• Classical methods
• Cut-and-cover
• Drill and blast
• Tunnel boring machines (TBMs)
• Immersed tunnels
• Tunnel jacking
• Other methods .

Classical Methods
 Among the classical methods are the
Belgian, English, German, Austrian,
Italian and American systems. These
methods had much in common with
early mining methods and were used
until last half of the 19th century.
 Excavation was done by hand or
simple drilling equipment.
 Supports were predominantly timber,
and transportation of muck was done
on cars on narrow gauge tracks and
powered by steam.
 Progress was typically in multiple
stages i.e. progress in one drift, then
support, then drift in another drift,
and so on.
 The lining would be of brickwork.
These craft-based methods are no
longer applicable, although some of
their principles have been used in
combination up to present day.
Nevertheless some of the world’s
great tunnels were built with these
methods.

The English method (crown-bar method, figure
left) started from a central top heading
which allowed two timber crown bars to be
hoisted into place, the rear ends supported
on a completed length of lining, the forward
ends propped within the central heading.
Development of the heading then allowed
additional bars to be erected around the
perimeter of the face with boards between
each pair to exclude the ground. The system
is economical in timber, permits
construction of the arch of the tunnel in
full-face excavation, and is tolerant of a
wide variety of ground conditions, but
depends on relatively low ground pressures.

 The Austrian (cross-bar) method required a
strongly constructed central bottom
heading upon which a crown
heading was constructed. The
timbering for full-face excavation
was then heavily braced against the
central headings, with longitudinal
poling boards built on timber bars
carried on each frame of timbering.
As the lining advanced, so was the
timbering propped against each
length to maintain stability. The
method was capable of withstanding
high ground pressures but had high
demand for timber.

• The German method (core-leaving method) provided a series of box headings
within which the successive sections of the side walls of the tunnel were
built from the footing upwards, thus a forerunner of the system of multiple
drifts. The method depends on the central dumpling being able to resists
without excessive movement pressure transmitted from the side walls, in
providing support to the top 'key' heading prior to completion of the arch
and to ensuring stability while the invert arch is extended in sections.
• The Belgian system (underpinning or flying arch method) started from the
construction of a top heading, propped approximately to the level of the
springing of the arch for a horseshoe tunnel. This heading was then extended
to each side to permit construction of the upper part of the arch, which was
extended by underpinning, working from side headings. The system was
only practicable where rock loads were not heavy.
• The first sizeable tunnel in soft ground was the Tronquoy tunnel on the St
Quentin canal in France in 1803, where the method of construction, based
on the use of successive headings to construct sections of the arch starting
from the footing, was a forerunner to the German system described above.

CUT & COVER METHOD
The principal problem to be solved in connection with this
construction method is to how to maintain surface traffic,
with the least disturbance during the construction period.
One method is to restrict traffic to a reduced street width,
another to direct traffic to a bypassing street.
 Another way of supporting the sidewalls of open trenches is
to substitute sheet-pile walls by concrete curtain walls cast
under bentonite slurry (ICOS method), and using steel
struts. This is especially a requisite in narrower streets
trimmed with old sensitive buildings with their foundation
plane well above the bottom level of the pit. This type of
trench wall becomes a requirement for maintenance of
surface traffic due to the anticipation of vibration effects
potentially harmful to the stability of buildings with
foundations lying on cohesionless soils.

DRILL AND BLAST
1.Before the advent of tunnel boring
machines, drilling and blasting was the only
economical way of excavating long tunnels through
hard rock, where digging is not possible.
2.Even today, the method is still used in the
construction of tunnels.

HOW DRILL AND BLAST IS BEING DONE.

Mechanical Drilling and Cutting-Crushing Strength of rock

TBM
• In various size Tunnel Boring Machines(TBM)
are used for drilling a vast type of tunnels .
• Transportation of muck , supporting and all
other actions are done automatically.
• Very useful in boring tunnel where all other
methods fail.
• A main method in use in now a days.

IMMERSED TUNNELS
1.THIS TYPE OF TUNNELS ARE PARTLY OR
WHOLLY ARE UNDERWATWER.
2.THEY DO NOT BLOCK THE ROOT FOR
SHIPS SO THERE IS NO PROBLEM OF
CONGESSION OF TRAFFIC AS IN CASE OF
BRIDGES OVER RIVERS OR SEAS.

TUNNEL JACKING
1.IT IS A PROCESS TO MAKE TUNNELS IN
ALREADY EXISTING BOADIES SUCH AS
ROADS ,RAILWAYS.
2.IN THIS METHOD ESPECIALLY MADE PIPES
ARE PUSHED BY A HYDRAULIC RAM IN
GROUND .
3.MAXIMUM DIAMETER OF TUNNEL BY
THIS METHOD IS AROUND 2.4 METER.

The choice of tunnelling method may be dictated by:
• geological and hydrological conditions,
• cross-section and length of continuous tunnel,
• local experience and time/cost considerations
(what is the value of time in the project),
• limits of surface disturbance, and many others
factors.
• Tunnel methods .
• Required speed of construction.
• Shape of tunnel.
• Managing the risk of variations in ground quality

THE OTHER SIDE
• Beside of many security measures , tunnelling is still
not full proof.
• Failure of automatic system will cause deadly results
as depicted in Hollywood flick Die Hard 4.0.
• High cost than bridges , but more fruitful from
previous.

NATM
NATM
NEW AUSTRIAN TUNNELING METHOD
By
ADIL BIN AYOUB
41-CE-13
B.Tech
CIVIL ENGINEERING
School of Engineering & Technology, BGSBU
Rajouri J&K

HISTORY OF NATM
• The term New Austrian Tunneling Method
Popularly Known as NATM got its name from
Salzburg (Austria).
• It was first used by Mr. Rabcewicz in 1962. It got
world wise recognition in1964.
• The first use of NATM in soft ground tunnel in
Frankfurt (Europe) metro in 1969.

DEFINITION OF NATM
• The New Austrian Tunneling Method is a
support method to stabilize the tunnel
perimeter by means of sprayed concrete
,anchors and other support and uses monitoring
too control stability.
• Main idea is to use the geological stress of the
surrounding rock mass to stabilize the tunnel
itself

BROAD PRINCIPLES OF NATM
• Mobilization of the strength of rock mass
• Shotcrete protection
• Measurements and monitoring
• Primary Lining
• Closing of invert
• Rock mass classification

MOBILIZATION OF STRENGTH
OF ROCK MASS

PRIMARY LINING
Wire mesh and steel ribs

WHY NATM
• Flexibility to adopt different excavation
geometries and very large cross sections.
• Flexibility to install additional support measures,
rock bolts, dowels, steel ribs if required.
• Easy to install a waterproof membrane.
• Easy to install primary support, i.e. shotcrete.

SUMMARY OF THE PROCEDURE
IN NATM
• SHOTCRETING AT THE EXCAVATED AREA(PRIMARY
LINING)
• PLACING OF THE WIREMESH ALONG THE FACEOF THE
TUNNEL
• ERECTION OF THE LATTICE GIRDER ALONG THE FACE OF
THE TUNNEL
• PERTICULAR TYPE OF ROCKBOLTING
• SHOTCRETING THE WHOLE ARRENGEMENT(SECONDARY
LINING)

CONCEPT OF 3D MONITORING
• 3D MONITORING IS NEW TECHNIQUE USING FOR TAKING
THE RIGHT ALIGNMENT OF THE TUNNEL
• OPTICAL TARGETS ARE USED FOR DETRMINIG THE
COORDINATES FOR MEASUREMENTS
• THE COORDINATES SHOULD BE CHECKED DAILY
• IT IS NECESSARY FOR THE TUNNEL AS BY IT WE KNOW
ANY DISPLACEMENT AND WRONG ALIGNMENTS

WHERE NATM IS USING IN
INDIA
• PRESENTLY IT IS USING WIDLELY IN
KASHMIR RAILWAY PROJECT
• THEY ARE USING IT IN THEIR TUNNELS
LIKE IN PIR PANJAL TUNNEL , T-74R, T-
48 ETC

NATM approach of design and execution of the tunneling in soft ground is
advantageous and scientific way in comparision to the old way of tunneling. This
system monitors rock mass deformation and design the support system with
reference to the rock mass type .
CONCLUSION

Rock Slope Stability Analysis
• A variety of engineering activities require
excavation of rock cuts.
• In civil engineering, projects include
transportation systems such as highways and
railways, dams for power production and
water supply, and industrial and urban
development.

Fig 1: Rock slope in Hong Kong supported with tensioned rock anchors
and reinforced concrete reaction blocks, and shotcrete.

• Figure 1 is a rock cut, with a face angle of about
60◦, supported with tensioned anchors
incorporating reinforced concrete bearing pads
about 1m2 that distribute the anchor load on the
face.
• The face is also covered with shotcrete to prevent
weathering and loosening between the bolts.
• Water control measures include drain holes
through the shotcrete and drainage channels on
the benches and down the face to collect surface
run-off.
• The support is designed to both ensure long-term
stability of the overall slope, and minimize rock
falls that could be a hazard to traffic.

Principles of Rock Slope Engineering
• The design of rock cuts for civil projects such as
highways and railways is usually concerned with
details of the structural geology.
• That is, the orientation and characteristics (such
as length, roughness and inﬁlling materials) of the
joints, bedding and faults that occur behind the
rock face.
• For example, Figure 2 shows a cut slope in shale
containing smooth bedding planes that are
continuous over the full height of the cut and dip
at an angle of about 50° towards the highway.

Figure 2: Cut face coincident with continuous, low friction bedding planes
in shale on Trans Canada Highway near Lake Louise, Alberta.

• Since the friction angle of these
discontinuities is about 20–25°, any attempt
to excavate this cut at a steeper angle than
the dip of the beds would result in blocks of
rock sliding from the face on the beds; the
steepest unsupported cut that can be made is
equal to the dip of the beds.
• However, as the alignment of the road
changes so that the strike of the beds is at
right angles to the cut face (right side of
photograph), it is not possible for sliding to
occur on the beds, and a steeper face can be
excavated.

• For many rock cuts on civil projects, the
stresses in the rock are much less than the
rock strength so there is little concern that
fracturing of intact rock will occur.
• Therefore, slope design is primarily concerned
with the stability of blocks of rock formed by
the discontinuities.
• Intact rock strength, which is used indirectly in
slope design, relates to the shear strength of
discontinuities and rock masses, as well as
excavation methods and costs.

Shear Strength of Discontinuities
• If geological mapping and/or diamond drilling
identify discontinuities on which shear failure
could take place, it will be necessary to
determine the friction angle and cohesion of the
sliding surface in order to carry out stability
analyses.
• The investigation program should also obtain
information on characteristics of the sliding
surface that may modify the shear strength
parameters.
• Important discontinuity characteristics include
continuous length, surface roughness, and the
thickness and characteristics of any inﬁlling, as
well as the effect of water on the properties of
the inﬁlling.

Deﬁnition of Cohesion and Friction Angle
• In rock slope design, rock is assumed to be a
Coulomb material in which the shear strength
of the sliding surface is expressed in terms of
the cohesion (c) and the friction angle (φ)
(Coulomb, 1773).
• Assume a number of test samples were cut
from a block of rock containing smooth,
planar discontinuity.
• Furthermore, the discontinuity contains a
cemented inﬁlling material such that a tensile
force would have to be applied to the two
halves of the sample in order to separate
them.

Fig 3 (a) Shear test of discontinuity

• Each sample is subjected to a force at right
angles to the discontinuity surface (normal
stress, σ), and a force is applied in the direction
parallel to the discontinuity (shear stress, τ)
while the shear displacement (δs) is measured
(Figure 3 (a)).
• For a test carried out at a constant normal
stress, a typical plot of the shear stress against
the shear displacement is shown in Figure 3 (b).

Fig 3 (b): plot of shear displacement vs shear stress

• At small displacements, the specimen behaves
elastically and the shear stress increases linearly with
displacement.
• As the force resisting movement is overcome, the
curve become non-linear and then reaches a maximum
that represents the peak shear strength of the
discontinuity.
• Thereafter, the stress required to cause displacement
decreases and eventually reaches a constant value
termed the residual shear strength.
• If the peak shear strength values from tests carried out
at different normal stress levels are plotted, a
relationship shown in Figure 3 (c) is obtained; this is
termed a Mohr diagram (Mohr, 1900).

Fig 3(c): Mohr plot of peak strength

• The features of this plot are;
• first, it is approximately linear and the slope of
the line is equal to the peak friction angle φp of
the rock surface.
• Second, the intercept of the line with the shear
stress axis represents the cohesive strength c of
the cementing material.
• This cohesive component of the total shear
strength is independent of the normal stress, but
the frictional component increases with
increasing normal stress.
• Based on the relationship illustrated on Figure 3
(c), the peak shear strength is deﬁned by the
equation.

• Friction Angle: The angle of internal friction is measure
of the ability of a material (could be rock or soil or
whatever) to withstand a shear stress.
• Cohesion: The force of attraction that holds molecules
of a given substance together.
OR
The sticking together of particles of the same substance.
Mohr plot of peak and residual strength is shown in Fig 3
(d).

Fig 3 (d): Mohr plot of peak and residual strength.

Rock mechanics for engineering geology (part 2)

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