DEEP FOUNDTION

Jyoti Khatiwada AnischitThis part is also useful for site investigation

DEEP FOUNDATION

DEFINITION If the depth of a foundation is greater than itswidth, the foundation is known as deepfoundation. In deep foundation the depth to width ratio isusually 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 Use1. End Bearing Piles2. Skin Friction Piles3. Compaction Piles4. Driven Piles5. 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.

Types of Piles (cont ’d)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

Types of Piles (cont ’d)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.

Types of Piles (cont ’d)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 Pi les (cont ’d)• Auger cast pilesAuger 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 foundationsWell 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 FoundationWells 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 DESIGNThe following loads are considered for the

analysis and design of well foundation:1.Dead load2.Live load3.Buoyancy4.Wind load5.Horizontal force due to water current6.Centrifugal forces7.Longitudinal forces8.Seismic forces9.Horizontal shear forces at bearings due

to longitudinal forces and seismic forces10.Forces due to tilt and shift.

TYP ES OF FOUN DATIONCaiss on s

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 pileoTo determine load carrying capacity of

individual pileOnly one type of pile below different columnsFor 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 layerIF 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 onLengthWidthMaterial ( concrete, steel, wood)Cross-section (square, circular, tubular)Installation procedure (driven, bored)Feasibility of constructionFeasibility of noise and vibration

3. RANGE OF PILE LENGTH & DIAMETERS

LENGTH :• Usually 10 – 30 m• Offshore application 70 – 100 mWIDTH/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 – chosenEstimate the axial capacityOne of the procedures is ‘Pile Load Test’

5. SETTLEMENT ANALYSIS

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

6. RESULTS & RECOMMENDATIONSPresented 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 site2. 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 construction2. The method is cumbersome. It needs sufficient storage space for all the materials used in the construction.

Augered PilesAdvantages……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.

DISADVANTAGES1. 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.

APPLICTION OF DEEP FOUNDATION

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

APPLICTION OF DEEP FOUNDATION

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

APPLICTION OF DEEP FOUNDATION

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

APPLICTION OF DEEP FOUNDATION

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

APPLICTION OF DEEP FOUNDATION

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 = 0, block size tends to infinite, it represents

continuity i.e. ground is made up of rock.

If is more, ground is moving towards fractured

ground.

Hence joints are very important parameter affecting

geotechnical behavior of ground.

𝑅𝑄𝐷𝐽 𝑛

• In determination of RMR (Rock Mass Rating):RMR is determined as an algebraic sum of six parameters given below:

1. Rock quality designation2. Joint spacing3. Joint condition4. Joint orientation5. Ground water condition6. 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

represents block size represents shear strength 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=𝑹𝑸𝑫𝑱 𝒏 × 𝑱 𝒓

𝑱 𝒂 ×𝑱 𝒘𝑺𝑹𝑭

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 reser

voirs, 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.

pressure soil allowable

weight-self including load Total footing of Area

footing of areau

uPq

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 11-35dbfV 0c

c

c 42

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

Design of two-way shear

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

columnsr rectangulafor

columns squarefor

21uuu

2uuu

dcdcqPV

dcqPV

Design of two-way shear

Allowable

Let Vu=fVc

4

dbfV 0cc 4ff

0c

u

4 bf

Vdf

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

Design of one-way shear

The ultimate shearing force at section m-m can be calculated

dcLbqV

22 uu

If no shear reinforcement is to be used, then d can be checked

Design of one-way shear

bf

Vd 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

us

adf

MA

f

The bending moment in each direction of the footing must be checked and the appropriate reinforcement must be provided.

Flexural Strength and Footing reinforcement

bf

Afa

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

Flexural Strength and Footing reinforcement

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.

Flexural Strength and Footing reinforcement

The reinforcement in one-way footings and two-way footings must be distributed across the entire width of the footing.

1

2

directionshort in ent reinforcem Total

widthbandin ent Reinforcem

b

footing of sideshort

footing of side longb

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.

Bearing Capacity of Column at Base

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

Bearing Capacity of Column at Base

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 BarsThe 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

General Requirements for Footing Design

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

General Requirements for Footing Design

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

TOWER OF PISA, ITALY

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.

TUNNELING

• Jyoti Anischit

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 TRAFFICS2.IN SEWERS3.IN MININGS4.IN RAIL TRAFFICS5.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 under- pinning, 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.

Road headers

Cut and Cover Method

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

BLAST1.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

NATMNEW AUSTRIAN TUNNELING METHOD

By ADIL BIN AYOUB

41-CE-13B.Tech

CIVIL ENGINEERINGSchool 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

SHOTCRETE PROTECTION

MEASUREMENTS AND MONITORING

PRIMARY LININGWire mesh and steel ribs

CLOSING OF INVERT

ROCK MASS CLASSIFICATION

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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

GeneralOptical Target

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.

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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.

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• 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.

ORThe 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.

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