1Behzad FatahiPhD, MEng, BEng (Hons), CPEng, MIEAust, NPER

University of Technology Sydney (UTS), and Coffey Geotechnics Pty Ltd, Sydney Office

Dams and Application of Dams and Application of Grouting and Soil Mixing for Grouting and Soil Mixing for

Ground ImprovementGround Improvement

49118Applied Geotechnics

Introduction to Dam EngineeringIntroduction to Dam EngineeringDam Flow Net and CutoffDam Flow Net and CutoffDam Filter DesignDam Filter DesignGround Improvement MethodsGround Improvement MethodsDeep Soil Mixing and Mass MixingDeep Soil Mixing and Mass MixingPermeation and Compaction GroutingPermeation and Compaction GroutingJet Grouting Jet Grouting

OUTLINEOUTLINE

DamsDams

Dam is a solid barrier constructed at a suitable location across a river valley to store flowing water.

Storage of water is utilized for following objectives:Hydropower IrrigationWater for domestic consumptionDrought and flood controlFor navigational facilitiesOther additional utilization is to develop fisheries

Structure of DamStructure of Dam

Heel

Gallery

Toe

Spillway(inside dam)

Crest

NWLNormalwater level

MWLMax. level

Free boardSluice way

Upstream Down stream

Heel: contact with the ground on the upstream side Toe: contact on the downstream side Abutment: Sides of the valley on which the structure of

the dam rest Galleries: small rooms like structure left within the dam

for checking operations. Diversion tunnel: Tunnels are constructed for diverting

water before the construction of dam. This helps in keeping the river bed dry.

Spillways: It is the arrangement near the top to release the excess water of the reservoir to downstream side

Sluice way: An opening in the dam near the ground level, which is used to clear the silt accumulation in the reservoir side.

Components of DamsComponents of DamsTypes of DamsTypes of Dams

Gravity Dams: These dams are

heavy and massive wall-like structures of concrete in which the whole weight acts vertically downwards

ReservoirForce

As the entire load is transmitted on the small area of foundation, such dams are constructed where rocks are competent and stable.

2Buttress Dam:Buttress Dam:

Buttress Dam Is a gravity dam reinforced by structural supports

Buttress - a support that transmits a force from a roof or wall to another supporting structure

This type of structure can be considered even if the foundation rocks are little weaker

These type of dams are concrete or masonry dams which are curved or convex upstream in plan

This shape helps to transmit the major part of the water load to the abutments

Arch dams are built across narrow, deep river gorges, but now in recent years they have been considered even for little wider valleys.

Arch Dams:Arch Dams:

Earth Dams:Earth Dams:

They are trapezoidal in shape

Earth dams are constructed where the foundation or the underlying material or rocks are weak to support the masonry dam or where the suitable competent rocks are at greater depth.

Earthen dams are relatively smaller in height and broad at the base

They are mainly built with clay, sand and gravel, hence they are also known as Earth fill dam or Rock fill dam

Position of Filters in a Typical Embankment Position of Filters in a Typical Embankment Dam SectionDam Section

Critical D/S Filter

FillCore

FoundationDrain

Filter

rip-rapFill

Downstream Filter: Prevention of Dam Core Erosion, Reduction of Excess Pore Pressure, Drainage of Seepage Water

Upstream Filter: Reduce Excess Pore Pressure, and stability during Rapid Drawdown

FiltersFilters

Used for: facilitating drainage preventing fines from being washed away

Used in: earth dams retaining walls

Filter Materials: granular soils geotextiless

Granular Filter DesignGranular Filter Design

Two major criteria:(a) Retention Criteria

(b) Permeability Criteria

- to prevent washing out of fines

- to facilitate drainage and thus avoid build-up of pore pressures

Filter grains must not be too coarse

Filter grains must not be too fine

granular filter

3Granular Filter DesignGranular Filter Design

Retention criteria:D15, filter < 5 d85, soil

(Terzaghi & Peck, 1967)

Permeability criteria:D15, filter > 4 d15, soil

average filter pore size

D15, filter < 20 d15, soilD50, filter < 25 d50, soil

US Army Corps of Engineers, USACE (1971)

PSD Curves for the soil and filter must be parallel

= 20

10

60

DDCu

Example Particle Size Distribution for a base soil is shown in the following figure, design a filter for this soil and plot the suggested gradation curves of this filters.

ICOLD Filter CriteriaICOLD Filter Criteria

YES

dsf = d85

Linearly Graded dsf = d50

Internally Unstable & Concave Upward**

dsf = d20

ENDRetention D15 < 4dsf

Permeability D15 > 4d15

Legend:

dsf =

d85 = D15 = dD* =

**

self-filtration size of the base 85% of the base 15% of the filter lower size of the gap risk of self-clogging

Base Gradation Curve Cohesionless

Broadly Graded Cu > 20

NO

Linearly Graded

Concave Upward

Internally Stable

Gap Graded

NO

YES

Gap Graded dsf = dD*

Dispersive D15 0.2 mm

Non Dispersive

D15 0.4 mm

Cohesive

(ICOLD, 1994)

Asphalt Concrete Core DamAsphalt Concrete Core Dam

Body (Earth/Rock Fill)

Transition Zones

Asphalt Concrete Core (ACC)

Body (Earth/Rock Fill)

What is an ACC dam?

ACC dam is an embankment dam with central bituminous core

Greater Ceres Dam, South Africa 1998East Dam, Hong Kong 1977(with two central cores)106m high, 485m long

Asphalt Concrete Core DamAsphalt Concrete Core Dam5000 years ago, natural bitumen was used in INDUS dam reservoir

Modern ACC dam construction started by Germans in 1962

Chinese constructed their first ACC dam in 1970

Norwegians Constructed their first ACC dam in 1978

Russians constructed some ACC dams with high bitumen content

Asphalt Concrete Core DamAsphalt Concrete Core Dam

4By now there are more than 70 dams with ACC in the world

Yele ACC dam with 140m height under construction in China is the highest ACC dam in the world

Why AC is being used in dam Construction?

Appropriate construction period is short

Mountainous and cold areasAreas with long raining season

Impervious soil is not available in the site or is costly to transport it

Asphalt Concrete Core DamAsphalt Concrete Core Dam

Excellent impervious element

Sufficient resistance against acting forces

Very well flexibility without cracking

High aging resistance

Self healing capability

High-quality connection between asphalt concrete and granular materials

Asphalt Concrete AdvantagesAsphalt Concrete Advantages

ACC and ACFACC and ACF

ACF ACC

Asphalt Concrete CoreAsphalt Concrete Facing

Advantages of ACCAdvantages of ACCAdvantages of ACCAdvantages of ACC

Application of only one asphalt concrete mix

Easier construction method

Less construction cost

Protection against aging

Protection against impact

Short construction period (simultaneous core and body construction)

ACC and ACFACC and ACF -- ContinuedContinued

Reduction in sliding safety factor

Inaccessibility for inspection or repair (except close to crest)

Rip Rap requirement for wave protection

Disadvantages of ACCDisadvantages of ACCDisadvantages of ACCDisadvantages of ACC

ACC and ACFACC and ACF -- ContinuedContinued

SaturatedSaturated

Composite DamsComposite Dams

Composite dams are combinations of one or more dam types. Most often a large section of a dam will be either an embankment or gravity dam, with the section responsible for power generation being a buttress or arch.

5Flow Net for DamsFlow Net for Dams

Impermeable boundary = flow line

fh

NN

HkQ =Flow per unit length in yFlow per unit length in y

Coefficient of permeabilityCoefficient of permeability

Number of equipotential drops

Number of equipotential drops

Number of flow channels

Number of flow channels

Total head loss

Total head loss

Submerged boundary = equipotential line

Impermeable boundary = flow line

Flow Net for Dams with Grout CurtinFlow Net for Dams with Grout Curtin

Flow Net for Dams with Grout CurtinFlow Net for Dams with Grout Curtin Flow Net for Dams with Grout CurtinFlow Net for Dams with Grout Curtin

How Grouting Is Used in Dam Foundation?How Grouting Is Used in Dam Foundation?

Grout curtains are used under dams where the foundation would otherwise pass too much seepage, or pass dangerous seepage.

These curtains are never completely water-tight; the reduced amount of seepage passing through them should be picked up in drainage holes downstream of the curtain

Typical layout of grout holes in a grout curtain

If the surface rock requires Improvement; blanket grouting could be appropriate.

Foundation problems can cause dams to collapse:

How Grouting Is Used in Dam Foundation?How Grouting Is Used in Dam Foundation?

6Above the GroundAbove the Ground High strength geotextileHigh strength geotextile Stabilisation bermsStabilisation berms Lightweight fill Lightweight fill (bottom ash, expanded polystyrene, etc.)(bottom ash, expanded polystyrene, etc.) Preload & surchargePreload & surcharge Surface CompactionSurface Compaction Dynamic CompactionDynamic CompactionFlexible InclusionFlexible Inclusion Vertical drains Vertical drains (wick drains, sand drains, etc.)(wick drains, sand drains, etc.) Vacuum consolidationVacuum consolidation Electro osmosis, etc.Electro osmosis, etc. Biotechnical StabilisationBiotechnical Stabilisation

Ground Improvement MethodsGround Improvement Methods Ground Improvement Ground Improvement -- continuedcontinuedSemiSemi--Rigid InclusionRigid Inclusion Stone columns Stone columns (dynamic replacement, (dynamic replacement, vibrovibro floatation, etc.)floatation, etc.) Deep soil mixing Deep soil mixing (dry, wet)(dry, wet) Mass mixingMass mixingRigid InclusionRigid Inclusion Concrete columns Concrete columns (displacement, CMC, etc.)(displacement, CMC, etc.) Jet grout columnsJet grout columns Piles Piles (precast, timber, CFA, etc.)(precast, timber, CFA, etc.)

Slope StabilisationSlope Stabilisation Nailing and AnchoringNailing and Anchoring Reinforced SoilReinforced Soil Other Soil Improvement MethodsOther Soil Improvement Methods

Deep Soil MixingDeep Soil Mixing

Wet soil mixing is the mechanical mixing of in situ soil with a cement grout slurry using a hollow stem paddle type mixer

Dry cement or lime powder is mechanically blended with the in situ soil using the in situ moisture of the soil to hydrate the binder

Wet Method

Dry Method

Deep Soil Mixing Deep Soil Mixing Wet MethodWet MethodGroundwater controlExcavation supportSoil and foundation stabilisationLiquefaction mitigation

Deep Soil Mixing Deep Soil Mixing Dry MethodDry MethodUseful for soils with high moisture contentUndrained shear strength of 150-200 MPa

Deep Soil Mixing Deep Soil Mixing -- continuedcontinued

7Deep Soil Mixing Deep Soil Mixing -- continuedcontinuedEffect of Time on Column Strength

Deep Soil Mixing Deep Soil Mixing -- continuedcontinued

Effect of Time on Column Permeability

Mass MixingMass Mixing

Mixing cement/lime with soft soils on soil surfaceUseful to construct working platformsLaboratory tests can be used to finalise the mixture

Concrete Injected Column (CIC)Concrete Injected Column (CIC)Concrete columns can be adopted, either using 450mm diameter displacement auger columns (DAC) or 600mm to 750mm Continuous Flight Auger (CFA) piles.

Concrete Injected Column (CIC) Concrete Injected Column (CIC) -- continuedcontinuedDisplacement Auger Columns (DAC) CFA piles are formed by screwing a continuous auger

into the ground to the design depth; concrete is then pumped at pressure down the stem of the auger to the bottom of the bore.

Concrete Injected Column (CIC) Concrete Injected Column (CIC) -- continuedcontinued

8 Ultimate pile resistance:Pu = Ps + Pb - W

W

Pb

Pu

Ps

Load to cause failure Shaft resistanceBase resistance

Ps = fs AsSkin friction

Surface area of the shaft

fs = ca + n tanNormal stress = hPile/soil friction angle

Pile/soil adhesion

Pb = fb AbBearing capacity at tip

Area of the base

fb = c Nc +q Nq + 0.3 B N Small, can be ignored

Concrete Injected Column (CIC) Concrete Injected Column (CIC) -- continuedcontinued

PERMEATION GROUTING :GROUT FILLS THE SOIL

PORES. ESSENTIALLY NO CHANGE IN THE VOLUME

OR STRUCTURE OF THE ORIGINAL GROUND.

DISPLACEMENT OR COMPACTION GROUTING

HYDRAULIC FRACTURE OR ENCAPSULATION OR

SQUEEZE GROUTING

JET GROUTING

Grouting MethodsGrouting Methods

Applications of GroutingApplications of Grouting

1. FILLING VOIDS TO PREVENT EXCESSIVE SETTLEMENT

2. TO INCREASE ALLOWABLE PRESSURE OF THE SOIL BOTH FOR NEW STRUCTURES AND / OR ADDITIONS TO EXISTING STRUCTURES.

3. CONTROL OF GROUNDWATER FLOW

4. GROUND MOVEMENT CONTROL DURING TUNNELING OPERATIONS

5. SOIL STRENGTHENING TO REDUCE LATERAL SUPPORT REQUIREMENT

6. SOIL STRENGTHENING TO INCREASE LATERAL AND VERTICAL RESISTANCE OF PILES.

7. STABILIZATION OF LOOSE SANDS AGAINST LIQUEFACTION

8. FOUNDATION UNDERPINNING9. SLOPE STABILISATION

Applications of Grouting Applications of Grouting -- continuedcontinued GROUTSGROUTS

DISPLACEMENT OR COMPACTION GROUTS : STIFF, LOW SLUMP (0-5 CM) MIXTURES OF CEMENT, SOIL, AND / OR CLAY AND WATER LIME SLURRIES ARE MOST COMMONLY USED IN ENCAPSULATION GROUTING

9IN WATER / CEMENT GROUTS, w/c= 0.5/1 6/1 HAVE BEEN

USED.IF 0.5/1 RATIO IS USED STRENGTH WILL BE HIGHER BUT IT

WILL BE HARDER TO INJECT. SEGREGATION AND FILTERING WILL BE LESS. CHEMICALS (LIKE CALCIUM LIGNOSULFONATE) ARE ADDED TO CONTROL FLUIDITY AND PENETRATION AND SETTING TIME (30 sec -- VERY LONG) AND PLASTISIZERS TO PREVENT FLOCCULATION.

IN SOIL / CEMENT GROUTS, VOLUMES OF SOIL 4-6 TIMES THE

VOLUME OF CEMENT ARE MOST COMMON ALTHOUGH

RATIOS FROM 1 TO 12 HAVE BEEN USED.

VOLUME OF THE MIXING WATER VARIES FROM ABOUT 3/4 - 2

TIMES THE VOLUME OF CLAY PER BAG CEMENT IN CEMENT-

CLAY GROUTS.

VOLUME OF THE MIXING WATER VARIES FROM 1/3-1 TIMES

THE LOOSE VOLUME OF SAND PER BAG OF CEMENT IN

CEMENT - SAND GROUTS

GENERALLY MINIMUM WATER CONTENT WHICH WILL STILL

YIELD AN INJECTABLE UNXIUIE IS USED.

SULFATES AND SULFATE BEARING GROUND WATER ARE

THE ENEMY OF CEMENT.

PARTICULATE GROUTS CANNOT BE INJECTED AS

PERMEATION GROUTS INTO SOILS FINER THAN MEDIUM TO

COARSE SANDS. THIS APPROXIMATELY CORRESPONDS TO

A PERMEABILITY OF ABOUT 5x10-4 cm/sec.

AREAS OF USE :

CEMENT GROUTS : FOR BOTH IMPERMEABILISATION AND STRENGTH INCREASE

SOIL, CLAY AND CHEMICAL GROUTS : IMPERMEABILISATION AND COMPACTION GROUTING

CLAY GROUTS : LIMITED USE (USUALLY FILLING VOIDS ETC)

CLAY-CEMENT GROUTS : FILLING VOIDS, MUDJACKING

TYPES I AND II PORTLAND CEMENT ARE SUITABLE FOR SOILS COARSER THAN 0.60 mm.

TYPE III PORTLAND CEMENT IS SUITABLE FOR SOILS COARSER THAN 0.42 mm. (BENTONITE: 0.25 mm)

PARTICLES 50 micron SIZE CAN BE INJECTED TO COARSE SAND (> 0.8 mm). COLLOIDAL SUSPENSIONS CAN BE INJECTED INTO MEDIUM SAND ( 0.1 TO 0.8 mm). FINE SANDS & SILTS REQUIRE NEWTONIAN SOLUTIONS OF LOW VISCOSITY.

THE ABILITY OF PARTICULATE GROUTS TO PENETRATE A FORMATION IS OFTEN INDICATED IN TERMS OF A GROUTABILITY RATIO. SOME GROUTABILITY RATIOS THAT HAVE BEEN PROVEN USEFUL ARE GIVEN BELOW:

10

GROUTING CONSISTENTLY POSSIBLE

GROUTING NOT POSSIBLE

GROUTING CONSISTENTLY POSSIBLE

GROUTING NOT POSSIBLE

24)()(

85

15 >=grout

soil

DD

N

11=grout

soilc D

DN

6=

groutR D

fissureofWidthN2 15 % EFFECTIVE CHEMICAL GROUTING MAY BE DIFFICULT, FOR FINES CONTENT > 20 % PERMEATION GROUTING WILL NOT BE POSSIBLE BUT CHEMICAL GROUTS NOT BE DISTRIBUTED ALONG AND THROUGH HYDRAULIC FRACTURES.

COMPACTION GROUTINGCOMPACTION GROUTING

LAYOUT OF HOLES IN NUMBER

LOCATION OF HOLES & INCLINATION

DEPTH

SEQUENCE OF HOLES GROUTED

PROCEDURE OF GROUTING INDIVIDUAL HOLE

Important Design Parameters

TYPICAL APPLICATION DETAILS ARE :

TRIANGULAR PATTERN USUALLY, 1.5 - 5 M SPACING

PRIMARY (~5 M) / SECONDARY HOLES, GROUT TAKES HOLES UNDER FOUNDATIONS, RATHER THAN OPEN

AREAS; PERIPHERAL HOLES FIRST

< # 200 % 10 - % 30, SAND IN COMPACTION GROUTING 100% PASSING NO.8 SIEVE, A COARSER SAND WILL CAUSE WATER TO BE DRIVEN OUT.

PRESSURES 0-4200 kN/m2

TWO BASIC METHODS FOR CONSTRUCTION:

1 . FROM TOP TO DOWN

2. FROM UP TO BOTTOM

GROUTING IS DONE IN STAGES, ONLY 0.75 - 1.0 m OF HOLE IS

GROUTED AT A TIME.

PROCEDURE FOR GROUTING FROM TOP TO BOTTOM

1. DRILL A HOLE TO THE TOP OF THE ZONE (MIN. 1.5 M)2. INSERT A CASING IN THE HOLE AND FILL THE ANNULAR

SPACE BETWEEN THE CASING AND THE HOLE WITH QUICK SETTING CEMENT.

3. DRILL THROUGH TIE CASING AND ADVANCE THE HOLE 1-2.5 m. NEVER EXCEED 3-3.5 METERS.

4. PUMP IN GROUT UNTIL THERE IS "REFUSAL" OR SLIGHT MOVEMENT OF THE GROUND SURFACE.

5. REPEAT THE PROCEDURE (ITEMS 3 AND, 4) AFTER HARDENING OF THE PREVIOUSLY PLACED GROUT UNTIL THE BOTTOM OF THE ZONE TO BE STABILIZED IS REACHED.

11

PROCEDURE OF GROUTING FROM BOTTOM TO UP:

1. DRILL A HOLE TO THE BOTTOM OF THE ZONE TO BE STABILIZED

2. PLACE CASING TO WITHIN A METER OF THE BOTTOM OF THE HOLE.THE CASING SHOULD BE A SNUG FIT AND MAY REQUIRE PUSHING OR DRIVING INTO PLACE.SOMETIMES IT IS DRIVEN ENTIRELY (i.e. PREDRILIING ELIMINATED)

3. PUMP IN THE GROUT UNTIL 'REFUSAL' IS ACHIEVED (OR SLIGHT)

4. RAISE THE CASING5. PUMP AGAIN AND REPEAT 4 AND 5 UNTIL THE GROUND

SURFACE IS REACHED.

IN MOST MIXED SOILS BEGINNING RATE WILL BE ON THE ORDER OF 0.3 m3/min. 3 -5 m3/min IS APPLIED IN SOILS WITH LARGE VOIDS. 0.003 -0.014 m3/min IS USED IN UNDRAINED CLAYS AND HIGHLY PLASTIC CLAYS.

PRESSURES : 350 KPA - 1700 KPA WITHIN 1.5 - 2 M OF THE SURFACE AND UP TO 3500 kPa OR MORE WHEN D > 6 M, SELDOM > 4200 kPa.

Jet GroutingJet GroutingJet grouting is a soil improvement technique which employs

high-speed fluid jets to erode soils. The resulting cavity is subsequently filled with grout to form a composite

material with enhanced characteristics.

12

Single system

Double system

Triple system

Grout is pumped down through the drilling rods and exits horizontal nozzles in the tool at high velocity

A two-phase internal system is employed for the separate supply of grout and air down to different, concentric nozzles.

Grout, air and water are pumped through three different lines to the tool.

Jet Grouting Jet Grouting Continued Continued

Single Double Triple

GroutAir

GroutAir

AirWater

Air Grout

Single Double Triple

GroutAir

GroutAir

AirWater

Air Grout

Jet Grouting Jet Grouting Continued Continued OH&S Issues because of high pressuresQuality control is necessary

Jet GroutingJet GroutingApplicable to all type of soils including clay

Sand and gravel particles increase the strength Nearly all soil types groutableLimited working space requiredAny cross-section of soilcrete possibleDesignable strength and permeabilityTreatment to specific subsurface locationsNo harmful vibrationsSafest method of constructionAbility to work around buried active utilitiesThe most effective means of direct underpinning of structures and utilitiesMuch faster than alternative methods

Jet GroutingJet GroutingAdvantages

Applications of Jet GroutingApplications of Jet GroutingAcknowledgementAcknowledgement

Some of grouting slides are takes from CE 468 Geotechnical Design Subject material presented by Dr. M. Ufuk ERGUN at the Middle East Technical University

Many thanks to Ballina Bypass Alliance (BBA), Austress- Menard, and Keller Ground Engineering for providing data.