ground improvement for tunnels & cross passages

1

Ground Improvement

for Tunnels & Cross Passages

Babak HamidiPhD, MEng, BEng, MIEAust, AGS, ISSMGE TC-211

16-18 June 2019 ATS Tunnel Design & Construction Short Course 2019

Main Objectives of Ground Improvement 2

• Strength increase

• Bearing capacity

• Slope and wall stability

• Liquefaction

• Deformation reduction

• Vertical (settlement)

• Horizontal

• Differential

• Permeability increase or reduction

• Cut-off of fluid ingress

• Incoming water

• Outgoing fluid

• Water drainage


https://www.youtube.com/watch?v=MS4H_u0ARpo

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Category Method PrincipleA. Ground

improvement

without

admixtures in

non-cohesive

soils or fill

materials

A1. Dynamic compaction Densification of granular soil by dropping a heavy weight from air onto

ground.

A2. Vibro compaction Densification of granular soil using a vibratory probe inserted into

ground.

A3. Explosive compaction Shock waves and vibrations are generated by blasting to cause

granular soil ground to settle through liquefaction or compaction.

A4. Electric pulse

compaction

Densification of granular soil using the shock waves and energy

generated by electric pulse under ultra-high voltage.

A5. Surface compaction

(including rapid impact

compaction).

Compaction of fill or ground at the surface or shallow depth using a

variety of compaction machines.

B. Ground

improvement

without

admixtures in

cohesive

soils

B1.

Replacement/displaceme

nt (including load

reduction using

lightweight materials)

Remove bad soil by excavation or displacement and replace it by good

soil or rocks. Some lightweight materials may be used as backfill to

reduce the load or earth pressure.

B2. Preloading using fill

(including the use of

vertical drains)

Fill is applied and removed to pre-consolidate compressible soil so that

its compressibility will be much reduced when future loads are applied.

B3. Preloading using

vacuum (including

combined fill and

vacuum)

Vacuum pressure of up to 90 kPa is used to pre-consolidate

compressible soil so that its compressibility will be much reduced when

future loads are applied.

B4. Dynamic

consolidation with

enhanced drainage

(including the use of

vacuum)

Similar to dynamic compaction except vertical or horizontal drains (or

together with vacuum) are used to dissipate pore pressures generated

in soil during compaction.

B5. Electro-osmosis or

electro-kinetic

consolidation

DC current causes water in soil or solutions to flow from anodes to

cathodes which are installed in soil.

B6. Thermal stabilization

using heating or freezing

Change the physical or mechanical properties of soil permanently or

temporarily by heating or freezing the soil.

B7. Hydro-blasting

compaction

Collapsible soil (loess) is compacted by a combined wetting and deep

explosion action along a borehole.

C. Ground

improvement

with

admixtures

or inclusions

C1. Vibro replacement or

stone columns

Hole jetted into soft, fine-grained soil and back filled with densely

compacted gravel or sand to form columns.

C2. Dynamic replacement Aggregates are driven into soil by high energy dynamic impact to form

columns. The backfill can be either sand, gravel, stones or demolition

debris.

C3. Sand compaction

piles

Sand is fed into ground through a casing pipe and compacted by either

vibration, dynamic impact, or static excitation to form columns.

Category Method PrincipleC4. Geotextile

confined columns

Sand is fed into a closed bottom geotextile lined cylindrical hole to form

a column.

C5. Rigid inclusions Use of piles, rigid or semi-rigid bodies or columns which are either

premade or formed in-situ to strengthen soft ground.

C6. Geosynthetic

reinforced column or

pile supported

embankment

Use of piles, rigid or semi-rigid columns/inclusions and geosynthetic

girds to enhance the stability and reduce the settlement of

embankments.

C7. Microbial methods Use of microbial materials to modify soil to increase its strength or

reduce its permeability.

C8 Other methods Unconventional methods, such as formation of sand piles using blasting

and the use of bamboo, timber and other natural products.

D. Ground

improvement

with grouting

type admixtures

D1. Particulate

grouting

Grout granular soil or cavities or fissures in soil or rock by injecting

cement or other particulate grouts to either increase the strength or

reduce the permeability of soil or ground.

D2. Chemical grouting Solutions of two or more chemicals react in soil pores to form a gel or a

solid precipitate to either increase the strength or reduce the

permeability of soil or ground.

D3. Mixing methods

(including premixing or

deep mixing)

Treat the weak soil by mixing it with cement, lime, or other binders in-

situ using a mixing machine or before placement

D4. Jet grouting High speed jets at depth erode the soil and inject grout to form columns

or panels

D5. Compaction

grouting

Very stiff, mortar-like grout is injected into discrete soil zones and

remains in a homogenous mass so as to densify loose soil or lift settled

ground.

D6. Compensation

grouting

Medium to high viscosity particulate suspensions is injected into the

ground between a subsurface excavation and a structure in order to

negate or reduce settlement of the structure due to ongoing excavation.

E. Earth

reinforcement

E1. Geosynthetics or

mechanically stabilized

earth (MSE)

Use of the tensile strength of various steel or geosynthetic materials to

enhance the shear strength of soil and stability of roads, foundations,

embankments, slopes, or retaining walls.

E2. Ground anchors or

soil nails

Use of the tensile strength of embedded nails or anchors to enhance

the stability of slopes or retaining walls.

E3. Biological methods

using vegetation

Use of the roots of vegetation for stability of slopes.

Chu, J., Varaksin, S., Klotz, U. & Mengé, P. (2009) State of the Art Report: Construction Processes. 17th International

Conference on Soil Mechanics & Geotechnical Engineering: TC17 meeting ground improvement, Alexandria, Egypt, 7

October 2009, 130.

Ground Improvement Techniques 3


TechSpan (Reinforced Earth Company)

Tunnel Type: Buried Structure 4

Tunnel Type: Cut and Cover 5


Sydney Metro Waterloo Station

Tunnel Type: Excavated/Bored/Pipe Jacking 6


Binningup Desalination Plant (SSWA)

Grouting Technology in Tunnelling 7


Kogler, K. (2013) Grouting Technology in Tunnelling. Geomechanics and Tunnelling 6, 3, 261-273.

Ground Tunnelling method Purpose of grouting Construction conditions Geometrical requirements Grout

material

rock or solid stone TBM consolidation from above ground grouted canopy or screen suspensions

alluvium or soil conventional waterproofing from underground face support mortars and

pastes

Compensation from shafts ring-shaped temporary support Solutions

prestress grouting of pressure tunnel compensation bodies emulsions

grouting to remedy a collapse Resins

polyamide

Construction Conditions 8


Arroyo, M., Gens, A., Croce, P., and Modoni, G. "Design of jet-grouting for tunnel waterproofing." 7th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground, Rome, 181-188.

Croce, P., Flora, A., and Modoni, G. (2014). Jet Grouting Technology, Design and Control, CRC Press, Boca Raton, FL, USA.


Grouting from Shafts

Grouting from above ground

Grouting from underground

Grouting from underground

Geometric Requirements 9


Canopy (umbrella)

Compensation body

Canopy with face support

Support ring

British Standards Institution (2001) BS EN 12716: Execution of Special Geotechnical Works - Jet Grouting.

Kogler, K. (2013) Grouting Technology in Tunnelling. Geomechanics and Tunnelling 6(3):261-273.

Guatteri, G., Koshima, A., Lopes, R., Ravaglia, A. & Pieroni, M. R. (2008) Historical Cases and Use of Horizontal Jet Grouting Solutions with 360o Distribution and Frontal

Septum to Consolidate Very Weak and Saturated Soils. 6th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground, pp. 287-294.

Geometric Requirements 10


Arroyo, M., Gens, A., Croce, P., and Modoni, G. "Design of jet-grouting for tunnel waterproofing." 7th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground, Rome, 181-188.

Filippini, R., Kovari, K. & Rossi, F. (2012) Construction of a Cavern under an Autobahn Embankment for the Ceneri Base Tunnel. Geomechanics and Tunnelling, 5, 2, 175-185.

Perri.3SARMC.1990.Jet Grouting in Tunneling - Consolidation in the El Silencio Manouvering Section of the Second Line Caracus Subway

Trunk, U. & Winkler, F. (2013) Jet Grouting in Tunnelling. Geomechanics and Tunnelling, 6, 3, 274-289.

Ceneri Base Tunnel, Switzerland 11


Filippini, R., Kovari, K. & Rossi, F. (2012) Construction of a Cavern under an Autobahn Embankment for the Ceneri Base Tunnel. Geomechanics and

Tunnelling, 5, 2, 175-185.

Jetting the foundation bodies

Driving the abutment headings

Bench excavation to complete profile

Concreting the abutments

Excavation of the top heading with jet

grout canopy and shotcrete support

Grout Material

Grout Definition Composition Main application

Mortars and

pastes

suspensions with high solid

content

water, cement and sand, possible with

additives W/C ratio < 1

filling of cavities and fissures

Suspensions fine suspension of undissolved

solids in a liquid

water, cement or fine cement, if required

bentonite PFA W/C value > 1

waterproofing and consolidation of gravelly and sandy

soils, joints and fissures in rock

Solutions solution of solids in solvent water, silicate and hardener synthetic resins

and plastics

waterproofing and consolidation of sandy and fine gravelly

soils

Emulsions mixtures of two or more liquids water, bitumen, emulgators water-insoluble

silicate hardener

waterproofing of fine sand soils

resin grouts two-component resins with

high viscosity

rubber and chemical hardener, possible with

fillers

waterproofing of very fine fissures and cracks mechanically

effective grouting or rock and building elements

PU foams polyurethane foam, mostly two

components

polyurethane with chemical hardner temporary waterproofing of large water passages in gravel

and rock

Polyamide melted polyamide granulate single-component polyamide granulate with

high viscosity

temporary and permanent waterproofing of large water

passages in soil and rock

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Grouting Technologies: Soil/Rock Grouting

• With or without pressure

• With or without packer

• Tube a Manchette (TAM)

13


Houlsby, A. C. (1990) Construction and Design of Cement Grouting - A Guide to Grouting in Rock Foundations. USA, John Wiley.

Storeb Aelt Tunnel Cross Passages, Denmark 14


• 1992- 1995

• Sandy-clayey glacial till: consolidated and made impervious by grouting with bentonite cement or ultra-fine cement slurry.

• Half length of each cross passage was treated from each side to keep borehole length to less than approximately 12 m long and maintain the necessary degree of accuracy.

Glacial deposits

Marl

Glacial ???

Melbourne West Gate Tunnel Southern Portal 15


WGT Inbound Portal Ground Conditions 16


WGT Inbound Portal Ground Conditions 17


Fractured Newer Volcanics (NVF) Core Sample

Slightly Weathered Newer Volcanics (NVS) Core Sample

Brecciated Newer Volcanics (NVB) Core Sample

Groundwater level

• Inbound: RL 3 m to RL 1.5 m

• Outbound: RL 5 m

WGT Inbound Portal 18


WGT Inbound Portal Grouting Sections 19


WGT Grouting Details

• Upstage grouting using packer and grouting at 6 m intervals

• Termination criteria:

• Maximum pressure: 2 * overburden at the bottom of the hole

• Flow rate: 5litres/min for 5 min

• Max Volume: 500 litres/stage

• Grouting stages

• Primary (at 12 m)

• Secondary

• Tertiary

• Quaternary

• Quintenary

20


WGT Site 21


WGT Site 22


Grouting Technologies: Jet Grouting 23


Jet Grouting Setup 24


Sequencing 25



Alignment and Variability 26



Modoni, G., Flora, A., Lirer, S., Ochmański, M., and Croce, P. (2016). "Design of Jet Grouted Excavation Bottom Plugs." Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 142(7), 04016018.

Overlapping 27



Liu, Y., Pan, Y., Sun, M., Hu, J., and Yao, K. (2018). "Lateral compression response of overlapping jet-grout columns with geometric imperfections in radius and position." Canadian Geotechnical Journal, 55(9), 1282–1294.

Modoni, G., Flora, A., Lirer, S., Ochmański, M., and Croce, P. (2016). "Design of Jet Grouted Excavation Bottom Plugs." Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 142(7), 04016018.

QA-QC: Drilling and Grouting 28


Controlling Alignment

• Correct location and angle at collar level

• Maintaining/verifying straightness

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QA-QC: Visual Observation & Measuring by Excavation 30


QA-QC: Coring 31


QA-QC: Indirect Tests 32


• Informative suggestions in EN12716:2001

• Cross-hole geophysical tests

• CPT

• SPT

• DPC

• PMT

• Other

• Calliper

• Inspection holes using painted pipes

• Acoustic monitoring (hydrophone)

• Temperature measurement

Jet

Recording holes


Langhorst, O. S., Schat, B. J., de Wit, J. C. W. M., Bogaards, P. J., Essler, D. R., Maertens, J., Obladen, B. K. J., Bosma, C. F., Sleuwaegen, J. J., and Dekker, H. (2007) Design and validation of jet grouting for the Amsterdam Central Station, 14th ECSMGE, 18-21.

QA-QC: Electrical Resistivity Tomography

• Recording & analysing the potential differences generated by an induced electric current around a borehole.

• Instrumentation introduced into the test hole consists of a multi-core cable with emission electrodes interspersed with receiving electrodes.

• Potential difference is set up between each emission electrode and the receiving electrode.

• Electric field around hole takes the form of a cylinder, 5m to 10m in diameter.

• Deflections in the resistivity equipotential lines identify features such as voids, loose zones, clay beds, etc.

• Resistivity

• Ground resistivity is usually tens of ohm-m

• Jet grouted column:

• Initially a few ohm-m.

• Increases over time as the material hardens →contrast diminishes & eventually reverses.

• Advantage: Provides results shortly after construction of the column has been completed without waiting for column exposure, core drilling, etc.

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QA-QC: Grout Mix & Spoil Quality

• Grout

• Apparent Viscosity (Marsh funnel test)

• Bulk Density: Mud balance test

• Bleeding (if specified)

• Unconfined Compressive Strength (if specified)

• Jet Grouted Material

• Bulk density (as specified)

• Unconfined Compressive Strength (where relevant)

• Setting time (if specified and applicable)

• Permeability (if required)

34


La Duchere Tunnel, France 35


• Blasting in weathered gneiss

• Extremely weathered rock covered by 15 to 20 m of clayey-sandy colluvium → collapse

• Collapse: 15-20 m diameter, 4 to 5 m depression

• Grouting works:

• Compaction grouting from surface

• Jet grouted canopy

Project 1: Metro Station 36


Project 1: Metro Station 37


Typical Borehole Log 38


Sample Cores 39


Project 2: Typical Cross Passage Grouting Detail 40


Up to 40 m deep

Typical Cross Passage Plan View 41


Typical Cross Passage Sections 42


Typical Cross Passage Isometric View 43


Cross Passage Jet Grouting from Under a Bridge 44


Cross Passage Jet Grouting from Under a Bridge 45


QA-QC – Electrical Resistivity Tomography 46


Thank You! Questions? 47


ground improvement for tunnels & cross passages

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