innovations in soil conditioning for soft ground …...epb (earth pressure balance) balance the soil...

Innovations in Soil Conditioning for Soft ground Tunneling

Equipment | Construction Chemicals | Rock Reinforcement | Life Time Care

Soil Conditioning and EPB TBMEPB TBM and controlling pressure with soil conditionerCreating soil conditionerScience of soil conditioningSoil characteristics and soil conditioningSilty sandy soil and soil conditioningClay soil and soil conditioningSoil conditioning and rheologyAnti-wear soil conditioner for longer tool life, lower energy use, more PPDHigh water remediation solutions with eco-friendly superpolymerSummaryQuestions?

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Innovations in Soil Conditioning for Soft ground tunnelingTTOPICS

EPB (Earth Pressure Balance)Balance the soil pressure at the cutter head with a counter pressure at the working chamberFace support for non-cohesive and cohesive soilsAdvancement speed-screw speed regulation of pressure

EPB tunneling

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Soil conditioner injection

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Pressure Balancing

Addition of Soil Conditioner to EPB Interface

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Creating Soil Conditioner

➢ Foam liquid fraction (€) dictates either the formation of kugelschaumor polyederschaum foam

➢ When € is less than 0.1 we form the desired polyederschaum foam➢ The formation of foam is inversely proportional to the surface tension

the desired y should be less than 20mN/m (Dyne/centimeter)

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Wetting of soil

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Surfactants

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Micellization of soil

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Electrostatic Repulsion

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Clay Dispersants

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Steric Repulsion

SOIL SOIL

dispersantFoam Chemical

absorption

Steric Repulsion

➢ Elasticity - soil conditioner withstands pressure, deformation and impact

➢ Disjoining Pressure - soil conditioning foam migrates tothe edges via capillary pressure (not drainage). The disjoining pressure is countered by a large charge of the conditioner chemistry (electrostatic repulsion)

➢ Ostwald Effect - gas diffusion increase bubble size andis mitigated by more robust wall strength

➢ Foam defects - entry, bridging and spreading are preventedby strong soil conditioning chemistry

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Engineering the Soil Conditioner

Foam is elastic and compressible

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cF 3% Soil Conditioner at ATM and 3 Bar

ATM Foam B BAR Foam ATM Foam

Why soil conditioners ?

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➢ Elasticity - soil conditioner withstands pressure, deformation and impact

➢ Rheology - control of soil (muck) paste formation ➢ Maintain EPB pressure and control face support➢ Density control of soil➢ Fluidization of adhesive clays➢ Carrier for sand and silt➢ Controlled foam collapse ➢ Air pressure control➢ Anti-clogging of mining tools & screw conveyor

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Concentration of Soil Conditioner Solution

➢ The aqueous concentration of soil conditioner cF

➢ Higher concentration (>5% aqueous) Effects the Ostwald factor- Gas diffusion increase bubblesize and is mitigated by more robust wall strength

➢ Lower concentration (<3% aqueous)Provides a dryer foam for silt and sand

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Soil Conditioner Parameters

Chemistry engineered for specific soil geology

FER = Foam Expansion Rate, FER = Qf/QL

FIR = Foam Injection Rate FIR=Qf/Qs=Qf/v x As

Typical ranges: FER = 10 – 25, FIR = 50 - 150,

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Soil Conditioning for different soil types

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Atterberg Limits for Common Clays

Clay is a finely-grained natural soil that combines one or more clay minerals.

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Clay Mitigation with Soil Conditioners

Clays possess a Bingham plastic rheology

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Clay Mitigation with Soil Conditioners

Atterberg limits and soil conditioning

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Clay clogging of TBM

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Clay with soil conditioner provides proper rheology

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Controlling Soil Rheology with Soil Conditioner

Normet SC-150 Rheology TestDrop table + untreated (left) & treated (right) sandy soil10 drop cycles

SAND – SiO2Courser than silt and finer than gravelInsoluble in waterDensity: 1.33 g/cm3

SILT- quartz /feldsparInsoluble in waterVery fine particleCarried in water due to small particle sizeDensity: 1.33 g/cm3

Kepler Density 74.04%

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Soil Conditioning for Sandy & Silty Soils

Water insoluble sand and silt

Rheology control to maintain pressure

Encapsulate the clay

FER higher for dryer foam 15-20

FIR 75-100

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Soil Conditioning of Sandy/silty Soils

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Silt/Sand Soil Insoluble in water

• A simple water/soil test clearly shows this

• Silty soil is not water soluble.

• Therefore the soil conditioner choice should be one that forms a cohesive network.

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Controlling Soil Rheology with Soil Conditioner

Treating a sandy/silt soil with Normet 190CF soil conditioner at cF 3%, FER 20, FIR 75

Adding component to foam to reduce wear and machine torque

Creates chemical bond to shield cutters

Creates an EP extreme pressure barrier to protect 3rd body abrasion

Stays in solution until contact with cutter metallurgy

Shields cutter from soil-cutter boundary facilitated wear

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Anti-Wear Soil Conditioning

The wear that occurs on the cutters encompasses all regions of friction (as shown below in relationship between friction and viscosity)Anti-wear technology creates a protective shield around the cutting tools

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Friction – Viscosity Diagram

Anti-wear and Extreme Pressure Fluid dramatically reduces friction and wear of the cutters

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Four Ball Wear and Extreme Pressure (EP) Tester

Extreme Pressure Load Maximum (kg) at 0.9mm scar DIA.

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(1) EP Test: TamSoil 830AW vs. Competition

Maximum Load Bearing Property of Fluid

0 50 100 150 200

Competitor A

Competitor B

Competitor C

NORMET AW EP Fluid

Extreme Pressure Load maximum (Kg)

Mm Wear Scar Diameter

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(2) Fluid Anti-Wear Test: 830AW vs. Competition

Small load/pressure long term load scars balls and increases diameter

Problem Statement & Solution

The wear phenomena of the TBM cutting tools is caused via third body abrasion, strain crystallization and earth-cutter interfacial deformation.

In function, it is impractical to chemically or physiochemically isolate third body abrasive soil.

Thus, it is more feasible to impart dispersion of soil and chemical absorption of an anti wear/extreme pressure chemical simultaneously.

This reduces the impact that agglomerates have on cutter wear and creates a chemically bonded shield on the cutter surface.

Therefore, anti-wear chemistry is activated at the cutter head or tools where it is needed to reduce wear.

Corrosion causes iron oxides to be created

Embrittlement of cutting tools

Leading to:Crack expansion,Increase in wear

24 hour rust prevention testing

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(3) Corrosion Protection

Corrosion prevention increases life of cutters by 50%

665B saline water corrosion test

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APPLICATIONS

Roadheader mining

HR TBM

Coal mining

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High Water remediation 1000CP

- EPB advance in coarse ground below groundwater(when foam & standard Polymers are not sufficient)

- EPB or HR TBMs with water problems:a. beginning of the ringb. after weekendc. after Bentonite injection (pressure control)

- Problem solver!

- Creation of a plug in the screw conveyor

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1000CP Eco-friendly water binding polymer

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1000 CP Eco-friendly water binding polymer

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TBM Water Control

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Unique Performance Points

Unique in performance & eco-friendly

• Quick reaction: < 60 seconds

• Very efficient: higher water uptake than the competition

• Works in saline conditions, too

• Stable (no segregation)

• Environmentally friendly carrier (biodegradable oil)

• Very low toxicity (especially vs. fish: NOEC > 1’000mg/l)

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Breakthroughs in soil conditioning

• Soil conditioners are an essential part in EPB tunneling

• Different soils require different soil conditioning chemistry and implementation

• Clay soil is especially challenging due to its proclivity for clogging the cutter headand require new specialized soil conditioners.

• Silty and sandy soil is hydrophobic and has low cohesion requiring soil conditionersto create a workable paste. New technology soil conditioner combines foam andrheology modifier

• New technology soil conditioner protects the cutters against wear and corrosion

• Water remediation technology keeps the job running with minimal downtime