ITAtech Design Guidance for Spray

Applied Waterproofing Membranes

Summarized by

Tarcísio B. Celestino

Aug. 2013

Problems due to water Ingress into tunnels

• Durability

• Functionality

• Aesthetics

• Safety

• Comfort

1970s – sheet membranes

2000s – spray applied membranes

Cost-Benefit

Typical Inflow Problems

• Cracks and fissures • Reinforcement shades in shotcrete • Low compaction zones • Steel sets • Interface between top heading and bench

Objectives of the Document

• Assessment of the project condition; potential benefits of the spray applied membranes

• Limitations of spray applied membranes for water proofing

• Potential impact on the structural design - composite shell

• Guide for technical specifications

Appendices

- Example specification

- Training certification

- Generic detail drawings

- Case studies

Properties

• Non reactive-curing by hydration or air-drying

• Reactive systems - curing by polymer reaction

• Produced and installed in situ against primary lining

• Secondary lining or protective layer (mortar or sprayed concrete)

• Sandwich-structure (concrete-membrane-concrete) is a quasi-monolithic structure

• Not a panacea but offers viable solution for a specific window of ground and hydrological conditions

Features • Benefits in complex geometry (niches, cross passages,

portals, etc.)

• Use of final lining shotcrete

• No need for mesh to build up shotcrete as required by sheet membranes

• Application by means of equipment already available on site

• 50-100m²/h manually by 3 operators; 180m²/h with robotic spraying

• Applied in limited sections (e.g. crown) or continuous waterproofing

• Continuity without discrete joints (no need for weld, injection tubes, etc.)

• No welded seams – simply connected by overlapping

• Easier and quicker location and repair of leaks

Features (cont.)

• Can be combined with other waterproofing systems

• Compatible with all concrete placement methods and

reinforcement

• No folding or stretching during casting or spraying of the

secondary lining

Installation Limitations

• Exposed to tunnel environment (temperature, water) which

may interfere with curing process

• Vulnerable to poor workmanship

• Training and accreditation of applicators required

• Close quality control required

• Surface preparation (some systems)

• Not appropriate to install when high levels of water inflow are

expected

• Appropriate only for isolated areas with trickling or running

water, tunnels through dewatered or pre-grouted rock masses

• Substantially wet: sheet membrane recommended

Waterproofing Approach Based on Water Ingress

Waterproofing Systems

1. Withstand full water pressure (“submarine”

system)

2. Withstand partial water pressure (“Umbrella

system)

3. Fully drained (no pressure on lining)

Spray applied membranes adequate for 1 and 2

Use of Submarine Systems

• Environmental restrictions to any water level

lowering

• Settlement restrictions due to consolidation

• Eliminate pumping costs

• Isolation of groundwater and tunnel (e.g. sewer

tunnels)

Drained and Undrained Tunnels

Systematic drainage system

• Drains installed at 5-10 m

intervals

• Dimpled sheets strips onto

primary lining connected to

invert drain

• Regulating shotcrete applied

prior to waterproofing

membrane

• Secondary lining

Localized drainage System

• Impermeable rock with

water through some cracks

• Dimpled drainage strips

• Drilled drainage holes, if

required

Mixed System

• Drainage as in previous cases • Membrane only in crown

Combination with Sheet Membrane

• Overlapping in dry areas

• Substrate treated with mortar

• Sheet membrane properly fixed and well stretched

• Minimum overlap 40cm or according to supplier’s instruction

• Compatibility between materials should be tested

• Not to align structural joints with waterproofing transition

Bonding

Water tightness promoted by:

• bonding between membrane and substrate

• bonding between membrane and secondary lining

• minimum thickness

• leakage only if defects aligned

• easy to treat defect

Remedial Measures in Case of Leakage

• Leak identification

• Drill hole (18-25mm) 50mm deep to primary

concrete

• Inject acrylic resin

• Observe and repeat injection if needed

• Remove packers and repair surface

Time between membrane and secondary lining

• Option 1 – Divert flow to invert through dimpled drainage strips, covered by shotcrete. All surfaces covered with membrane

• Option 2 – Insert packers with drainage tubes. Take drainage to drainage system. Spray membrane to all surfaces. Inject through packers or allow drainage to continue in permanent case

• Option 3 – Spray membrane to all surfaces other than area of ingress. Allow membrane to cure fully. Inject water sealing resins, complete spraying membrane.

Dealing with water pressure during construction

Time between membrane and secondary lining

• If pressure relieved permanently or during membrane installation, not critical

• If membrane will withstand pressure, make sure membrane is cured before

• Curing characteristics of membrane may vary from product to product

Bonding

• Essential for waterproofing

• Good for structural reasons

• Minimum value required: 0,5 MPa

• Double bonding

• Reduction of total lining thickness due to

monolithic behavior of composite shell lining

Crack bridging

• Bridging cracks of up to 2.5mm. Performance

depends on elongation and tensile strength

• Wider cracks require increased membrane

thickness and agreement of manufacturer

• Structural and economic consequences of

thicker membranes

Durability

• Chemical aggressivity of groundwater should

be known beforehand

• Possible to deal with some degree of

aggressivity

Flammability

Avoid fire risk during spraying and before

secondary lining

Trials and Testing

• If required, Certificates of compliance to

ITAtech Example Specification shall be

provided, or other special requirements

• Suitability of materials, equipment, grouting

gear and fixings

• Compatibility with first and second lining

Application Requirements

• Spraying equipment feeding material at regular rate at velocities which promote adhesion, and minimum rebound

• Meet required pressures, volumes and ratios of product components

• Spraying operatives with certified training according to ITAtech scheme

• Equipment maintenance and cleanliness

• Approved Quality Audit System

• Correct surface preparation, if required

Substrate preparation

Surface preparation

• Closed surface

• No trapped air

• Time needed for preparation

• Material consumption

• Regulating layer: 1 to 3cm with 4mm max-

aggregate

Substrate surface finishing

• Shotcrete

• Layer of gunite (4mm aggregate)

• Smooth finished

Potential causes of failure

• Poor application, poor workmanship, lack of training

• Damage to membrane before final lining

• Two colored layers useful to detect damage

• Exceptionally rough surfaces

• Excess of water (running)

• Exposure to heat, freezing, UV.

All conditions addressed in specification and QC

Quality Control Coverage • Visual inspection for defects • Substrate visible • Membrane not suitably opaque • Damage

Spray paint

Additional layer of membrane with 200mm overlap

Thickness

• Depth of wet film: gage during application. Number

of locations as specified. Correction if needed.

• Average thickness from quantity sprayed and area

Thickness

Two layer application

Two colors

Thickness Cut-out inspection patches • Randomly located • Typically 50mm • Repaired by overs praying

• min 0.5 MPa within 28 days

• In case of water, diversion must be maintained

during 28 days

Bond do Substrate

Integrity Testing

Non-destructive Holiday detection, Continuity

Verification and Spark Testing

Single Shell Lining (SSL) Composite Shell Lining (CSL) Double Shell Lining (DSL)

Design Aspects

DSL typical for deep tunnels which anticipate high

water pressure

Composite Shell Lining

2nd lining: shotcrete or cast in situ concrete

Quasi-monolithic behavior like single-shell lining

Structural Behavior

SSL – OK but poor waterproofing

CSL – Test at SINTEF

• Design should limit shear stress acting on the

joint as a function of membrane thickness

(research underway).

• Numerical analyses

Watertightness classes

Properties of Spray Applied Membrane

Watertightness Test

Application Requirements

• Substrate temperature between + 5°C and +40°C

• Ventilation according to usual needs

• No other works carried out in the vicinity, dust

suppression measures, if needed.

• Sufficient lighting

• Fire detection and suppression

• Personal protective equipment

• Exclusion zones

• Eye wash and first aid facilities

Defects

• Inspection detects and marks defects

• If after repairs defects still persist, membrane shall be removed and replaced.

• Adjacent sections of membrane shall overlap by a minimum as defined by manufacturer.

Quality Control Testing During Construction

Details – Drained Road Tunnel

Details – Undrained Road Tunnel

Details – Membrane overlapping

Details – Interface with sheet membrane

Details – Metal Insertions

BASF

BASF

NORMET

NORMET

Stirling Lloyd

Stirling Lloyd

Mapei

Mapei

Thank you!

tarcisio@themag.com.br

tbcelest@usp.br