Upload
marcelo-apolo
View
18
Download
3
Embed Size (px)
Citation preview
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