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Παρασκευή, 10 Ιουλίου 2020

Παρουσίαση της τεχνολογίας και των εφαρμογών των γαλβανισμένων πλεγμάτων οπλισμού των ασφαλτικών ταπήτων από τον Ing. Marco Vicari του Τεχνικού Τμήματος του Ομίλου Maccaferri (στην Αγγλική)

Road Mesh THE USE OF DOUBLE TWIST STEEL WIRE MESH AS A REINFORCEMENT FOR ASPHALT PAVEMENTS Eng. Marco Vicari Technical Department SUMMARY 1 – MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Background130 130 yearsyearsFor over 130 years, Officine Maccaferri has researched, designed and developed solutions to solve problems related to the Civil Engineering and Construction Market.100 100 countries countries5 continentsOfficine Maccaferri’s worldwide headquarters are located in Bologna, Italy. The Company has on-the-ground operations in almost 100 countries worldwide and employs 2,472 people.The Company promotes the most sophisticated high-quality products – including woven hexagonal wire mesh steel products, geosynthetics and fibers.continents SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION SOIL REINFORCEMENT SOLUTIONSSoil reinforcement Mechanically Stabilized Earth WallsSlope Revegetation GREECE 2005: Egnatia highway 30 m high RSS with Paralink and Terramesh System ALBANIA 2008: Durres – Pristina highway 40 (below) +35 (above) m high RSS with Paralink and Terramesh System INDIA 2011: Sikkim airport 80 m high RSS with Paralink and Green/Terramesh System The Pavements: Design and Problems Introduction: terminology WEARING COURSE BINDERBASEFOUNDATIONSUBBASE (optional) SUBGRADEMain structural element (durable) BOUND MATERIALPavement foundation GRANULAR MATERIAL OVER SOIL Existing soilBOUND MATERIAL: high stiffness, crack and deformation resistant GRANULAR MATERIAL OVER SOIL: adequate platform to place layer above GROUND STABILISATIONWhen a geosynthetic is placed as a tensile element at the bottom or within a flexible UNBOUND base (or sub-base) course to eventually increase the bearing capacity of the subgrade thus having: (i) improvement of the service life; (ii) an equivalent performance with a reduced structural section;ASPHALT REINFORCEMENTSame as above but within the BOUND layer, to increase the service life of the pavement by preventing fatigue and reflective cracksBASAL REINFORCEMENTThe reinforcement is used at the embankment-subgrade interface to enhance the resistance of the embankment to avoid failure through excessive deformation or shear in the foundation ASPHALT REINFORCEMENT GROUND STABILISATION Bound layers Unbound layersBASAL REINFORCEMENT Basal reinforcement over soft soils Basal reinforcement over piles Basal reinforcement over voids PAVEMENT SOLUTIONSAsphalt ReinforcementDrainage & separation Ground StabilizationTRADITIONALINNOVATIVE KAZAKHSTAN 2003: Tiba Kimitsu IC Tateyama Highway Soil stabilisation of the roads for the Atyrau oilfield with Macgrid EGS BELGIUM 2009 Asphalt overlay reinforced with glass fiber geogrid Macgrid AR MACCAFERRI SOLUTIONS FOR ROADS Maccaferri is able to provide pavement and ground stabilisation products to provide solutions for the rigorous demands of today’s roads MACCAFERRI SOLUTIONS FOR ROADS Maccaferri is able to provide pavement and ground stabilisation products to provide solutions for the rigorous demands of today’s roads Unpaved roads1 - UNPAVED ROADS Unpaved roads GIROUD-HAN DESIGN METHOD DESIGN EQUATION The presence of the reinforcement is taken into account by the factors J and Nc Unpaved roads GIROUD-HAN DESIGN METHOD RESULTS COMPARISON – GIROUD & HANRut depth = 50 mm; tyre pressure = 550 kPa; 1000 passes; axle load = 80 kN Parking decks and soil platforms2 –PARKING DECKS, HEAVY DUTY PAVEMENTS, WORKING PLATFORMS Parking decks and soil platforms Working platformsHeavy duty pavementsParking decks TYPICAL PROBLEMS• Almost impossible access to the site • Difficult compaction of construction layers • Insufficient bearing capacity for pavement construction • Great volume of soil materials to be excavated and exported and/or imported while using standard solutions • Time pressure • Costs Parking decks and soil platforms The problem is similar to that of unpaved roads, but in this case: - unchannelized low volume traffic loads; - randomly distributed surchargesReinforcement is provided by 1-3 layers of bi-oriented geogridsGeotextile for separation/drainage (not considered in this PPT) Parking decks and soil platformsPRACTICAL RESULTS Comparison of zr and zu for similar wheel loads and tire pressures show that the deck thickness can be reduced by 30-50 % by using geogrid reinforcement. The best results are obtained with 2 - 3 layers of equally spaced geogrids at vertical centres of 150 – 300 mm. Bi-oriented geogrids are used; their range is usually 20-50 kN/m Paved roads: reinforcement of the unbound layers3 – PAVED ROADS: UNBOUND LAYERS W.C. BINDER BASEFOUNDATIONSUBGRADE Paved roads: reinforcement of the unbound layers AASHTO METHOD FOR UNREINFORCED ROADS (2003)According to this method it is possible to define a Thickness Index Is or Structural Number SN (cm).SN = a1d1 + a2d2M2 + a3d3M3 Where: ai is the ith layer coefficient, di is the thickness of the ith layer, Mi is the drainage coefficient for the ith layer. Paved roads: reinforcement of the unbound layers AASHTO METHOD FOR REINFORCED ROADSThe structural contribution of an extruded geogrid can be quantified by:SN = a1d1 + LCR a2d2M2 + LCR a3d3M3 Where: LCR = Layer Coefficient Ratio LCR is determined only from laboratory testing on flexible pavement systems with and without geogrid32 Paved roads: reinforcement of the unbound layers GEOGRID POSITIONINGMACGRID XXMACTEX xxWeak subgrade (CBR < 3) Base > 250 mmWeak subgrade (CBR < 3) Base < 250 mm Paved roads: reinforcement of the bound layers4 – PAVED ROADS: BOUND LAYERS W.C. BINDER BASEMACGRID ARor ROAD MESHFOUNDATIONSUBGRADE Paved roads: reinforcement of the bound layers GS in the bound layers • Presently there are no validated mechanistic-based models for reflective cracking in AC pavements. • For an accurate evaluation of the benefits due to a reinforcement in an asphalt pavement time-consuming FEM computations are required. • For no design method is currently available • For MacGrid AR and ROAD MESH only it is possible to design:A) reinforced overlays by means of OLCRACK software (Prof. Brown, Nottingham University) B) pavement rehabilitation (for Road Mesh only) by means of a design equation (Prof. Al-Qadi, USA) 35 Paved roads: reinforcement of the bound layers ROADMESH IN OVERLAYS: OLCRACK software Load [kN]40Radius [mm]150Std Dev. of Wheel Path0Axles in 1st year (million)1Growth rate (%)Project Title: M 50 EIRE0Thickness [mm]Poissons ratioOverlay140Base1002300Sub Base300300Subgrade0.35Stiffness [MPa] 500080CRACK 100 Spacing [m] 1000 Shear Modulus 1 Width Factor ITS TEST DATA 1500 Failure Strain 0.25 Fatigue Slope 100 Specimen Diam.36 Maccaferri Reinforced Overlay Design Report of Analysis Project :M 50 EIREMaccaferri Ltd. Oxford, UKInput Data Road Mesh BottomReinforcement type: Position of Reinforcing:80 kN 679 kPaDesign Axle Load : Contact Pressure :Pavement Structure Thickness [mm] Poisons ratioPaved roads: reinforcement of the bound layersStiffness [MPa]Overlay1400.355000Base1002300Sub Base300300Subgrade80ROADMESH IN OVERLAYS: OLCRACK softwareOutput Data Improvement Factor :3.1 3.1Overlay life with reinforcing (years): Overlay life without reinforcing (million axles): Overlay life without reinforcing (years):1.52.0 2.0Overlay life with reinforcing (million axles):Annual Traffic :1,000,000Level in overlayPlot of crack propagation in overlay 160 140 120 100 80 60 40 20 0 1E-06 0.00001 0.00010.0010.010.1110Number of Wheel Passes (millions)Top-downBottom-upInterface37 SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Pavement failuresWHY DO ROADS FAIL?• Fatigue • Surface stresses • Thermal loads Concrete and flexible pavements• Lack of bearing support Under-design, poor drainage, settlements• Existing discontinuities Cracks, joints, widenings Pavement failuresFATIGUEOccurs in areas subjected to repeated traffic loadings (wheel paths). Can be a series of interconnected cracks in early stages of development. Develops into many-sided, sharp-angled pieces, usually less than 0.3 m on the longest side, characteristically with an alligator pattern, in later stages. Pavement failuresSURFACE STRESSES A rut is a longitudinal surface depression in the wheel path. It may have associated transverse displacement. Pavement failuresTHERMAL LOADS Low temperatures Termal cracking: Due to the thermal gradient between the upper and bottom layers Pavement failuresLACK OF BEARING SUPPORT Due to an under-design of the pavement structure (bound or unbound layers) with respect to the bearing capacity of the soil Pavement failuresLACK OF BEARING SUPPORT Due to an under-design of the pavement structure (bound or unbound layers) with respect to the bearing capacity of the soiloriginal profileasphalt layerweak subgrade or underlying layersubgrade deformation Pavement failuresEXISTING DISCONTINUITIES The major distress in HMA overlays, with a prematur transmission of cracks within 1-2 years SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Solutions for pavement distressesEFFECTIVENESS OF PAVEMENT REINFORCING MATERIALSCrack propagation Solutions for pavement distressesEFFECTIVENESS OF PAVEMENT REINFORCING MATERIALS Crack propagation (cm)8 073A1A543A1B1C5 4 33B2STEEL1 02 051015202530354045Loads number (x1000)0 Not reinforced 1A Nonwoven GT without emulsion 1B Nonwoven GT with emulsion 1C Nonwoven GT impregnated with elastomeric bitumen 2 Steel mesh3A Polyester geogrids 3B Fiberglass geogrid 4 5SAMI Woven GT What is Road Mesh?THE ROAD MESH REINFORCEMENT 8cm Transverse Reinforcing Rod16cmDouble Twisted Hexagonal Mesh Road Mesh is manufactured from double twisted steel wire mesh with transverse reinforcing rods evenly spaced 16 cm centres. The hexagonal mesh size is complying with EN 10223-3. The wire has a zinc coating complying with EN 10244-2 Class A. Road Mesh is covered by EN 15381 What is Road Mesh?THE ROAD MESH REINFORCEMENT What is Road Mesh?THE ROAD MESH REINFORCEMENT ROAD MESH TYPEF WIRE MESH (mm)F TRANSVERSE ROD (mm)TENSILE STRENGTH MD/XD (kN/m)L2.44.440 / 40S2.74.950 / 50Length: 25 – 50 m Width: 2 - 3 – 3.3 – 4 m What is Road Mesh?TENSILE TESTS ON ROAD MESHXD: 40 kN/mMD: 40 kN/mIn accordance with EN 15381 What is Road Mesh?THE ROAD MESH REINFORCEMENT TWarp• Bi-Directional Strength • Full Interlock Into Matrix • 3D Open Structure • RobustTWeft THE ROAD MESH REINFORCEMENT INTERLOCKING: can you see the layer of Road Mesh? SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Laboratory and field experiencesNOTTINGHAM UNIVERSITY (UK)The research investigated the effectiveness of different interlayer systems (geogrid, steel reinforcement and fiberglass grid) in preventing the reflection of cracks in HMA overlays. A repeated load shear test was first used to evaluate the interface shear strength and stiffness for unreinforced and reinforced samples. Only steel reinforcement provides interface shear stiffness comparable to the unreinforced case; both geogrid and glass fibre caused a significant reduction in the interface shear stiffness. Laboratory and field experiencesNOTTINGHAM UNIVERSITY (UK)The test results have shown that steel reinforcement improves the fatigue life by a factor up to 3, well above the other materials performance Crack propagation (cm)Load Cycles (#) Laboratory and field experiencesCAGLIARI UNIVERSITY (I)The research investigated the crack propagation process in the presence of steel reinforcement based on a finite element (ANSYS) model. The figure shows the crack development as a function of the load cycles (40 kN) at different frequencies (10 and 20 Hz): by making reference to a crack 1 mm deep, the reinforcement increases the pavement life by a factor variable between 3 and 12 (at 20 Hz and 10 Hz respectively). Laboratory and field experiencesSMART ROAD (USA)Results of the FE models were compared with actual stress and strain measurements at the Smart Road using a classical fatigue law (Arizona DOT): N = 9.33 10-7 et-3.84 The life improvement is pronounced at intermediate and high temperatures and is approximately 1.4 times with respect to the unreinforced section (at 25°). Laboratory and field experiencesCATANIA UNIVERSITY (I)The research focused on the capacity of non-destructive pavement measurement techniques to quantify the increase in terms of resistance to deformation given to flexible reinforced pavements by steel mesh, was carried out elaborating data coming from a survey conducted with Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) on an experimental section 250 meters long on a national road (SS 121) in West Sicily. Laboratory and field experiencesCATANIA UNIVERSITY (I)After five years of service a visual inspection testing of the pavement sections with steel reinforcement showed an extension of Residual Life by a factor of two when compared with the equivalent pavements without reinforcement.Residual Lifewith Road Mesh = 2 x Residual Lifeunreinforced Laboratory and field experiencesUNIVERSITY OF ILLINOIS (USA) LIFE-CYCLE COST ANALYSIS (LCCA) In the LCCA, the following conditions were assumed: 1- a conventional HMA overlay can serve for 10 years so that 4 consecutive HMA overlays are needed for a design life of 50 years; 2- HMA and steel netting costs are 50 $/ton and 6 $/m2, respectively; 3- no maintenance and user costs are included. Long-term service life analysis of the reinforced overlay shows a reduced pavement rehabilitation frequency, from five to two times in the 50 year design period. In this case, the reinforced overlay results in a cost benefit of 7 %. However, the cost-benefit margin of the reinforced overlay would be significantly greater when frequent routine maintenance, such as crack sealing, and user costs, are considered. Laboratory and field experiencesROAD MESH PERFORMANCES The performance of Road Mesh in asphalt pavement layers have been thoroughly investigated in the last 10 years through a number of research projects carried out by Universities and Road Authorities around the world The main results of the researches in terms of FATIGUE LIFE IMPROVEMENT (FLI) due to the Road Mesh are quite similar in terms of reinforcement’s effectiveness:- Nottingham Univ.: - Cagliari Univ.: - Smart Road: - Catania Univ.: - Univ. of Illinois:FLI ≈ 3 FLI > 3 FLI ≈ 1.4 FLI ≈ 2 FLI ≈ 1.8 SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Road Mesh applicationsASPHALT REINFORCEMENT Road Mesh reinforcement can produce a threefold increase in the service life of pavements by reducing fatigue, reflective, thermal and settlement cracking. Road Mesh applicationsASPHALT REINFORCEMENTMacGrid AR Glass reinforced woven geogridRoad mesh Steel Wire Road Mesh applicationsROAD MESH FOR FATIGUE PROBLEMSRoad Mesh is able to absorb the horizontal tensile stresses resulting from existing cracks and traffic loads, thus increasing the pavement life. Road Mesh applicationsROAD MESH FOR RUTTINGRoad Mesh is installed at the base of the overlay (> 60 mm) thus intersecting the shear slip circles, eventually reducing the surface rutting Road Mesh applicationsROAD MESH FOR RUTTINGApplication of Road Mesh in Palermo (I) to reduce the rutting problems at the bus stops due to the horizontal loads (braking) Road Mesh applicationsROAD MESH FOR TRANSVERSE CRACKS Overlays on jointed concrete pavementsThe active joint is a discontinuity which tends to propagate to the road surface. Road Mesh is installed within the overlay to absorb the tensile forces SUMMARY 1 –MACCAFERRI OVERVIEW 2 – MACCAFERRI SOLUTIONS FOR ROADS 3 – DISTRESSES AND FAILURES IN PAVEMENTS 4 – REINFORCEMENTS FOR PAVEMENTS5 – ROAD MESH: LABORATORY AND FIELD EXPERIENCES 6 – ROAD MESH: APPLICATIONS 7 – ROAD MESH INSTALLATION Road Mesh installationMILLING – To ensure no surface potholes or cracks.CLEANING – As per normal Road ConstructionPLACE the Road-Mesh – inside of roll in contact with the road.FLATTEN the Road-Mesh using 1 or 2 roller passesANCHOR using nails or other method (slurry seal or blinding)TACK COAT application to seal/fill cracks or fix new asphalt to surfacePLACE ASPHALT - Using Wheel or Tracked PaverCOMPACT ASPHALT - Using Steel or Rubber Wheel RollerSAMPLING – To check the quality of the installation work Road Mesh installation1 - MILLING Road Mesh installation2 - CLEANING Road Mesh installation3 – ROAD MESH DEPLOYMENTROADMESH DEPLOYMENT Road Mesh installation3 – ROAD MESH DEPLOYMENT Road Mesh installation3 – ROAD MESH DEPLOYMENT Road Mesh installation3 – ROAD MESH DEPLOYMENT Road Mesh installation3 – ROAD MESH DEPLOYMENT Road Mesh installation4 – FLATTENING OF ROAD MESH Road Mesh installation5 – ANCHORING FIXING OPTIONS • Slurry Seal • Blinding • Nailing Road Mesh installation5 - FIXING BY SLURRY SEALSlurry seal (15-17 kg/m2) can be applied over any surface, but is generally quite expensive Road Mesh installation5 - FIXING BY BLINDINGA technique perfected by a contractor in the UK, where a thin surfacing of asphalt is spread over the bulk of the mesh, thereby reducing the shear force caused by the new layer of asphalt. Very few nails are used with this technique, so is quick and economical Road Mesh installation5 - FIXING BY BLINDING Road Mesh installation5 - FIXING BY NAILINGNailing is carried out using a Hilti or Spit gun and is quiet quick. For larger projects, the number of guns is increased to improve productivity. Road Mesh installation5 - FIXING BY NAILING Road Mesh installation5 - FIXING BY NAILINGNail Positioning Road Mesh installation5 – ANCHORING & OVERLAPPING Road Mesh installation5 – ANCHORING & OVERLAPPING 2 meshes (15 cm) for adjacent panels2 meshes (30 cm) in the Longitudinal Direction Road Mesh installation6 – TACK COAT Road Mesh installation6 – TACK COAT Road Mesh installation7 – PLACING THE HMA Road Mesh installation8 – COMPACTION OF HMA Road Mesh installation9 – HMA SAMPLING CONCLUSIONS CONCLUSIONSWHAT ROAD MESH DOES.. 1 - Limits deformations in an overlay to a strict minimum (steel is more rigid than any other reinforcing material)2 - Absorbs the tensile stresses beneath the asphalt layers (the tensile strength is the same in both directions) 3 - Locks the asphalt aggregates into the mesh openings (interlocking assured by the large mesh size: no delamination problems) CONCLUSIONSWHAT ROAD MESH DOES.. 4 - Increase the pavement’s design life (by 1.5-2 times), thus reducing the maintenance costs 5 - Both steel and asphalt can be fully recycled Roadmesh •Overlays– – – – •Extends life x 1.4 – 1.9 Reduce thickness 10 - 20% Halves rutting At least 60mm overlay, preferably moreWidening– Longitudinal cracking •Peat subgrade– Control cracking due to differential settlement
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