P&H Foundation Systems 2011

Patrick and Henderson Foundations4/3/2011 P&H Foundation Systems By Shelton L. Stringer, PE, GE, PG, EG Earth Systems Global Inc. © 2011 Earth Systems Global Inc. The Patrick and Henderson Tensionless Pier (P&H Pier) The P&H Pier consists of a large, cast-in-place cast in place pier foundation to support monopole towers (US Patent No. 5,586,417, Canadian Patent 2205502, Chinese Patent 201020166104.7). © 2011 Earth Systems Global inc. 1 5 Provinces 5 Provinces 4900+ Built 4200+ sinceBuilt 2000  5700+ 149 Projects   28 States. 200+ Projects Earth Systems Southwest © 2011 Earth Systems Global inc. A smarter choice P&H Foundations Built Supporting Wind Energy Projects 27 States. – The smallest footprint available. 2 .Patrick and Henderson Foundations 4/3/2011 Advantages of the P&H Pier     P&H foundations are the most economical available for wind turbine support. – 25% to 35% less than the cost of a gravity spread foundation – About 3% to 6% savings in total project development costs P&H foundations are the most environmentally green. with far less ground disturbance than a gravity spread foundation – Uses far less total concrete and steel than a gravity spread foundation with much quicker assembly Fewer materials make the P&H foundations a more attractive ecological and environmental solution for foundation support. P&H pier foundations 40-feet deep Used Anderson Drilling “Big Stan” 18foot diameter auger rig.Patrick and Henderson Foundations 4/3/2011 SNYDER WIND ENERGY PROJECT Scurry County.0-megawatt wind turbines on 105 m towers. d Height to Blade Tip = 150 m. BUFFALO MOUNTAIN WIND ENERGY PROJECT Anderson County. 492 feet! 21 Vestas V90 3. 3 .8-MW turbines on 80-meters towers P&H Pier foundations are on reclaimed land from coal mine spoils © 2011 Earth Systems Global inc. Tennessee    Tennessee Valley Authority project 15 towers Vestas V80 1. Texas      Tallest wind turbines in the United States to date. 5 to 10.Patrick and Henderson Foundations 4/3/2011 P&H Pier Construction in China 内蒙古.5 m) Cranes set an outer corrugated metal can (CMP) in the hole. 2009 2 .   © 2011 Earth Systems Global inc. y Typical depth 25 to 34 feet (7.Goldwind 750 kW Turbines in Inner Mongolia 中国金风科技内蒙古达茂，2台750KW 风机，目前已经并网发电。 4/3/2011 7 Construction of the P&H Pier  Construction of the pier begins by digging a hole with an excavator or drill rig. Rock sites require controlled pre-blasting.中国. typically 12 to 16 feet diameter (3.9 m). 4 .7 to 4. Threaded steel rods (encased in PVC sleeves) are arranged with a template that matches the base flange of the tower. inner CMP is set concentric within the hole. A concrete floor slab and top collar is cast.   Construction of the P&H Pier – A smaller. © 2011 Earth Systems Global inc. – A lower plug of concrete and the excavated spoils are placed within the inner can. 5 . typically 10 to 12 feet diameter (3. – Foundation concrete is placed between the two CMP cans.7 m). These rods are set and bolted to an embedment ring within the annular space between CMP cans.0 to 3.Patrick and Henderson Foundations 4/3/2011 Construction of the P&H Pier  Sand-cement slurry is placed as backfill between the outer CMP and the excavation sides. forming a hollow cylinder. load-deformation (p-y) curve. Pier rotation and deflection are dependent on compressibility of the soil or rock.   © 2011 Earth Systems Global inc.  and cohesion.Patrick and Henderson Foundations 4/3/2011 Construction of the P&H Pier  The tower is bolted to the threaded rods extending above the concrete. The ultimate passive resistance is dependent on the shear strength of the surrounding soil or rock (friction angle. expressed as a non-linear. The rods are post-tensioned to keep the concrete in compression (hence tensionless) during loading. 6 . c).   How the P&H Pier works  The lateral and moment capacity i developed is d l d by b side id bearing b i as the rigid pier is free to rotate within the earth. The grout trough beneath the base flange is filled. extreme    Foundation rotational stiffness to avoid resonance and excessive vibrations Design Loads  Loads come from the wind turbine manufacturer based on IEC. CsW = 0. 7 . < 10 km. minimum design force controls.78 MN-m) Seismic loads.000 ft-kips (14 . 2 to 5 mm operational.8S1/(R/I) . IEC Typical Extreme Wind Loads (unfactored): – Axial 140 – 575 kips (700 . non-building structure.000 to 58.2550 kN) – Lateral 70 – 200 kips (300 – 900 kN) – Moment 10. are generally less than design wind loads – Exception: 2010 California Building Code. Overturning stability with a global safety factor of at least 2 against extreme loads Pier rotations and deflections should remain within a tolerable range – – – – typically. – GL & IEC Rules of applying EQ + Operational Load   © 2011 Earth Systems Global inc.San Andreas & Garlock faults. even in moderate seismic regions. 10 to 20 mm extreme 1 mm/m rotation – operational 3 mm/m rotation .Patrick and Henderson Foundations 4/3/2011 Key Geotechnical Issues  The geotechnical report for the project is the basis for the properties of the soil or rock in analyses. active faults. K = M/.  = rotation t ti Normal requirement: K = 20 to 60 GN-m/radian  Greatly exaggerated rotation from FEM M 3D Finite Element Modeling (FEM) Half Model Loading at Top of Tower Tower P&H Pier Ground © 2011 Earth Systems Global inc.Patrick and Henderson Foundations 4/3/2011 Rotational (Rocking) Stiffness    Important factor for performance of wind turbine foundations Rotational Stiffness. 8 . where M = moment. © 2011 Earth Systems Global inc. displacements recorded by transducers Tower frequency changes when considering SoilStructure Interaction The wind turbine natural frequency should be a margin away from the rotor rotation frequency to avoid dynamic amplification.Patrick and Henderson Foundations 4/3/2011 FEM Results Lateral D f Deformation ti of Pier Tower Frequency Verification Testing    Frequency q y response p of tower recorded by accelerometers. 9 . Patrick and Henderson Foundations 4/3/2011 P&H Rock & Pile Anchors Foundations Guantanamo Bay. Cuba 2004 4 – NEG-Micon 950 kW on P&H anchor foundations using Con-Tech self-drilling anchors in conglomerate © 2011 Earth Systems Global inc. 10 . Massachusetts Hull II Wind Project 2006       Vestas V-80 1 1.8MW 8MW turbine on 80-m tower 67 feet of landfill over dense rock Supported on P&H pile anchor foundation Piles driven to rock and rock anchors extended below Two rows of piles Featured at 2006 AWEA Conference © 2011 Earth Systems Global inc. 11 .Patrick and Henderson Foundations 4/3/2011 Hull II Wind Project. 12 .Patrick and Henderson Foundations 4/3/2011 Locust Ridge.0 MW turbines on rock anchor foundations   Setting g the anchor bolt cage g shown at right Placing concrete for cap shown below Ground Anchor Components      Unbonded length (free stress zone) Bonded Length Anchor or Tendon Grout Anchor Head & Bearing Plate © 2011 Earth Systems Global inc. Pennsylvania Gamesa 2. 13 .Patrick and Henderson Foundations 4/3/2011 High Strength Anchor Bars PTI Proof Testing & Maintenance Checks   Initial Proof Test each bolt to 133% of design load (DL) Periodic Maintenance Program to check and retension anchors at 3 months and 1 year © 2011 Earth Systems Global inc. Patrick and Henderson Foundations 4/3/2011 The P&H Pile Anchor Foundation Note Void (gap) between cap and pile anchor US Patents 7.505 & 7.618. 14 .217 Chinese Patent 201020166104.533.7 Mind the Gap   Di Disconnected t d Pil Pile Foundation F d ti No structural connection between anchor and cap The gap is the key Gap allows post-tensioning of anchor and retensioning Pile Anchor uplifts and cap compresses the subgrade Post-tensioning improves subgrade modulus by confinement and compression     © 2011 Earth Systems Global inc.