SEMINAR Introduction to Continuous Flight Auger (CFA) piling Thursday 21/8/2013 Facilitator: Martin Larisch 1
Brief History of Piling Contractors, its capabilities and market Introduction to CFA piling 2
Piling Contractors (Qld) Pty Ltd 1995 History Started as a one rig operation in Queensland in 1983 We expanded into NSW in 1999 and WA in 2006 Now work nationally Acquired by Keller Group plc in 2006 3
The Keller Group GLOBAL SCALE LOCAL FOCUS 4
The Keller Group 5
Safety Improvements 60.0 50.0 40.0 30.0 20.0 10.0 Incidence rate (L.T.I. Per 100 employees) Frequency rate (L.T.I. Per 1 million Man Hours) Severity rate (Avg. Work days Lost Per Occurrences) 0.0 2007 2008 2009 2010 2011 2012 2013 6
Safety Improvements 7
Key Techniques Large diameter bored piles up to 3m diameter 76m deep Driven pre-stressed piles 550mm octagonal up to 32m single length Continuous flight auger piles up to 1.2m diameter 32m deep Mine Fill in joint venture with Keller Ground Engineering Contiguous and Secant Pile Retaining Walls 8
Key Techniques Diaphragm and Slurry Walls Marine piling using leaders off falsework or barges Driven steel tubes, sheets and steel sections and ductile piles Large diameter shafts up to 6m diameter 76m deep 9
Technical Capability Technical Activities, Representative Memberships and Industry Engagement We take a lead role in the technical activities of the Piling and Foundation Specialists Federation (PFSF) and the Concrete Institute of Australia (CIA). Many of our engineering staff are Members of the major national and international professional institutions. We have a Graduate Training programme approved by Engineers Australia to train new graduates and technicians in our speciality, building the future engineers and managers of our industry. R&D / Technical Papers Our staff publish and present technical papers at local, regional and international seminars and conferences and we maintain a strong commitment to research and development. 10
National Coverage 11
Non displacement piles - Continuous Flight Auger (CFA) piles 12
Non displacement piles - Continuous Flight Auger (CFA) piles 13
Pile types and pile systems (AS2159-2009) Displacement piles Driven piles Screw auger piles Non-displacement systems Conventional bored piles CFA piles Barrettes Hard rock drilling 14
Non displacement piles - Continuous Flight Auger (CFA) piles (process after Brueckner Grundbau) 15
Non displacement piles - Continuous Flight Auger (CFA) piles (process after Brueckner Grundbau) 16
Non displacement piles - Continuous Flight Auger (CFA) piles (Schematic of the CFA auger after Slatter, 2000) 17
Non displacement piles - Continuous Flight Auger (CFA) piles (Forces acting on the auger during augering after Viggiani, 1993) Q = Pull down force applied by piling rig M = Torque applied by piling rig P = Soil resistance at auger tip N = Auger weight z = auger length / drill depth τ = Friction between surrounding soil and soil in auger l = auger pitch d = Outer auger diameter d 0 = Auger stem diameter 18
Non displacement piles - Continuous Flight Auger piles (Introduction) CFA piles were developed in the 1940 s in the USA, introduction in Europe during early 1970 s with the invention of the first hydraulic piling rigs The system has been available in Australia since the 1980 s Possible diameters for CFA piles: 450mm 1200mm Standard diameters in Australia are 450, 600, 750, 900 and 1200mm Depth up to 35m and more possible Common depth up to 20m with standard equipment Common diameters 450, 600, 750 and 900mm 19
Non displacement piles - Continuous Flight Auger piles (Applications) CFA piles are commonly used as foundation piles for: Buildings and bridges Pile rafts CFA piles are used for retaining structures as: Soldier piles Contiguous piles Secant piles Pile loads are usually smaller than for conventional bored piles but generally bigger than for auger displacement piles 20
Non displacement piles - Continuous Flight Auger piles (Applications) Soldier pile wall Contiguous pile wall Secant pile wall 21
Retaining structures (e.g. secant pile wall) 22
Non displacement piles - Continuous Flight Auger piles (Applications) CFA piles are suitable for: Generally for all types of structures with low to medium vertical loads Penetration and removal of underground obstructions Piles with single length reinforcement cages up to 18m CFA piles should be considered carefully for: Soft soil conditions or contaminated ground High strength rock Piles next to existing buildings Strata which require penetration of stiff layers Raked piles 23
Non displacement piles - Continuous Flight Auger piles (Advantages & Disadvantages) Advantages: Very cost effective piling system with high production rates Installation in stiff soils / weak rock possible Suitable for changing and non-homogenous ground conditions Disadvantages: Cage installation after pouring process might be difficult Limited capacity for bending moments, lateral forces and tension forces Might cause uncontrolled over excavation if penetration rate is not constant 24
Non displacement piles - Continuous Flight Auger piles (Suitable ground conditions) CFA piles are suitable for: Medium to very dense sands / gravels Stiff to hard clays Generally all types of weak or weathered rock (exception see below) Installation below the ground water table CFA piles are NOT suitable for: High strength, unfractured rock Soft soil conditions Changing strata 25
Load transfer through CFA piles Loads will be transferred through skin friction and / or base resistance 26
Non displacement piles - Continuous Flight Auger piles (Risks) Stationary augers used to transport loose granular material and water 27
Non displacement piles - Continuous Flight Auger piles (Risks) CFA augers are soil conveyors! Signs of severe side loading can include: Surface coning/depressions Difficulty extracting augers Unexpectedly high torque demand on machine 28
Non displacement piles - Continuous Flight Auger piles (Risks) Risk of over-excavation in loose sand layers 29
Non displacement piles - Continuous Flight Auger piles (Risks) Piles drilled too close can result in concrete blow through 1 2 Concrete Sand layer 30
Non displacement piles - Continuous Flight Auger piles (Risks B63) Second pass as per B63 Clause 6.2.3: To ensure the base of the pile socket is clean, adopt a multi-pass technique using a minimum of two passes. After commencement of discharge of concrete withdraw the auger 500 mm and drill back down to the toe of the pile to pick up any contaminated concrete before re-commencing concreting of the pile. Verify the use of the multi-pass technique from the pile monitoring records." 31
Non displacement piles - Continuous Flight Auger piles (Quality control) Operator controls operations via computer data 32
Non displacement piles - Continuous Flight Auger piles (Quality control) Computer monitoring systems are common for some systems to monitor: Depth, penetration rate & extraction rate Torque Pull down forces Rotation Concrete Volume 33
Non displacement piles Continuous Flight Auger piles (Quality control) Pile record sheet 34
Non displacement piles - Continuous Flight Auger piles (Risks B63) Breakout (Clause 6.2.2) No breakouts are to be performed RMS needs to ask for documentation of contractors at tender time to ensure contractors provide suitable equipment Concrete life (Clause 6.2.3) Concrete life should be extended to 4 hours. With current concrete technology this can be achieved easily. 45 minutes is not realistic in some remote locations or inner city projects Concrete oversupply should be at least 5% (not 8%) but could be as much as 40% (function of soil conditions) 35
Non displacement piles - Continuous Flight Auger piles (Risks B63) Concrete pressure (Clause 6.2.3) Concrete pressure can be zero as sensor is located at the top of the mast. If the stem is filled with concrete the pressure sensor shows zero but concrete is still delivered to the pile via gravitational forces Different rig monitoring systems monitor data in different ways, it is important to understand the particular monitoring system when analysing the installation records Monitoring (Clause 6.3 (f)) Monitoring mm/rev is unusual, better monitor rev/m or rev/min 36
Non displacement piles - Continuous Flight Auger piles (Quality control) Concrete quality is crucial (workability, strength, pump-ability, bleeding) 37
Non displacement piles - Continuous Flight Auger piles (Quality control) Computer monitoring systems: PDA & CAPWAP Pile-top Force Comparison Load-settlement response 38
Non displacement piles - Continuous Flight Auger piles (Quality control) Low strain integrity tests (PIT) 39
What else: Importance of safe working platforms (typically 400 kpa platform requirement) Get early involvement of a piling specialist Compare what you get for your money Rigs and technologies are readily available, look for specialists knowledge Keep in mind rigs are very heavy high tech machines when you specify tolerances outside the Australian Standards or code of practice Any further questions? 40
Feedback & Discussion: Did the presentation meet your expectations? What do take home? Any further questions? 41
Thanks for your active participation and attention SEMINAR Introduction to Continuous Flight Auger (CFA) piling Thursday 21/8/2014 Facilitators: Martin Larisch 42