Piling
Datasheets
Continuous flight auger (CFA)
Driven
Rotary
Continuous
    Flight Auger
       Piles (CFA)




              Technical Data           The Continuous Flight Auger (CFA...
Continuous
        Flight Auger
           Piles (CFA)




          Further information           Low Headroom
          ...
Instrumentation
and Automation
    of CFA Piling




                 Technical Data

                       Application
 ...
Instrumentation
and Automation
    of CFA Piling




          Further information           system has been developed. AU...
Enlarged
    Pile Heads




        Technical Data

                 Application
  Floor slabs with or without
   load tra...
Enlarged
             Pile Heads




          Further information           c) Hardstanding areas and road               ...
CFA-LC®

Continuous Flight
Auger Piling with
     Low Cut-off




          Technical Data

                  Application
...
CFA-LCTM

        Continuous Flight
        Auger Piling with
             Low Cut-off




          Further information  ...
CFA-TC®& CFA-PL®

      New Continuous
           Flight Auger
     Piling Techniques




              Technical Data

  ...
CFA-TCTM & CFA-PLTM

            New Continuous
                 Flight Auger
           Piling Techniques




           ...
Cementation Skanska
Maple Cross House
Denham Way
Maple Cross
Rickmansworth
Hertfordshire
WD3 9SW
Tel: 01923 423100
www.ska...
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Piling Datasheets

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All About the specialist piling we do

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Piling Datasheets

  1. 1. Piling Datasheets Continuous flight auger (CFA) Driven Rotary
  2. 2. Continuous Flight Auger Piles (CFA) Technical Data The Continuous Flight Auger (CFA) process is virtually vibration free and one Application of the quietest forms of piling, making it Well suited to soft and/or water ideal for environmentally sensitive areas. bearing ground where deep The method enables piles to be formed in casings or bentonite suspension would otherwise be required. water-bearing strata, without the need for casing or bentonite. It is suitable for Diameters generally within the constructing piles in most strata: gravels, range of 300mm to 1200mm with maximum depths normally up to sands, silts, clays and soft rocks and in 29 metres. Used for bearing piles mixtures of strata. and contiguous, interlocking and The original CFA technique allowed secant piled walls. for placing a mortar fill. In 1981 Integral enlarged heads Cementation Skanska was the first to can be formed. extend the process to allow for structural concrete provision, "CONCORE", and Advantages • Quietest known form of piling introduced this to the UK in that same • Virtually vibration free year. • All rigs fully instrumented • Quick and economical • Limited headroom rigs available Construction Process CFA piles are formed by drilling to the Patents required depth using a hollow stem UK Patent No. 2303868 UK (Div) Patent No. 2328700 continuous flight auger. After reaching the UK Patent No. 2362665 designed depth, a high slump concrete is UK Patent No. 2358211 then pumped through the hollow stem. UK Patent No. 2355750 UK Patent No. 2362912 While the concrete is being pumped, the UK Patent No. 2356659 auger is withdrawn at a controlled rate, UK Patent No. 2334543 removing the soil and forming a shaft of Australia Patent No. 714365 fluid concrete extending to ground level. USA Patent No. 6116819 USA Patent No. 6168350 A reinforcing cage is then inserted into the Canada Patent No. 2228518 fluid concrete. Reinforcing cages with Europe Pub No. 0937825 lengths up to 12 metres are common; Europe Patent No. 0842329 (Belgium, France, Germany, greater lengths can be installed with the Ireland, Netherlands, Spain) assistance of cage vibrators. The Company has a large fleet of CFA Trademarks rigs. Pile diameters range from 300mm to AUTO-CFA® 1200mm, and depths of 30 metres or more continuously displays the boring and CFA-TC® CFA-PL® are possible giving load capacities up to concreting parameters. During the drilling CFA-LC® 7500kN. Several patented refinements are phase, the depth of the auger, speed of rotation CCFA® available related to the use of casings and penetration rate are displayed. CEM® (CFA-TC®, CFA-PL® and use in low cut- Subsequently, during the concreting phase a off piles (CFA-LC®). continuous record of concrete pressure and rate of pumping is shown; the display is Instrumentation presented in a manner that highlights under- To maintain the highest standard of pile supply and over-supply of concrete, compared construction, Foundations Skanska has with the target value. undertaken considerable research and On completion of a pile, a computer development into instrumentation. This printout can be generated for viewing. The full has resulted in sophisticated computerised data of pile construction details are stored in a equipment, "AUTO-CFA®", to monitor, data logger module, which is returned at control and record the CFA pile regular intervals to our Head Office. The data installation. A computer, positioned in the is then analysed by a separate program, as a cab directly in front of the operator, further check on the integrity of each pile. 10/07/08 Rev 3
  3. 3. Continuous Flight Auger Piles (CFA) Further information Low Headroom Some rigs in the fleet can be converted to Cementation Skanska operate in low headroom modes, of 8m, Maple Cross House 11.5m and 14m clearance. The depths and Denham Way diameters which can be achieved in low Maple Cross Rickmansworth headroom vary, and require discussion of Hertfordshire the Client's individual requirements. WD3 9SW United Kingdom Tel: +44 (0)1923 423100 Bored Pile Wall Fax: +44 (0)1923 423681 Temporary and permanent bored pile walls can be constructed using the CFA cementation@skanska.co.uk www.skanska.co.uk technique. They can be designed to function as a simple or a propped Offices cantilever and also to support vertical Head Office +44 (0)1923 423100 loads. North +44 (0)1302 821100 The three main types of bored pile South West, Midlands & Wales +44 (0)1454 453200 walls which are commonly constructed Scotland +44 (0)1698 735899 are: Contiguous, Interlocking and Secant. Northern Ireland +44 (0)28 9024 2746 The selection of a particular type of bored Republic of Ireland +353 (0)1296 0790 pile wall will depend on the soil and loading conditions. † 10/07/08 Rev 3
  4. 4. Instrumentation and Automation of CFA Piling Technical Data Application Monitoring and Control of CFA Pile construction process. Provides a permanent record of the installation process. Improvement of contract management through analysis of pile records. Suitable for use constructing Contiguous and Secant walls, and with Low Headroom rigs. Advantages • Operators no longer have to constantly control the rig, minimising fatigue • Operators have additional freedom to monitor other activities around the rig, adding to site safety and efficiency • The concreting phase is more reliable when automated, reducing over supply of concrete • Productivity can be increased to a level where the rig characteristics determine the limiting elements • The automatic system provides Automation of CFA Piling assurance of the quality of each installation. consistency in pile installation and The process of constructing Continuous Computer based systems display and record reduces the potential for differential settlement, resulting in Flight Auger (CFA) piles has progressed the significant actions that affect the successful a more cost effective design, with substantially in recent years and now installation of every pile. savings for the client represents a major technique in the piling The challenge has been to develop these Patents market. systems from a role of recording the pile UK Patent No 2303 868 Piles are constructed by drilling with a execution details to controlling the process. UK Patent No 2328 700 continuous flight auger to the required The more advanced instrumentation International Patent No systems employed record all the relevant data depth and pumping the concrete through PCT/GB96/01855 the hollow stem of the auger during its for subsequent examination. It is then possible Trademarks extraction. Use of this technique, as with to check the installation of every pile either AUTO-CFA® all piling solutions, is not without risk. manually or automatically and to present the Construction risks can be minimised once results statistically to evaluate rig-driver the process is understood and the hazards performance. addressed. When such a management tool became Cementation believes that quality available it was apparent that the installation should never be sacrificed for expediency of CFA piles could be more reliably performed and has developed CFA piling into a cost using less concrete and in a more cost effective effective, reliable and efficient method of manner. This promoted the use of real time installing piles in most ground conditions. displays showing how the installation is Reliable installation of the pile requires progressing so that the operator can take any that sufficient concrete is delivered to the necessary corrective action. auger tip to prevent any ingress of spoil Despite the presentation of real-time from the walls of the bore which may graphical and numeric displays as guide, contaminate the cross section of the pile. drivers have been unable to maintain concrete Reliance is placed on instrumentation injection volumes within 10% of the to ensure a high level of control and give requirements. As a result, an electronic control 10/07/08 Rev 1
  5. 5. Instrumentation and Automation of CFA Piling Further information system has been developed. AUTO- CFA® replaces the manual operation so Cementation Skanska that pile installation can be controlled Maple Cross House automatically by the monitoring Denham Way computer. Maple Cross Rickmansworth To achieve automation, the recipe for Hertfordshire CFA pile installation has been carefully WD3 9SW developed by assessing statistically the United Kingdom Tel: +44 (0)1923 423100 significant aspects of the process and Fax: +44 (0)1923 423681 instructing corrective action to be taken where needed to both increase cementation@skanska.co.uk www.skanska.co.uk productivity and enhance pile performance. Offices Research has been conducted on both Head Office +44 (0)1923 423100 the theoretical and practical aspects of North +44 (0)1302 821100 excavation with a focus on determining South West, Midlands & Wales +44 (0)1454 453200 the best boring technique. This has Scotland +44 (0)1698 735899 culminated in the development of a process which can consistently maintain Northern Ireland +44 (0)28 9024 2746 the load bearing capacity of CFA piles. Republic of Ireland +353 (0)1296 0790 Having proven the success of the enhanced installation technique which may be generally adapted to most ground conditions, the requirements have been programmed into the control systems on the piling rig computers to control the boring and the lifting of the auger. Automated concreting allows the progress of the pile installation to match the speed of auger withdrawal. The target The operators now have additional freedom to delivery can be adjusted at any time monitor other activities around the rig, adding during the concreting phase to suit the to site safety and efficiency. ground conditions. In addition, any interruptions to the The main benefit of automation of the concrete delivery, for example when concreting phase is that the process can be awaiting the next load of concrete, can be carried out reliably. This allows a reduction in detected automatically and the concreting the over supply of concrete. Productivity can phase paused until the supply is resumed. be increased to a level where the rig The key benefit is the speed with which characteristics determine the limiting the system can react in contrast to elements. These factors are greatly appreciated operator reaction times. by the piling contractor. After full evaluation and commissioning of the first automated rig, The automatic system provides consistency in the success has been outstanding and a pile installation and reduces the potential for program of equipping the entire differential settlement, an aspect welcomed by Cementation fleet of CFA piling rigs is clients. This consistency in pile performance now in progress. results in a more cost effective design, with savings for the client Benefits of Automation Operators no longer have the strenuous task of constantly controlling the rig and are delighted with this simple innovation which minimises fatigue. 10/07/08 Rev 1
  6. 6. Enlarged Pile Heads Technical Data Application Floor slabs with or without load transfer platforms or reinforced granular blankets Raft foundations with or without load transfer platforms or reinforced granular blankets Hardstanding areas and road embankment supports with load transfer platforms or reinforced granular blankets Advantages • Slab construction more economical • Reduces punching shear • Eliminates expensive pile trimming • Barriers and membranes can be laid over pile heads • Eliminates expensive trimming and sealing Patents UK Patent No 2334543 UK Patent No 2363152 UK Patent No 2378471 Ireland Patent No 2001/0545 Europe Patent No 0937825 Europe Patent No 1283307 US Patent No 6168350 US Patent No 6168350 US Patent No 6641333 The requirement for integral enlarged pile During the concreting operation a sufficient heads has increased greatly as a result of head of concrete is maintained, to ensure the engineers and main contractors looking integrity of the integral enlarged pile head for the most efficient and economical during the extraction of the head former. foundation solutions for their clients. Pile reinforcement can project through the Cementation Skanska has developed a enlarged pile head if required or be terminated range of specially adapted head formers below the finished head level to meet for use with DCIS, precast driven or bored particular design requirements. piling techniques. Typical Site Applications The Process Piles are installed on a square or triangular Specially adapted head formers are driven grid pattern to support the following: or drilled into the ground at the start of the piling operation depending on the piling a) Floor slabs with or without load transfer process in use and the site ground platforms or reinforced granular blankets. conditions. Formers are generally conical b) Raft foundations with or without load in shape and up to 900mm in diameter, transfer platforms or reinforced granular however square heads can also be blankets. accommodated with certain processes. 10/07/08 Rev 1
  7. 7. Enlarged Pile Heads Further information c) Hardstanding areas and road As heads are an integral part of the pile embankment supports with load construction and are finished at ground level, Cementation Skanska transfer platforms or reinforced expensive pile trimming is eliminated. Under Maple Cross House granular blankets. slab barrier and/or waterproofing membranes Denham Way can be laid directly over pile heads so that Maple Cross Rickmansworth Advantages expensive cutting and sealing around pile Hertfordshire The enlarged pile heads reduce the effects shafts is not necessary. † WD3 9SW of punching shear and therefore more United Kingdom Tel: +44 (0)1923 423100 economical slab constructions can be Fax: +44 (0)1923 423681 used. cementation@skanska.co.uk www.skanska.co.uk Offices Cast-in-Situ Piles with Enlarged Heads Head Office +44 (0)1923 423100 North +44 (0)1302 821100 Typical Applications South West, Midlands & Wales Load Transfer Platform or +44 (0)1454 453200 Reinforced Granular Blanket Scotland +44 (0)1698 735899 Northern Ireland +44 (0)28 9024 2746 Reinforced Republic of Ireland +353 (0)1296 0790 Concrete Slab Raft Foundations Piles with Enlarged Heads Load Transfer Platform or Reinforced Granular Blanket Embankment Hardstanding Embankment Construction Drainage and Sub-Base Layer Piles with Enlarged Heads 10/07/08 Rev 1
  8. 8. CFA-LC® Continuous Flight Auger Piling with Low Cut-off Technical Data Application Well suited to soft and/or water bearing ground where deep casings or bentonite suspension would otherwise be required. Diameters generally within the range of 600mm to 1200mm with maximum depths normally up to 27.5 metres. Used for bearing piles and contiguous, interlocking and secant piled walls. Particularly suitable for basement construction where bearing piles are required to terminate below ground. Advantages • Quietest known form of piling • Virtually vibration free • All rigs fully instrumented CFA-LC® • Quick and economical Low Cut-off CFA Technique The term “low cut-off” describes piles Patents UK Patent No. 2303868 where the finished concrete and UK (Div) Patent No. 2328700 reinforcing cage levels are several metres UK Patent No. 2362665 below existing ground. Low cut-off piles UK Patent No. 2358211 UK Patent No. 2355750 are often specified when the proposed by manually bailing-out the concrete, but the UK Patent No. 2362912 basement slab level is several metres practical limit is 1-2 metres. Moreover it is UK Patent No. 2356659 below pile installation level. Australia Patent No. 714365 generally impractical for the reinforcing cage USA Patent No. 6116819 The standard CFA piling technique to be pushed down below ground to the Canada Patent No. 2228518 does not lend itself to achieving low cut- required level. Europe Patent No. 0842329 offs. Conventionally the full-length (Belgium, France, Germany, Cementation Skanska has developed a hollow stem flight auger is first advanced unique technique which extends the range of Ireland, Netherlands, Spain) to founding depth. Concrete is then CFA piling to include true low cut-off levels, Trademarks pumped through the stem to the base of i.e. concrete and reinforcement. The technique AUTO-CFA® the pile. The flight auger is slowly CFA-TC® has been assigned the designation CFA-LC®. CFA-PL® withdrawn whilst concrete pumping For this technique a unique casing drive CFA-LC® continues. The soil carried on the auger is system is used to allow a non-rotating casing CCFA® removed from the pile head position. to be inserted into the ground at the same time CEM® After the auger has been completely as the auger is advanced. removed it is normal to clear the pile head The CFA rig installs the casing, usually to with a 360º excavator to reveal the below the concrete cut-off level. The auger concrete at the head of the pile. A then continues to bore to the founding depth. reinforcing cage is then inserted into the At this stage concrete is pumped through the concrete. hollow stem to the base of the auger in the Exceptionally, contractors are normal manner. When the tip of the auger is sometimes asked to reduce the cast level an agreed distance above the cut-off level, no of the concrete. This can be carried out further concrete is pumped. The low cut-off 10/07/08 Rev 2
  9. 9. CFA-LCTM Continuous Flight Auger Piling with Low Cut-off Further information can then be achieved by several means, water or bentonite, while the auger is removed. depending on site conditions. The reinforcing cage is placed as above. The Cementation Skanska With the simplest method, when the fluid may be pumped through the auger stem, Maple Cross House concrete has risen to the desired level the or alternatively, down a double-flight Denham Way auger is removed from the casing by a “bentonite” auger. Maple Cross Rickmansworth direct lift. The auger boring head is fitted In yet another variation of the technique, Hertfordshire with a special flap which retains the soil the concrete can first be placed up to ground WD3 9SW on the auger, leaving an open cased bore level. The CFA auger is then used to remove United Kingdom Tel: +44 (0)1923 423100 above the concrete. The reinforcing cage concrete down to the required depth and the Fax: +44 (0)1923 423681 can be placed into the casing and if reinforcing cage installed as previously necessary, pushed down to the required described. cementation@skanska.co.uk www.skanska.co.uk level by means of a special attachment Whichever of the three methods is used, fitted to the flight auger. the rig is then used to withdraw the casing Offices Alternatively, depending on the nature of which it then transports to another pile Head Office +44 (0)1923 423100 the underlying strata and the water table, position. With the unique casing drive system North +44 (0)1302 821100 it may be imprudent to attempt to create there is no need for an attendant service crane South West, Midlands & Wales +44 (0)1454 453200 an empty bore in the casing. In these to handle the temporary casing. † Scotland +44 (0)1698 735899 instances the casing can be flooded with Northern Ireland +44 (0)28 9024 2746 Republic of Ireland +353 (0)1296 0790 10/07/08 Rev 2
  10. 10. CFA-TC®& CFA-PL® New Continuous Flight Auger Piling Techniques Technical Data Application Well suited to soft and/or water bearing ground where there is a high risk of bore instability during construction. CFA-TCTM particularly suitable close to structures which may be affected by standard CFA, because of loose soil over hard strata. CFA-PLTM particularly suitable to prevent negative skin friction, and/or provide protection to concrete in hard environments. Diameters generally within the range of 600mm to 1200mm with maximum depths normally up to 27.5 metres. Used for bearing piles and contiguous, interlocking and secant piled walls. Particularly suitable for CFA-TC® & CFA-PL® basement construction where bearing piles are required to Two New CFA Techniques terminate below ground. Cementation Skanska has developed two new techniques which extend the range of Advantages from the sides of the bore. This phenomenon • Quietest known CFA application. The techniques have been assigned the designations CFA-TC® can cause damage to adjacent structures, form of piling • Virtually vibration free and CFA-PL®. whether above or below ground. • All rigs fully instrumented Both techniques are patented and both The CFA-TC® technique installs a casing, • Quick and economical to a suitable depth, during the advance of the make use of a unique casing installation Patents system. This allows a non-rotating casing flight auger and this prevents the auger from UK Patent No. 2303868 to be inserted into the ground at the same flighting the softer overlying strata. UK (Div) Patent No. 2328700 The CFA rig installs the casing, completes the UK Patent No. 2362665 time as the auger is advanced. UK Patent No. 2358211 bore to founding depth and then removes the UK Patent No. 2355750 CFA-TC® casing at the end of the concreting phase. It UK Patent No. 2362912 then moves to another pile position. There is UK Patent No. 2356659 This refers to the use of a temporary casing during CFA pile construction, and no need for an attendant service crane to Australia Patent No. 714365 USA Patent No. 6116819 virtually eliminates settlement of the handle the temporary casing. Canada Patent No. 2228518 surrounding soil. The effectiveness of the new CFA-TC® Europe Patent No. 0842329 technique is demonstrated overleaf, showing (Belgium, France, Germany, A well-known problem, sometimes Ireland, Netherlands, Spain) called 'flighting' can occur when the upper the measured settlement of the ground strata is relatively loose or soft compared surrounding CFA piles, at two sites with Trademarks similar ground conditions, in Glasgow. AUTO-CFA® with the underlying founding strata. In Where no casing was used, settlement at a CFA-TC® these conditions the rate of advance of the CFA-PL® auger (per revolution) can be much less in distance of 1m from the piles was 13.8 mm. CFA-LC® the underlying strata than in the 'softer' Settlement decreased further away from the CCFA® piles, but could still be detected up to a CEM® overlying strata. The auger, which acts as a vertical conveyor, tends to draw soil distance of approximately 14 metres. 10/07/08 Rev 2
  11. 11. CFA-TCTM & CFA-PLTM New Continuous Flight Auger Piling Techniques Further information In contrast, when a casing was installed CFA-PL® by the CFA-TC® technique, settlement at This technique refers to the installation of a Cementation Skanska four points each a distance of 1m behind a permanent liner during the construction of a Maple Cross House piled wall. It gave an average of 1mm, CFA pile. Denham Way over a period of eight days of piling. Permanent liners may be required for one Maple Cross Rickmansworth Further advantage of the CFA-TC® of several reasons, as follows: Hertfordshire WD3 9SW technique is the ability to position piles more accurately than without casing. At • to protect the concrete in aggressive ground United Kingdom Tel: +44 (0)1923 423100 the Glasgow contract the average plan conditions Fax: +44 (0)1923 423681 deviation at ground level, of the 75 wall • to avoid the effects of 'downdrag' caused piles installed, was 24mm from true by ground settlement. cementation@skanska.co.uk www.skanska.co.uk position. Verticality was also better than • to avoid loading adjacent structures and for uncased piles. services, often below ground. Offices Head Office +44 (0)1923 423100 The wall thickness of the permanent liner will North +44 (0)1302 821100 UNCASED CFA PIL E, CADOG AN STREET, GL ASG OW be determined by the specific site conditions. South West, Midlands & Wales +44 (0)1454 453200 0 The use of a steel liner coated with a -2 bituminous layer, often called a 'slip layer', can G RO UND SETTLEMENT (m m) Scotland +44 (0)1698 735899 -4 Northern Ireland +44 (0)28 9024 2746 -6 prevent all three of the above problems. Alternatively a plastic liner can be used in Republic of Ireland +353 (0)1296 0790 -8 -10 place of the coated steel liner. With the CFA-PL® technique these -12 -14 -16 permanent liners can be installed by the CFA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 DISTANCE F ROM PILE (m ) rig during pile construction. The casing drive system (referred to earlier) requires little 3 2 modification to be used for installation of 1 0 -1 permanent liners. Because the liners are -2 -3 installed at the same time as the pile is bored, -4 -5 there is no annular gap around the liner, i.e. it is in intimate contact with the soil. † 1 2 3 4 5 6 7 8 D AY S C A SED C FA PILIN G, A TLA N TIC QU A Y , GLA SGOW 10/07/08 Rev 2
  12. 12. Cementation Skanska Maple Cross House Denham Way Maple Cross Rickmansworth Hertfordshire WD3 9SW Tel: 01923 423100 www.skanska.co.uk

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