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Foundation Specialists, Inc., Legaspi Towers 200, 107 Paseo De Roxas, Makati City 1226, Philippinws.  Phone +63 2 8817 6826   e-mail address  CLICK THIS

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Bored Piles by Foundation Specialists.

Bored piles are cast in place cylindrical piles excavated either by use of rotary equipment operated augers , buckets, under static drilling fluid or large drill bit (for hard rock) with reverse circulation,  with chisel grab and casing oscillator for bouldery ground,  with large diameter DTH hammers and compressed air (drilled piles), among others.

Most common large diameter bored piles, are installed through an overburden of cohesive or cohesionless soil strata, with or without water table, down to firmer ground, to achieve the design bearing capacity by skin friction, base bearing or both, to serve as foundation piles for residential, commercial, institutional buildings, industrial complexes or infrastructures.

Bored piles installed in common soil with the presence of water table, generally require the use of a short temporary steel casing and a drilling fluid as static suspension to provide support to the surrounding soil while excavating the pile and until complete backfill of the pile excavation with concrete, in order to prevent cave-in of the excavation and destabilizing the surrounding soil formation.

The preparation and handling by most effective drilling fluid, Bentonite Mud, is a sophisticated technology by itself and requires a complete set up of dedicated equipment and  (basic) field laboratory.

The most common  diameters of  bored piles range from  0.6 meter to 3.0 m meters, likewise length can range from few meter to sixty or more meters, depending upon design loads and soil parameters.

Bored piles can be heavily reinforced if required by design, rebar cages usually are prefabricated in segments with length and weight depending upon available commercial  lengths of rebars and  available lifting equipment. Splicing of rebar cages can be done  by lap splice, welded lap splice or mechanical threaded couplers. Casting is done by pouring concrete with the design strength and slump as required, through watertight segmental Tremie Pipes, starting from the pile bottom and letting the tremie pipe bottom-end remain at least 3 meters submerged in concrete until the completion of pouring, to guarantee the pile continuity and the final good quality of the concrete cast.

Drilling fluids, if needed,  can be water, a suspension of bentonite (bentonite mud), a suspension of polymers, depending upon soil type, soil conditions, presence and elevation of water table, chemical properties of water table (Ph, Salinity).

Steel casings can be temporary, in which case the wall thickness is usually big enough to allow many uses, are provided with collars for easy handling by vibro hammers  and diameter slightly larger than bored piles’ nominal diameter, to allow  easy passage of drilling tools.  Permanent casings, if needed, are sacrificial casings and as such the wall thickness is as small as allowed by the need to drive the casing through the ground.

Bored piles are commonly employed for bridge foundations, on land and water, because the   versatility of bored piles design and execution allows the construction of practically any needed diameter, including the very large diameters, and the pile reinforcement can be provided as heavy as needed by seismic design and the codes (it is not uncommon to have double wall rebar cages in order to accommodate all the needed bars, however care shall be taken to leave sufficient space between bars for concrete to flow through).

Bored piles are also used to form retaining walls (see PileWall), as contiguous pile wall or secant pile wall or aligned pile wall, with or without post tensioned soil anchors as tie back .

Bored piles testing is usually done in two (2) stages, first stage testing to verify design assumptions and achievable design load , is done before starting the execution of the working piles: test piles are installed in the proposed construction area, as per design, and tested, first for integrity and continuity  by P.I.T. (Pile Integrity Test) then for load bearing capacity , either by Static Load Test or by Dynamic Load Test PDA, (Pile Dynamic Analysis). At times the Designer might require a Pull-out test and a lateral load test.

Once the design pile capacity has been confirmed, Bored Piles construction  for  the working piles starts and quality control is then done on representative piles. Quality Control consists of testing the material used for the bored piles, i.e. reinforcing bars and concrete, then testing of the piles at random with PIT  and PDA, and predetermined piles with static pile load test. Predetermined piles can also be tested using the cross-hole ultrasonic test, by inserting instruments through vertical pipes installed within the reinforcing steel cage all throughout the bored pile length.   



Survey Works : The first step to be taken, when starting a project involving the installation / execution of Cast in Place Reinforced Concrete Bored Piles is to survey the working areas, establish fix reference points and proceed to stake out the piles’ positions.

                                                                                                                                          EQUIPMENT: Depending upon the diameter and depth of the Bored Piles and site conditions, the Contractor will mobilize the proper Bored Piling Rig(s), the support equipment and the proper Boring Tools as needed. Temporary Casings  (Or Permanent Casing if required) will be at site, as well as a Vibrohammer  to drive the casings. The Bored Piles will be excavated using crane mounted or self-propelled rotary drilling rig with telescopic Kelly bars, drilling bucket and auger of proper diameter. If Boulders are expected to be found in the soil formation where Bored Piles have to be executed, Chisel and Grab shall also be mobilized and kept ready at site. This equipment is selected for each project based on its capability to execute bored piles of the required diameter and length, and in accordance with the dimensions of working areas.  Service Crane(s), Wheel Loader, Backhoe, Genset(s), Water Pumps, Welding Machines, Equipment, Plants and Tools for Reinforcing Bar Cages Fabrication, and other Support Equipment and Tools will also be mobilized to site, as needed.


TEMPFACIL: Containerized Office fully furnished and equipped, Containerized Field Warehouse, “Portalet(s)” (Portable Toilets), a covered area foe equipment maintenance will be proved at site.


INSTALLATION & RETRIEVAL OF TEMPORARY CASING: Temporary casings of proper diameter and thickness will be installed in the exact pile position, to stabilize the hole. The rebar cage will hung from the top of temporary casing while additional segments  are being spliced, and eventually, during concrete pouring, in order to keep the Rebar cage centered and straight. At the end of Pouring the temporary casing is extracted.


Stage 2 jpegBORING THE PILE POSITIONS: The excavation of the piles will proceed using a drilling bucket  and  or an auger as needed, depending on the quality and strength of the soil.  If boulders are encountered, the same will be broken and removed using  chisel and grab. The excavation of the pile will proceed until the design depth is reached. The excavated soil will be brought to the surface by the auger/bucket and will be loaded to dump trucks for proper disposal. If Piles haveto be executed in the presence of Water Table, it is important to identify the exact elevation of it . so that the head elevation of the  drilling fluid employed  will be kept sufficiently higher than that of the water table, in order maintain inside the borehole a higher hydrostatic pressure than the one existing outside and thus helping to prevent cave-in when excavating cohesionless soil.  When executing Bored Piles using water of Polymer  suspension as drilling fluid , fine in suspension in the drilling fluid will precipitate to the bottom of the excavation in abour 30 minutes once  pile design depth has been reached and the drilling tools retrieved.  Before installing the rebar cage, the bottom of the pile will have to be properly cleaned up, by removing all the fines and  debris by means of a “cleaning bucket” with a sealable bottom.  For Piles in unstable granular ground Static Bentonite Suspension, as drilling fluid, is advisable.  The handling of Bentonite Mud is a Technology in itself and must be mastered in order to take full advantage of it.


INSTALLATION OF REBAR CAGES AND TREMIE PIPES: Once the pile bottom is cleaned, the fabricated rebar cages will be installed, segment by segment, into the hole, well secured, in sequence, to each other. After all the segments of the  rebar cage   are installed inside the bored hole,  the whole rebar cage will be suspended from the top of the steel temporary casing, with  the bottom  about 10 centimeters higher than the bottom of excavation, in order to keep it straight and centered in the hole  Next  the tremie pipes will be installed down to the pile excavation bottom. A feeding hopper will be installed at the top of the tremie pipe, and  a paper plug will be inserted inside the top tremie pipe to serve as the interface between the concrete being poured and the drilling fluid filling the excavation, with the purpose of preventing dropping and washing the concrete. For very large pile diameters, two tremie pipes are used for pouring each pile, in order to have an even raise of the concrete in the excavation, while pouring. The Tremie Piles will be shortened gradually while the concrete is raising inside the excavation, care shall be taken to maintain the tremie pipes’ bottom end always submerged by about and no less than 3 meters inside the raising concrete, to avoid “cutting” the piles


POURING OF CONCRETE: The concrete to be poured shal be self-levelling,  made such by reducing water and obtaining the 8” slump by using super plasticizer additives   Concrete will be conveyed to the pile by direct pouring, with the transit mixer dumping concrete directly to the feeding hopper topping the tremie pipes.  The pouring of concrete will be done using high slump (7-8”) concrete to assure that the pile will eventually be filled up with concrete, inside and outside the Reinforcing Bars Cage.. The concrete will be poured into the top hopper of the tremie pipe and will be delivered to the bottom of the pile by the tremie pipes. The bottom of the tremie pipe will be left submerged in concrete to prevent  forming “dirty “ joints t. While pouring proceeds, the yield of the concrete inside the pile will be measured after every transit mixer has completely discharged its load. 3-4meters of tremie pipe will be left submerged in the concrete and the shortening of the tremie pipes  will proceed  by removing segment by segment of tremie pipe from the top.  If by design the pile head is at Ground Level, the pile will have to be over poured with concrete overflowing the bore hole itself until all contained impurities or debris will have been flushed out and the pile will be thus ready for the pile cap.   ff overflowing the pile with concrete is not possible, the pile will be overpoured by a volume of concrete  sufficient to carry all so called “dirty Concrete above the Pile cut-off elevation. Temporary casing is usually 2,5 to 3.0 meters long, in which case,  at the end of pouring the tremie pipes will be removed ahead of lifting off the casing, but if the temporary casing is a long one,  the temporary casing will be removed while leaving the tremie pipe secured in place and with its bottom 3 to 4  meters submerged in concrete, so that if after removing the casing the concrete level will go down below pile cut-of elevation, additional concrete will be poured, as needed, thru the tremie pipes still in place. The “dirty” concrete will eventually be chipped off, in preparation for pile cap.. 


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Foundation Specialists, Inc. 

46 years of successful projects
in the Philippines, South East Asia, PNG, West Africa and the Middle East.

PCAB Contractor's License Number 7437 
General Engineering & General Building Contractor -AAA-
with Specialty in Foundations -AAA-

Foundation Specialists, Inc. [FS] is well known as a DESIGN & BUILD CONTRACTOR, for Vertical and Horizontal Construction. [FS is still often mentioned as the Builder of LRT 1 , which we have  built in the early 1980s, from foundations to copings, including the seismic re-design of its Foundations on Bored Piles].   As It is a truism that  “No Structure is safe and durable unless is built on good foundations”: FS is known as Builder of Durable & Safe Structures:  ●CAREFUL STUDY OF GROUND CONDITIONS,  and ●ADEQUATE  FOUNDATIONS  MAKE  Foundation Specialits' WORKS. SAFE, DURABLE & EARTQUAKE RESISTANT,  and that is based on records.   In the field of Deep Foundations and Soil Consolidation FS has designed and developed Methods and Technologies for STABLE & SAFE FOUNDATIONS in the most diverse and most challenging soil and site conditions. 

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