Survey Works - Staking of Piles' Positions   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 At the end of Pouring the temporary casing is extracted.   BORING 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 no less than 3 meters inside the raising concrete, to avoid “cutting” the piles  POURING CONCRETE INTO BORED PILES BY TREMIE PIPES: 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..