All materials to be used for the piling concrete works shall meet the requirements as specified under relevant specifications of a project, and any cement to be used for concrete piles shall be a suitable combination of GGBFS, satisfying ASTM C989, CEM II to BS EN 197-1:200 or BS 4246-1996 & OPC type I to ASTM C150 or CEM I to BS EN 197-1 2000: or BS-12 and as approved and required by consultant / client.
The British Standards referred to in this Specification are listed below, together with any other references specified. Any differences between their requirements and this Specification shall be submitted to the consultant for ruling.
- Piling work to conform to requirements of BS 8004, Foundations.
- Concrete work to conform to requirements of BS 8110-1997, Structural Use of Concrete.
- The static analysis shall normally be in accordance with BS-8004, BS-8110 or ASTM D1143 and other applicable British or American Standard.
- Load testing of piles to comply with all requirements of “Building Regulations & Recommendations for Structural Design & Concrete Practice”
Temporary Casing
Generally cast-in-situ (bored) piles with temporary casing method BS 2004 and BS 8004 will be permitted for execution. Installing bored cast in situ piles using CFA will not be permitted. Immediately after the drilling, the reinforcement has to be placed; ensuring a minimum concrete cover of 75 mm, and the pile has to be cast.
Drilling Operation
- Where required, casing pipes shall penetrate ahead of the removal of soil, likewise during drilling above the ground-water table.
- In the vicinity of underground water, additional water has to be filled up during the drilling. The hydro-static head pressure shall be at least 1.0 m above the ground water table when filled boring tools are extracted.
- Casing shall extend to a sufficient depth below the stiff/solid strata to adequately seal off the unstable soil material.
- Casing pipes shall not be deepened by means of jetting.
- Immediately, after the drilling, the reinforcement has to be placed, providing a concrete cover of 75 mm, and the pile has to be cast.
- Temporary casing shall be removed by vibration method; other method of casing removal shall not be permitted. Except in some cases/piles when casing removal by vibrator will affect the existing services/buildings, in such cases consultant may approve the rotation method for casing removal.
Pile Concreting
- Pile Concreting is to be done through tremie-pipes or equivalent devices to prevent segregation.
- Each pile shall be installed to the correct lengths as designed and approved by consultant or when the pile toe reaches the end socket in the recommended bearing strata.
- The contractor shall submit to consultant before start of piling works, a detailed description of the equipment, materials and procedures that will be used for the piling work.
- The description shall include equipment specifications, including catalogue data, manufacture’s published specifications, loading capacities, protective devices, and test apparatus, detailed installation procedures test procedures as well as references concerning previously completed piling work.
- Piles shall be installed accurately in their required locations. In vertical direction, piles shall not be out of plumb by more than one (1%) percent from the perpendicular. In plan, pile shall not deviate more than 75mm in any direction at pilling platform level.
- Installation procedures shall be such that adjacent piles shall not heave or move laterally. All installation procedures shall be subject to the consultant‘s approval. Permanently installed shells shall be cut off at the pile cut-off level.
- Daily records of each pile shall be produced by the contractor. The records shall give detailed information on the type, diameter, length, location, penetration into bearing strata, piling platform level related to zero level, Date driven, Date casting Depth from piling plat form level to toe, cut off level, top concrete level, Length of temporary casing, length of permanent casing and details of any obstructions encountered. Records shall be submitted in duplicate to consultant every following working day.
- Each cast-in-situ pile shall be filled with quality concrete up to at least 600mm above the cut-off level of the pile to allow for complete removal of slush and other foreign matters etc. from the main pile and thus obtain sound and uniform concrete. Pouring concrete into the pile shall be carried out using the tremie pipe method as well as the concrete pump. Pouring concrete into pile shall be stop when complete removal of slush and other foreign matter has been ensured, or as directed by the consultant Engineer.
- After concreting to the required level, the temporary steel casing will be withdrawn by Vibration.
- The heads of concrete piles shall be incorporated with in-situ concrete pile caps, etc., and the concrete in the head of the pile shall be carefully broken away from the reinforcement which shall then be cleaned and
- Straighten as shown on the Drawings (approved by consultant) or as directed. The pile shall be cut off at the specified level and the concrete surface shall be horizontal, plane and free from all loose aggregate.
Pile Testing Requirements
Basics For Test Piles
The contractor shall carry out successful foundation load tests in order to prove the suitability of the pile foundation selected with particular type of soil. The results of the tests shall be submitted in a format for approval by the ENGINEER. The contractor is requested to include his price for test piles and testing of piles in the erection price of his offer.
Piling Type Tests (Preliminary Pile Test)
Prior to piling commencement the contractor shall install one test pile of each type proposed. The piles shall be test loaded in conformity with the relevant Standards, e.g. ASTM D 1143, BS 8004, or DIN 1054.
The piles shall be considered as acceptable in case the obtained load-settlement/heave diagrams do not indicate movements beyond permissible limits as per the relevant Standards or written in this section. It is to the discretion of consultant to test any pile up to destruction.
Piling Foundation Routine Test (Working Pile Test)
In addition to the above tests the contractor shall perform routine tests at working foundations in order to guarantee the design requirements given in this Specification at 2% of the working piles, with minimum of 2 piles for each type.
The integrity of the piles shall be carried on 100% of piles.
Details for Pile Tests
- The contractor shall execute the test piles using the same equipment which he intends to use for execution of all the piles. The test piles should be of the same length and same type as the piles proposed for the project.
- The loading tests of piles shall be in accordance with the procedure outlined in ASTM D1143 as well as ISSMFE recommendation on “Axial pile loading tests”, Part 1, static loading. Type tests (preliminary pile tests) are to be loaded to either 200% of the anticipated design load, or to the ultimate bearing load, or up to destruction. For routine tests (working pile tests) a loading to 150% of the design load is required.
- Vertical movements shall be measured by means of at least three dial gauges; horizontal movements shall be measured by two dial gauges only, all with a precision of 1/100 mm
Test Reports
Reports on pile testing shall be submitted to the ENGINEER and shall contain, among others, the following information:
– Layout of test equipment and description.
– Pile identification, diameter and length.
– Sketch of soil conditions and ground water location.
– Complete records of level, load cell and dial gauge readings against date and time throughout the test, preferably in tabulation form.
– Graphs of load and settlement/heave versus time.
– Graphs of settlement/heave versus load.
– Remarks concerning any unusual occurrences during the loading of the pile.
Evaluation / Conclusion
An acceptable design load will be determined by consultant based on the results evaluations of the loading test of a pile. Generally, a pile shall not have a total settlement of more than 1.5% of pile diameter or residual (net) settlement, after removal of the ultimate or maximum load, exceeding 6 mm, whichever is less. The pile not satisfying the above mentioned criterion will be considered insufficient to carry the required loads and will be treated as failure. A pile shall be considered satisfactory if it satisfies the entire criterion stated under relevant sections of BS 8004, in addition to the above mentioned criteria.
If the result of the test on the pile(s) is not to the satisfaction of consultant, the contractor shall change the system or the design of the piles,
and choose any type of piles approved by the consultant for which test piles will be constructed and the loading test performed until the contractor gets successful results without extra cost and without extension of time.
For working piles residual or net settlement shall not exceed 4.5mm, after removal of all loads.