Table of Contents
- General
- Bearing Capacity
- Preparatory Works
- Materials
- Concrete
- Reinforcement
- Manufacture of Piles
- Load Tests
- Ground Water
1. General
1.1 Scope
This specification covers the requirements for the manufacture of driven cast-in-situ reinforced concrete piles. Items not specifically covered herein or in the codes, regulations and construction drawings referred to shall be determined in accordance with good engineering practice and to the satisfaction of Company.1.2 Definitions
For the purpose of this specification the following definitions shall apply. “
Company” shall mean the Company Construction Superintendent, or his appointed representative. “
The Contractor” shall mean the organisation appointed by Company to execute the work or part of the work covered by this specification. “
Approved” shall mean approved by Company.
“Approved equal” shall mean of equal quality and properties and approved by Company.
1.3 Codes, Standards and Regulations
The latest editions of the codes, standards and regulations listed below and also those further mentioned in this specification shall be strictly applied.1.4 Supplementary Documents
This specification shall be read in conjunction with the various contract documents and the construction drawings issued by Company.2. Bearing Capacity
2.1 Pile Design
The Contractor shall design and quarantee the piles for the worst combinations of the below listed loadings, acting on the top of the pile at about 0,50 m below grade ( except the negative skin friction ).
| Gross | bearing | capacity | of pile | |||
| Type of load | ....kN | ...kN | ||||
| Net vertical load | ||||||
| Uplift | ||||||
| Horizontal | load | |||||
| Bending | moment | |||||
| Negative | skin | friction |
2.2 Responsibility
The responsibility for the bearing capacity of the piles with due observance of the specified settlement limits rests entirely with the Contractor. However, the design, construction and tip elevation of the piles are subject to Company’s approval.3. Preparatory Works
3.1 Setting Out
Sufficient bench marks and base lines will be provided near the plant battery limits by Company. The Contractor shall carry out and will be responsible for all detailed setting out and levelling in accordance with the construction drawings.4. Materials
4.1 Cement
4.1.1 The cement to be used shall be normal blast furnace cement. It shall be supplied by an approved firm and shall comply in all respects with.
4.1.2 Each consignment of cement shall be accompanied by a manufacturer’s test certificate showing that the material has been tested in accordance with.
4.1.3 Cement shall be delivered to the site in undamaged dry bags and stored in a weather-proof shed with a raised wooden floor. Cement may only be supplied in bulk after Company has approved the proposed methods of delivery and storage.
4.1.4 Cement in bags shall not be stocked to a height greater than 2 m and shall be stored in such a way that it is used in the sequence of delivery.
It shall not be allowed to store different brands of cement in the same room.
4.1.5 Cement that has become air set or is hard and lumpy or has deteriorated in any other way shall not be used.
4.1.6 Cement stored longer than 12 weeks shall be tested before it is used as per clause 4.1.2.
The Contractor shall have the required tests performed by an approved laboratory as directed by Company and shall supply Company with two copies of all relevant test certificates.
4.2 Aggregates
4.2.1 Fine aggregates shall consist of clean, inert, hard, durable, uncoated grains of natural sand free from silt, loam and clay and it shall comply in all respects with.
Coarse aggregates shall consist of clean, inert, hard, durable, uncoated pieces of crushed stone or gravel, free from silt, loam and clay and it shall comply in all respects with.4.2.2 Tests on aggregates for grading, soundness, freedom from deleterious substances and general compliance with the above standards or codes shall be carried out before any concrete is poured. Prior to the initial source of aggregate being agreed or to any subsequent change of source, or when otherwise directed by Company, tests shall be carried out in accordance with.
The Contractor shall have the required tests performed by an approved laboratory and shall supply Company with two copies of all relevant test certificates.4.2.3 Each type of aggregate shall be separately stored in bins or in stock piles on defined and prepared areas. Contamination of the materials and mixing of the various types and sizes prior to use shall be prevented. Adjoining heaps shall be separated by approved bulk heads and a timber, concrete or asphalt base shall be constructed for each stockpile.
4.3 Water
4.3.1 Water for making and curing of concrete shall be clean, fresh and free from oil and injurious amounts of acid, alkali, organic matters and other deleterious substances.
4.4 Reinforcing Steel
4.4.1 Shapes and qualities of reinforcing steel shall comply with.
4.4.2 The Contractor shall supply a quarantee and test certificate issued by the manufacturer of the steel for each grade and parcel of reinforcement material.
4.4.3 The Contractor shall provide means for ready identification of all grades of reinforcing steel other than mild steel.
4.4.4 Each grade of reinforcing steel shall be stored separately on timber or concrete supports suitably spaced and of sufficient height to keep the steel clear of the ground.
5. Concrete
5.1 Quality and Composition
5.1.1 The concrete shall have a compression strength of N/mm2 ( Kgf/cm2 ) at 28 days, determined on standard cubes. For definition of compression strength see clause 5.3.5.
5.1.2 The cement content shall not be less than 360 kg/m3of concrete.5.1.3 The composition of the concrete shall be in accordance with the code mentioned in clause 1.3.
5.1.4 The concrete shall be as dry as is practicable for working into the forms and around the reinforcement. The slump shall not be more than mm.
5.1.5 The Contractor shall assign a competent person on a full time basis who shall supervise all stages in the preparation and placing of the concrete. All tests on materials, the making of cubes and the maintenance and calibration of all mixing and measuring plant shall be carried out under his direct supervision.
5.2 Mixing and Placing
5.2.1 Approved power driven-revolving drum type mixers shall be used, equipped with suitable mechanisms for measuring water. The volume of materials per batch shall not exceed the manufacturer’s rated capacity for the mixer. Mixers with worn or badly bent blades shall not be used.
5.2.2 The time allowed for mixing, after all ingredients have been placed in the mixer, shall be as ordered by Company, but shall not be less than 2 minutes for drums of one cubic meter capacity or less. For drums in excess of one cubic meter the mixing time shall be increased by 30 seconds for each cubic meter or fraction thereof in excess of one cubic meter.
All concrete must be thoroughly mixed to an even colour and consistency throughout.5.2.3 The entire contents of the drum shall be discharged before the materials for the succeeding batch are fed into the drum. No remixed, re-tempered, excessively wet or partially set concrete shall be permitted in the work. The drum of the mixer shall be thoroughly cleaned of all adhering concrete at frequent intervals during continuous operation. Mixers which have been out of use for more than 30 minutes shall be cleaned before any fresh concrete is mixed.
5.2.4 Concrete shall be placed in position within one hour after the mixing water has been added. If the concrete is continuously mechanically agitated this period may be increased to two hours.
5.3 Tests
5.3.1 Standard compression tests shall be made in accordance with the code mentioned in clause 1.3.
5.3.2 Unless satisfactory evidence of strength is produced from reliable sources, to the satisfaction of Company, a preliminary compression test shall be made both prior to the commencement of the work and subsequently whenever any important change is to be made in the materials or in the proportions of the materials to be used. Such a test shall consist of 6 cubes, of which 3 shall be tested at 7 days and 3 at 28 days.
5.3.3 During the work 2 sets of 3 cubes shall be made for each 250 meters of pile length, installed by each rig, for the compression tests.
The cubes shall be made in the presence of Company and shall be marked with the number of the pile from which they were taken. On set shall be tested at 7 days and the other set at 28 days.5.3.4 The cubes shall be tested by an independent laboratory, approved by Company. The records of the test results shall be submitted in two-fold to Company.
5.3.5 The standard of acceptance shall be in accordance with relevant project specification..
5.3.6 Standard slump tests shall be made in accordance with the code mentioned in clause 1.3. The slump of the concrete shall be tested on the site at the time of placement, at least once per day and further as directed by Company. If the results do not comply with clause 5.1.4 of this specification, a second test shall be made. When this fails as well, the concrete shall be rejected.
6. Reinforcement
6.1 Reinforcing steel shall be bent in cold condition. Bars which have been bent and straightened again shall not be used.
6.2 Immediately before placing the concrete the reinforcing steel shall be free from loose mill scale, loose rust, oil, paint, grease, dirt or other matter which may reduce its bond to the concrete.
6.3 Bars shall be accurately placed and adequately secured in position. A minimum protective cover of 45 mm shall be provided over the main reinforcement. Longitudinal bars shall be of one stretch, by means of butt-welding the standard length of bars, in order to obtain an electrically continuous reinforcement for grounding purposes.
6.4 The reinforcement shall extend along the whole length of the pile. The spiral reinforcement shall be at least f 5 mm at a 200 mm pitch and shall be securely welded to the main reinforcement. The main reinforcement shall not be less than 0,8% of the pile cross section and in agreement with the actual design conditions given in clause 2.1.
6.5 The pile reinforcement shall extend 50 times the rebar diameter above the cut-off level. If the cut-off level is not given on the drawing, it shall be assumed at 0,50 m below the plant datum.
7 Manufacture of Piles
7.1 General
7.1.1 Jetting shall not be applied, except in special cases and then only when permitted by Company in writing. When jetting is applied, it shall be carried out in such a manner that the bearing capacity of the piles already in place and the safety of existing adjacent structures is not impaired. The method and depth of jetting are subject to Company’s approval. Jetting shall be stopped not less than 2,00 m above the final expected tip elevation.
7.2 Location
7.2.1 No pile shall be driven out of plumb or out of specified rake more than 1% of the pile length nor deviate more than 60 mm from its designed location at grade. Piles, which are not driven in the correct place or alignment, shall, if required by Company, be pulled out and replaced. The hole left in the ground after with-drawal of a pile shall be filled with sand.
7.3 Driving
7.3.1 The tube shall be driven to such a depth that the pile will meet the requirements laid down in this specification.
7.3.2 The first pile to be installed with a particular rig shall be one located at or close to one of the soundings shown on the piling plans.
7.3.3 For piles located at or close to a sounding, the tube shall at least be driven to the tip elevations shown on the piling plans. The number of blows required to drive the tube over the last 0,25 m to the required tip elevation shall be used as a guidance for the adjacent piles to be installed with the same rig in the area covered by the same sounding.
In case of any variation or change in the driving conditions, such as another type of hammer or a different stroke, a new blow count shall be made at or close to a sounding.
7.3.4 For each pile a blow count record shall be made, providing the following data, in metric units:
- pile number
- date of installation
- number of blows per 0,25 m penetration over the last 2,00 m, except for those piles installed at or close to a sounding for which a blow count shall be made over the entire pile length.
- weight and stroke of hammer or energy per blow.
- final tip elevation with respect to the plant datum.
- actual grade elevation near the pile with respect to the plant datum.
7.3.5 Should for a particular pile the required number of blows not be obtained at the expected tip elevation, the Contractor shall inform Company and continue driving only with their agreement.
7.3.6 Should for a particular pile the required number of blows be obtained at a level higher than the expected tip elevation, the Contractor shall inform Company and stop driving only with their agreement.
7.3.7 After the tube has been driven it shall be inspected. If the presence of soil or a continuous leakage is established, the tube shall be filled with a mixture of sand and gravel over a height of minimum 5,00 m, after which it shall be withdrawn and redriven.
8. Load Tests
8.1 General
8.1.1 The piles to be tested will be designated by Company.
8.1.2 The test pile shall be provided with a concrete head, the surface of which being flat and perpendicular to the pile axis.
8.1.3 The pile shall be loaded by means of a hydraulic jack, placed on the pile head in such a way that the load is always well centered on the pile axis. The counter weight shall be formed by a steel platform of sufficient strength, loaded with concrete or metal blocks or other heavy material.
8.1.4 The settlement of the pile shall be measured by means of an accurate level and two measuring staffs, attached to either side of the pile , or by means of two fleximeters.
Readings shall be regularly made and checked against a fixed point in the distance. The readings shall have a precision of not less than 0,10 mm.
8.1.5 All testing equipment will be subject to Company’s approval.
8.2 Test Procedure
8.2.1 The pile shall be progressively loaded in steps of one quarter of the required gross bearing capacity ( see clause 2.1). Each step shall be sustained until the settlement has ceased.
The maximum test load shall be equal to 1,5 times the required gross bearing capacity.
8.2.2 The pile shall be unloaded twice, namely after the settlement has ceased under a test load equal to the required gross bearing capacity (fourth step) and under a test load equal to 1,5 times the required gross bearing capacity (sixth step). In both cases the rebound of the pile shall be measured during two hours.
8.2.3 The settlement will be considered to have ceased when.
8.3 Standard of Acceptance
8.3.1 The test results will be acceptable if the permanent settlement of the pile does not exceed 2,5 mm due to a test load equal to the required gross bearing capacity, nor 7 mm due to a test load equal to 1,5 times the required gross bearing capacity.
8.3.2 The permanent settlement is defined as the difference between the level of the pile head prior to applying any test load and after the subject test load was removed since two hours.
9. Ground Water
9.1 Ground Water Data
Appendix to The Standard Specification for The Manufacture of Driven Cast-in-Situ Reinforced Pilesconcrete
A 1. General
A 1.1. Scope
The standard specification for the manufacture of driven cast-in-situ reinforced concrete piles, BN-SP-JL2 shall be used as a basis for the job specification. Where necessary, clauses shall be modified to comply with client’s requirements or to suit local conditions. However, no commercial clauses shall be added, since these belong in the commercial contract documents.
In this appendix the specification clause numbers are preceded by the letter “ A “.
A 2. Bearing Capacity
A 2.1. Pile Design
The gross bearing capacity should be equal to the nett bearing capacity plus the allowance for negative skin friction.
The contractors should be given all soil data required to design the piles.
A 2.2. Responsibility
The Contractor should be made entirely responsible for the design and bearing capacity of the piles, since a piling system is bought. Company should indicate on the piling plans the minimum required tip elevation of the driving tube for piles located at or close to a sounding, in order to indicate into which soil layer the piles should be driven. For bidding purposes, Company shall state the (estimated) average pile length(s) in the requisition.
A 3. Preparatory Works
A 4. Materials
A 4.1. Cement
For quality and tests on cement refer to the applicable local code or standard. It should be noted that in some countries blast furnace cement could be of a lesser quality than Portland cement.
A 4.2.Aggregates
For material and grading of aggregates refer to the applicable local code or standard.
A 4.3. Reinforcing Steel
For quality and shape of reinforcing bars refer to the applicable local code or standard.
A 5. Concrete
A 5.1. Quality and Composition
A 5.1.1. The required compression strength at 28 days to be specified, depends on the definition of this strength in the applicable code. (See also clause A 5.3.5 above).
The average compression strength at 28 days should not be less than 35 N/mm2 ( 350 kgf/cm2 ).
A 5.1.2. The maximum size of aggregates should be specified if this is optional in the code.
A 5.1.3. The slump of the concrete should be in accordance with the Contractor’s specifications.
It varies per piling system, since it depends on the methods of placing and densification.
A 5.2. Tests
A 5.2.2. For the standard of acceptance reference should be made to the relevant clauses of the applicable local code.
A 6. Reinforcement
A 7.Manufacture of Piles
A 7.2. General
In the soil conditions are such that during pile driving heaving can occur of piles already installed, such types of piles which can not be re-driven should not be used.
A 7.3. Driving If particular noise requirements are applicable during the construction phase, these should be referred to in the job specification.
A 8. Load Tests
A 8.2.Test Procedure
If a pile does not meet the requirements laid down in the standard specification under clause 8.3., a re-test should be considered, following the more extensive procedure described below. ( This procedure is used by the Laboratory for soil mechanics at Delft ).
The pile shall be progressively loaded in steps of one quarter of the required bearing capacity. Each step shall be continuously sustained for 4 hours. After each step the pile shall be unloaded and five quick repetitions of loading and unloading shall be carried out. Each repetition shall last about 10 minutes ( 5 minutes loaded and 5 minutes unloaded ).
The maximum test load shall be 1,5 times the required bearing capacity.
After the last series of repetitions has been carried out the pile shall be unloaded and the rebound measured during two hours.
The settlement shall be measured by means of a precision level and two measuring staffs firmly attached to either side of the pile, the reading shall have a precision of not less than 0,05 mm.
A 8.2.3. For piles driven into sandy soils the settlement can generally be considered to have ceased when the displacement measured over a period of 15 minutes does not exceed 0,10 mm. For piles driven into clay soils this criterion should be determined per case, in consultation with the soil consultant.
A 8.3. Standard of Acceptance
From experience it is known, that when the procedure laid down in clause A 8.2., is used, the first extra settlement ( ³ 0,20 mm ) due to the five loading repetitions occurs between 40 and 60% of the ultimate bearing capacity of the subject pile.
The permissible safe bearing capacity can then be calculated, taking into account a factor of safety of 2.
A 9. Ground Water
A 9.2. Data
As the Contractor is kept responsible for the bearing capacity of the piles he should be given an analysis of the ground water, so that he can form himself an opinion about its effect on the piles.
Also the presence of possible artesian water or subsoil water currents should be brought to the Contractor’s attention.