Table of Contents
1. General
1.1 ScopeThis specification covers the requirements for the installation of pre-cast 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. Pile Characteristics
2.1 Bearing Capacity
The required gross bearing capacity is
2.2 Dimensions
Length :
Section of shaft :
Section of bulb :
2.3 Concrete Quality and Reinforcement
3. Driving Equipment
3.1 Rigs
The piling rings shall be of such a type and capacity that the piles can be installed at the proper locations and raking piles at the correct rake, without being impaired.3.2 Hammer
The type and weight of the hammer shall be appropriate for the piles to be driven.3.3 Follower
A follower shall be present on the site during the entire piling period. It shall have a length of not less than 1,00 m.3.4 Approval
All piling equipment which the Contractor brings on the site will be subject to Company’s approval.4. Preparatory Works
4.1 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.4.2 Pile Handling
The piles shall be transported and handled in such a way that they are not damaged. The methods of transportation and handling are subject to Company’s approval. The piles will have marked lifting points and shall be picked up at these points only.5. Pile Driving
5.1 General
5.1.1 The piles shall not be driven before the corresponding test cubes have met the strength requirements laid down in specification.
5.1.2 During driving, each pile shall be protected by a pile helmet, provided with packing and wooden dolly.
5.1.3 Jetting shall not be applied, except in special cases and then only when permitted by Company. 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.
5.1.4 Any piles which have been damaged during driving shall be repaired or replaced as directed by Company.
5.1.5 During the installation of the first pile cluster it shall be checked whether the driving of a pile causes previously installed piles to heave. For this purpose the adjacent piles shall be provided with accurate level marks immediately after their installation.
If no heaving has taken place such a check does not need to be repeated for other pile clusters, unless Company decide otherwise. If heaving has occurred such a check shall also be made on following pile clusters, as directed by Company. Heaved piles shall be re-driven to the required depth.5.1.6 If in a particular case driving has to be continued beyond grade a follower shall be used (see also clauses 3.3 and 5.3.2 ).
5.1.7 If, after installation, a pile needs to be lengthened the quality of concrete to be used shall be similar to that of the pile.
The required reinforcement will be determined by Company, for each individual case.5.2 Location
5.2.1 The orientation of the piles shall be as shown on the piling plans.
5.2.2 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 withdrawal of a pile shall be filled with sand.5.3 Depth
5.3.1 The first pile to be driven with a particular rig shall be one located at or close to one of the soundings shown on the piling plans.
5.3.2 Piles located at or close to a sounding shall be driven to the tip elevations shown on the piling plans.
The number of blows required to drive these piles over the last 0,25 m to the required tip elevation shall be used as a guidance for the adjacent piles to be driven 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 the use of a follower, another type of hammer or a different stroke, a new blow count shall be made at or close to a sounding.
5.3.3 For each pile a blow count record shall be made, providing the following data, all in metric units:
- pile number
- data of fabrication
- data of installation
- length of pile
- number of blows per 0,25 m penetration over the last 2,00 m, except for those piles driven 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.
5.3.4 If for a particular pile the required number of blows is not obtained at the expected tip elevation, the Contractor shall inform Company and continue driving only after their approval.
5.3.5 If for a particular pile the required number of blows is obtained at a level higher than the expected tip elevation, the Contractor shall inform Company and stop driving only after their approval.
6. Loads Tests
6.1 General
6.1.1 The piles to be tested will be designated by Company.
6.1.2 The test pile shall be provided with a concrete head, the surface of which shall be flat and perpendicular to the pile axis.
6.1.3 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 counterweight shall be formed by a steel platform of sufficient strength, loaded with concrete or metal blocks or other heavy material.
6.1.4 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.6.1.5 All testing equipment will be subject to Company’s approval.
6.2 Test Procedure
6.2.1 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.
6.2.2 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 to1,5 times the required gross bearing capacity ( sixth step ). In both cases the rebound of the pile shall be measured during two hours.
6.2.3 The settlement will be considered to have ceased when
6.3 Standard of Acceptance
6.3.1 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.
6.3.2 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.
Appendix to The Standard Specification for The Installation of Pre-Cast Reinforced Concrete Piles
A 1. General
A 1.1. Scope
The Standard specification for the installation of pre-cast reinforced concrete piles BN-SP-JL1 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. Pile Characteristics
A 2.1.Bearing CapacityThe gross bearing capacity should be equal to the nett bearing capacity plus the allowance for negative skin friction.
A 2.2. Concrete Quality Reinforcement
The concrete quality and type and amount of reinforcement should be stated in the job specification.
A 3. Driving Equipment
A 3.2. Rigs
If particular noise requirements are applicable during the construction phase, these should be referred to in the job specification.
In case piles have to be driven in an existing plant, special provisions to the rig may be required, such as a spark cap.
A 4. Preparatory Works
A 5. Pile Driving
A 5.2. Depth
The depth to which the piles have to be driven should be determined by Company in consultation with the soil consultant. The driving contractor should be responsible for the proper installation of the piles, but not for the determination of the tip elevations, since such a piling contractor does not normally have an adequate knowledge of soil mechanics and the pile lengths are determined by Company/soil consultant anyhow ( this contrary to cast-in-situ piles, in which case a piling system is bought, for which the contractor should be made entirely responsible ).
A 6. Load Tests
A 6.2. Test Procedure
If a pile does not meet the requirements laid down in the standard specification, under clause 6.3, 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 readings shall have a precision of not less than 0,05 mm.
A 6.2.3 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 clayey soils this criterion should be determined per case, in consultation with the soil consultant.
A 6.3. Standard of acceptance
From experience it is know, that when the procedure laid down in clause A 6.2, 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.