PILING 9.1 General

Unless otherwise specified, all piling shall conform in all respects to the Civil Engineering Code of Practice CP 2004 `Foundations' issued by the `British Standards Institution, London'.

The type of pile to be used at each structure, where piling is required, shall be as indicated on the Drawings or as directed by the S.O.

9.1.1 Ground Conditions

It shall be the Contractor's responsibility to carry out further sub-surface investigation if he has any doubt about the available information or if he considers further information necessary or desirable. Such investigation by the Contractor shall be entirely at his own expense and shall have the S.O.'s prior approval in writing.

The S.O. shall be supplied free of charge with two (2) copies of the results of all such investigation by the Contractor.

In addition to submitting the records required, the Contractor shall report immediately to the S.O. any circumstances which indicate that the ground conditions differ from those expected by the Contractor from his interpretation of the results of soil investigation carried out by SAJH and which affect adversely the bearing capacity of the pile.

The Contractor's attention is, however, drawn to the fact that suitable founding strata may be encountered at depths which require the actual installation of different lengths of pile and which may give rise to considerable variation within any particular site or pile groups.

9.1.2 Setting Out

The pile layout and the number of piles shown on the Drawings are provisional only. The Contractor shall, before commencing any part of the piling work ascertain from the S.O. the layout of the piles required.

The Contractor shall set out the piles from the main grid lines of the proposed structure or such base lines as shall be agreed with the S.O.

The main setting out for piles shall be completed prior to commencement of piling. Secondary or individual pile setting out shall be completed and agreed with the S.O. not less than 24 hours prior to commencing work on the piles concerned. All main setting points, lines, stations and the like shall be suitably protected, maintained and undisturbed.

For a pile cut-off at or above ground level the maximum permitted deviation of the pile centre from the centre point shown on the Drawings shall not exceed 75mm in any direction. For a pile cut off below ground level an increase in the verticality tolerance is permitted up to 1 in 75 from the finished pile.

9.1.3 Piling equipment

The piling equipment shall be capable of speedily and efficiently installing piles of the specified types, sizes, lengths and safe working loads.

The type of piling equipment shall be suitable for the type of piles to be driven and shall be that of a system which produces the minimum noise during driving.

The Contractor shall provide sufficient number of units to ensure completion of piling work according to programme.

Before any piling work is commenced, the Contractor shall submit to the S.O. full details of the pile driving equipment and the method of carrying out the work which he intends to use. Such information shall include a full description of the piling frame, hammer, helmet and packing and of a method of handling and pitching piles and supporting them during driving, and of the proposed driving procedure set to give penetration to the required level and of the proposed set for the working load on the pile and the method of calculating it. Any revisions to these proposals which, in the light of ensuing experience, appear desirable, shall also be submitted for the approval of the S.O. prior to implementation of said revisions.

The piling frame shall be of sturdy construction, supported on an adjustable base, securely guyed and with ample toggle connections to leaders so that the pile is firmly held at all times. The type and weight of hammer shall be to the approval of the S.O. and the weight of the hammer shall be at least half that of the pile or otherwise specified. In general, a heavy hammer with a short drop should be used in preference to a light hammer with a longer drop. Single or double acting diesel or air operated hammers may also be employed. The Contractor shall submit confirmation of hammer energy per blow to the satisfaction of the S.O. All plant being used shall be maintained in a satisfactory condition and any items suffering wastage or damage shall be promptly replaced or repaired.

No piling shall be carried out without the approval in writing of the S.O. of the equipment and method of working and any revisions to these as described above, and the Contractor shall submit all of his proposals at least three weeks before the date on which he intends to use the plant on the Site.

9.1.4 Programme

The Contractor shall submit to the S.O. his proposed programme for the execution of the piling work at least seven days before commencement of the work. In addition, the Contractor shall inform the S.O. daily of the programme of piling for the following working day and shall give adequate notice of his intention to work outside normal hours, if this has already been approved by the S.O.

9.1.5 Pile driving

Unless otherwise specified, pile driving shall be as specified hereunder. The driving equipment to be used shall be of such type and capacity to the approval of the S.O. If drop hammer is used, it shall be of a free fall type and the weight of the hammer shall be as specified in CP 2004.

Piles shall be pitched accurately in the positions as shown on the Drawings. At all stages during driving and until the pile has set or driven to the required length, all exposed piles shall be adequately supported and restrained by means of leaders, trestles, temporary support or other guide arrangements to maintain position and alignment and to prevent buckling and damage to the piles.

Each pile shall be driven continuously until the specified set and/or depth has been reached. However, the S.O. may permit the suspension of driving if he is satisfied that the rate of penetration prior to the cessation of driving will be substantially re-established on its resumption or if he is satisfied that the suspension of driving is beyond the control of the Contractor.

A follower (long dolly) shall not be used for driving end bearing piles. It may be used for driving frictional piles with prior approval of the S.O. The contractor shall inform the S.O. without delay if an unexpected change in driving characteristics is encounted.

Where required by the S.O. set shall be taken at approved intervals during the driving to establish the behaviour of the piles. A set shall be taken only in the presence of the S.O. unless otherwise approved. The Contractor shall provide all facilities to enable the S.O. to check driving resistances.

Retrieve checks, if required, shall be carried out in accordance with an approved procedure.

A detailed record of the driving resistance over the full length of each pile shall be kept. The log shall record the number of blows for every 300mm of pile penetration.

The final set of a pile other than a friction pile, shall be recorded either as the penetration in millimetres per 10 blows or as the number of blows required to produce a penetration of 25mm.

When a final set is being measured, the following requirements shall be met:-

a) The exposed part of the pile shall be in good condition, without damage or distortion;

b) The dolly packing shall be in sound condition;

c) The hammer blow shall be in line with the pile axis and the impact surfaces shall be flat and at right angle to the pile and hammer axis; d) The hammer shall be in good condition and operating correctly; e) The temporary compression of the pile shall be record if required.

Piles shall be driven in an approved sequence to minimise the detrimental effects of heave and lateral displacement of the ground. When required, levels and measurements shall be taken to determine the movement of the ground or any pile resulting from the driving process. If any pile rise occurs as a result of adjacent piles being driven, the Contractor shall submit to the S.O. his proposals for correcting this and to avoid the same in subsequent work.

9.1.6 Preliminary and Working Test Piles

A preliminary test pile is a pile installed at the Site before the commencement of the main piling work for the purpose of establishing the driving criteria for subsequent working piles and for confirming the adequacy of the pile design, dimensions and bearing capacity. Preliminary test piles shall be of the same materials and driven or formed with the same plant and in the same manner as the working piles.

A working test pile is a pile which is installed as part of the permanent foundation works. No work on working test piles shall proceed until the testing of the preliminary test pile has been completed to the satisfaction of the S.O.

After testing of trial piles the S.O. will direct the lengths of piles to be supplied or manufactured. He will also direct the lengths of any extension piles to be supplied or manufactured.

9.1.7 Load tests

The Contractor shall submit to the S.O. for approval complete details of the testing equipment he intends to use for testing piles. All loading tests shall be carried out and comply with the conditions as described in Section 9.4 of the Specification on pile testing.

The S.O. will select the location of the preliminary test piles and the working piles to be load tested.

The S.O. will decide upon the necessity for testing working piles, and may select for testing one or more working piles which the Contractor shall drive in advance of the remaining piles at the Site. Piles selected for this purpose shall be constructed or driven, with the same equipment as proposed for the main piling work, to the depths required by the S.O. The remaining piling at the Site shall not proceed until the testing of the advance working pile has been completed to the satisfaction of the S.O. and meets the requirements for acceptance specified herein. The S.O. will also instruct the testing of further piles during the course of the piling work.

the commencement of piling work. The Contractor shall also employ at each site a specially qualified foreman together with the necessary gang of trained personnel and labour experienced in the installation of the piles.

9.1.9 Piling Records

The Contractor shall keep a record of all piles driven at the Site. The record shall contain such details as specified or otherwise as required by the S.O. The Contractor shall also submit to the S.O.'s Representative within 24 hours a copy of the field record of the piling work done each day.

On completion of all piling work at each site, the Contractor shall prepare and submit to the S.O.'s Representative two (2) sets of a complete drawings showing details of all piles driven at the Site.

All pile test records shall be considered as confidential and shall not be disclosed by the Contractor to any third party without the express permission in writing of the S.O.

9.2 Precast Reinforced Concrete Piles