Steel Sheet Piling Specification

Section 4 Steel Sheet Piling Work

SECTION 4 STEEL SHEET PILING WORK MATERIALS Steel sheet pile sections

4.01

Steel sheet piles shall be weldable structural steel to BS EN 10025 Grade S275. Steelwork and accessories for use in the system of lateral support shall be as Section 15 - Structural Steel Work. Testing of steel sections and accessories shall be as Section 15 - Structural Steel Work. Fabricate special and non-standard sheet piles including corner piles and junction piles from sheet pile sections approved for use in the Works. Provide sheet piles in single continuous lengths unless otherwise specified. INFORMATION TO BE PROVIDED

Tender submission

4.02

Submit the following information when specified in the tender documents: (i)

Type of sheet pile proposed including proprietary name, grade of steel, sectional modulus and qualities.

(ii)

Proposed sequence for installation of sheet piles.

(iii)

Details of special or non-standard piles.

(iv)

Details of initial trenching and guide frames.

(v)

Details of pile driving equipment selected including proprietary names.

(vi)

Proposed method of pitching and driving piles to the tolerances given in Clause 4.10.

(vii)

Contingency proposals for the remedy of piles installed outside the tolerances.

(viii) Detailed calculations of the proposed sheet piles and the system of lateral support of sheet piles prepared by a Registered Structural Engineer when specified. (ix)

Proposed sequence of excavation and installation of system of lateral support if applicable.

(x)

Proposed system to monitor the effect of excavation and dewatering on adjacent buildings, pavements, public or private services and any other structures or permanent features as Clause 4.06.

(xi)

Undertaking that the noise caused by the sheet piling works shall satisfy the legislation currently in force.

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Section 4 Steel Sheet Piling Work

Provision of details before commencement of works

4.03

When specified, submit detailed drawings with the method statements showing: (i)

The setting out arrangement for construction of the pile wall in relation to the Site and to adjoining structures. Each pile shall be annotated with a reference number and length.

(ii)

The sub-division of the pile wall into panels for the purposes of driving.

(iii)

The location of corner and closure piles.

(iv)

Proposed work on standard piles, e.g. holes for lifting.

(v)

Design for the fabrication of corner, closure, taper and other non-standard piles.

(vi)

The proposed sequence of driving by panel and by individual pile.

(vii)

Design of the guide frames required at all locations in the Works to support piles for pitching and driving within required tolerances.

(viii) Design of lateral support if applicable, including details of connections of walings, strutting, bracing, posts and splicing of members and sequence of construction and sequence of subsequent removal if applicable. Do not change the method of installing sheet piles without approval. WORKMANSHIP Preliminary ground investigation

4.04

The Contractor shall carry out any additional preliminary ground investigation he deems necessary to ascertain the nature of the ground and sub-soil, including the oversite water table level and the nature of the materials, (whether naturally occurring or otherwise), into which the sheet piles shall be installed. Allow for liaising with the SO regarding access to the Site and the execution of ground investigation works. Keep all nuisance to a minimum and make good drill holes, trial pits etc., after completion in accordance with the SO's requirements.

Existing services

4.05

Comply with the following when it is necessary to carry out any work in the vicinity of utility services:

Monitoring system and ground settlement

4.06

(i)

Advise the relevant utility undertaking at least 7 days before commencement of the Works.

(ii)

Excavate by hand to a depth sufficient to ascertain the position of service pipes etc. to ensure that these services are not damaged .

Provide a system to monitor the effects of sheet piling work, subsequent excavation and dewatering on adjacent buildings, pavements, public or private services and any other structures or permanent features. The monitoring system must be adequate to effectively monitor ground movement. Do not lower the ground water table level beyond the boundary of the Site unless otherwise specified, and adopt the approved measures to control and monitor ground water table levels.

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Section 4 Steel Sheet Piling Work

Pre-load struts or braces and carry out grout injection if required by site conditions to minimise ground settlement. Lateral support

4.07

Design by a Registered Structural Engineer when specified, the system of lateral support to the sheet piles to resist horizontal soil and water pressure arising from sub-soil conditions. Construct the system of lateral support as Section 15 - Structural Steel Work when detailed design is provided. Install members of the system of lateral support as excavation proceeds in stages in accordance with the approved construction sequence in the method statement as Clause 4.03 (viii) or the designed sequence provided, whichever is applicable.

Marking

4.08

Identify sheet piles on Site by marking with the relevant number in accordance with the approved drawings of the sheet pile arrangement. Mark the length on each pile and calibrate the pile at 1 m intervals along the length to permit checking by the SO.

Welding and splicing

4.09

Welding shall be in accordance with Section 15 - Structural Steel Work. Sheet piles not exceeding l2 m long shall be in single lengths. Piles in excess of l2 m may be spliced with approval. Splice sheet piles by full strength butt welding and maintain the true vertical alignment. Form special and non-standard sheet piles by full strength butt welding.

Tolerance

4.10

Install sheet piles within the following tolerances: (i)

Deviation from the correct line at ground level: Not exceeding 15 mm.

(ii)

Deviation from verticality of individual piles in any direction: (a)

Generally: Less than 1 : 400.

(b)

For end piles in panels and for guide piles: Less than 1 : 500.

Notwithstanding these specified tolerances, piles shall always be driven to ensure that the stated dimensions of any permanent structural elements are not reduced. Pitching

4.11

Provide rigid guide frames at upper and lower levels on both sides of the sheet piles. Accurately set out and interlock piles within the guide frames. Guide frames shall be designed to maintain piles in their true positions within tolerance during driving.

Driving

4.12

Keep noise and vibration to a minimum when driving sheet piles. Comply with the legislation currently in force in connection with noise control. Drive piles to the specified penetration with high frequency vibration pile drivers. For hard driving only, other methods could be adopted if approved. Extract and re-drive sheet piles installed outside tolerance. Replace any extracted piles that the SO considers as unfit for re-driving. Alternatively, the SO may approve the insertion of taper or other non-standard piles or other methods of correcting the plumb of piles.

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Section 4 Steel Sheet Piling Work Drive sheet piles in any length or panel progressively, with the top of no individual pile exceeding 600 mm below the top of the adjacent piles. Obstructions

4.13

Advise the SO immediately when obstructions are encountered that prevent the installation of any sheet piles to the specified penetration. Adopt an approved method for overcoming the obstruction which, depending on actual circumstances, may include: (i)

Withdrawing the sheet piles, excavating for and removing the obstruction, backfilling and subsequently re-driving the sheet piles.

(ii)

Leaving the sheet piles at the depth of penetration achieved, excavating for and removing the obstruction, backfilling and subsequently completing the installation of the sheet piles.

(iii)

Driving the sheet piles on either side of the piles obstructed to the full penetration specified, removing the obstruction during general excavation work and subsequently completing the driving of the piles obstructed. This method of removing obstructions may only be adopted with the express permission of the SO.

(iv)

Driving through the obstruction under controlled conditions. Replace any sheet piles damaged through the adoption of this method.

(v)

Withdrawing and temporarily removing sheet piles, boring through the obstruction from ground level with approved drilling equipment and subsequently replacing and re-driving the piles.

Provide temporary propping/bracing to obstructed sheet piles when a significant length of pile remains above the general top level of adjacent piles. Extraction

4.14

Do not extract sheet piles unless otherwise specified.

Burning off

4.15

Burn off the tops of sheet piles driven to full penetration to the level required when specified. Burn off the tops of sheet piles damaged by hard driving when so directed.

Sheet pile record

4.16

Provide the SO with a record, in duplicate, for sheet piles driven the previous day giving for each pile its identity number and the reference of the rig used. The following data shall also be included: (i)

Date sheet pile pitched.

(ii)

Length of completed sheet pile and whether spliced.

(iii)

Type of pile drivers used at all stages to achieve specified penetration.

(iv)

Depth of penetration below an agreed datum level.

(v)

Details of any driving damage.

(vi)

Alignment of completed sheet pile.

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Section 4 Steel Sheet Piling Work

(vii)

Re-use steel sheet pile from other site

4.17

Details of any obstructions encountered and measures adopted for overcoming the same if applicable.

Re-use of steel sheet piles from other site is permissible if they are used as temporary works and their physical conditions are considered satisfactory by the SO.

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