Method Statement For Sheet Piling

What is the method statement for sheet piling?

The method statement for sheet piling describes the procedures and methodology for the installation of sheet piles which serve as excavation support and earth retention during the project construction stage.

What is the difference between bored piling and sheet piling?

Bored piling is defined as the removal of soil by boring or excavation forms a void before reinforced concrete piles are produced while sheet piling is a form of driven piling using thin interlocking sheets of steel to obtain a continuous barrier in the ground.

Method Statement For Sheet Piling [Template]

1. Scope

The sheet piling process will be carried out to enlarge the existing canal from 50 m to 65 m in width of (Name of the location). There are various stages and techniques of construction. In the first phase of the widening canal, the contractor is required to construct a temporary flow diversion to deal with intense storms from upstream during construction.

Earth-retaining steel structures will be installed to form the flow diversion canal with approximately a length of 320 m and a width of 40 m. After the completion of the temporary canal construction, the existing canal will be sealed off for construction activity. Marine cofferdam cells will then be constructed on the southern side of the canal.
(Name of Contractor) will be responsible for upgrading and widening existing canal structures.

2. Purpose

The method statement for sheet piling is submitted here for the purpose of better understanding the client as to how the different elements of the project will be executed through a disciplined approach.

It will act as communication among various parties and personnel involved in the project, giving an idea of the methods, procedures, safety measures, and prudent techniques that will be adopted for the successful completion of the works. Serving as a working document, the method statement shall identify the responsibilities of the contractor and its staff and also ensure that the quality of work meets the standard specification.

3. Reference Documents

A. Working Procedures of Normal ‘Press In Method’
B. Working Procedures of Normal ‘Water Jetting Method’
C. Sheet Piling Plan (subjected to revision in length)
D. Silent Piler Machine Model ECO100 Catalogue
E. Silent Piler Machine Model SA100 Catalogue
F. Silent Piler Machine Model SA150 Catalogue
G. Lifting Plan
H. Mill Certificates & Factory Production Certificates

4. List of Equipment
A. Surveying Total Stations
B. Theodolites
C. Silent Piler Machines
D. Welding Consumables
E. Crawler Crane (80 tons)

5. Procedures for Site Compound Setup
5.1 Permit
All works will only be allowed to commence upon approval of the permit-to-work by the contractor.

5.2 Daily Toolbox Meeting
Daily toolbox meetings shall be conducted prior to the daily commencement of work, briefing, and highlighting all job scopes and hazards involved to all site personnel.

5.3 Pre-start Investigation & Survey
Prior to the commencement of site works, an external survey will be carried out to confirm the existing area over sheet piling locations and the condition of the existing environment. A photographic record will be taken during dismantling, which will be maintained as a construction record.

5.4 Location of Site
The project site is located at the (Name of the location).

5.5 Scope of Work
The scope of work for constructing a temporary flow diversion canal as planned in stage 1 of the flow diversion scheme is summarized as follows:
a. Setting out and location markings
b. Installation of sheet pilings and construction of marine cofferdam cells
c. Completion sheet piling works and cofferdam cells

5.6 Organization Chart
The tentative work schedule for works in this Method Statement for Sheet Piling is as follows:
“Insert the organizational chart here“

5.7 Site Procedures & Methodology
Prior to the beginning of work, the contractor shall locate the position of work by establishing and marking the sheet pilings. The sheet pilings shall be constructed in accordance with the details on the plans and all work shall be performed in a workmanlike manner.

Following up on the completion of sheet piling insertions, ground monitoring devices will be installed to monitor and control major ground movement in the vicinity of the site. Ground monitoring devices shall be installed and calibrated properly before starting excavation activity.

a. Site Inspection / Preparation
Site inspection, site clearance, cable detection, and utility diversion/ protection are to be carried out along sheet pile alignment according to all available information. Trial trenches are to be carried out by the main contractor to confirm the location of the existing services prior to the driving of sheet piles.

b. Safety Measures
Before the start of installation work, metal hoarding, and safety nets shall be erected and installed around the vacant land where it is to be carried out by the main contractor, if necessary.

c. Certificate
All operators and welders shall carry relevant certificates/licenses during the work. Likewise, all lifting operation-related certifications shall be submitted prior to work commencement.

d. Signboards All installation works will be carried out within the hoarded working compound area, therefore signboards for traffic control and pedestrian are needed to install by the main contractor, if necessary. The working area shall be barricaded by the main contractor if the operation is in a public area. For night operation, warning lights shall be arranged by the main contractor.

e. Setting out
Setting out of sheet piles to be conducted by the main contractor surveyor, to set out the internal wall of the sheet piles and the position of each pile and to establish TBMs on-site for determining the cut-off levels of sheet piles.

The Methodology of the Installation of Sheet Piling

Conventionally, sheet piles have been vibrated or pounded into the ground. However, such a method inevitably generates excess noise and vibration that could affect the stability of structures in the site vicinity.

Therefore, silent pilers will be introduced to utilize press-in force (the set criteria of the pile is set as a maximum of 800 kN or to the designed length, whichever comes first) and hydraulically jack in piles into the ground. Generally, the normal ‘Press In Method’ will be applied.

Wherever there is encountering difficult soil conditions, an auxiliary ‘Water Jetting Method’ will be introduced to enable piles to be pressed into. In addition, the water jetting method can be utilized as a means to significantly improve productivity and cost, as well as optimize the sheet pile section required.

1. Hoisting Technique of Sheet Piles

Hoisting of Sheet piles for installation by Crawler crane.
a. Lifting crane shall be selected, based on the weight of the members to be lifted.
b. Working access and area shall be good and wide enough for this type of work including swing operation.
c. The lifting supervisor shall be assigned for the operation. Riggers, signalmen and etc. shall be well organized. They shall be instructed clearly about the operation.
d. Crawler crane shall park at the pre-determined positions. Sheet piles lay down area shall be selected at the early stage.
e. Ensure the shackle has a valid LG certificate before use.
f. The maximum hoisting capacity for shackles is 8 tons.
g. Handle it carefully & slot it into the pre-cut center hole diameter of 50mm at the top of sheet piles. (100mm from the top of sheet piles)
h. Push the shackle into a pre-cut center hole (referred to as item g).
i. Rigger man will ensure the shackle fully tightens.
j. The whole lifting operations should be supervised by the lifting supervisor.
k. Once the sheet pile has been inserted into the silent piler chuck by crane and pressed at least 3/4 length of the sheet piles into the ground, the silent piler operator will confirm and ensure everything is in order before giving instructions to the trigger man to release the shackle. The shackle must be reachable by a man’s height.
l. Repeat it again for the next installation & extraction of sheet pile or H-beam.

Normal Silent Sheet Piling Method

The sheet piling is started from a reaction stand which simulates the top of sheet piles. After positioning the reaction stand vertically on the proposed alignment, the initial 3-4 pieces of sheet piles shall be pitched and pressed in using the silent piler machine to the required depth.

Counterweights, often in the form of sheet piles are used to provide an initial reaction force. Upon completion of the installation of the initial 3-4 pieces, the counterweights and reaction stand shall be removed. Then, installation for the remaining sheet piles shall continue. The next sheet pile shall be pitched into the chuck of the silent piler machine. After checking the verticality and alignment, the sheet pile shall be pressed in into the required depth.

If necessary, the sheet pile shall be joined by welding to achieve the required penetration length. However, prior to completing the driving of the sheet pile, the silent piler machine is released from the anchoring piles. Then, the main body of the silent piler machine is lifted and traveled forward.

The main body is lowered and the feet are clamped on the next three piles. The silent piler machine shall complete the driving of the sheet pile and the upper portion of the machine move forward to allow the next sheet pile to be pitched. The next sheet pile shall be pitched into the chuck of the silent piler machine. After checking the verticality and alignment, the sheet pile shall be pressed in into the required depth.

If necessary, the sheet pile shall be joined by welding to achieve the required penetration length. However, prior to completing the driving of the sheet pile, the silent piler machine is released from the anchoring piles. Then, the main body of the silent piler machine is lifted and traveled forward.

The main body is lowered and the feet are clamped on the next three piles. The silent piler machine shall complete the driving of the sheet pile and the upper portion of the machine move forward to allow the next sheet pile to be pitched. The above procedures shall be repeated to press in the subsequent sheet piles to complete the sheet pile wall. 

Silent Sheet Piling with Water Jetting

This method executes the driving work as follows: A water-conveyance pipe (water supply hose) with a nozzle attached at the tip is welded to the U-shaped section of the driving steel sheet pile with a pipe band. The jet water supplied from a water jet pump is injected through the nozzle to reduce the driving resistance, driving the steel sheet pile into the soil. After the pile is correctly driven into the soil, the water jet is shut off, and the jet pipe is extracted from the soil to apply to the next steel sheet pile.

This method is designed to feed the water supplied in a water tank into the water jet pump, which, in turn, pressurizes and feeds the water through the water supply hose and pipeline for injection from the nozzle.

On the other hand, the water jet joint method is intended to facilitate smooth, accurate, and damage-free driving of steel sheet piles by reducing point resistance, skin friction resistance, and joint friction resistance caused by driving operation with the aid of a water jet from the water jet pump. Injection of water jet into sandy soil can cause pore water pressure in soil particles to temporarily increase, leading to easily moving soil particles and resultant so-called ‘liquefaction.’

This phenomenon is used to reduce the point resistance of the steel sheet pile. In addition, excess water may flow along the side of the steel sheet pile out to the surface, helping reduce the skin friction resistance.

Furthermore, washing off sand from the joints of already driven steel sheet piles causes eliminated ‘wedge phenomenon’ of joints, leading to reduced joint friction resistance. When the injection is interrupted after the completion of pile driving, the water propagates through the soil to produce the so-called water-binding phenomenon, contributing to more consolidated soils than before.

This phenomenon helps stabilize the already driven steel sheet piles and produce proper reaction forces allowing the driving of subsequent steel sheet piles. Sometimes it is reported that the ‘use of the water jet jointly method for driving of steel sheet piles can cause loosened soils in the surrounding ground and resultant caved-in road surfaces and/or damaged houses, and thus the water jet jointly method is never adopted.

In practice, however, proper control of water flow and pressure helps produce the water-binding phenomenon in the site soils after completion of driving, and the soils become consolidated, having little effect on the surrounding sites.

This suggests that safe, secure, and environment-friendly methods should be selected for driving steel sheet piles, and the water jet jointly method is the most reliable among the currently available methods.

This might interest you: Method Statement for Bored Piles

Vibratory Excavator Method Statement of Sheet Piling

Due to unpredictable soil conditions on-site, the contractor may face difficulties in using the silent piler method. It could vary soil profiles at certain locations which impose higher resistance to driving stresses and thus limit the usage of the silent piler method. For such circumstances, a vibro-mounted excavator is advisably used to tackle the hard soil condition problems.

The vibro drivers are specifically designed to be mounted directly on the stick of excavators. The vibro-mounted excavator is an efficient hydraulic vibratory hammer that reduces the cohesion of soil through vibration and allows for an easy drive in sheet piles. Despite the advantages, excavators in the current market have limited boom length.

Hence this method is only suitable for the installation of sheet piles with lengths less than 14m. Sheet piles will be laid down at a reachable distance from vibro-mounted excavator.

Then, the driver will clamp to the end of the sheet pile. It will be pitched up and vibrated in place until the required toe level is reached. Contractors shall ensure that vibration limits are not exceeded during sheet pile extraction by using the vibration method.

Vibratory Hammer Method Statement of Sheet Piling

Due to the limitation of the vibro-mounted excavator, the vibratory hammer would be used to tackle hard ground conditions and install sheet pile lengths of more than 14m. As of common procedure, sheet piles will be transported and off-loaded on-site at work locations.

The temporary frame guide beam will be fixed at survey lines in order to ensure verticality and alignment of sheet piles. The guide frame will consist of vertical end members (legs) along with two I-beams that will be fixed horizontally, with a gap provided between their faces in order to allow for the pitching of the sheet piles.

Then, the vibratory hammer’s clutches will pitch the sheet pile and lift it up by the crawler crane. The sheet piles will be attached to a safe line with features of release shackle attachment. Then, it will be pitched down by the vibration force of the hammer. During the operation, the contractor has to be careful and ensure that vibration limits are not exceeded.

2 Extraction Process of Sheet Piles

Silent Method

The sheet pile extraction using the silent piler method is a unique self-moving technique that enables the machine (silent piler) to extract along with the sheet piles which were driven earlier. The silent piler machine is lifted by a service crane/excavator to “sit in” the existing sheet piles. The main body is lowered and the feet are clamped on the sheet piles. The sheet piles extraction operation then commenced.

This extraction operation is the reverse of the installation operation. After the chuck of the silent piler machine had gripped on the first sheet pile, the sheet pile is pulled vertically upwards.

If necessary, the sheet pile shall be cut to facilitate the extraction works. However, prior to completing the extraction of the sheet pile, the silent piler machine is released from the anchoring piles. Then, the main body of the silent piler machine is lifted and traveled backward. The main body is lowered and the feet are clamped on the next three piles. The silent piler machine shall complete the extraction of the first sheet pile.

The upper portion of the machine moves back to allow the next sheet pile to be extracted. The above procedures shall be repeated to extract the subsequent sheet piles to complete the sheet pile extraction work.

Vibration Method
Sheet piles tend to be easy to be extracted by the vibration method. After backfilling or completion of a permanent structure, the vibratory hammer will be brought in together with a crawler crane. Crane will lift the vibratory hammer to work locations and clamp the sheet pile.

Once power is generated, the vibration force induced by the hammer will reduce the cohesion of soil and start to pull out sheet piles. At the same time, the crawler crane will gently adjust its boom radius to pull up sheet piles.

The same operation will be repeated until each sheet pile is lifted up. Contractors shall ensure that vibration limits are not exceeded during sheet pile extraction by using the vibration method. All extracted sheet piles and materials will be loaded and transported off-site.

3 Fabrication Procedure of Sheet Piles

Most of the 30 m sheet piles will be joining on-site due to transport difficulty for 21m length (a normal lorry truck can only fit a maximum of 18m length). Asides from that, a total of 18 corner piles will be pre-fabricated prior to installation. They are especially needed for sharp turning points at the seaside.

Due to the nature of the work, the tapered pile will also be fabricated and installed at every 180th sheet pile. The purpose of the tapered pile is to adjust and ensure the vertical alignment of sheet piles.

Sheet Piles Jointing Fabrication

2 pieces of sheet piles will be selected, lifted, and placed at the designated location for jointing in welds. After placing, lifting gears will be detached. Welders start to prepare and grind one of the edges of sheet piles until it becomes a beveled edge. After that, both ends of sheet piles (one end with the normal edge, another end with a bevel edge) are to be put together, merged, and jointed as per the welding details stated below.

The sheet pile will be left for a cooling down of 3 hours before lifting. Then, the lifting team will rig the sheet pile properly and flip over it. After that, welding will be carried out on another side of the sheet pile joint.

Corner Pile Fabrication

A corner pile is a special sheet pile to create a T-section and form an interlocking element to connect sheet piles so that they can be combined with special corner profiles. Before the start of work, 2 nos. of sheet piles in length 21m will be selected and laid properly at the fabrication yard.

Firstly, the sheet pile will be cut in half and left for cooling down for about a few hours. Angle bars with a size of 100x100x12mm will be welded onto another sheet pile at an interval of 3.5m.

Welding details of the angle bar with the sheet pile can be referred to as attachment F: Sheet Pile Fabrication Detail. Then, the half-cut sheet pile is lifted and slotted into pre-joint angle bars spacing. The sheet pile alignment will be adjusted so that it is in the right position.

Afterward, welders will start to weld and joint angle bars and sheet pile. Finally, fabricated sheet piles will be shifted to another storage location waiting for installation.

Tapered Pile Fabrication

If at any time the sheet pile wall vertical alignment is tilted and out of the line of the connection slot, the contractor will provide a tapered pile to insure succeeding piles are vertical. 2 nos. of sheet piles will be selected and laid properly at fabrication yard. In the first step of the cutting sequence, the sheet pile will be cut along its diagonal line.

After it is left for cooling down for 3 hours, it will be lifted and put adjacent to another sheet pile. Next, it will be adjusted and confirmed in position before another joint welding begins.

The welder will start to weld the joint at both sides as per details in attachment F: Sheet Pile Fabrication Detail. After that, splice plates will be welded to strengthen the connection of sheet piles. Finally, the fabricated sheet piles will be shifted to another storage location for installation. The investigation should be carried out to review the cause and ensure there is no ‘de-clutching’ of sheet piles.

6. Appendices of the Method Statement for Sheet Piling
APPENDIX A
ATTACHMENT: LOCATION LAYOUT PLAN
APPENDIX B
ATTACHMENT: CONSTRUCTION DRAWING
APPENDIX C
ATTACHMENT: SILENT PILER MACHINE MODEL ECO100
CATALOGUE
APPENDIX D
ATTACHMENT: SILENT PILER MACHINE MODEL SA100
CATALOGUE
APPENDIX E
ATTACHMENT: SILENT PILER MACHINE MODEL
SA150 CATALOGUE
APPENDIX F
ATTACHMENT: SHEET PILE FABRICATION
DETAILS
APPENDIX G
ATTACHMENT: WELDING PROCEDURE
SPECIFICATIONS

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