METHOD STATEMENT FOR INSTALLATION OF PRECAST REINFORCED

CONCRETE PILES USING HYDRAULIC INJECTION SYSTEM

PROJECT :- CADANGAN PEMBINAAN IBU PEJABAT POLIS DAERAH SIPITANG,

SABAH

1. PURPOSE

The purpose of this method statement is to establish guidelines and

requirements for the installation of 300mm x 300mm EC piles to the foundations

for the Police Headquarters. This method statement is not meant to be

exhaustive, sufficient only to define stages and processes.

2. REFERENCE

BS 8004 : 1986 Code of Practise For Foundations

The main function of bearing piles is to transfer the load to lower levels of the

ground which are capable of sustaining the load with an adequate factor of

safety and without settling at the working load by an amount detrimental to the

structure that they support. Piles derive their carrying capacity from a

combination of friction along their sides and end bearing at the pile point or

base. The former is likely to predominate for piles in clays and silts and where

long sockets are formed in soft rocks. The latter applies to piles terminating in a

stratum such as compact gravel, hard clay or rock.

Piles should be installed to the prescribed depth, resistance or set per blow

without damage to the pile shafts or the bearing stratum and records of the

installation process should be maintained.

The load should be applied concentrically with the axis of the pile.

3. The System

The ZYC Injection System is an innovative hydraulic injection piling system which

is free of noise, vibration and pollution. The system allows for a smooth, simple

and rapid pile installation process while adhering to the most stringent

environmental protection requirements. It is generally more cost effective than

conventional piling systems and is more suitable when piling adjacent to

sensitive structures or in urban areas where a clean noise-free and vibration-free

piling system is essential. The system ensures that piles are installed with a high

level of accuracy and a 100% quality check on all injected piles since each pile is

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subjected to twice the working load, effectively individually load testing each

pile. The guesswork and uncertainty associated with conventional piling systems

is therefore eliminated.

The system is able to install a wide range of square pile sizes from 125mm x

125mm to 400mm x 400mm and spun piles from 300mm to 600mm diameter. It

can be easily manoeuvred around site and with its wide base and low centre of

gravity it is suitable for various types of ground conditions. It is easily

dismantled for transportation and is generally of low maintenance.

The system is also able to handle individually cast pile lengths exceeding 12m,

thus reducing the number of welded joints within a pile length.

4. The Machine

The ZYC Injection Machine utilises a system for installing piles using the

clamping-type pile driving mechanism, which is the main working mechanism to

clamp and drive the piles into the ground. It consists of hydraulic cylinders for

driving the piles, a pile clamping box, and hydraulic cylinders for clamping the

piles.

The ZYC Hydraulic Injection machine comprises:

a) Main body of the machine mounted with crane and operation room on

top.

b) Pile driving cylinders and horizontal beam.

c) Longitudinal moving mechanism.

d) Horizontal moving mechanism.

e) Matching weight and matching weight beam.

f) Steel dead weights.

The components are delivered by trailers to site where they are assembled using

mobile crane.

A copy of the ZYC Hydraulic Injection machine brochure is enclosed.

The Proposed Injection Machinery for this project consists of 1 No. ZYC320B-B

(320 tonnes) for installation of 300mm x 300mm piles

5. The Pile Loading

The ZYC Injection System injects the piles with a continuous and evenly applied

loading up to a load of twice the specified working load, with the load held for

30 seconds after no further penetration has been observed.

Concrete Pile (for this project)

300mm x 300mm Piles Design Load 1050 kN

A certain quantum of piles within this particular project will not be able to be

installed with the conventional centre mechanism loading system due to the

constraints of the site. Therefore, a side piling attachment will be utilised. This is

basically the same as the centre piling mechanism, with clamping system and

installation method identical, although the pressure loading capability is reduced

due to the eccentricity of the overall machine weight.

For general information purposes, the total weight of the machine with all

counterweights may be 100 tonnes. However, from experience and machinery

maintenance view points, the machine is only loaded to about 80 Tonne. Since

side piling is only able to utilise 50% of the load for pressure injection, the

maximum load that may be applied when side piling is undertaken will be 400

kN.

6. Platform / Access

All platforms and access at or to the piling locations shall be provided by the civil

works contractor. The proposed platform levels shall be approved prior to survey

setting out.

The ground conditions are to be examined for suitability for the stability and

movement of the piling rig, and conditions corrected as deemed necessary. Steel

plates shall be provided if necessary for the even distribution of the weight of

the machine.

7. Setting Out

Based on the design layout of the piles, the positions of the piles are set out on

site and pegs installed by a competent surveyor engaged by the main contractor.

These set out pegs are checked for correctness before the piling operation

commences. Due to the high accuracy of set up and positioning of the machine

prior to driving, the normal tolerance of 75mm deviation of the pile from

required position can easily be attained.

8. Delivery of Piles

All required piles will be delivered by trailer and offloaded by 25 Tonne mobile

crane.

The piles will be stored on firm, flat ground, with timber supports between

subsequent layers, to avoid any undue bending in the piles.

9. Driving Method

The driving method ensures that the works are conducted with the minimum of

noise and disturbance, and with minimum damage to the pile being injected.

Each pile will be driven continuously until the specified set and/or depth has

been reached.

The driving method is by means of clamping and injecting the piles into the

ground with the following steps:

a. At first, the pistons of two (2) pile driving cylinders are withdrawn to raise the pile-driving box to the high position.

b. The pre-cast pile is lifted and placed into the centre of the pile-driving

box.

c. The pile-driving cylinders from four (4) directions are then engaged to

clamp the pile tight.

d. Then by manipulating the hand lever of the pile-driving valve, the pile-

driving cylinders are extended to produce pressure to drive the pile

into the ground.

e. Once the pile has been driven into the ground, the pile driving

cylinders release the pile and return to steps (a), (b), (c) and (d) again

until the pile has been fully driven into the ground.

The piles are therefore driven into the ground vertically, without any forcible

corrections, thereby adhering to the requirement for the finished pile to be

within the maximum deviation from the vertical of 1 in 75.

In some soils the vertical and lateral displacement or heave resulting from

subsequent piling may carry with it piles that have already been installed. This

may cause end bearing piles to be lifted off their bearing stratum. If lifting is

suspected, careful levelling from a datum unaffected by the piling should be

made on the heads of piles already driven before and after driving subsequent

piles. Risen piles which depend largely on end bearing and which are capable of

being redriven should be redriven to the specified resistance.

10. Pile Meter and Load Meter

As the pile is being injected into the ground, both the injected pressure (Mpa)

and the corresponding load (KN) can be read instantly from the Pressure Meter

and Load Meter in the control room.

A table of injection pressure (Mpa) and the corresponding load (KN) tabulated by

the machine manufacturer is herein enclosed for reference.

11. Pile Installation Record

A pile installation record form is enclosed. For every pile installed, a record is

kept of the load bearing in KN throughout the length of installed pile at intervals

of 0.5m. The piles will be marked to show the depth of penetration in 0.5m

intervals.

Any unexpected driving conditions will be noted in the record.

12. Pile Jointing

Each pile extension subsequent to initial pile is jointed using a full perimeter V-

Butt weld, with the verticality of the extension pile checked prior to welding.

The upper and lower end plates are cleared of any undesired material and

seated. Any concrete laitance is then removed by hand hammer and the joint

area cleaned using wire brush. Welding is then undertaken using an AC Arc

Welder utilising 4mm welding rods.

13. Cutting of Pile Head

Upon excavation to required level and provision of blinding concrete as working

surface within the pilecap, breaking of the piles to cut off level will be

performed. This is done by first vertical cutting into the sides of the protruding

pile using a petrol driven concrete saw, followed by breaking of the concrete

using compressed air driven concrete breakers. All debris is then removed from

within the pilecap, and the resultant protruding reinforcement bars prepared for

inclusion within the pilecap reinforcement cage.

The concrete is normally stripped to a level such that the remaining concrete will

project 50mm to 75mm into the pilecap. The pile reinforcement should be

exposed for a length sufficient to permit it to be bonded into the pilecap.