8 Execution

8.1 General

8.1.1 All reasonable precautions should be taken during piling operations (which shall include pile, equipment and material handling ) so as to ensure safety on and around the site and to minimise risk of damage and influence of vibrations and noise on people and adjacent properties.

8.1.2 The execution of displacement piles shall be carried out with a sequence which is in accordance with subclause 7.4.

8.1.3 Before starting piling works a plan of execution describing piling equipment, the installation method, the location of the first pile and a global sequence of installation of the piles should be available and approved.

8.1.4 Where possible trial drives or the initial piles should be installed close to positions of soil investigation.

8.2 Site preparation

8.2.1 The working platform shall be prepared and maintained in such a way that operations can be carried out safely and effectively.

8.3 Equipment and Methods

8.3.1 General

The piling equipment should comply with EN 996.

8.3.2 Impact hammer

8.3.2.1 Piles, casings or drive tubes shall be driven with a suitable hammer, which allows penetration to the prescribed depth or attains the required resistance without damage and limiting environmental disturbance.

8.3.2.2 For top driven piles the driving system shall be coaxial and sit squarely on the pile or drive tube.

8.3.2.3 The impact velocity and the weight of the ram shall be chosen to suit the pile and soil conditions (see subclause 7.7).

8.3.3 Vibrating hammer

8.3.3.1 Piles, casings or drive tubes shall be driven with a suitable vibrating hammer which allows penetration to the prescribed depth or attains the required resistance without damage and limiting environmental disturbance.

8.3.3.2 The vibrating hammer should be placed centrally on the pile head or drive tube.

8.3.3.3 The centrifugal force, the vibration frequency and the displacement amplitude of the vibrating hammer shall be chosen to fit the pile and soil conditions.

8.3.3.4 A combination of vibratory and impact driving can also be considered where a vibrating hammer is usually used for pitching and initial installation and an impact hammer is used for driving piles to required resistance or depth.

8.3.3.5 If damage to structures or services in the vicinity is likely to occur, piles or tubes should be driven with vibrating hammers regulated independently in eccentric moment and frequency.

8.3.4 Equipment for screw piles

The torque and pressure shall be selected so that piles or drive tube can penetrate to prescribed depth or attain the required resistance without damage and avoiding unacceptable soil disturbance.

8.3.5 Equipment for jacked piles

8.3.5.1 The pressure and reaction system shall be selected so that the pile can penetrate to the prescribed depth or attain the required resistance without damage to the pile or the reaction structure.

8.3.5.2 A calibrated load measuring device shall be incorporated in the jacking system.

8.3.6 Auxiliary equipment

8.3.6.1 When pile cut off level is below ground or water level a follower can be placed coaxial between helmet and pile top.

8.3.6.2 To minimise energy loss the follower should have approximately the same dynamic stiffness as the pile (see 7.8.1).

8.3.7 Drive tube

The drive tube shall be free from significant external or internal variation of the diameter which might prevent the proper formation of the pile.

EN 12699:2001 Execution of special geotechnical work – Displacement piles