The cross-sectional dimensions of the pile shall not be less than those proposed by the Contractor nor should they exceed them by more than 0.015 x B (B = pile dimension, diameter or side). No face of a precast pile shall deviate by more than 6 mm from a straight edge 3 m long laid on the face. The cen- troid of any cross section of the pile shall not deviate by more than 12 mm from the straight line con- necting the centroids of the ends. 

## 5.4.6.6 Sequence for construction 

The sequence of construction of piles shall be to the approval of the Engineer and shall be arranged so as to minimise the vertical and lateral displacement of piles already installed. Levels of the tops of ad- jacent piles or the structures founded upon them or any other structure shall be measured at intervals while a pile is being installed. Driven piles driven which have risen, shall be re-driven or forced down to the original resistance. 

## 5.4.6.7 Driving piles 

The Contractor shall submit for the Engineer’s approval details regarding the suitability efficiency and energy of his driving equipment. 

Precast concrete piles shall not be driven until the concrete has achieved the specified characteristic strength. 

Cast-in-situ driven piles with steel casing shall be bottom driven by using a casing which shall not dis- tort or buckle during driving. Concrete casing shall be driven on the pile shoe using a mandrel. 

Each pile shall be driven continuously until the approved set and/or depth has been reached except that the Engineer may permit the suspension of driving will be substantially re-established on its resump- tion or if he is satisfied that the suspension of driving was beyond the control of the Contractor. 

A follower (long dolly) shall not be used except with the approval of the Engineer who will then re- quire the set to be revised to take into account the reduction in the effectiveness of the hammer blow. 

The final set of each 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 25 mm. 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 and packing if any 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 angles to the pile and hammer axis. 

The Contractor shall give adequate notice and provide all facilities to enable the Engineer to check driving resistances. A set for the purposes of the Contractor shall only be taken in the presence of the Engineer unless otherwise agreed. 

At the start of the work and in new areas or sections, sets shall be taken at intervals during the last 3 m of driving to establish the behaviour of piles. 

The Contractor shall inform the Engineer without delay if an unexpected change in driving character- istics is noted. A detailed record of driving resistance over the full length of the nearest available pile shall be taken. 

Redrive checks if required shall be carried out by a procedure to be agreed by the Engineer. 

Piles shall be driven in an approved sequence to minimize the detrimental effects of heave and lateral displacement of the ground. 

