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## 5.4.6.2 Types of piles 

Bearing piles shall be driven reinforced concrete, precast concrete or cast in-situ concrete piles. All concrete shall be in sulphate resisting cement Type V. 

## 5.4.6.3 Design of piles 

Piles shall be generally designed in accordance with appropriate DIN standard and the materials and work shall conform to the requirements of the Employer’s Requirements. Piles shall be designed to sustain the specified loads with settlements not exceeding those specified. Allowance shall be made in the design for the incidence of negative skin friction where appropriate and for resisting the necessary tensile forces due to the swelling and heave of any soil stratum. Piles shall be designed to have a bear- ing capacity of at least 2.5 times the working load. In extreme cases (such as Earthquake loading case), piles shall be designed to have a bearing capacity of at least 2.0 times the extreme load. 

If pile tests are carried out, capacity of the piles shall be calculated according to the safety factors giv- en in Section 5.4.6.14 instead. In this case, working load bearing capacity and extreme load bearing capacity shall be the taken the same value. 

The permissible load of piles shall be modified where necessary to allow for particular conditions: piles in close proximity or in groups, soil strength, groundwater level, and other relevant factors. 

For earthquake loading (lateral loadings) , the reactions and displacement of the pile group supporting a structure shall be analysed in 3-dimensions and the displacements in horizontal direction shall be checked. The lateral bearing capacity should be assessed by treating the soil around as ultimate limit state (limit equilibrium) and/or elasto-plastic (p-y curves). 

The piles shall be of sufficient cross-section and length to sustain loads specified without settlement exceeding the following: 

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These settlements shall include both permanent and elastic deflections. Measurement of the settlement shall be made on first achieving the specified load. Measurement of the settlement shall be made at the point of application of the load. 

Where piles in place are subjected to handling, stacking and pitching or bending moments and/or shear forces, these shall be combined with the vertical loads (either in compression or tension) to satisfy the design requirements. 

The average compressive stress in the concrete of bearing piles under working load shall not exceed 25% of the characteristic cube strength at 28 days, calculated on the total cross sectional area of the pile shaft. 

Pile spacing shall be limited to a minimum value of 3*D (D is maximum pile dimension). Otherwise, the group effect shall be considered to reduce the bearing capacity and increase in settlement by con- sidering type of soil. 

## 5.4.6.4 Preliminary test piles 

After the Engineer has approved the Contractor’s proposals and calculations for the proposed piling system preliminary test piles shall be constructed as instructed by the Engineer. These shall be loaded to 2.0 times the working load to prove the design and system and to demonstrate that the safe load re- quirements can be achieved by the piling method proposed. 

