Driven pile construction control procedures and design

The depot of the MRT Chaloem Ratchamongkhon line in Bangkok was designed and constructed as an elevated concrete platform structure of some 250 000 m², supported by 17 000 driven prestressed, precast concrete piles. The design of piles considered full hydrostatic pressure in the long term, with soft clay negative skin friction due to the ongoing land subsidence. These requirements required that the piles be founded sufficiently in a deep sand stratum in order to ensure an adequate factor of safety against bearing capacity failure. This paper reports on the rigorous construction control procedures that were implemented with the aid of a pile driving analyser, in order to ensure that the design requirements were achieved. The procedures included monitoring the drive system performance, driving stresses, assessment of pile integrity and evaluation of pile capacity. The timely development and implementation of these procedures was fundamental to the early completion of piling, and to confidence in the integrity and capacity of the piles.