TengizChevroil Future Growth Project – The Design of Temporary Haul Roads

The 36 kilometre haul road for the TengizChevroil Future Growth Project (TCO FGP) at the Tengiz oilfield in Western Kazakhstan provided a unique opportunity to examine the dynamic effect of heavy traffic loading on earthworks. The haul road was constructed to facilitate transport of 252no partially constructed module units from a purpose built terminal in the Caspian Sea to the construction area within the oilfield. The ground underlying the haul road comprises recent, predominantly granular deposits with palaeo-channels of very soft cohesive material up to 4 metres thick. The module units, weighing up to 2300 tonnes, were transported on multi-wheeled trailers imparting a maximum distributed ground bearing pressure of 80kN/m2. The project strategy was that areas underlain by soft cohesive soils would not be treated but a budget would be allocated for maintenance during operation of the road. The haul road was designed using quasi-static loading with checks using limit equilibrium and finite element methods. The construction programme allowed instrumentation installed during the ground investigation to be used to complete a dynamic embankment trial to monitor settlement and pore water pressure response in the underlying soils, which was supplemented by further monitoring during haul road operation. The monitoring indicated that adoption of the quasi-static approach for traffic loading does not realistically reflect short duration dynamic loading on earthworks and that the quasi-static approach is highly conservative when applied to moving loads.