TengizChevroil future growth project, Kazakhstan – the design of temporary haul roads

Abstract

The 36km haul road for the TengizChevroil future growth project 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 252 partially constructed module units from a purpose-built terminal in the Caspian Sea. The ground underlying the haul road comprises recent, predominantly granular deposits with palaeo-channels of very soft cohesive material up to 4 m thick. The module units, weighing up to 2300 t, were transported on multi-wheeled trailers imparting a maximum distributed ground bearing pressure of 80 kN/m2. All areas underlain by soft cohesive soils were not treated, but a budget 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.